TWI239130B - Optical parametric oscillator with distributed feedback grating or distributed bragg reflector - Google Patents

Abstract

The invention relates to a simple and effective laser device for generating laser radiation from an optical parametric oscillator (OPO) by implementing a distributed feedback (DFB) or distributed Bragg reflector (DBR) structure, in the laser oscillator. The nonlinear crystal used in the OPO of the present invention can be a birefringence phase-matched crystal or a quasi-phase-matched crystal.

Description

1239130 V. Description of the invention (1) [Field of the invention] The present invention relates to a device utilizing a non-green per-radiation device, and in particular, the invention is a Bragg-based optical material or a laser gain material near or near it. Internal structure, through a light = ^ (Bragg dif fraction) grating emission device. The pre-reference oscillator (0P0) generates a laser radiation laser [transmits the optical fiber of the reflection optics at one time, and then emits. Point, the radiating substance grating, the phenomenon of the increase of the radiation, the background of the radiation system] the invention discussed satisfies the Bragg grating, the middle wavelength, and the lattice wavelength. Because of this, the laser increases the dispersion of the laser because the two ends of the sway must be able to form a two-bulb made of two types of cloth, which is called a common cloth, which is divided into two types. The Bragg diffraction grating is a kind of optical component λ m (λ = 2ηΛ〆m) where n is the refractive index seen by this light wave, and Λ #this grating m is a positive integer. Also, this wavelength; the I J system is called m-th order. This' a Bragg diffraction grating system can be manufactured in a $ fiber grating. When a Bragg diffraction grating system is manufactured at both ends to replace a group of laser resonators, the mirror surface system is called a decentralized Bragg reflector (DBR) and the Larag reflector (DBR) laser system has a simple and convenient formula. In the Bragg reflector (DBR) laser, a laser surface optical resonance mirror is generated, which is replaced by a laser gain grating diffraction grating. In addition, a Bragg diffraction is on the entire laser gain material, which is not limited to the laser end. The decentralized optical feedback caused by this grating element is laser oscillation near the Rag wavelength. This type of laser feedback (DFB) laser. Due to a decentralized feedback

1239130 V. Description of the Invention (2) (DFB) Different longitudinal modes (i0ngitudinai mQde) inside the laser have different laser gains, which is easy to generate laser output in a single longitudinal mode. Laser and decentralized Bragg reflector (DBR) lasers also have the advantage of simplicity. These decentralized Bragg reflector (DBR) and decentralized feedback (DFB) structures have been widely used in various applications of semiconductor lasers. However, the wavelength of a semiconductor laser is limited by the energy If (energy band gap) of the semiconductor material, and cannot be arbitrarily followed by one of these distributed Bragg reflector (DBR) and distributed feedback (DFB) grating periods. Choose to make a wide-area change. One way to modulate a laser wavelength is to use a non-linear optical material. As early as 1962 AD, A. Armstrong et al. Proposed the non-linear frequency conversion technology of quasi-phase matching (QPM) in Phys Rev. 127 (1962) 1918. For example, solid-state laser-excitation optical parameter generation (OPG) and optical parameter oscillation (OPO) from periodically polarized lithium niobate (PPLN) have provided effective and widely Laser source of domain modulation (^ Myers et a 1. Journal of Optical Society of America B, vol. 1 2 (1 9 9 5) PP · 2102- 21 1 6). However, the 'optical parameter generation system produces a broadband radiation. At mid-infrared wavelengths, the solid-state laser-excitation optical parameter generation (0PG) of periodically polarized lithium niobate crystals (PPLN) may have a spectral width exceeding several nanometers (nm). Therefore, in order to obtain effective narrow-line laser light shots,

1239130 V. Description of the invention (3) The optical parameter oscillator (opo) equipped with (QPM) is a universal device. A conventional linear cavity optical parameter oscillator (OP0) can benefit the high f 1 n e s s e value of its resonator to produce a narrower line width output, but Thai half still has multiple longitudinal mode outputs. To obtain a single longitudinal mode output, an operator usually must adopt a more complex resonance design (such as Bosenberg et al., Applied Physics Letters 5 vol. 61 (1992) PP · 3 7 8- 3 8 9). Therefore, if an operator can manufacture a decentralized Bragg reflector (DBR) or decentralized feedback (manufactured in a non-linear optical substance of an optical parameter oscillator, this g can be

To get any wavelength in this oscillator adjustment range. In particular: ^ J one of the distributed feedback (DFB) inside the linear optical material, the result of this non-selected Bragg wavelength is the laser output of single frequency oscillation. In view of this, the applicant is attempting to improve the knowledge skills, sauce, and hacking. [Summary of the Invention] of π k ^ In order to solve the above and other problems, the main purpose of the present invention / a simple and effective laser device is to provide a non-linear manufacturing of a Bragg diffraction grating through this, Optical surface ^ Laser radiation is generated in the material. However, the non-linear optical material used in the optical parameter oscillator and oscillator unit of the present invention may be a bijective f (OP0) body or a quasi-phase matching crystal. 、 Eye-matching crystal Another object of the present invention is to provide a simple and effective two-position system, which implements a point in this non-linear optical substance.

Page 10 1239130 V. Description of the invention (4) (DFB) or decentralized Bragg reflector (DBR), so as to generate a laser with a narrow bandwidth through an optical parameter oscillator. However, the non-linear optical material used in the optical parameter oscillator (OP0) of the present invention may be a birefringent phase-matched crystal or a quasi-phase-matched crystal. Among them, the distributed feedback (DFB) structure performs periodic refractive index modulation on the entire non-linear optical substance, so that the light beam with a wavelength matching this modulation period will cause optical oscillation; the distributed Bragg reflector (DBR) system will The modulation of the periodic refractive index is implemented at both ends of the non-linear optical substance, so that a light beam with a wavelength matching this modulation period will cause optical oscillation. The main feature of the present invention is to provide a laser device which uses a non-linear optical element to generate a laser with a narrow bandwidth through an optical parameter oscillator (OP0). The non-linear optical element has a Diffraction feedback (DFB) of light refraction effect; gratings, by which a specific period of the distributed feedback grating, oscillates at least one wavelength of the optical parameter mixing wavelength, and obtains a highly efficient laser output. Another feature of the present invention is to provide a laser device, which uses a non-linear optical element to generate a laser with a narrow bandwidth through an optical parameter oscillator (OP0). The non-linear optical element has a The light-refracting dispersion Bragg reflector (DBR) structure uses the Bragg reflector with a specific period to oscillate at least one wavelength of the mixing wavelength of the optical parameters to obtain a high-efficiency laser output. Preferably, the distributed feedback (DFB) structure or the distributed Bragg reflector (DBR) structure reflects electromagnetic waves near the first-order (1) or second-order (2) Bragg wavelength (also = 2 ηΛ g), where , Λ # 系 一 布拉

