HK1064810A

HK1064810A - Tunable organic vcsel system

Info

Publication number: HK1064810A
Application number: HK04107395.2A
Authority: HK
Inventors: P. Spoonhower John; A. Agostinelli John; E. Kruschwitz Brian; B. Kahen Keith; A. Lebens John
Original assignee: 伊斯曼柯达公司
Priority date: 2002-10-16
Filing date: 2004-09-24
Publication date: 2005-02-04

Description

Tunable organic vertical resonant cavity surface emitting laser system

Technical Field

The present invention relates generally to Vertical Cavity Surface Emitting Lasers (VCSELs) or micro-cavity lasers, and more particularly to organic micro-cavity lasers or organic VCSELs. More particularly, the present invention relates to a method of wavelength tuning an organic laser resonant cavity.

Background

Since the mid-80 s (Kinoshita et al, IEEE Journal of Quantum electronics, volume QE-23, No. 6, 6 months 1987), Vertical Cavity Surface Emitting Lasers (VCSELs) based on inorganic semiconductors have been studied. At the present level, AlGaAs-based VCSELs emitting at 850nm have been manufactured by many companies for over 100 years (Choquette et al Proceedings of the IEEE, Vol. 85, No. 11, 11/1997, 11 months). With the success of these near infrared Lasers, attention has been turned in recent years to other inorganic material systems to fabricate VCSELs that emit in the visible wavelength range (Wilmsen et al, Vertical-Cavity Surface-Emitting Lasers, Cambridge university Press, Cambridge, 2001). Visible lasers are used in many fields such as displays, optical storage read/write, laser printing and short-range telecommunications using plastic optical fibers (Ishigure et al, Electronics Letters, volume 31, No. 6, 16/3 1995). Although many laboratories in industry and large institutions worldwide are devoted to this research, most work has been limited to manufacturing available laser diodes (edge emitters or VCSELs) that produce light output across the visible spectrum.

To produce VCSELs at visible wavelengths, it is desirable to abandon inorganic-based systems, placing an emphasis on organic-based laser systems because organic-based gain materials have many advantages over inorganic-based gain materials in the visible spectrum. For example, typical organic-based gain materials are characterized by very low unpumped scattering/absorption losses and high quantum efficiency. Organic lasers are relatively inexpensive to manufacture, can be made to emit over the entire visible spectrum, can be scaled to any size, and, more importantly, can emit multiple wavelengths (e.g., red, green, and blue) from one chip than inorganic laser systems. Finally, the gain bandwidth of organic lasers is large, especially when compared to inorganic lasers. In the last few years there has been an increasing interest in the fabrication of organic based solid state lasers. Laser gain materials are known as either high molecular or small molecular materials, and have employed many different resonant cavity structures, such as microresonator (U.S. Pat. No. 6,160,828 to Kozlov et al, 12.2000, entitled "organic VCSEL"), waveguide, ring microlaser, and distributed feedback (see also e.g. Rep. prog. Phys. 63, 729. su. 762 to Kranzelbinder et al, 2000, and 5,881,083 to 1999, 3.9.9, entitled "conjugated polymers as materials for solid state lasers"). All of these structures have a problem in that in order to generate laser light, the resonant cavity must be excited by optical pumping using other laser sources. It is more preferred to pump the laser cavity electronically, as this will generally result in a more compact and more easily modulated structure.

One major obstacle in the implementation of electrically pumped organic lasers is that the organic materials have a low carrier mobility, typically at 10^-5cm²/(V-s) of the order of magnitude. Low carrier mobility can create a number of problems. Devices with lower carrier mobility are generally limited to using very thin layers in order to avoid large voltage drops and ohmic heating phenomena. These thin layers cause the lasing mode to penetrate the sacrificial cathode and anode, which greatly reduces the lasing threshold (Kozlov et al, Journal of Applied Physics, Vol.84, No. 8, 10/15/1998). Because electron-hole recombination in organic materials is governed by Langevin recombination (the rate of recombination is proportional to carrier mobility), low carrier mobility can generate orders of magnitude more charge carriers than singlet excitons; one consequence of this is that charge-induced (polaron) absorption will become dominantThe loss mechanism (Tessler et al, Applied Physics letters, Vol.74, No. 19, 10/5 1999). Assuming that the internal quantum efficiency of the laser device is 5%, the lowest laser emission threshold reported so far is adopted to be 100W/cm²(Berggren et al Letters to Nature, vol. 389, 2 d 10/1997), and the aforementioned depletion mechanism was tentatively ignored, the lower limit obtained at this time for the electrically pumped laser emission threshold was 1000A/cm². If these loss mechanisms are included, the lasing threshold will be well above 1000A/cm²This is the highest current density reported to date, which organic devices are capable of withstanding (Tessler et al, Advanced Materials, 1998, 10, number 1).

One way to overcome these difficulties is to use crystalline organic materials as the lasing medium rather than amorphous organic materials. This method has recently been adopted (Schon et al, Science, vol.289, 28/7/2000) to construct a Fabry-Perot resonator with single crystal tetracene as the gain material. Greater current densities can be achieved with crystalline tetracenes, thicker layers can be used (since the carrier mobility is about 2 cm)²V-s) and the polaron absorption is much lower. The use of crystalline tetracene as the gain material will yield about 1500A/cm²The room temperature laser threshold current density.

As an alternative to organic laser electrical pumping, non-coherent source light pumping may be used, such as Light Emitting Diodes (LEDs), inorganic (McGehe et al, Applied Physics letters, Vol. 72, No. 13, 30/3/1998) or organic (Bergren et al, U.S. Pat. No. 5,881,089, 1999, 3/9, entitled "article comprising an organic laser"). This possibility benefits from an unpumped organic laser system with total loss (-0.5 cm) of scattering and absorption at the lasing wavelength location^-1) A large reduction, especially when a host-dopant combination is used as the active medium. Even with such small losses, organic lasers have so far reported the smallest amount of optical pumping, depending on the design of the waveguide laser (et al Letters nature, volume 389, 1997, 10/2)The threshold can only reach 100W/cm². Because the power density of the existing inorganic LED can only reach-20W/cm at most²Therefore, in order to achieve the optical pumping process by the incoherent light source, different approaches must be taken. In addition, in order to lower the lasing threshold, a laser structure that minimizes the gain volume must be selected; VCSEL-based micro-resonant cavity lasers meet this standard requirement. The VCSEL-based organic laser resonant cavity can enable the threshold of the optical pumping power density to be lower than 5W/cm². Thus, practical organic laser devices can be driven by optical pumping with a variety of readily available incoherent light sources, such as LCDs.

Organic based gain media also have some disadvantages, but can be overcome by careful design of the laser system. The optical and thermal damage thresholds of organic materials are low. In order to be able to predict irreversible damage to devices, these devices have pumping power density limits. In addition, organic materials are sensitive to many environmental factors, such as oxygen and water vapor. If one could have a way to reduce the sensitivity to these variables, the lifetime of the device would generally be increased.

One advantage of organic-based lasers is that because the gain material is generally amorphous, these devices are less expensive to manufacture than lasers containing gain materials (both inorganic and organic) that require high crystallinity. In addition, the organic amorphous gain material-based laser can be manufactured in a large area without manufacturing a large-area single crystal material; therefore, it can be scaled to any size to achieve higher power output. Because they are amorphous in nature, organic-based lasers can be produced on different substrates; therefore, materials such as glass, flexible plastics and Si can be used as the support of these devices. Thus, there is a greater cost advantage and choice in determining a useful support material for an amorphous organic-based laser.

Tunable inorganic VCSELs are well established in the art. Many tuning mechanisms have been proposed, each with its characteristics. Chang-Hasnain (IEEE Journal on selected Topics in Quantum Electronics, volume 6, No. 6, month 11/month 12 2000) recently reviewed various advantages of wavelength tunable VCSELs. The text focuses on a micromechanical tunable inorganic VCSEL. Wavelength continuous tuning is a large feature of micromechanical or microelectromechanical (MEM) devices, especially inorganic VCSELs, that tune the wavelength output of a solid state laser source. The tuning range for inorganic VCSELs with micromachined, deformable thin film mirrors was 15nm as reported by Larson et al, appl. Phys. Lett.68(7), 1996, 2.12.s. With the advancement of movable mirror design, a tuning range of 19.1nm has been reported (Sugihwo et al, appl. Phys. Lett.70, 3/2 1997). The physical basis of such MEMs tuning devices is to change the optical path length of the laser cavity. The most direct way to change the optical path length of the laser cavity is to move the laser mirror. Early work on thin film lasers using this tuning mechanism was described in Smiley, U.S. Pat. No. 3,573,654, entitled "narrow band tunable laser oscillator Amplifier", filed 1971, 4/6. The use of movable curved mirror elements on MEM tunable VCSELs has also been reported. These structures can provide improved performance in quality control of single mode operating lasing modes over a wide tuning range. U.S. patent application publication No. 2002/0048301(Wang et al, 5/4/2000); 2002/0031155(Tayebati et al, 26/6/1998); and 2002/0061042(Wang et al, 28/9/2001) specify, among other things, the design of movable mirror tuning structures.

