DE10123137C1 - Integrated optical field width transformer for adiabatic monomode field matching uses integrated optical waveguide with opposing vertical and lateral tapers - Google Patents

Abstract

In the integrated optics, cross-sectional changes in the connection of waveguides by means of field width transformers are adjusted by an adiabatic field adaptation. Photonic crystals represent artificial gratings, the periodic structures of which are adapted to the wavelength of the light wave. Integrated defect waveguides are generated by interrupting the periodic structures. Due to their small dimensions, photonic crystals are difficult to handle and can only be connected to other optical components with great difficulty. To couple the defect waveguide (12) to an integrated optical waveguide (3), the field width transformer (1) according to the invention therefore has both a vertical tapering (14) and an opposing lateral tapering (15) of the integrated optical one in a taper area (13) Waveguide (3). The ratio of height (H) to width (B) is dimensioned using known numerical methods in such a way that monomode in the waveguide (3) and optimal field overlaps are guaranteed. The field width transformer according to the invention can be monolithically integrated with one or more further field transformers of the same or different types to form dual or multiple adapters, so that an optimal and versatile coupling of photonic crystals to different optical components is possible.

Description

The invention relates to an integrated optical field width transformer for adiabatic, monomodal field adaptation between a optical component and a planar waveguide circuit associated integrated-optical waveguide, which in a taper area continuous, except for at least one between the waveguide layer and Buffer layer arranged vertical layer tapering of the conductive layer Has waveguide height.

In the integrated optics, the connection of waveguides cross over cut changes on. The propagating light waves must either undergo a widening or concentrating field width change to abrupt transitions with poor coupling efficiency as a measure to avoid coupling losses. The goal is an adiabatic field adaptation, at which maintains the guided light output in one mode.

Photonic crystals represent artificial two-dimensional gratings whose periodic structures are adapted to the wavelength of the light wave. By forming periodic hole arrangements (or also column arrangements) in the light-guiding semiconductor material right into the underlying buffer layer, different resulting refractive indices can be generated. In this way, band gaps can be created in whose energy states or frequencies the light wave cannot propagate ("forbidden zone"). This gives the possibility, by locally changing the refractive index in a photonic crystal, to produce a waveguide as an "allowed area" with possible energy states or frequencies for the light waves, in which the light is guided reliably even with sharp changes in direction. While transmissions can occur in conventional light waveguides due to the laws of refraction, the light wave in the defect waveguide cannot leave it due to its energy state. One possibility for the generation is the provision of areas without deep etching, so that the "spreading ban" for the waves is lifted in this area. In this case one speaks of a "defect waveguide". Such defect waveguides based on photonic crystals are characterized by a strong optical constriction. This property enables extremely small optical components with areas of a few 10 µm ^{2 to} be realized. These small components, in which the diameter of the defect waveguide is in a range of 1 µm, can practically not be used as individual components. In addition, the problem of optical coupling to other optical components, which is very large with a field diameter of an optical glass fiber in the region of 12 μm, has not yet been solved. There are first approaches to both problems in the prior art.

In addition to the generally known possibility of using photonic crystals Pour edge length of less than 100 µm into a substrate and through To expose grinding and polishing to the end faces, it is from the Essay [I] "Low-loss channel waveguides with two-dimensional photonic crystal boundaries "(C.J. Smith et al., Appl. Phys. Lett., Vol. 77, No. 18, Oct. 2000, pp. 2813-2815), via a layered waveguide without lateral To couple field guidance. In both cases, however, only a few percent Coupling efficiency achieved, which are unacceptable for practical applications.

Several approaches have been published for coupling the photonic crystal to its environment using the principle of simple transformation of the optical field. From article [II] "Coupled-resonator optical waveguide: a proposal and analysis" (A. Yariv et al., Opt. Lett., Vol. 24, No. 11, June 1999 , pp. 711-713) and the Article [III] "Propagation and second harmonic generation of electromagnetic waves in a coupled-resonator optical waveguide" (Y. Xu et al., J. Opt. Soc. Am. B, Vol. 17, No. 3, March 2000 , pp. 387-400) it is known to change the lattice spacing of the photonic crystal. However, the integration of a field transformer directly into the material of the photonic crystal, the production of which requires a very time-consuming lithography writing process and highly precise structuring in the nano range, is unsatisfactory from an economic point of view. For the adiabatic transformation of the field by changing the translational symmetry laterally, the article [IV] "Adiabatic coupling between conventional dielectric waveguides and waveguides with discrete translational symmetry" (Y. Xu et al., Opt. Lett. 25, Vol. 25 , No. 10, May 2000 , pp. 755-757) describes a coupling / decoupling via a layer waveguide outside the photonic crystal, which is designed in the form of individual columns. For reasons of stability, however, this type of photonic crystal is less interesting than a photonic crystal which is based on the formation of holes. The waveguides required for the coupling described must also be so thin that the lateral formation of a tip is very difficult to manufacture. A photonic crystal with column formation is also from the article [V] "Photonic crystal waveguides: Out-of-plane losses and adiabatic modal conversion" (M. Palamaru et al., Appl. Phys. Lett. 78, Vol. 78, No 11, March 2001 , pp. 1466-1468). The waveguide is created by eliminating several rows of columns. It also has holes to change its refractive index. The light wave always strives in areas with a higher refractive index. An adiabatic transformation of the field by reducing the hole diameter of the defect waveguide at its end in a taper area is described. In the direction of the reduction, the columns in the taper area are also reduced in order to support the coupling-in / coupling-out effect. Holes and columns show a decreasing depth in the taper area. Here too, the integration of the field transformer into the material of the photonic crystal is questionable from an economic point of view. In addition, a defined, highly precise modification of the etching depth in the extremely small structures is technologically very difficult to achieve. In addition, the taper area is extremely sensitive to mechanical interference.