1239130 V. Description of the invention (5) The period of the grating diffraction grating, and η is the equivalent refractive index seen by the Bragg wavelength in this medium, and it has this distributed feedback (DFB) structure or this distributed Bragg reflector (DBR) structure. The laser device can oscillate at this Bragg wavelength λ. The Bragg wavelength λ can be any non-linear mixing wavelength. Preferably, the non-linear optical element is made of a substance having a second-order nonlinear optical coefficient. Preferably, the optical parameter oscillator (0P0) is inside a bulk non-linear crystal and has a distributed feedback (DFB) structure with a built-in photore fraction effect. Preferably, the optical parameter oscillator (oop) is inside a waveguide non-linear crystal and has a built-in photorefractive effect distributed feedback (DFB) structure. Green, ΐ 允 allows the optical parameter oscillator (〇P〇) to be in a bulk (bulk) non-reflector (_structure θ builds a decentralized Bragg light refraction effect. Better: this optical parameter oscillator (〇p 〇) system (waveguide) nonlinear crystal chaos dispersive Bragg ... (body-center junction; better-built-in light refraction effect, this nonlinear optics a sci-fi body.% To the Japanese-Japanese system pair If the refraction phase-matching crystal is better, this nonlinear optics is better, a ^ is better, skin non-birth w:? System-a quasi-phase-matching crystal. Ping Yi 1 Wang 1 This nonlinear optics discriminates the total g ^.% Yo Day-to-day System

Page 12 1239130 V. Description of the invention (6) Linear optical crystals' such as: lithium niobate, or lithium group acid, or the same optical crystal doped with impurities. Another feature of the present invention is to provide a laser device, which uses a non-linear optical element to generate a laser with a narrow bandwidth through an optical parameter oscillator (0P0). The non-linear optical element has a Diffuse feedback (DF Β) or decentralized Bragg reflector (DBR) structure of light refraction effect, and wherein the method of adjusting the optical refractive index is to irradiate a light beam so as to penetrate above the non-linear optical element of the light refraction effect One photomask. Preferably, the photomask has a grating design. After irradiating a light beam, a spatial light intensity change that matches the Bragg condition of the optical parameter oscillator (OP0) is generated after the photomask. Preferably, the light beam is an optical writing beam, which has the effect of inducing a space charge (s p a c e charge) inside the non-linear optical material of the light refraction effect. Preferably, the light beam is located at a wavelength of visible light or ultraviolet (UV) light. Preferably, the non-linear optical element is made of a second-order nonlinear optical coefficient. Another feature of the present invention is to provide a laser device, which uses a non-linear optical element to generate a laser with a narrow bandwidth through an optical parameter oscillator (oop), wherein the non-linear optical element is It has a distributed feedback (DF B) structure or a distributed Bragg reflector (DBR) structure formed by a light refraction effect, and wherein the optical refractive index is modulated

Page 13 1239130 V. Description of the invention (7) The method uses two intersecting laser beams with an appropriate angle between the interference light refraction effect to pass through the wind method to produce a spatial optical intensity in a linear optical element. Here, the non-degree modulation causes the optical refractive index modulation. & Intersection 'the better optical optical in this space' The periodic fringes (0P0) of this interference fringe are expected to be fitted with this optical parameter. Another feature of the present invention is to provide a thunder angle. It is a linear optical element, which uses a lifetime narrow-band laser through a light wind meter. Among them, the non-linear oscillator (OP0) produces an electro-optic effect (electr0_〇ptic ff). A non-linear optical element with a feedback optical (DFB) grating and a decentralized light effect formed by 'a pp' is used to calculate / 'ζ to add a refractive index having a direction of electron transmission. This fold == periodically adjusts the period of operation of the optical parameter vibrator (_) along the thunder. = The system is matched with a nonlinear optical KDUTU laser device, which uses a narrow bandwidth of a lifetime. Emperor 2, the dispersed g. Which produces light through an optical parameter oscillator (OP0). For a long time, this non-linear optical element has an electrical rate of 斤. The period of this refractive index modulation. The 4-digit oscillator (0P0) expects your car owner in Prague {Go 4, expressed as .i kg ~ the amount of change in emissivity, in its simplified form, ^ (1/2) rn3E, where r This crystal = electric first

Page 14 1239130 V. Description of the invention (8) Number, η is the refractive index without voltage applied, and E is an electric field inside the crystal. Another feature of the present invention is to provide a laser device which generates a narrow-frequency laser via an optical parameter oscillator (OP0). The optical parameter oscillator has a wave shape (c) on the surface of a nonlinear optical waveguide. rrugated) distributed feedback (DFB) structure, whereby the distributed feedback of evanescent waves on the surface of the waveguide is sufficient to start the optical parameter vibration. Preferably, the distributed feedback (DFB) structure is fabricated by using methods such as material etching, thin film coating, lithography, ion implantation, and combinations thereof. Another feature of the present invention is to provide a laser device which generates a narrow-frequency laser via an optical parameter oscillator (OP0). The optical parameter oscillator has a non-linear optical waveguide (wavegu i de) surface with a A corrugated decentralized Bragg reflector (DBR) structure, by which the decentralized feedback of evanescent waves on the waveguide surface is sufficient to start the optical parameter oscillation. The DBR structure is preferably made by using various methods and combinations thereof. The decentralized Bragg reflector such as material etching, thin film overlay, and lithographic process are manufactured. Another feature of the present invention is to provide a laser device which generates a narrow-frequency laser via an optical parameter oscillator (0P0). The optical parameter oscillator has a decentralized feedback (DFB) inside a non-linear optical waveguide. ) Structure or a decentralized Bragg reflector (DBR) structure, whereby, here,