When the MEM device is used in combination with a grating out-coupling device, they can be used to tune the inorganic laser cavity. John h.jerman et al, in U.S. patent application publication No. 2001/0036206 (filed 3/12/2001), disclose the use of a micro-actuator to change the angle of a micro-mirror that functions to tune a laser having the Littman-Metcalf configuration. An advantage of this particular configuration is that the light output direction does not change with wavelength tuning. This particular resonant cavity configuration is an example of the application of the MEM wavelength control device in an external resonant cavity laser. These devices are referred to as MEM-ECL devices. The Littman-Metcalf configuration is but one example of the many MEM-ECL device laser configurations described in this patent application.

Alternative methods of varying the optical path length of the laser cavity of thin film inorganic lasers have also been reported. These alternative methods are generally non-mechanical. These alternative approaches generally involve varying the optical path length of the laser cavity by varying the refractive index of one or more sections of the device. Many approaches rely on thermal or thermo-mechanical mechanisms by which inorganic VCSELs are tuned. Both mechanisms are based on the temperature dependence of the refractive index, thereby changing the optical path length within the laser resonant cavity. Fan et al, Electronics Letters, Vol.30, No. 17, 8/18, 1994 reported that the introduction of an integrated thin film heater in an inorganic VCSEL device resulted in a tuning range of about 10 nm. The tuning process is purely per thermal mechanism. Chang-Hasnain et al describe the thermo-electric mechanism in Electronics Letters, Vol.27, No. 11, 1991, 5/23. At this time, other structures for controlling temperature are introduced into the inorganic VCSEL. If the current in the device is appropriate, the laser can be cooled by the Peltier effect, shifting the laser emission in the blue wavelength direction. Under other conditions, the current will heat the device, which in turn shifts the laser emission in the red wavelength direction. Low threshold devices tuned by thermal mechanism are described in IEEE Photonics Technology Letters, Wipiejewski et al, Vol.5, No. 8, 8 months 1993. In addition, there is a tuning mechanism due to the accumulation of free electron carriers in the laser cavity, the so-called plasma effect (see, for example, appl. phys. lett. 62(3), 1993, month 1). The carrier density lowers the refractive index and lowers the laser output wavelength. The tuning range of these devices is very limited. The method has the defects of limited frequency response during modulation; the tuning rate is also very small.

Many other methods of controlling the wavelength of inorganic VCSELs have also been reported, all relying on refractive index changes to achieve tuning. E.a. avrutin et al, appl.phys.lett.63(18), page 2460 (1993), describes the introduction of one or more refractive index changing layers in the distributed Bragg emitter (DBR) section of a device. The laser cavity is constructed from end mirrors, and a DBR is typically used as one of the end mirrors.

In contrast to methods of tuning laser cavities by changing the optical path length of the laser cavity or by changing the angle with a grating output coupler, MEM devices can be used to select the output of different laser oscillators. See Optical Fiber Communication Conference (OFC) proceedings technical Digest Postconference Edition, volume 70, 2002, 3 months, American society of optology, B.Pezeshki et al. The multi-wavelength laser array produces a discrete wavelength optical output over a wavelength tuning range. After the output of the single laser cavity device is selected by the optics and MEM tilting mirrors, those appropriate, selected wavelength outputs are directed into the output fiber. Wavelength selection is achieved by controlling the angle at which the MEM tilts the mirror in the system.

Kozlov et al, in us patent 6,160,828 (12.12.2000), disclose organic VCSEL devices capable of wavelength tuning. Similar to the inorganic material matrix system, wavelength tuning is achieved by changing the optical path length of the laser cavity. Two different embodiments are disclosed. In a first embodiment, the laser organic layer providing optical gain is in the form of an optical wedge or tapered layer. The thickness of the organic layer in the device varies in the lateral direction. Different sections of the optically pumped wedge device may produce outputs of different wavelengths. The smooth tuning range of such organic devices is much larger than that of inorganic devices; the tuning range is reported to be 50nm or greater. In another embodiment, the second (upper) mirror element may be translated relative to the rest of the device structure to produce a change in optical path length. A lens is introduced into the resonant cavity to direct light into the second mirror element. Even with both types of devices, it is difficult to control the lateral mode structure of the laser emission, since the effective volume in the resonant cavity depends only on the spot size of the pump beam. In wedge devices, the spectral width of the laser output is also related to the pump beam spot size in the device structure. In addition, if a lens is introduced into the resonant cavity, the resonant cavity with such a length will have a plurality of longitudinal modes. It would be difficult to achieve smooth resonant cavity tuning in such structures. The additional lenses add cost and complexity to the system and further complicate optical alignment.

What is needed is better control of the laser optical mode and tuning wavelength of an organic tunable VCSEL, while maintaining the advantage of a larger tuning range for organic tunable VCSELs as compared to inorganic VCSELs.

Disclosure of Invention

The present invention may satisfy one or more of the aforementioned needs. Briefly, in accordance with one embodiment of the invention, there is provided a system for mechanically tuning the optical wavelength emitted from an organic laser resonator device, comprising: a multilayer film structure, wherein the multilayer film structure is pumped by an incoherent photon source; and a microelectromechanical mirror assembly proximate the multilayer film structure, wherein the microelectromechanical mirror assembly varies a cavity length of the organic laser cavity device.

In accordance with another embodiment of the present invention which satisfies one or more of the above-mentioned needs, there is provided a system for tuning the optical wavelength emitted from an organic laser resonator device, comprising: an organic laser resonator structure pumped by an excitation method, wherein the organic laser resonator structure comprises: a support body; a first dielectric stack for receiving and transmitting a pump beam and reflecting laser light within a prescribed wavelength range; one or more controllable refractive index dielectric control layers; an organic active region for receiving the pump beam transmitted from the first dielectric stack and emitting laser light; a second dielectric stack for reflecting the pump beam and the laser light transmitted from the organic active region back into the organic active region, wherein the first and second dielectric stacks and the organic active region together generate the laser light; and means for controlling the refractive index of the dielectric control layer.

Other features and advantages of the present invention will become more apparent with reference to the following description and drawings, in which like numerals are used to refer to like features common to the figures wherever possible.

Brief Description of Drawings

FIG. 1 is a cross-sectional side view of an optically pumped organic laser resonant cavity device;

FIG. 2 is a cross-sectional side view of an optically pumped organic-based vertical cavity laser containing a periodically structured organic gain region;

FIG. 3 is a cross-sectional side view of an optically pumped two-dimensional phase-locked organic vertical cavity laser array device;

FIG. 4a is a cross-sectional side view of an optically pumped tunable organic VCSEL system incorporating a MEM device that functions to vary the optical path length of the laser cavity;

FIG. 4b is a top view of an optically pumped tunable organic VCSEL system employing a dual support beam structure;

FIG. 4c is a top view of another embodiment of an optically pumped tunable organic VCSEL system using a cantilever beam structure;

FIG. 4d is a top view of another embodiment of an optically pumped tunable organic VCSEL system using a multi-arm beam (two or more) structure;

FIG. 4e is a top view of another embodiment of an optically pumped tunable organic VCSEL system using a film structure;

FIG. 5 is a cross-sectional side view of another embodiment of an optically pumped tunable organic VCSEL system using a multilayer film structure having periodically structured organic gain regions and also containing MEM devices that function to vary the optical path length of the laser cavity;

FIG. 6 is a cross-sectional side view of a prior art organic laser cavity device containing a wedge-shaped organic active region;

FIG. 7 is a cross-sectional side view of a prior art electrically pumped organic vertical cavity laser;

FIG. 8 is a cross-sectional side view of another embodiment of a prior art electrically pumped organic vertical resonant cavity laser;

FIG. 9 is a block diagram illustrating the operation of yet another embodiment of a tunable organic VCSEL system;

FIG. 10 is a schematic diagram of a tunable organic VCSEL system incorporating MEM devices whose function is to select the output wavelength of an organic laser cavity device using an electrically pumped organic vertical cavity laser;

FIG. 11 is a schematic diagram of a tunable organic VCSEL system incorporating MEM devices whose function is to select the output wavelength of an organic laser cavity device using an optically pumped organic vertical cavity laser;

FIG. 12 is a cross-sectional side view of another embodiment of an optically pumped tunable organic VCSEL system using an optically pumped multilayer film structure with periodically structured organic gain regions and two-dimensional phase locking, in addition to MEM devices that function in conjunction with gratings for laser cavity tuning to change the angle of the mirrors;

FIG. 13 is a cross-sectional side view of another embodiment of an optically pumped tunable organic VCSEL system using an electrically pumped multilayer film structure and additionally a MEM device that functions in conjunction with a grating for laser cavity tuning to change the angle of the mirrors;

FIG. 14 is a cross-sectional side view of a tunable organic VCSEL system showing another means for varying the optical path length;

FIG. 15 is a cross-sectional side view of another embodiment of a tunable organic VCSEL system;

FIG. 16a shows a prior art electrostatically tunable MEM grating or an analog tunable grating comprising a piezoelectric actuator;

FIG. 16b shows another prior art electrostatically tunable MEM grating or an analog tunable grating incorporating a piezoelectric actuator;

FIG. 17 shows an alternative embodiment of an electrically tunable diffraction grating; and

figure 18 is a cross-sectional side view of another embodiment of a tunable organic VCSEL system.