The integration of a field transformer in the photonic crystal is therefore on the one hand disadvantageous in terms of production technology, on the other hand it does not allow better handling of the photonic crystal, which is very sensitive to destruction due to the integrated tapering. Field width transformers, which are monolithically integrated as a separate optical component in a planar waveguide circuit, are much easier to manufacture and less sensitive to use. The integrated combination then has a size that is easy to handle and is largely insensitive to mechanical interference. Such an integrated combination is, for example, from the paper [VI] "Monolithic Integration of Lasers, Photodiodes, Waveguides and Spot Size Converters on GaInAsP / InP for Photonic IC Applications" (M. Hamacher et al., IRPM2000, May 2000 , USA, paper MAY 3, p21.24). The “spot size converter” described here is a polarization-independent field width transformer designed as a rib waveguide as an interface between the planar waveguide circuit (“optical chip”) and a glass fiber. For this purpose, the rib waveguide has a lateral taper, which runs from the integrated optical waveguide on the chip to the glass fiber. As a result, the field guidance in the waveguide layer is continuously reduced, so that the guided light wave drifts downward in the direction of the substrate. Lateral drifting apart of the shaft is intercepted by a constant focusing rib ("outer rib").

The state of the art on which the present invention is based is described in US Pat EP 0890121 discloses. It becomes an optical field transformer adiabatic, monomodal field adaptation described for a Coupling an optical fiber as an optical component to an integrated optical waveguide of a planar waveguide circuit in the form of a is formed photonic integrated circuit. The field transformer,  the as an independent component with the circuit mono is integrated lithically, has a ribbed waveguide, which in one Taper area is provided with a vertical tapering of the rib height. This can be executed with changing inclination and runs down to the Buffer layer underneath the waveguide layer. This is in Taper area constantly narrowed and forms a constant focus rib for the light wave to be guided. The vertical taper is also used Field guidance in the rib area continuously decreased and the light wave after pushed below and intercepted laterally by the focusing rib. there the propagation image of the optical field is also adjusted so that the known field width transformer is polarization independent. The one with the known field width transformer components to be coupled such a size ratio that a simple tapering adiabatic, monomodal field adaptation can be brought about. to Coupling with another optical component compared to the conventional components significantly reduced dimensions known field transformer, however, is not suitable.

The object of the present invention is therefore a field widths Transformer of the generic type described at the outset form that it is used for field matching between an integrated optical Waveguide and an optical component is suitable, the dimensions conditions are considerably lower than that of the integrated optical waveguide. there the good performance characteristics of the known field width trans formators for larger component dimensions are retained.

The solution according to the invention for this task for an integrated optical field transformer for the adiabatic, monomode field Match between an optical component and a planar Waveguide circuit associated integrated-optical waveguide exists therefore in that the optical component has a photonic crystal at least one generated in a periodic hole arrangement  Defective waveguide, from which the vertical taper towards the integrated optical waveguide extends, and that the integrated optical Waveguide one for vertical tapering of the waveguide height continuously has opposite lateral tapering of the waveguide width.

The field width transformer according to the invention as a bidirectional optical Component is monolithically integrated with the photonic crystal. Thereby ensures that the optical field remains in the material with the higher refractive index a divergence of the optical field with high numerical aperture is avoided, as in simple collision coupling points occurs. Due to the high refractive index semiconductor material The good field width adjustment is achieved through a strong constriction. The Field width transformer has a double counter in its taper area current tapering. Starting from the integrated optical waveguide the light-guiding waveguide in the field width transformer in the direction of the Defective waveguides are becoming ever narrower and at the same time always higher. Thereby put the Cross-sectional dimensions of the integrated optical waveguide on the one side and the defect waveguide on the other side initial and Final cross-section of the waveguide in the field width transformer in the first Approximation firm. There is a continuous between its two ends Cross-section transfer for adiabatic adaptation of the two optical Fields. However, the main criteria for the change history are the matches the focus of the field and the maintenance of single mode in the waveguide to avoid radiation losses when adapting the field and to achieve a high coupling efficiency. The field focus indicates the center of the propagation field, its location in the waveguide layer depends on the material composition. Only when the Field focus of the propagation fields to be coupled, at least vertically  match, the greatest possible field overlap can be achieved. To determine the focal points and to calculate the eigenmodes of a Light wave depending on the height and width dimensions of the Waveguides exist in a number of commercially available computers supported calculation rules that are well tried and easily applied can be.