Page 15 1239130

V. Description of the invention (9)

Optical parameters oscillate inside the waveguide. The optical feedback of the electromagnetic waves can be enough to start the Bragg. The distributed feedback reflector (DBR) structure is of the photorefractive type. (D F B) Structure or this dispersion type The above-mentioned light refraction effect [preferred implementation Although the present invention is described below, however. In addition, it is used to limit the eigenvalue to be reduced to the following scientific parameters of the present invention: Zhenyingyi, in which the internal device of the vibrator is composed of two light beams with an angular frequency m ^ ^ Α ω ω s + ω Generally speaking, == ω is better The 'this decentralized return to the museum can be described from the city structure (DFB) structure or this decentralized Prague + ·,,, f, a detailed description of the types of electro-optics effects described above.] 3 ί The detailed description and preferred parts of the preferred embodiment that allow various forms of the female embodiment are described in detail and introduced. The disclosure is used to prove the principle of the present invention, and; The present invention will be broader and fixed in embodiments. The optical feedback of the diffraction grating in the device is used to establish the optical parameter oscillation in the first and second groups. The first figure is the introduction of the conventional Ichiura laser ({) 111111) 1 仏 61〇10 system excites a laser ^ and a linear optical element 30, and the laser is formed by ^ a mirror surface 20 in total. In an optical parameter process, the pump photon system generates ~ two photons according to the following relationship. This high-frequency photon system is called signal light (s 丨 gna ^

And

1239130 V. Description of the invention (10)-~~ — 2ΐ11 ί, which is idle light (idler). These resonator mirrors 20 can be f 1 U light, can also exhaust this idler (idler), or both. Μ Ϊ Ϊ Ben ^ Ming, these resonator mirror surfaces of Xiyou Technology are replaced by a non-linear I =-? One distributed feedback (DFB) structure or a distributed cloth 12 # &# DBR) structure to replace , As shown in Figure 2. Non-linear optical elements with an internal (DFB) structure or a decentralized Bragg reflector may be included in Figures 21 to 6 of any device 40, 43, 44, 45, 46. The linear mi;:; learning parameter used by the exhaustor (〇p〇)-not '[fold = ΐϊ light: r: rr has a cycle over the entire length: two cycles or this-Bragg grating cycle, Λ " , Which satisfies Prague Λ g, m: mA 〆2ns, or Λ g 'e πιλ 〆2ni and 丄 二 和 信 Vt #: and the wavelength of this idle photon, and n Figure 2C is the light I of the present invention, as seen by the light Equivalent refractive index. In the linear optical monolithic material, a non-structural schematic diagram is used for the two oscillators (OPPO). This non-linear: Bragg reflector (DFB) junction Bragg diffraction grating 50 has two mirrors on both ends of these two pieces of material. In addition, the two Bragg diffraction gratings are used as the optical parameter of the present invention.

Page 17 1239130 V. Description of the invention (11)

The segment retains the continuous non-linear optical material 5 5-1 conversion. Figure 3a is used in the optical parametric waveguide of the present invention, one of the optical waveguides used in a decentralized feedback (0P0), which is not a β), is a schematic diagram of a gigabyte. This non-linear optical waveguide fi fl μ // m phase structure over the entire device length, that is, a series of distributed wave-fed (DFB) structures 80 above the scattered 40, ^ 60 reflect the ^ skin B) Structure 8〇. This decentralized recursive optical waveguide dissipates waves inside the surface of the wind well to create this non-linear_made in-appropriate material; the surface of this board; the optical wave J linear optical waveguide system can be used for example ^ In the present situation, a non-T Rnrt7 ^ W uses the annealed proton exchange method (M · L · Bt aa1 · 〇Ptics Letters ν〇ΐ · 23 (^ 9 91) ρρ · 1 84 4 ~ 1 84 6 ) To be fabricated on the surface of a lithium niobate substrate. The third embodiment of the Bragg diffraction grating is a periodic refractive index change embedded in the content of the non-linear optical waveguide 60, that is, an embedded distributed feedback (DFB) structure 84. The embedded distributed The feedback structure (DFB) 8 4 can be generated, for example, by a light refraction effect, ion implantation, or thermal material dii fusion. When using the light refraction effect, write light

The beam can pass through an optical mask or use laser interference fringes to produce a periodic periodic variation in the intensity of the writing light. When using ion implantation or thermal penetration, the lithographic mask required for the lithographic process can be made first. This mask; ^ a space period that meets the conditions of Bragg diffraction, and then use this mask with the lithography process to make a mask of appropriate material on the surface of the waveguide, to shield the area that does not need to change the refractive index, only the refraction needs to be changed Rate of the exposed area ^ and

1239130 V. Description of the invention (12) Perform ion implantation or thermal penetration. If so, the embedded distributed feedback (DFB) structure 84 can directly provide distributed optical feedback to the light waves inside the non-linear optical waveguide 60. Fig. 3c of another embodiment of the Bragg diffraction grating is to make a periodic electrode 87 on the nonlinear optical waveguide 60. Applying a voltage to this periodic electrode 87 can generate a period through the electro-optic effect. If the refractive index changes, the periodic electrode 87 and the non-linear optical waveguide 60 can be added with a buffer layer 90, such as silicon dioxide (SiO2), if necessary, to avoid light waves. Loss due to direct contact with electrode 87. If so, the electro-optic effect decentralized feedback (DFB) structure can directly provide decentralized optical feedback to the light waves inside the non-linear optical waveguide 60. The (DBR) structure 5 0 ′ remains the same as the non-linear optical waveguide 55 between the decentralized Bragg reflector (dbr) 50. Figure 4b of another embodiment of the decentralized Bragg reflector (DBR) is a periodic refractive index change embedded in the content of the non-linear optical waveguide 60, that is, the embedded decentralized Bragg reflection is (DBR) 5 4 ' This internal refractive index change that hinders periodicity can be, for example, a photo-refractive effect, ion implantation (丨 〇 Figure 4a is one of the optical waveguides used in the optical parameter oscillator (〇p〇) of the present invention. Overview of the structure of the distributed Bragg reflector (DBR). The difference from the structure of the distributed feedback (DFB) is that instead of setting the Bragg diffraction grating over the entire length of the device, this preferred embodiment is a nonlinear optics On the surface or inside of the waveguide 60, these Bragg diffractive gratings are fabricated at both ends of the device, that is, a diffuse Bragg reflector (implantation) or thermal mate (fial diffusiQn)