To facilitate understanding, identical reference numerals have been used, wherever possible, to designate identical features that are common to the figures.

Detailed Description

In the present invention, the term denoting vertical cavity organic laser devices (VCSELs) is used interchangeably with its shorthand form "organic laser cavity device". The organic laser cavity structure may be fabricated as a large area structure containing a plurality of organic laser cavity devices and may be optically pumped using Light Emitting Diodes (LEDs).

A cross-sectional side view of a vertical cavity organic laser device 10 is shown in figure 1. The substrate 20 may be optically transmissive or opaque depending on the target direction of optical pumping or laser emission. The light transmissive substrate 20 may be clear glass, plastic, or other transparent material such as sapphire. Alternatively, opaque substrates include, but are not limited to, semiconductor materials (such as silicon) or ceramic materials if both optical pumping and laser emission are performed through the same surface. A bottom dielectric stack 30 is deposited on the substrate 20 followed by an organic active region 40. The substrate 20, bottom dielectric stack 30, and organic active region 40 form a multilayer film structure 45. The top dielectric stack 50 is then deposited on the multilayer film structure 45. The pump beam 60 optically pumps the vertical cavity organic laser device 10. The pump beam 60 comes from a photon source 65. The photon source 65 of the pump beam 60 may be an incoherent source such as a Light Emitting Diode (LED) emission. Alternatively, the pump beam may be from a coherent laser source. Fig. 1 shows laser emission 70 from top dielectric stack 50. Alternatively, by appropriate design of the reflectivity of the dielectric stack, the laser device can be optically pumped through the top dielectric stack 50 and lasing can be achieved through the substrate 20. If the substrate is opaque, such as silicon, both optical pumping and laser emission are performed through the top dielectric stack 50.

The preferred material for the organic active region 40 is a small molecule organic matrix-dopant complex, typically deposited by high vacuum thermal evaporation. Host-dopant complexes are desirable because they produce very little unpumped scattering/absorption loss for the gain medium. Small organic molecules are preferred because vacuum deposited materials deposit more uniformly than spin-on polymer materials. The host materials used in the present invention are also preferably selected so that they are sufficiently absorptive of the pump laser beam 60 and capable of delivering a high percentage of the excitation energy to the dopant material via the F * rster energy delivery principle. The F * rster energy transfer principle, which involves the radiationless transfer of energy between a host and a dopant molecule, is well known to those skilled in the art. An example of a host-dopant complex useful for red-emitting lasers is tris (8-hydroxyquinoline) aluminum (Alq) as the host and [4- (dicyanomethylene) -2-tert-butyl-6- (1, 1, 7, 7-tetramethyljulolidine (juliody) -9-enyl) -4H-pyran ] (DCJTB) as the dopant (1% by volume). Other emission wavelengths other host-dopant complexes may be employed. For example, for green wavelengths, a useful combination is based on Alq as the host and [10- (2-benzothiazolyl) -2, 3,6, 7-tetrahydro-1, 1, 7, 7-tetramethyl-1H, 5H, 11H- [1] benzopyrano [6, 7, 8-ij ] quinolizin-11-one ] (C545T) as the dopant (0.5% by volume). Other organic gain region materials may be polymers such as polyphenylene vinylene derivatives, dialkoxyphenylene vinylenes, poly-p-phenylene derivatives, and polyfluorene derivatives, see commonly assigned U.S. Pat. No. 6,194,119 to Wolk et al, entitled "methods of Forming Heat transfer elements and organic electroluminescent devices", and references therein, issued 2.27.2001. The organic active region 40 functions to receive the transmitted pump beam 60 and emit laser light. The organic active region may generate spontaneous emission if the bottom dielectric stack 30 or the top dielectric stack 50 is not present.

The bottom and top dielectric laminates 30 and 50 are each preferably deposited by conventional electron beam deposition and each comprise alternating high index and low index dielectric materials, such as TiO₂And SiO₂. Other materials may also be used, such as Ta₂O₅As a high index layer. The bottom dielectric stack 30 is deposited at a temperature of about 240 c. During deposition of the top dielectric stack 50, the temperature is maintained at about 70 ℃ to avoid melting of the organic active material. In an alternative embodiment of the invention, the top dielectric stack is replaced by depositing a reflective metal mirror layer. Typical metals are silver or aluminum, which have a reflectivity above 90%. In this alternative embodiment, both pump beam 60 and laser emission 70 may be performed through substrate 20. Both the bottom dielectric stack 30 and the top dielectric stack 50 may reflect laser light within a specified wavelength range depending on the desired emission wavelength of the vertical cavity organic laser device 10.

Using very precise vertical microresonator, very low threshold (less than 0.1W/cm) can be achieved²Power density) to achieve laser emission conversion. This low threshold enables the incoherent light source to be used for pumping instead of a focused laser diode output, which is common in other laser systems. Examples of pumping sources are UV LEDs, or arrays of UV LEDs, such as from Cree (in particular XBRIGHT)^900 UltraViolet Power Chip^An LED). The light emitted by these sources is around 405nm in wavelength and is in the form of a chip, which is known to produce 20W/cm²Left and right power density. Thus, even taking into account the reduced utilization efficiency due to device packaging and the LED's broad angular emission profile, the brightness of the LED is sufficient to pump the laser cavity, which is on the order of the lasing thresholdSeveral times higher.

If the vertical cavity organic laser device 80 further employs the active region design shown in FIG. 2, the efficiency of the laser can be improved. The organic active region 40 includes one or more periodic gain regions 100 and organic spacer layers 110 disposed on either side of the periodic gain regions 100, the spacer layers 110 being arranged such that the periodic gain regions 100 are aligned with antinodes 103 of the device standing wave electromagnetic field. As shown in fig. 2, a pattern 120 of the laser standing wave electromagnetic field in the organic active region 40 is schematically depicted therein. Since stimulated emission is strongest at antinode 103 of the electromagnetic field and negligible at node 105, it is naturally appropriate to form active region 40 as shown in FIG. 2. The organic spacer layer 110 does not undergo stimulated or spontaneous emission and does not substantially absorb the wavelength of the lasing emission 70 or the pump beam 60. An example of a spacer layer 110 is the organic material 1, 1-bis- (4-bis (4-methylphenyl) -amino-phenyl) -cyclohexane (TAPC). TAPC is effective when used as a spacer material because it absorbs little of the energy of the laser emission 70 or pump beam 60 and, in addition, has a refractive index that is slightly lower than that of most organic matrix materials. The presence of a refractive index difference is useful because it can help to maximize the overlap between the antinodes of the electromagnetic field and the periodic gain region 100. As described below in the present invention, the use of periodic gain regions 100, rather than bulk gain regions, results in higher power conversion efficiency and significantly reduced unwanted spontaneous emission phenomena. The position of the periodic gain region 100 is determined using standard optical matrix methods (Corzine et al, IEEE Journal of Quantum Electronics, Vol.25, No. 6, 6. 1989). For good results, the thickness of the periodic gain region 100 should be no greater than 50nm to avoid deleterious spontaneous emission phenomena.