1239130 V. Description of the invention (13): The method is generated. When using the photorefractive effect, write = photomask or use laser interference fringe to generate periodic changes between public and public; and when using ion implantation, it can be required in the second process. Lithography mask, this mask has a conforming cloth: system = space period, and then use this mask to cooperate with the lithography process on the wave table. 2 = When the material is masked, mask the area without changing the refractive index ^ And the area where the refractive index is to be changed is exposed and ion implantation or ion implantation is performed. If so, the embedded distributed Bragg reflector (DBR) junction, structure, and ° are provided to directly provide distributed optical feedback to this nonlinear optics. Light waves in the waveguide. Another 4c diagram of the implementation of this Bragg Diffraction Reflector (DBR) is a non-linear optical waveguide 60. A periodic electrode 57 is made at both ends. A voltage is applied to this periodic electrode 57 and it can be generated by the electro-optic effect. The periodic refractive index changes, and the periodic electrode 57 is non-linear ^ between the waveguide 60, if necessary, a buffer layer (Buffer layer MOO, such as silicon dioxide (Si02)) can be added to avoid light waves and the electrode 57 The loss caused by direct contact. If so, the electro-optic effect decentralized Bragg reflector (DBR) structure can directly provide the decentralized Bragg feedback to the internal optical waves of this non-linear optical waveguide 60. Figure 5 shows a dynamic frequency shift (Chirped) Bragg Diffraction Grating's schematic diagram, which is another preferred embodiment of the distributed feedback (DFB) structure or the distributed Bragg reflector (DBR) structure of the nonlinear optical material used in the present invention. Generally, the Bragg diffraction grating system can have an arbitrary refractive index change in space, which is reflected by this Bragg condition and the spatial Fourier component (Four ier

Page 20 1239130 V. Description of the invention (14) Component) matching optical wavelength. Therefore, the reflection spectrum of a Bragg diffraction can correspond to the Fourier transform spectrum of this Bragg diffraction grating. A dynamic frequency-shifted Bragg diffractive grating system has a wide Fourier transform spectrum and is therefore suitable for wideband optical parameter oscillator (0P0) operation.

FIG. 6 is a schematic diagram of a cascaded Bragg diffraction grating, which is used as a distributed feedback (DFB) structure or a distributed Bragg reflector (D-preferred embodiment) of a nonlinear optical material used in the present invention. . This cascaded cloth 2: The grating system is suitable for oscillating in a Bragg grating (90, 95, ..., 99) with different grating periods in an optical parameter oscillator (oop) to generate different wavelengths. At the same time, several kinds of thunder are generated through the optical parameter oscillator (〇p〇). Therefore, the wavelength of the grating of the CaSCaded Bragg diffraction grating is all in the optical parameter oscillator (〇p 明光 数据). Oscillator (0P0) can see A ^ due to 0 Shita. ^ J generates multiple laser waves with 冋 k, a gain material of nonlinear optical element parameter oscillator (0P0) with photorefraction effect, In the first two years, the light refraction effect can be used to write a cloth or a waveguide element refraction effect material, using the writing beam ^ = grating two in a light into a space charge with space modulation Modulation, shape connection, this nonlinear light $ Y imitation refractive materials electro-optical effect vehicle spatial intensity variation for modulation. For Second write beam of beam of space-based writing can use this light intensity modulation = t- spatial effect, especially on the non-linear optical refractive element

1239130 V. Description of the invention (15) The Fang Zhi mask is implemented, in which a specific period of light intensity generated during this period matches the expected Bragg refraction grating mask. The light beam is written in an interference manner to this fringe period, which matches the expected Bra Two laser beams with an appropriate angle. This optical refraction effect is a non-linear optical crystallinity, and then the optical refraction effect is written. When an electro-optic nonlinear crystal system is used as a gain substance, it is diffracted in this single block or wave Bragg. Raster. First of all, micromanufacturing is performed on an electrode distribution system with an electrode distribution and a Bragg structure distribution. In these crystals, the refractive index changes caused by the induction inside the crystal, thereby diffracting the grating in a grating. For example, if a cut) periodically polarized lithium niobate crystal < equipped with an optical parameter oscillator (0P0) is used as a periodic microelectrode and an electrical Bragg diffraction grating is applied. Δ η- (1/2) r33n3Ez where the refractive index change of these microelectrode systems is at Δ n = 1 0-depleted, etc. If a non-linear optical waveguide system is used for the photomask to change in space after being illuminated by a light beam, The light intensity changes periodically. For example, using a phase non-linear optical material whose interference lattice refracts the grating period. Furthermore, they can also cross directly to form a periodic interference strong Lag diffraction grating in. An optical parameter oscillator (0P0) may be implemented in the crystal system. An electrical electrode system may be used on the nonlinear crystal, where this match. When a voltage is applied to the electric field strength, the electro-optical effect forms an electro-optical cloth inside the crystal, a thickness of 0.5 mm, and a ζ cut plane (ζ-: PPLN) is used for a quasi-phase phase. The ± z surface of the crystal can be suppressed. A voltage stage of about 100 volts is formed according to the following equation. Optical parameter oscillator

Page 22 (16) ^ ~~ --—— 1239130 V. Description of the invention (0P0), technique, making lithographic etching grating. The device (DBR) becomes an optical parameter and the film is overlaid. Take the waveguide and the modified form on the waveguide (reading that the Bragg diffraction grating system can use lithography to etch the surface of the waveguide. It is often used in semiconductor processing to form a wave-shaped Bragg winding on this nonlinear waveguide. A 5 decentralized feedback (DFB) or decentralized Bragg reflection-a jade body laser, the Bragg reflection system of this dissipated wave is sufficient to form a U 2 oscillation. Alternatively, the Bragg diffraction grating system can be formed using the shadow etching technique to form The non-linear waveguide said that a layer of material film was first coated on this non-linear film. The film was chemically or plasma etched to non-linearly reach a Bragg diffraction grating. Experimental results] By = lithium niobate crystal system A photorefractive effect material, which is transmitted in a periodic extremely sharp S 晶体 bell crystal (ρρ [Ν), should be formed into $ 八 # 4 The system is written in the form of a knife formed by the photorefractive effect Feedback (DFB) structure or divided DBR) structure. In particular counties, Li Yimin = two f-type Bragg reflections are ρρΤΜΛ, which can be distinguished from a periodically polarized lithium niobate crystal Bragg reflection, which can use a distributed feedback (DFB) structure or a dispersed 0P0), DBR) structure. Instead of simplifying the optical parameters of the oscillator, the design of the optical parameter oscillator (0P0) will be within PPLN). In this experiment, periodically polarized lithium niobate crystals (DFB) gratings are used. Photorefractive effect decentralized feedback (ί 性 极化 Polarized lithium niobate crystal (PPLN) dispersed decentralized fractional decimeters> number of oscillations. Among them, one by the photorefractive effect shaped feedback (DFB) grating system uses ultraviolet light Irradiation penetrates this week

1239130 V. Description of the invention (17) Periodically polarized niobate chain crystal (PPLN) is fabricated by using a photomask, and another decentralized feedback (DFB) grating formed by the light refraction effect uses two channels. 5 3 An interference fringe of a laser beam of 2 nm wavelength is written into this periodically polarized lithium niobate crystal (PPLN). In the ultraviolet (UV) mask method shown in Fig. 7, a non-homogeneous ultraviolet (UV) light emission from a 20 f mercury lamp is irradiated to a chromium mask having a period of 50 m and a 50% duty cycle. This Mercury Radon is an ultraviolet (UV) wave filter that covers only one and can penetrate only 3 65 UV of the mercury emission spectral line. After passing through the ultraviolet (UV) chirper, the light intensity of 3 6 5 nm incident on the photomask is about 0 · 3 W / c m 2. This reticle is in direct contact with a 4 cm long, 0.5 mm thick, 28 // m period and end-polished periodically polarized lithium niobate crystal (PPLN). Its chrome thumb vector ( A grating vector) is a quasi-phase-matched (QPM) grating vector aligned with the crystal's X direction. When ultraviolet (UV) radiation is transmitted through the mask, the temperature of this periodically polarized sharp acid crystal (PPLN) is from 20 to 3 minutes. C rose to 160. C, and from 160 to 2 hours. C is reduced to 20. C. In this way, the ultraviolet (UV) -induced light refraction effect distributed feedback (DFB) grating can be recorded in a periodically polarized lithium niobate crystal (PPLN). This 1 / zm distributed feedback (DFB) grating period system can be periodically polarized in a sharp acid crystal (PPLN) at a temperature of 1 15 · 4 ° C and a pump ed of 106 nm. Generates oscillations for 4 · 0 8 5 // m idle photons. The corresponding signal wavelength is 1 4 38.8 nm. Passive Q-switch (Q —swi tched) with 9 // J / pulse pulse energy and 73 0 ps pulse width Er-doped garnet (Nd: YAG) laser pump decentralized return

1239130 V. Description of the invention (18) Feed (DFB) periodically polarized lithium niobate crystal (ppln), this distributed feedback | feed (DFB) optical parameter oscillator (opo) signal system can be at 1 4 3 8. 8 i nm is generated. The signal spectrum was measured after a monochromator with a length of 1/2 m and was measured with an InGaAs so-called rigid instrument. The resolution of this monophotometer is 3 A, which has a slit opening of 10'm and an infrared grating of 30.1 ines / mm. The pulse width of the 73 0 {) 3 pump is approximately equal to the round trip time of the periodically polarized lithium niobate crystal (PPLN) with a length of 4 cm, so it will not pass through the periodic polarization of the specific recording film. Optical parametric vibration i is formed on the surfaces of both ends of the lithium niobate crystal (PPLN). Figure 8 shows the optical parameter oscillator (opo) and optical parameter generation (OPG) signal spectra at different temperatures. It can be seen from Figure 8 that although the optical parameter generation (0PG) wavelength is shifted with temperature, the optical parameter oscillator (OP0) signal wavelength is dispersed due to the light refraction effect inside the periodically polarized lithium niobate crystal (PPLN). The feedback (DFB) grating remains unchanged. At 1 15 · 4 ° C, this optical parameter generation (0PG) wavelength system partially overlaps with the optical parameter oscillator (0P0) signal wavelength, and the conversion system between the two is greatly improved by a factor of three. The measured spectral width of the distributed feedback (DFB) optical parameters of the oscillator (OP0) signal is 3A, and the measured spectral width of the optical parameter generation (0PG) signal is 3 nm. When the pump energy is 6 · 7 5 J, the output signal energy is 1 # J, which is equivalent to 15% of the signal light energy conversion rate. ~ Since the distributed feedback (DFB) grating vector system is in the X direction of the crystal, this distributed feedback (DFB) grating may be expected to be a space charge in the X direction.