By employing a phase-locked organic laser array device 190, the laser area can be increased while maintaining its spatial coherence, as shown in fig. 3. In order to form the two-dimensional phase-locked organic laser array device 190, organic laser resonator devices 200 separated by inter-pixel regions 210 must be defined on the surface of the VCSEL. In order to obtain the phase locking effect, it is preferable to exchange luminance and phase information among the organic laser resonator devices 200. This is preferably achieved by a small amount of built-in index or gain steering, for example by modulating the reflectivity of one of the mirrors, so that the laser emission is slightly confined to the device area. In one embodiment, the reflectivity modulation effect is achieved by patterning and patterning the regions 220 in the bottom dielectric stack 30 using standard photolithography and etching techniques, thereby forming a two-dimensional array of cylinders 211 on the surface of the bottom dielectric stack 30. The remainder of the organic laser microresonator device structure is deposited on the previously patterned bottom dielectric stack 30. In one embodiment, the laser pixels are circular in shape; however, other shapes are possible, such as rectangular. The interval between the pixels is 0.25 to 4 μm. For larger pixel spacing, the lock-in array operation can also be performed; however, this reduces the efficiency of the use of the optical pumping energy. The etching depth is preferably 200-1000 nm deep to form the etching region 220. If etching through just an odd number of layers to the bottom dielectric stack 30, it is possible to significantly shift the longitudinal mode wavelength in the etched region from the peak of the gain medium. This prevents the generation of laser emission in the inter-pixel region 210 and significantly reduces the spontaneous emission phenomenon therein. The ultimate purpose of forming etched regions 220 is to confine the lasing slightly to organic laser cavity device 200, to leave the inter-pixel regions 220 free from lasing phenomena, and to emit phase-locked coherent laser light using phase-locked organic laser array device 190.

Figure 4a is a cross-sectional side view of an optically pumped tunable organic VCSEL system 230 that contains MEM devices for varying the optical path length of the laser cavity. It is readily understood that the system 230 is envisioned as two separate subsystems: a multi-layer film structure 300 and a microelectromechanical mirror assembly 310. The multilayer film structure 300 is comprised of a substrate 20, a bottom dielectric stack 30, an organic active region 40, and one or more index matching layers 240 and 250. At this point, the substrate 20 is transparent to the light of the pump beam 60. The light of pump beam 60 is received by multilayer film structure 300 and then spontaneous emission occurs. The top dielectric stack 290 and the bottom dielectric stack 30 form an end mirror for the organic laser resonator. The microelectromechanical mirror assembly 310 is comprised of a bottom electrode 260, a support structure 270, a top electrode 275, a support arm 272, an air gap 280, a mirror mount (teter) 285, and a top dielectric stack 290. The laser firing 70 is through the top dielectric stack 290. A voltage source (not shown) applied between the bottom electrode 260 and the top electrode 275 varies the thickness t of the air gap 280 through electrostatic interaction, thereby changing the cavity length of the organic laser resonator device. The result of the change in the length of the organic laser cavity is a change in the wavelength of the optically pumped tunable organic VCSEL system 230. Although top dielectric stack 290 is depicted with a certain curvature, one skilled in the art will appreciate that a substantially planar top dielectric stack 290 may also be employed, which may be considered as another embodiment of the present invention. Without modulating the reflectivity of a mirror, as shown in figure 3, so that the lasing emission is slightly confined to the device region, it is difficult to achieve basic single mode operation in a VCSEL. Thus, curved top dielectric stack 290 is well suited for applications that focus on lateral mode control or do not employ the previously described lateral confinement structure. The resonant cavity shown in figure 4a is illustrated as a semi-symmetrical structure and is also one of a class of Fabry-Perot resonant cavity structures. The output wavelength of the resonant cavity is determined by the following mathematical relation

nλ/2＝L_opt

Where n is an integer, λ is the wavelength, L_optIs the one-way optical path length in the resonant cavity. Varying the thickness t of the air gap 280 changes the optical path length. The top dielectric stack 290 may include one or more index matching layers; not shown in fig. 4 a. These index matching layers (including index matching layers 240 and 250) minimize optical reflection at the interface of air gap 280 and adjacent layers, and also improve device efficiency. The bottom electrode 260 and the top electrode 275 are made of a conductive material, typically a metal, and the electrodes are ring-shaped. Transparent conductive electrodes such as indium-tin-oxide (ITO) or polymeric materials may also be employed. If the optics of the latter class of materialsThe losses are low and a ring configuration is not necessarily required. The support structure 270 is typically aluminum, titanium-tungsten (Ti-W), or silicon nitride (SiN)_x) The thickness of the support structure is sufficient to provide mechanical support. The thickness of the support structure 270 is typically 2000nm, while the thickness of the mirror mount 285 is typically 100 nm and 200 nm. The mirror mount 285 is made of a similar material, but is thinner in order to allow some flexibility under the influence of the electrostatic field provided by the tuning voltage source. It is necessary to provide an additional electrically insulating layer (not shown) between the bottom electrode 260 and the mirror mount 285. The layer is made of an insulating material. The support structure 270 exhibits at least one support arm 272 that mechanically stabilizes the top dielectric stack 290 at the desired distance t. To achieve this, the support structure 270 preferably has a suitably large inherent tensile stress.

The geometry of the support structure is shown in fig. 4 b-4 e. Fig. 4b is a top view of an optically pumped tunable organic VCSEL system 230 using a dual support beam structure. The top dielectric stack 290 is seen through the center of the structure and is mechanically supported by two support arms 272 disposed on opposite sides of the top mirror stack 290. The two support arms 272 are formed by etching through the support structure 270 along the illustrated regions and then removing the sacrificial material to form the air gaps 280 shown in fig. 4 a. The bottom electrode 260 can be seen in the area where the support structure 270 is etched.

Figure 4c is a top view of an alternative embodiment of an optically pumped tunable organic VCSEL system 232 using a cantilever beam structure. The cross-section of the optically pumped tunable organic VCSEL system 232 is the same as in fig. 4 a. The top dielectric stack 290 is visible through the center of the structure and is mechanically supported by a single support arm 272 disposed on one side of the top dielectric stack 290. The support arms 272 are formed by etching through the support structure 270 along the regions shown and then removing the sacrificial material to form the air gaps 280 shown in figure 4 a. The bottom electrode 260 can be seen in the area where the support structure 270 is etched.

Figure 4d is a top view of another embodiment of an optically pumped tunable organic VCSEL system 234 utilizing a multi-arm beam (two or more) structure. The cross-section of the optically pumped tunable organic VCSEL system 234 is the same as in fig. 4 a. The top dielectric stack 290 is seen through the center of the structure and is mechanically supported by a plurality of support arms 272 that are approximately symmetrically positioned on several sides of the top dielectric stack 290. The support arms 272 are formed by etching through the support structure 270 along the regions shown and then removing the sacrificial material to form the air gaps 280 shown in figure 4 a. The bottom electrode 260 can be seen in the area where the support structure 270 is etched. It should be noted that while the embodiment of fig. 4d shows 4 support arms 272, it is contemplated that more than 3 or 4 support arms 272 may be used and are considered within the scope of the present invention.

Figure 4e is a top view of another embodiment of an optically pumped tunable organic VCSEL system 236, which employs a film structure. The cross-section of the optically pumped tunable organic VCSEL system 236 is the same as in fig. 4 a. The top dielectric stack 290 is seen through the center of the structure and is mechanically supported by a continuous support arm 272 in the form of a film. The continuous support arm 272 may be formed by etching a plurality of release holes 273 through the support structure 270. To form the air gaps 280 shown in FIG. 4a, an etchant may be passed deep into and through the release holes 273 and then the sacrificial material removed.

Figure 5 is a cross-sectional side view of another embodiment of an optically pumped tunable organic VCSEL system 320 that employs a multilayer film structure 330 having periodically structured organic gain regions and also includes a MEM device that functions to vary the optical path length of the laser cavity. In this embodiment, the microelectromechanical mirror assembly 310 is the same as that of FIG. 4a, except that the multilayer film structure 330 has been modified. The multilayer film structure 330 is based on the vertical cavity organic laser device 80 shown in fig. 2. The multilayer film structure 330 is comprised of a substrate 20, a bottom dielectric stack 30, an organic active region 40, and one or more index matching layers 240 and 250. At this point, the substrate 20 is transparent to the light of the pump beam 60. The light of pump beam 60 is received by multilayer film structure 330 and then spontaneous emission occurs. The top dielectric stack 290 and the bottom dielectric stack 30 form an end mirror for the organic laser resonator. The microelectromechanical mirror assembly 310 is comprised of a bottom electrode 260, a support structure 270, a support arm 272, a top electrode 275, an air gap 280, a mirror mount 285, and a top dielectric stack 290. The laser firing 70 is through the top dielectric stack 290. A voltage source (not shown) applied between the bottom electrode 260 and the top electrode 275 varies the thickness t of the air gap 280 through electrostatic interaction, thereby changing the cavity length of the organic laser resonator device. The result of the change in the length of the organic laser cavity is a change in the wavelength of the optically pumped tunable organic VCSEL system 230. Although top dielectric stack 290 is depicted with a certain curvature, one skilled in the art will appreciate that a substantially planar top dielectric stack 290 may also be employed, which may be considered as another embodiment of the present invention. The organic active region 40 includes one or more periodic gain regions 100 and organic spacer layers 110 disposed on either side of the periodic gain regions 100, the spacer layers 110 being arranged such that the periodic gain regions 100 are aligned with antinodes 103 of the device standing wave electromagnetic field (see fig. 2). As shown in fig. 2, a pattern 120 of the laser standing wave electromagnetic field in the organic active region 40 is schematically depicted therein. Since stimulated emission is strongest at antinode 103 of the electromagnetic field and negligible at node 105, it is naturally appropriate to form active region 40 as shown in FIG. 2. The organic spacer layer 110 does not undergo stimulated or spontaneous emission and does not substantially absorb the wavelength of the lasing emission 70 or the pump beam 60. In applications where single mode characteristics are desired but the tuning range is limited, it may be desirable to use the structure of fig. 2 with periodic gain regions 100. Without modulating the reflectivity of a mirror, as shown in figure 3, to confine the lasing emission slightly to the device region, it is difficult to achieve basic lateral single mode operation in a VCSEL. Thus, curved top dielectric stack 290 is well suited for applications that focus on lateral mode control or do not employ the previously described lateral confinement structure. The resonant cavity shown in figure 5 is illustrated as a semi-symmetrical structure and is one of a class of Fabry-Perot resonant cavity structures. The output wavelength of the resonant cavity is determined by the following mathematical relation

nλ/2＝L_opt

Where n is an integer, λ is the wavelength, L_optIs the one-way optical path length in the resonant cavity. Varying the thickness t of the air gap 280 changes the optical path length. The top dielectric stack 290 may include one or more index matching layers; not shown in fig. 5. These index matching layers (including index matching layers 240 and 250) minimize optical reflection at the interface of air gap 280 and adjacent layers, and also improve device efficiency. The bottom electrode 260 and the top electrode 275 are made of a conductive material, typically a metal, and the electrodes are ring-shaped. Transparent conductive electrodes such as indium-tin-oxide (ITO) or polymeric materials may also be employed. If the optical losses of the latter type of material are low, a ring-shaped configuration is not necessarily required. The support structure 270 is typically aluminum, titanium-tungsten (Ti-W), or silicon nitride (SiN)_x) The thickness of the support structure is sufficient to provide mechanical support. The thickness of the support structure 270 is typically 2000nm, while the thickness of the mirror mount 285 is typically 100 nm and 200 nm. The mirror mount 285 is made of a similar material, but is thinner in order to allow some flexibility under the influence of the electrostatic field provided by the tuning voltage source. It is necessary to provide an additional electrically insulating layer (not shown) between the bottom electrode 260 and the mirror mount 285. The layer is made of an insulating material. The support structure 270 exhibits at least one support arm 272 that mechanically stabilizes the top dielectric stack 290 at the desired distance t. To achieve this, the support structure 270 preferably has a suitably large inherent tensile stress. As described with respect to the optically pumped tunable organic VCSEL systems 230, 232, 234, 236, the optically pumped tunable organic VCSEL system 320 may employ a dual support beam structure, a cantilever beam structure, a multi-arm beam structure, or a film structure to mechanically stabilize the top dielectric stack at a desired position.

Figure 6 is a cross-sectional side view of a prior art tapered microresonator device that incorporates a tapered organic active region 350. The thickness t of the wedge-shaped organic active region 350 is from the leftEdge 360 varies continuously from edge 370 to edge. Since the gain bandwidth of the emissive material in the tapered organic active region 350 is wide, the tapered microresonator device 340 can be tuned over a wide spectral region by varying the thickness of the laser cavity. The tapered microresonator 340 is excited by the pump beam 60 and produces a laser emission 70. The pump beam 60 is at X a distance d from the right edge 370₀The point excites a tapered microresonator device 340. The bottom mirror 380 and the top mirror 390 together with the wedge-shaped organic active region 350 constitute a laser cavity. The mirrors 380 and 390 may be in the form of metal films or dielectric laminates. The wavelength of the laser emission 70 is related to the thickness t and the refractive index of the material in the wedge-shaped organic active region 350. By varying X₀The location of the spots, such that different sections of the tapered microresonator device 340 are excited by the pump beam 60, results in different lasing 70 wavelengths. By moving the tapered microresonator device 340 relative to the pump beam 60, X can be varied by varying d₀The purpose of the location.

Fig. 7 is a cross-sectional side view of a prior art electrically pumped organic vertical cavity laser 400. A bottom mirror 380, a top mirror 390, and an organic active area 410 are deposited on the transparent substrate 20. In this embodiment, the organic active region 410 is composed of a lower layer and is capable of electroluminescence, and when a current flows through the organic active region 410, laser light is generated. As is known in the art, the bottom layer of the organic active region 410 is composed of a hole transport layer 420, an emission layer 430, and an electron transport layer 440. If both the bottom and top mirrors 380 and 390 are made of non-electronically conductive materials, it may be necessary to include electrodes 450 and 460 in the electrically pumped organic vertical cavity laser 400. At this time, the electrodes 450 and 460 are substantially transparent to emit light emitted from 430 and preferably comprise indium-tin-oxide (ITO) or other electronically conductive material. If the top mirror 390 and the bottom mirror 380 are electronically conductive layers, a current source 470 may be applied to these layers, or to the electrodes 450 and 460. It should be appreciated that any combination of mirror types and electrode arrangements are contemplated as embodiments of the present invention. By proper design of the top mirror 390, the laser emission 70 can exit the electrically pumped organic vertical cavity laser 400 via the top mirror 390. This is achieved by making the top mirror 390 slightly less reflective than the bottom mirror 380.

Fig. 8 is a cross-sectional side view of another embodiment of a prior art electrically pumped organic vertical resonant cavity laser 480. A bottom mirror 380, a top mirror 390, and an organic active area 410 are deposited on the transparent substrate 20. In this embodiment, the organic active region 410 includes a bottom layer and is capable of electroluminescence, and when a current flows through the organic active region 410, laser light is generated. This mechanism of electrical excitation of the device is known as electrical injection. As is known in the art, the bottom layer of the organic active region 410 is composed of a hole transport layer 420, an emission layer 430, and an electron transport layer 440. If both the bottom and top mirrors 380 and 390 are made of non-electronically conductive materials, it may be necessary to include electrodes 450 and 460 in the electrically pumped organic vertical cavity laser 400. At this time, the electrodes 450 and 460 are substantially transparent to emit light emitted from 430 and preferably comprise indium-tin-oxide (ITO) or other electronically conductive material. If the top mirror 390 and the bottom mirror 380 are electronically conductive layers, a current source 470 may be applied to these layers, or to the electrodes 450 and 460. It should be appreciated that any combination of mirror types and electrode arrangements are contemplated as embodiments of the present invention. By proper design of the top mirror 390, the laser emission 70 can exit the electrically pumped organic vertical cavity laser 400 via the bottom mirror 380. This is achieved by making the top mirror 390 slightly more reflective than the bottom mirror 380.

Figure 9 is a block diagram 500 illustrating the operation of another embodiment of a tunable organic VCSEL system. The figure shows another system for mechanically tuning the optical wavelength emitted by an organic laser resonator device. The pumping source shown in block 510 excites a plurality of organic vertical cavity laser devices shown in block 520. Block 520 represents various types of organic resonant cavity laser devices, the details of which are shown in FIGS. 1-8 and FIGS. 12-18 (as a single device or group of devices, referenced herein as 10, 80, 190, 230, 320, 340, 400, 480, 702, 1000 and 1050). The organic vertical cavity laser device structure is designed such that each organic vertical cavity laser device generates laser light of substantially different optical wavelengths. The pump source in block 510 may be a source of photons for excitation or a power source. Block 530 depicts a beam directing optic for directing the optical laser output of the organic vertical cavity laser device structure to a microelectromechanical mirror assembly, which is depicted in block 540. The optical lens comprises conventional lenses or mirrors, as known to the person skilled in the art. The optical laser is directed to the other beam directing optics shown in block 550 by adjusting the micro-electromechanical mirror assembly in block 540. The optical lens comprises a conventional lens or mirror known to the person skilled in the art. Block 560 describes the selection of laser output. In this block, one optical wavelength from one of the multiple organic vertical cavity lasers is selected and then exits the device at the system output.