1239130 V. Description of the invention (19) Field E f. However, the z-polarized (z-polarized) pumped electric field induced space-charge electric field induced change in refractive index is a second-order effect inside lithium niobate, which is expressed as: Δ n〇2ne 3 (rsiEx) V 2 Equation (1) where η and η-2.2 are normal and abnormal refractive indices, respectively, and r 5-3 2 pm / V is the electro-optic coefficient of lithium niobate. In a stable equilibrium state, it is caused by thermal diffusion. Dominant and approximated by non-empty carriers, the speciality of this space charge electric field is about Εχλ27ι1 < βΤ / (Aq) »105V / m, where kB is Boltzmann's constant and q is an electron The charge amount, 4 0 K is the crystal temperature, and Λ ~ 1 // m is the distributed feedback (DFB) grating period. Although this space charge electric field is the index ellipsoid of the rotating niobate, and The incident optical electric field is slightly depolarized (de ρο 1 arize). The refractive index change seen by this laser is only △ n «1CT9 according to equation (1). However, since it penetrates the optical cover Curtain ultraviolet (UV) diffraction, the intensity of the writing beam is along the crystal Direction changes spatially. This means that the space charge distribution will also change along the Z direction. As the light refraction effect charges change along the Z direction, the space charge electric field ζ of the Z component will also be sharply polarized periodically. The acid undergoes a first-order refractive index change in the crystal (PPLN), which is expressed as: △ nz = n33r33Ez / 2 »105 Equation (2) where r33 = 31pm / V and ΕZ = ΕΧ are used in the calculation. = 105 V / ΠΓ The amount of refractive index change is much larger than calculated by equation (1). In the present invention, the optical parameters of the periodically polarized lithium niobate crystal (PPLN) oscillate

Page 26 1239130 V. Description of the invention The dispersed optical feedback of the (20) device (ΟΡΟ) is similar to the distributed feedback (DFB) diode laser with a wave grating above the gain material. However, this wave-shaped light refraction effect distributed feedback (DFB) grating system can provide sufficient optical feedback and can generate a signal light with a bandwidth that reaches the limit of the resolution of a single optical instrument. In order to use the X-direction space charge electric field in a periodically polarized lithium niobate crystal (PPLN) to further investigate the possibility of a distributed feedback (DFB) optical parameter oscillator (OP0), a photorefractive effect distributed feedback (DFB) grating It was written using a laser beam with an interference of 5 3 2 nm, as shown in Figure 9. The circular laser beam is shaped as an elliptical beam with an optical axis ratio of about 1:50 using a lenticular lens group. Subsequently, the 5 3 2 n m laser with an average power of 2000 m W is separated by a beam splitter (b e a m s p 1 i 11 e r) and divided by 34. The angles were recombined to produce 0.91 on a periodically polarized lithium niobate crystal (PPLN) with a length of 5 cm, a thickness of 0.5 mm, a period of 1 1 / zm, no film on the end, but optical polishing on the end. 3 / Z m period interference fringes. The maximum intensity of this interfering laser beam is approximately 0 · 5 W / cm2 °. This 91. 3 # m period of distributed feedback (DFB) grating system is designed at 8 2. At a temperature of C, an optical parameter oscillator (0P0) oscillating at 3.778 / m in a periodically polarized lithium niobate crystal (PPLN) excited at 5 3 2 nm has an idle photon wavelength. This pump laser is a passive Q-switched, doubled erbium-doped garnet (Nd: YAG) laser, which is a periodic polarized niobic acid with a repeatability of 6. 59 kHz and a pulse width of 43.0 ps. In a lithium crystal (PPLN), a pulse energy of 2 # J is generated. These interfering 5 3 2 nm laser beams are in a single periodically polarized lithium niobate crystal (PPLN)

Page 1239130

5. In the description of the invention (21), a periodic space charge in the-X direction can be clearly seen. Temperatures around 6 200 nm are characterized by the jewels of L., B. and B. Bebe, and eight related optical parameters. OPG) signal, however, this experiment could not find any evidence to complement equation (1), the small optical refractive index change caused by f (DFB) optical parameter oscillator (0P0). Knife-in-type mouth-feeding while continuously irradiating 5 3 2nm interference light on this periodically polarized lithium niobate crystal (PPLN), this experiment also irradiates ultraviolet (UV) with an intensity of 53mW / cm2 to the periodically polarized niobate On the + z surface of the lithium crystal (ppLN), the optical parameter oscillator (0P0) signal of the distributed feedback (DFB) was observed again at the output. 3 6 5nm ultraviolet rays (UV) are attenuated along the z-direction in the sharp acid meridian, and will be written by the so-called two-photon photorefraction effect method (L. Hesselink, et al., Science 28 2 (1 9 98 ) pp. 1 0 8 9) and induction to obtain a wave-shaped distributed feedback (DFB) structure. Figure 10 shows that at different temperatures, the optical parameter oscillator (OP0) and optical parameters of the periodically polarized sharp acid M crystal (PPLN) generate the spectroscopic spectrum. It can be seen from Fig. 10 that although the optical parameter generation (0PG) is adjusted by using temperature, the scattered feedback optical (DFB) optical parameter oscillator (opo) signal wavelength of 619 · 3 nm will still match and must be matched. Here the light refraction effect decentralized feedback (DFB) grating remains unchanged. At 82.4. C. The optical parameter generation (0PG) wavelength partially overlaps with this optical parameter oscillation (OP0) signal wavelength, and the signal intensity is the strongest. When this experimental system moves the pump beam along the ζ direction and in the longitudinal direction, and then the beam is incident from a deeper portion of the crystal, the distributed feedback (DFB) optical parameter oscillator (OP0) signal system gradually decreases. ,this

Page 28 1239130 V. Description of the invention (22) This is due to the spatial modulation of the deflection feedback (DFB) grating in the z-direction light refraction effect, which causes the UV light to decay along the z-direction of the crystal, which gradually decreases. In this experiment, the signal width of the distributed feedback (DFB) optical parameter oscillator (0P0) signal is also 3 A. Due to this photorefractive effect effect, according to the electro-optic effect, it falls into the category of electro-optical phenomena. The above experimental system can be summarized as a distributed feedback (DFB) structure or a distributed Bragg reflector (DBR) structure formed by the electro-optic effect Optical parameter oscillator (OP0) used in the present invention. In general, the refractive index changes of the photorefraction effect and electro-optic effect are very small compared to the proposed etching or overlaying distributed feedback (DFB) structure or distributed Bragg reflector (DBR) structure. Therefore, the above experimental system can be intuitively inferred that the etched or cladding distributed feedback (DFB) structure or the distributed Bragg reflector (DBR) structure of the nonlinear optical element of the optical parameter oscillator (OP0) should also fall into this Within the scope of the invention.