Fig. 10 is a schematic diagram of a tunable organic VCSEL system 565 incorporating a MEM device whose function is to select the output wavelength of an organic laser cavity device using an electrically pumped organic vertical cavity laser. Current source 570 provides the excitation means for organic vertical cavity laser structure 580 and produces multiple optical wavelengths. The organic vertical cavity laser device structure 580 is a fixed wavelength organic laser cavity device array. In this embodiment, the organic vertical cavity laser device structure 580 is comprised of electrically pumped organic vertical cavity lasers 480, wherein each electrically pumped organic vertical cavity laser 480 is fabricated to produce laser light of a substantially different wavelength. Selecting the laser light emitted by each device provides a way to tune the output of tunable organic VCSEL system 565 in a step-wise fashion. The step size (or wavelength interval) depends on the wavelength difference between any two electrically pumped organic vertical cavity lasers 480. The light emitted by a particular electrically pumped organic vertical cavity laser 480 is selected by operating the mirror assembly 620. In one embodiment, mirror assembly 620 uses a micro-electromechanical mirror. In the embodiment shown in fig. 10, the laser light emitted by a particular electrically pumped organic vertical cavity laser 480 is selected by varying the tilt angle of the mirror assembly 620. The selected beam 590 is passed through the system to the output selection fiber 640. The unselected optical beams 600 pass through a tunable organic VCSEL system 565 to unselected outputs 650. Shutters 670 or other beam blocking devices may prevent unselected beams 600 from exiting tunable organic VCSEL system 565. The beam directing optics 610 direct the emitted laser light to a mirror assembly 620. The other beam directing optic 630 directs light from the reflective mirror assembly 620 to an output selection fiber 640. The beam directing optics 610 and 630 use common optical elements such as mirrors and lenses. In some cases, it is desirable to make small and lightweight systems with micro-optical lenses. Output selection fiber 640 transmits the laser light to system output 660. Although optical fibers are used as output selection devices in this embodiment, it is to be understood that other conventional means of selecting or filtering optical wavelengths, such as mirrors, shutters, filters, and the like, may be used in this manner.

Fig. 11 is a schematic diagram of an alternative embodiment of a tunable organic VCSEL system 565 that contains a MEM device whose function is to select the output wavelength of an organic laser cavity device using an optically pumped organic vertical cavity laser. The photon source 680 generates a pump laser beam 690 and provides the excitation means for the organic vertical cavity laser device structure 700 and generates a plurality of optical wavelengths. The photon source 680 may be a Light Emitting Diode (LED), a laser, or any other incoherent light source. The organic vertical cavity laser device structure 700 is a fixed wavelength organic laser cavity device array. In this embodiment, the organic vertical cavity laser device structure 700 is comprised of optically pumped organic vertical cavity laser devices 10, wherein each of the optically pumped organic vertical cavity laser devices 10 is fabricated to produce laser light of a substantially different wavelength. Alternatively, other optically pumped laser devices may be used in this embodiment, such as a tapered microresonator device 340 (see FIG. 6) may be used to generate the multiple optical wavelengths. At this time, excitation is suitably performed using a laser as the photon source 680. By varying the position and angle of the pumping beam 690, substantially identical tapered microresonator devices 340 can be made to produce laser light of substantially different wavelengths. Selecting the laser light emitted by each device provides a way to tune the output of tunable organic VCSEL system 565 in a step-wise fashion. The step size (or wavelength interval) depends on the wavelength difference between any two vertical cavity organic laser devices 10. The light emitted by a particular vertical cavity organic laser device 10 is selected by operating the mirror assembly 620. In one embodiment, mirror assembly 620 uses a micro-electromechanical mirror. In the embodiment shown in fig. 11, the laser light emitted by a particular vertical cavity organic laser device 10 is selected by varying the tilt angle of the mirror assembly 620. The selected optical beam 590 is passed through a tunable organic VCSEL system 565 to an output selection fiber 640. The unselected optical beams 600 pass through a tunable organic VCSEL system 565 to unselected outputs 650. Shutters 670 or other beam blocking devices may prevent unselected beams 600 from exiting tunable organic VCSEL system 565. The beam directing optics 610 direct the emitted laser light to a mirror assembly 620. The other beam directing optic 630 directs light from the reflective mirror assembly 620 to an output selection fiber 640. The beam directing optics 610 and 630 use common optical elements such as mirrors and lenses. In some cases, it is desirable to make small and lightweight systems with micro-optical lenses. Output selection fiber 640 transmits the laser light to system output 660. Although optical fibers are used as output selection devices in this embodiment, it is to be understood that other conventional means of selecting or filtering optical wavelengths, such as mirrors, shutters, filters, and the like, may be used in this manner.

Figure 12 is a cross-sectional side view of another embodiment of an optically pumped tunable organic VCSEL system 702 that employs an optically pumped multilayer film structure having a periodically structured organic gain region and two-dimensional phase locking in conjunction with a grating assembly. In one embodiment, to change the angle of the mirror, a MEM device used in conjunction with a grating for laser cavity tuning is used in grating assembly 704. In this embodiment, the grating assembly is made up of elements 730, 740, 750, 760, 770, 780, and 790. In fig. 12, a pump beam 60 excites a light-pumped multilayer film structure 705. The optically pumped multilayer film structure 705 is similar to multilayer film structure 45 (see fig. 1) and comprises a support 20, a bottom dielectric stack 30, an organic active region 40, and one or more index matching layers 710. In the embodiment shown in fig. 12, the organic active region is of the type that contains etched regions 220 and inter-pixel regions 210 and forms a phase-locked organic laser array 190 (see fig. 3), although it will be appreciated that other arrangements of organic active regions 40 similar to those previously described may be used. The deposited index matching layer 710 forms part of the optically pumped multilayer film structure 705. The role of the index matching layer 710 is to encapsulate the organic active region and protect it from air and moisture exposure, while improving the optical efficiency of the device by reducing reflections at the air interface. Light output 715 from the optically pumped multilayer thin film structure 705 is directed to the surface of the diffraction grating 790 by an optical lens 720. In one embodiment, the optical lens 720 is composed of micro lenses. The diffraction grating 790 is a reflective grating. This structure, consisting of cantilever beam 750, rotary comb drive motor 760, rotary motor mount 770 and movable mirror 780, can provide a tuning mechanism for the tunable organic VCSEL system of this embodiment. Elements 750, 760 and 770 constitute MEM electrostatic rotary actuators and can change the angle of the movable mirror 780. The cantilever beam 750 is connected to a support (not shown) at a base connection point 740. The movable mirror 780 is caused to rotate about the pivot 730 by the movement of the entire MEM electrostatic rotary actuator. When an electrical potential is applied to the rotating comb drive motor 760 element, a voltage source (not shown) causes it to produce a rotational motion. This embodiment shows an arrangement of optical components called Littman-Metcalf laser resonator. The MEM rotation actuator is designed to enable the movable mirror 780 to rotate about a pivot point 730 that is located in the resonant cavity at a position that keeps the optical half-wavelengths of all wavelengths equal in number. The diffracted beam 810 is reflected by the movable mirror 780 and provides optical feedback for the laser cavity. This design is desirable because laser output beam 800 is output at a fixed angle, regardless of the selected wavelength. The design also provides a mode hop free (smooth) wavelength tuning effect for tunable organic VCSEL systems.

Figure 13 is a cross-sectional side view of another embodiment of a tunable organic VCSEL system 702 employing an electrically pumped multilayer film structure with a periodic structured organic gain region and two-dimensional phase locking in conjunction with a grating assembly 704. In a preferred embodiment, to change the angle of the mirrors, a MEM device used in conjunction with a grating for laser cavity tuning is used in grating assembly 704. In this embodiment, the grating assembly is made up of elements 730, 740, 750, 760, 770, 780, and 790. In fig. 13, a current source 570 energizes an electrically pumped multilayer film structure 820. The electrically pumped multilayer film structure 820 comprises a support 20, a bottom dielectric stack 380, an organic active region 410, electrodes 450 and 460, and one or more index matching layers 710. The electrically pumped multilayer film structure 820 is similar to the electrically pumped organic vertical cavity laser 400 (see fig. 7) except that the top mirror 390 is not included as part of the structure. The deposited index-matching layer 710 forms a portion of an electrically pumped multilayer film structure 820. The role of the index matching layer 710 is to encapsulate the organic active region and protect it from air and moisture exposure, while improving the optical efficiency of the device by reducing reflections at the air interface. Light output 715 from electrically pumped multilayer thin film structure 820 is directed to the surface of diffraction grating 790 by optical lens 720. In a preferred embodiment, the optical lens 720 is composed of micro-lenses. The diffraction grating 790 is a reflective grating. This structure, consisting of cantilever beam 750, rotary comb drive motor 760, rotary motor mount 770 and movable mirror 780, can provide a tuning mechanism for the tunable organic VCSEL system of this embodiment. The cantilever 750, rotary comb drive motor 760 and rotary motor mount 770 constitute a MEM electrostatic rotary actuator and can change the angle of the movable mirror 780. The cantilever beam 750 is connected to a support (not shown) at a base connection point 740. The movable mirror 780 is caused to rotate about the pivot 730 by the movement of the entire MEM electrostatic rotary actuator. When an electrical potential is applied to the rotating comb drive motor 760 element, a voltage source (not shown) causes it to produce a rotational motion. This embodiment shows an arrangement of optical components called Littman-Metcalf laser resonator. The MEM rotation actuator is designed to enable the movable mirror 780 to rotate about a pivot point 730 that is located in the resonant cavity at a position that keeps the optical half-wavelengths of all wavelengths equal in number. The diffracted beam 810 is reflected by the movable mirror 780 and provides optical feedback for the laser cavity. This design is desirable because laser output beam 800 is output at a fixed angle, regardless of the selected wavelength. The design also provides a mode hop free (smooth) wavelength tuning effect for tunable organic VCSEL systems.

Figure 14 is a cross-sectional side view of another embodiment of a tunable organic VCSEL system 1000 that employs a refractive index controllable material to tune the laser wavelength. The tunable organic VCSEL system 1000 includes a substrate 20. The pump beam 60 is below the substrate 20 and passes through the substrate 20. The bottom electrode 1010 is above the substrate 20 and is preferably transparent to the pump laser beam 60. The bottom electrode 1010 may be, for example, ITO. Alternatively, in a configuration where the pump beam 60 is above, an opaque bottom electrode may be used.

The bottom dielectric stack 30 and the organic active region 40 are both on top of the bottom electrode 1010. The top dielectric stack 50 is located over the organic active region 40, thereby forming a laser resonant cavity. A dielectric control layer 1020 is provided between the bottom dielectric laminate 30 and the top dielectric laminate 50, which functions to control the optical cavity length of the laser resonant cavity. Since the laser wavelength is proportional to the optical cavity length, the laser wavelength can be tuned accordingly. Top electrode 1030 is positioned above top electrode stack 50. The controller 1040 functions to control the refractive index of the dielectric control layer 1020.

In one embodiment, the dielectric control layer 1020 comprises a variable refractive index material whose refractive index is controlled by an applied electric field. Candidate materials are electro-optic materials such as lithium niobate, or liquid crystal layers. The refractive index of the dielectric control layer 1020 as a function of the applied electric field is as follows

Where E is the applied electric field and n₀Is the refractive index in the absence of an electric field and r is the electro-optic coefficient. The controller 1040 of this embodiment is a voltage source applied between the top electrode 1030 and the bottom electrode 1010.

In a second embodiment, the dielectric control layer 1020 comprises a photorefractive material. The candidate material is Fe⁺³Doped lithium niobate. In this case, the controller 1040 is a light source, such as a UV lamp, and the refractive index varies with the brightness. In a third embodiment, the dielectric control layer 1020 comprises a thermally sensitive material and the controller 1040 is a heat source, such as a resistive heating element. The dielectric control layer may change the wavelength of the laser light by thermal expansion and/or by thermally induced refractive index changes, i.e.

Where Δ T is the temperature change based on the steady state temperature, L_opt，oIs the optical resonance cavity length at steady state temperature, n_dcIs the refractive index of the dielectric control layer, and L_dcIt is the actual thickness of the dielectric control layer.

Figure 15 is a cross-sectional side view of another embodiment of a tunable organic VCSEL system using another grating assembly 704, namely an electrically tunable grating 792 of the Littrow structure. Littrow structures are known in the art and feature a grating that returns light by diffraction to the direction it came from. Thus, a portion of the light output 715 from the electrically pumped multilayer film structure 820 is returned to its original location in the form of the diffracted beam 810. By varying the period of the electrical pumping grating 792, the Littrow wavelength can be varied, thereby tuning the lasing wavelength. A voltage source (not shown) may vary the period of the electrically tunable grating 792. Output coupling can again be achieved with a zeroth order (zeroethorder) beam from the electrically tunable grating 792. In fig. 15, a current source 570 energizes an electrically pumped multilayer film structure 820. The electrically pumped multilayer film structure 820 comprises a support 20, a bottom mirror 380, an organic active region 410, electrodes 450 and 460, and one or more index matching layers 710. The electrically pumped multilayer film structure 820 is similar to the electrically pumped organic vertical cavity laser 400 (see fig. 7) except that the top mirror 390 is not included as part of the structure. The deposited index-matching layer 710 forms a portion of an electrically pumped multilayer film structure 820. The role of the index matching layer 710 is to encapsulate the organic active region and protect it from air and moisture exposure, while improving the optical efficiency of the device by reducing reflections at the air interface. Light output 715 from electrically pumped multilayer thin film structure 820 is directed to the surface of diffraction grating 792 by optical lens 720. In one embodiment, the optical lens 720 is composed of micro lenses. The diffraction grating 792 is a reflective grating having a tunable grating period. Such structures are known in the art, such as electrostatically tunable MEM gratings or analog tunable gratings comprising piezoelectric actuators (see, for example, DARPA Quartely report F30602-97-2-0106).

Figures 16a and 16b show prior art electrostatically tunable MEM gratings or analog tunable gratings, respectively, incorporating piezoelectric actuators. In fig. 16a, the flexible grating structure 791 is constituted by a cantilever beam supported on a reed (flexure) and driven by electrostatic comb drive linear motors 797 on opposite sides. The period of the electric pump laser grid 792 can be easily changed by driving the comb drive motor 797. In FIG. 16b, the membrane grating 793 comprises periodic structures forming a grating, which structures are on the deformable membrane 794. The piezoelectric actuator 799 deforms the membrane, thereby changing the period of the grating.

Referring back to FIG. 15, diffracted beam 810 is diffracted by electrically tunable grating 792 to provide optical feedback to the laser cavity. This design is desirable because the laser output beam 800 is output at a fixed angle, independent of the selected wavelength. The design also provides a mode hop free (smooth) wavelength tuning effect for tunable organic VCSEL systems. By properly selecting the input angle of the electrically tunable grating 792 and using blazed facets (blazedfacest), the grating 792 is designed to have a desired output coupling efficiency. Tunable organic VCSELs can also be obtained using electrically tunable gratings in Littrow structures and optically pumped multilayer film structures.

In fig. 17, an alternative embodiment of an electrically tunable grating 792 is shown. The electro-optic grating 900 is comprised of a fixed grating 910 having a periodic surface structure. An electro-optic layer 920, preferably a liquid crystal layer, is in contact with the fixed grating 910. The electro-optic layer 920 is encapsulated on both its upper and lower sides by conductive layers 930 and 932, respectively, which are also supported on substrates 934 and 936, respectively. When the electro-optic layer 920 is a liquid crystal layer, suitable means are employed to maintain the distance between the conductive layers 930 and 932, as is known. The conductor 932 is a transparent conductor such as indium-tin-oxide (ITO). Conductive body 930 may be a reflective metal or a transparent conductive body. Preferred reflective metals include aluminum, silver and gold. Application of a voltage across the electro-optical layer changes the refractive index of the electro-optical layer 920, thereby changing the diffraction characteristics of the electro-optical grating 900. If the conductive layer 932 is a transparent electrical conductor, light from the electrically pumped multilayer film structure 820 of FIG. 15 is incident on the fixed grating 910 through the substrate 934. The electrically tunable grating embodiments can be applied in Littrow structures to form tunable organic VCSELs.

Figure 18 is a cross-sectional side view of another embodiment of a tunable organic VCSEL system 1050 that employs a material with a controllable refractive index to tune the laser wavelength. Those skilled in the art will appreciate that this embodiment is a combination of two tuning mechanisms; one mechanism involves tuning the laser wavelength using a material with a controlled refractive index; while the second mechanism involves using MEM devices to change the optical path length of the laser cavity. In addition, one skilled in the art will recognize that other combinations of tuning mechanisms are possible and are contemplated as within the scope of the present invention. Tunable organic VCSEL system 1050 includes a substrate 20. The pump beam 60 is below the substrate 20 and passes through the substrate 20. The bottom electrode 1010 is above the substrate 20 and is preferably transparent to the pump laser beam 60. The bottom electrode 1010 may be, for example, ITO. Alternatively, in a configuration where the pump beam 60 is above, an opaque bottom electrode may be used.

In a second embodiment, the dielectric control layer 1020 comprises a photorefractive material. The candidate material is Fe⁺³Doped lithium niobate. In this case, the controller 1040 is a light source, such as a UV lamp, and the refractive index varies with the brightness.

In a third embodiment, the dielectric control layer 1020 comprises a thermally sensitive material and the controller 1040 is a heat source, such as a resistive heating element. The dielectric control layer may change the wavelength of the laser light by thermal expansion and/or by thermally induced refractive index changes, i.e.