| Schematic description i The first picture is an optical reference | Oscillation state (〇Pc〇 > μ! Ϋΐ ^ Figure 2a is the outline d surface view of the present invention, such as the province: 3! The light of the present invention; see J: the general introduction of the musical instrument (〇p〇). Section 4a, summary; early block material-minus; used by Qing Hujin-non-linear ". ^ d, Q u non-n ^ Lag reflector (DBR) structure ^ picture is the well wind 4 of the present invention a 戸 Using the linear optical turbidity nine-parameter oscillator (0P0)-an outline of the decentralized feedback (DFB) structure 4 b One of the non-linear light ^, a schematic diagram of the optical parameter oscillator (ΟΡΟ) used, especially the waveguide The fifth diagram of the first-class decentralized Bragg reflector (DBR) is shown in Figure ^. It shows the outline of the chirped Bragg diffraction grating (DFB). The decentralized feedback of the non-linear optical material used in the present invention is compared. Jiayi ^ " Another auto example of constructing or decentralized Bragg reflector (DBR) structure. Figure 6 ~ is used as' ~ outline diagram of cascaded Bragg diffraction grating (Dfb used in the present invention Non-linear optical materials with dispersed feedback 轫 / earth J structure or another type of distributed Bragg reflector (DBR) structure Example. First / said system, using an ultraviolet (UV) writing mask one Bragg diffraction grating photorefractive effect in crystals distributed to a nonlinear photorefractive effect

Page 30 1239130 Schematic description of the diagram --- An outline of the optical parameter oscillator (0P0). θ $ Figure 7: Measurement signal spectrum of optical refracting effect (DFB) optical parameter (5P, 0P0). ^ 2 is a schematic diagram of the two-photon photorefractive effect decentralized feedback (DFB) optical parameter oscillator (〇ρ〇) using a parent fork laser beam in a photorefraction effect non-linear optical crystal into a Bragg diffraction grating. Figure y is the measured signal spectrum of the two-photon photorefractive effect decentralized feedback (DFB) optical parameter oscillator (0P0) in Figure 9. Explanation of component symbols · 10 pump lasers ω S, ω i, ω p angular frequency 3 0 non-linear optical element 2 0 optical reflecting mirror surface 4 0, 4 3, 4 4, 4 5, 4 6 device 2, 3 numbered 50, 54 embedded decentralized Bragg reflector (dbr) 5 5 nonlinear optical material 5 7 periodic electrode 6 0 nonlinear optical waveguide 7 0 suitable material substrate 80 distributed feedback (DFB) structure 8 4 inside Embedded distributed feedback (08) structure 8 7 electrodes 90, 95, 99 Bragg grating 100 buffer layer

Page 31

Claims (1)