In fig. 18, a MEM device is included to vary the optical path length of the laser cavity. The MEM device is on top of index matching layers 240 and 250. The microelectromechanical mirror assembly 310 is comprised of a bottom electrode 260, a support structure 270, a top electrode 275, a support arm 272, an air gap 280, a mirror mount 285, and a top dielectric stack 290. The laser firing 70 is through the top dielectric stack 290. A voltage source (not shown) applied between the bottom electrode 260 and the top electrode 275 varies the thickness t of the air gap 280 through electrostatic interaction, thereby changing the cavity length of the organic laser resonator device. Although top dielectric stack 290 is depicted with a certain curvature, one skilled in the art will appreciate that a substantially planar top dielectric stack 290 may also be employed, which may be considered as another embodiment of the present invention. Varying the thickness t of the air gap 280 changes the optical path length. The top dielectric stack 290 may include one or more index matching layers; not shown in fig. 18. These index matching layers (including index matching layers 240 and 250) minimize optical reflection at the interface of air gap 280 and adjacent layers, and also improve device efficiency. The bottom electrode 260 and the top electrode 275 are made of a conductive material, typically a metal, and the electrodes are ring-shaped. Transparent conductive electrodes such as indium-tin-oxide (ITO) or polymeric materials may also be employed. If the optical losses of the latter type of material are low, a ring-shaped configuration is not necessarily required. The support structure 270 is typically aluminum, titanium-tungsten (Ti-W), or silicon nitride (SiNx), and is thick enough to provide mechanical support. The thickness of the support structure 270 is typically 2000nm, while the thickness of the mirror mount 285 is typically 100 nm and 200 nm. The mirror mount 285 is made of a similar material, but is thinner in order to allow some flexibility under the influence of the electrostatic field provided by the tuning voltage source. It is necessary to provide an additional electrically insulating layer (not shown) between the bottom electrode 260 and the mirror mount 285. The layer is made of an insulating material. The support structure 270 exhibits at least one support arm 272 that mechanically stabilizes the top dielectric stack 290 at the desired distance t. To achieve this, the support structure 270 preferably has a suitably large inherent tensile stress.

A system wherein the incoherent photon source is a lamp.

A system wherein the incoherent photon source is a light source other than a light emitting diode.

A system for mechanically tuning the optical wavelength emitted from an organic laser resonator device, comprising: a) an organic vertical cavity laser device structure comprising a plurality of organic vertical cavity laser devices pumped via an excitation means such that the plurality of organic vertical cavity laser devices produce a plurality of optical wavelengths; and b) a mirror assembly that receives the plurality of optical wavelengths emitted from the organic vertical cavity laser device structure and directs a selected one of the optical wavelengths to the system output.

The system wherein the organic vertical cavity laser device structure is a fixed wavelength organic laser cavity device array.

The system, wherein the organic vertical resonant cavity laser device structure is a tunable wavelength organic laser resonant cavity device array.

The system wherein the excitation means comprises an optical pumping means.

The system wherein the excitation device comprises a laser source.

The system wherein the excitation device comprises a light emitting diode.

The system wherein the excitation means comprises an incoherent light source other than a light emitting diode.

The system wherein the excitation means comprises electron injection.

A system for tuning the optical wavelength emitted from an organic laser resonator device, comprising: a) an organic laser cavity structure pumped via an excitation device, wherein the organic laser cavity structure comprises: a1) a support body; a2) a first dielectric stack for receiving and transmitting a pump beam and reflecting laser light within a prescribed wavelength range; a3) one or more controllable refractive index dielectric control layers; a4) an organic active region for receiving the pump beam transmitted from the first dielectric stack and emitting laser light; and a5) a second dielectric stack operative to reflect the pump beam and laser light transmitted from the organic active region back into the organic active region, wherein the first and second dielectric stacks cooperate with the organic active region to generate laser light; and b) means for controlling the refractive index of the dielectric control layer.

The system wherein the dielectric control layer is an electro-optical layer and the refractive index control means is an applied electric field.

The system wherein the dielectric control layer is a photorefractive layer and the refractive index control means is a photon source.

A system wherein the dielectric control layer comprises a temperature dependent refractive index and the refractive index control means is a heat source.

A system for tuning the optical wavelength emitted from an organic laser resonator device, comprising: a) a multilayer film structure, wherein the multilayer film structure is pumped by a photon source and comprises: a1) a support body; a2) a first dielectric stack for receiving and transmitting a pump beam and reflecting laser light within a prescribed wavelength range; a3) one or more controllable refractive index dielectric control layers; a4) an organic active region for receiving the pump beam transmitted from the first dielectric stack and emitting laser light; and a5) a second dielectric stack operative to reflect the pump beam and laser light transmitted from the organic active region back into the organic active region, wherein the first and second dielectric stacks cooperate with the organic active region to generate laser light; b) a microelectromechanical mirror assembly proximate the multilayer film structure, wherein the microelectromechanical mirror assembly varies a resonant cavity length of the organic laser resonant cavity device; and c) means for controlling the refractive index of the dielectric control layer.

A system, further comprising: c) a plurality of microelectromechanical mirror assembly supports with air gaps therebetween; d) a top electrode layer in contact with the microelectromechanical mirror assembly; and e) a bottom electrode layer.

A system wherein the microelectromechanical mirror assembly is a cantilevered assembly.

A system wherein the microelectromechanical mirror assembly is a membrane assembly.

The system wherein the microelectromechanical mirror assembly includes at least one dual support beam.

System in which the optical wavelength depends on the variable cavity length [ according to the mathematical relation n (lambda/2) ═ L ] of the organic laser cavity device_opt]。

A system, further comprising: one or more index matching layers over the multilayer film structure.

A system, further comprising: one or more index matching layers integrated within the microelectromechanical mirror assembly.

A system wherein one or more index matching layers are proximate to a multilayer film structure.

A system wherein the photon source is a light emitting diode.

A system wherein the photon source is a laser.

A system wherein the photon source is an incoherent light source other than a light emitting diode.

The system wherein the dielectric control layer comprises a refractive index temperature profile layer and the refractive index control means is a heat source.

A system for tuning the optical wavelength emitted from an organic laser resonator device, comprising: a) a multilayer film structure, wherein the multilayer film structure is pumped by an incoherent photon source and comprises: a1) a support body; a2) a first dielectric stack for receiving and transmitting a pump beam and reflecting laser light within a prescribed wavelength range; a3) an organic active region for receiving the pump beam transmitted from the first dielectric stack and emitting laser light; and a4) at least one index matching layer; b) a grating assembly proximate to the multilayer film structure, wherein the grating assembly is capable of changing a cavity length of the organic laser resonator device; and c) a controller for tuning the optical wavelength emitted from the organic laser cavity device.

An optical wavelength tuning system, wherein the grating assembly is selected from the group consisting of: the structure comprises a Littman-Metcalf structure, a Littrow structure and an electronic tunable grating.

An optical wavelength tuning system wherein the incoherent photon source is a light emitting diode.

An optical wavelength tuning system wherein the incoherent photon source is a lamp.

An optical wavelength tuning system in which the incoherent photon source is a light source other than a light emitting diode.

A system wherein the controller causes rotational movement of the movable optical wavelength tuning mirror.

A system wherein the controller can vary a period of the electrically tunable grating.

The system wherein the controller can vary the refractive index of the electro-optical layer.

A system for tuning the optical wavelength emitted from an organic laser resonator device, comprising: a) a multilayer film structure, wherein the multilayer film structure is electrically activated and comprises: a1) a support body; a2) a first dielectric stack for receiving and transmitting a pump beam and reflecting laser light within a prescribed wavelength range; a3) an organic active region for receiving the pump beam transmitted from the first dielectric stack and emitting laser light; and a4) at least one index matching layer; b) a grating assembly proximate to the multilayer film structure, wherein the grating assembly is capable of changing a cavity length of the organic laser resonator device; and c) a controller for tuning the optical wavelength emitted from the organic laser cavity device.

Claims

1. A system for mechanically tuning the optical wavelength emitted from an organic laser resonator device, comprising:

a) a multilayer film structure, wherein the multilayer film structure is pumped by an incoherent photon source; and

b) a microelectromechanical mirror assembly proximate the multilayer film structure, wherein the microelectromechanical mirror assembly varies a cavity length of the organic laser cavity device.

2. The system of claim 1, further comprising:

c) a plurality of supports of a microelectromechanical mirror assembly, with air gaps between the supports;

d) a top electrode layer in contact with the microelectromechanical mirror assembly; and

e) and a bottom electrode layer.

3. The system of claim 1, wherein the microelectromechanical mirror assembly is a cantilevered assembly.

4. The system of claim 1, wherein the microelectromechanical mirror assembly is a membrane assembly.

5. The system of claim 1, wherein the microelectromechanical mirror assembly comprises at least one dual support beam.

6. The system of claim 1, wherein the optical wavelength is in accordance with the mathematical relationship n (λ/2) ═ L_optDepending on the variable cavity length of the organic laser cavity device.

7. The system of claim 1, further comprising: one or more index matching layers over the multilayer film structure.

8. The system of claim 1, further comprising: one or more index matching layers integrated within the microelectromechanical mirror assembly.

9. The system of claim 8, wherein one or more index matching layers are proximate to the multilayer film structure.

10. The system of claim 1, wherein the incoherent photon source is a light emitting diode.