1239130 I. Patent application scope 1. A laser device that uses a non-linear optical element to generate laser radiation through an optical parameter oscillator (0P0), wherein the non-linear optical element has a built-in Bragg The diffraction grating oscillates one wavelength in the frequency conversion of the optical parameter to form a laser output. 2. The laser device according to item 1 of the scope of patent application, wherein the Bragg diffraction grating is a decentralized feedback (DF Β) structure, which has a grating period that matches the Bragg condition, so that the optical parameter Laser oscillation is formed in the oscillator (OP0). 3. The laser device according to item 1 in the scope of the patent application, wherein the Bragg diffraction grating is a decentralized Bragg reflector (DBR) structure, which has a grating period that matches the Bragg condition, so that the optical Laser oscillation is formed in the parameter oscillator (OP0). 4. The laser device according to item 1 of the scope of patent application, wherein the Bragg diffraction grating is a dynamic chirped grating structure, which has a broadband spatial frequency component that matches one of the Bragg conditions. Optical parameter oscillator (0P0) allows wideband laser amplification or oscillation. 5. The laser device according to item 1 of the scope of the patent application, wherein the Bragg diffraction grating is a cascaded grating structure, which has a complex grating period matching the Bragg condition, whereby the optical parameter oscillator is used. A multi-wavelength laser oscillation is formed within (0P0). 6. A laser device that uses a non-linear optical element to generate a narrow-frequency laser through an optical parameter oscillator (OP0), wherein the non-linear optical element has a dispersion type formed by a light refraction effect Feedback (DFB) grating structure, by which at least one wave in the optical parameter mixing is oscillated Page 32 1239130 6. The scope of patent application is long. 7. A laser device which uses a non-linear optical element to generate a narrow-frequency laser through an optical parameter oscillator (0P0), wherein the non-linear optical element has a dispersion type formed by a light refraction effect A Bragg reflector (DBR) structure whereby at least one wavelength of the optical parameter mixing is oscillated. 8. The laser device according to item 6 or 7 of the scope of the patent application, wherein the distributed feedback (DFB) structure or the distributed Bragg reflector (DBR) structure has a condition that satisfies the Bragg condition Λ g = m and / 2 A periodicity Λ g of η, where η is the Bragg wavelength; equivalent refractive index seen by I, and m is a positive integer, so that the laser device can vibrate at the wavelength λ. 9. The laser device according to item 6 or 7 of the scope of patent application, wherein the Bragg wavelength 1 is any wavelength of the non-linear mixed wavelengths. 10. The laser device as described in claim 1, 6, or 7, wherein the non-linear optical element is a non-linear optical crystal having a second-order non-linear optical coefficient. 1 1. The laser device according to item 6 of the scope of the patent application, wherein the optical parameter oscillator (OP0) is inside a single nonlinear crystal and has a decentralized feedback (DFB) structure with a light refraction effect. . 12. The laser device according to item 6 of the scope of the patent application, wherein the optical parameter oscillator (OP0) is inside a waveguide nonlinear crystal and has a decentralized feedback (DFB) structure with a light refraction effect. 1 3. The laser device according to item 7 in the scope of patent application, wherein the light Page 33 1239130 VI. Scope of patent application The scientific parameter oscillator (0P0) is located inside a single nonlinear crystal and has a decentralized Bragg reflector (DBR) structure with light refraction effect. 14. The laser device according to item 7 in the scope of the patent application, wherein the optical parameter oscillator (OP0) is inside a waveguide nonlinear crystal and has a decentralized Bragg reflector (DBR) with a light refraction effect. structure. 15. The laser device according to item 10 of the scope of patent application, wherein the non-linear optical element is a birefringent phase-matching nonlinear optical crystal. 16. The laser device according to item 10 of the scope of patent application, wherein the non-linear optical element is a quasi-phase-matched nonlinear optical crystal. 1 7. The laser device according to item 10 of the scope of the patent application, wherein the second-order nonlinear optical crystal system is a photorefractive effect nonlinear optical crystal, which is selected from the following material groups, including: niobic acid The above crystals of lithium, lithium tantalate, and impurity doped. 1 8. A laser device using a non-linear optical element to generate a narrow-frequency laser through an optical parameter oscillator (0P0), wherein the non-linear optical element has a dispersion formed by a light refraction effect A Bragg reflector (DBR) structure or a decentralized Bragg reflector (DBR) structure, and wherein the fabrication of the optical refractive index variation is irradiating a light beam so that the light beam penetrates a photomask above the non-linear optical element. 19. The laser device according to item 18 in the scope of the patent application, wherein the photomask has a specific grating design. After the light beam is irradiated, an oscillator matching the optical parameter is generated after the photomask ( OP0) Spatial light intensity changes under Bragg conditions. 20. The laser device according to item 18 of the scope of patent application, wherein the light Page 34 1239130 VI. Scope of Patent Application The beam is an optical writing beam, which has the effect of inducing a space charge inside the optical material with a non-linear optical refraction effect. 2 1. The laser device according to item 18 of the scope of patent application, wherein the light beam is located at one of the wavelengths of visible light or ultraviolet (UV) wavelength. 22. The laser device according to item 18 of the scope of patent application, wherein the non-linear optical element is a non-linear optical crystal having a second-order non-linear optical coefficient. 2 3. A laser device using a non-linear optical element to generate a narrow-frequency laser through an optical parameter oscillator (OP0), wherein the non-linear optical element has a dispersion formed by a light refraction effect Feedback structure (DFB) structure or decentralized Bragg reflector (DBR) structure, and wherein the optical refractive index change is made using an interference optical refraction effect writing method, thereby having two crossed mines with an appropriate angle The light beam can generate interference fringes through the interference effect, thereby generating spatial optical intensity modulation in the non-linear optical element. 24. The laser device as described in item 23 of the scope of the patent application, wherein the periodicity of the interference fringes is matched to the Prague conditions desired for the operation of the optical parameter oscillator (OP0). 2 5. A laser device that uses an electro-optical non-linear optical element to generate a narrow-frequency laser through an optical parameter oscillator (OP0), wherein the electro-optical non-linear optical element has an electro-optic effect A distributed feedback (DFB) structure, and wherein a spatially modulated electric field is applied to the electro-optic non-linear optical element, whereby a refractive index along the laser transmission direction is periodically modulated in space, and the refractive index Modulation Periodic System Page 35 1239130 VI. Scope of patent application The Prague conditions that are expected to be operated by this optical parameter oscillator (0P0). I 2 6. A laser device that uses an electro-optical non-linear optical element to generate a narrow-frequency laser through an optical parameter oscillator (OP0). The electro-optical non-linear optical element has a A distributed Bragg reflector (DBR) grating formed by electro-optic effect, and a spatial modulation electric field is applied to the electro-optic non-linear optical element, thereby periodically changing a refractive index in the laser transmission direction in space. And the periodicity of the refractive index modulation is matched to the Bragg condition expected by the operation of the optical parameter oscillator (OP0). 2 7_—A laser device that generates a narrow-frequency laser through an optical parameter oscillator (OP0). The optical parameter oscillator has a distributed feedback (DFB) structure on the surface of a non-linear optical waveguide. The optical feedback of the dispersed Bragg electromagnetic waves that dissipate waves on the surface of this waveguide is sufficient to start the optical parameter oscillation. 28. The laser device according to item 27 in the scope of the patent application, wherein the distributed feedback (DFB) structure is manufactured by a method selected from the group consisting of material etching, ion implantation , Thin film overlay, lithographic process, and combinations thereof. 29. A laser device that generates a narrow-bandwidth laser via an optical parameter oscillator (OP0). The optical parameter oscillator has a decentralized Bragg reflector (DBR) on the surface of a non-linear optical waveguide. ) Structure, by which the optical feedback of the dispersed Bragg electromagnetic wave that dissipates waves on the surface of the waveguide is sufficient to start the optical parameter oscillation. 1239130 on page 36 6. The scope of patent application is 30. The laser device as described in item 29 of the scope of patent application, wherein the distributed Bragg reflector (DBR) structure is manufactured by the following group method, It includes: material engraving, material implantation, film overlay, lithography process, and combinations thereof. 31 · —A laser device that generates a narrow-frequency laser via an optical parameter oscillator (0P0). The optical parameter oscillator has a distributed feedback (DFB) structure or a dispersion inside a non-linear optical waveguide. Bragg reflector (DBR) structure, whereby the optical feedback of the dispersed Bragg electromagnetic waves inside the waveguide is sufficient to start the optical parameter oscillation. 32. The laser device according to item 31 of the scope of patent application, wherein one of the distributed feedback (DFB) structure and the distributed Bragg reflector (DBR) structure is a type of light refraction effect. 3 3. The laser device according to item 31 of the scope of patent application, wherein one of the distributed feedback (DFB) structure or the distributed Bragg reflector (DBR) structure belongs to an electro-optic effect type. 34. The laser device as described in item 31 of the scope of the patent application, wherein one of the distributed feedback (DFB) structure and the distributed Bragg reflector (DBR) structure utilizes one selected from the following groups: Method for making, including: thermal infiltration, ion implantation, lithography process, and combinations thereof Page 37