With the field width transformer according to the invention, a good Alignment of the two waveguides in the manufacturing process to each other efficiently Couplings through adiabatic field adaptation in a mode with losses of less than -1 dB can be achieved. Compared to the one mentioned above solution approaches for a known in the field of photonic crystals Coupling can be seen here as a significant increase in performance. Compared to the known approaches for an adiabatic field fit has the field width transformer according to the invention essential better use properties because it has a large mechanical Stability. It is also much easier to manufacture. Farther are due to the monolithic integration of the invention Field width transformer with the photonic crystal dimensions in created an area that is easy to use at all enable such small optical components.

Defective waveguides in photonic crystals are very narrow (e.g. 0.7 µm) and relatively high (e.g. 1.2 µm). Essential for efficient field adjustment at the field width transformer according to the invention is in good agreement alignment of the two focal points, that is, a good field overlap. However, this can be the case with the defect waveguides, which are caused by deep etching of the Extend hole arrangement down into the buffer layer, depending of the material composition, if necessary, not only by abrasion the waveguide layer can be reached in the taper area. With a continuation The field width transformer according to the invention is therefore provided that the vertical tapering of the waveguide height up to the buffer layer  extends. The good field adaptation to the defect waveguide of the photo African crystal is then over the strong constriction in the high refractive index Semiconductor material achieved by the vertical tapering of the light-guiding Waveguide layer continuously down through this material down to the low-index optical buffer layer.

In the manufacture of optical components, in particular, is also based on their size dimensions to be observed, those in the monolithic integration in semiconductor materials also as low as possible for cost reasons, but still should be manageable. If according to a next invention the vertical and lateral tapering of the integrated optical Waveguide with changing inclinations, the length of the Taper range can be reduced to the absolutely necessary minimum. There will also be an improvement in the shifting of the vertical Spreading image achieved. Basically, the two tapering can with different inclinations or in the case of linear tapering different slopes.

The present invention is based on counter-double tapering ("Taper") of the light-guiding waveguide layer. It can be for example, a buried waveguide that insulates laterally and has a high refractive index contrast to its surroundings. According to Another embodiment of the invention can also provide that the Integrated optical waveguide is a ribbed waveguide that is vertical and has lateral tapering in the area of its rib. Opposite the horizontal The structure of a buried waveguide includes rib waveguides vertical structuring through simple mask technology with deep etching easier to manufacture. The opposite tapering in the fiction Appropriate field transformer can then be relative in terms of manufacturing technology simply by the appropriate geometric design of the rib of the Rib waveguide can be realized.  

As already explained above, a photonic crystal is only through the monolithic integration with the field width transfer according to the invention mator relatively easy to use. There are also different connections of the photonic component islands with adjustment tolerances in the submicro range of meters to other optical components possible. For that it is in accordance a next embodiment of the field width transformer according to the Invention particularly advantageous if the integrated optical waveguide with at least one further integrated optical waveguide Field width transformer is connected monolithically integrated. Through this constructive design is an optical adapter with two or more Interfaces created internally via the integrated optical waveguide, which can be a ribbed waveguide in particular, connected. The first interface is always with the defect waveguide connected photonic crystal, the other interface in the further However, span transformers are freely available. These can be used Coupling to different components can be designed differently. In particular, it can be provided after the next invention is continued be that the at least one further field width transformer for Field adaptation to another defect waveguide in a photonic Crystal is formed. The further field width transformer then has one identical construction to the first field transformer. In the design complete networks can then be used as a multiple optical adapter optical networking of a variety of optical crystals in monolithic Integrated design manufactured on a common optical chip become.

Furthermore, according to another embodiment of the invention, too be provided that the at least one further field width transformer for Field adaptation to a single-mode optical fiber is formed. In order to is a coupling of the photonic component islands via or multiple glass fibers integrated into an environment outside the monolithic Chips possible. The further field width transformer can in particular  as disclosed in EP 0890121 formed with a TM focusing rib his. The adapter no longer has a symmetrical structure, but instead shows different interfaces. The connecting one Optical waveguide integrated in the adapter first shows the defect waveguide coming a flattening widening, which then in again an increasing narrowing passes over. In the middle between the Interfaces, the integrated optical waveguide has a cross section, adapted to the optical field of a photonic circuit (PIC) is. This can also be the further optical component to be coupled, if according to a next development of the invention the at least one additional field transformer for field adaptation to a photonic Circuit is formed. With such an adapter can then complete optical circuits in a common optical integration getting produced.

The merge described is particularly useful if all Components involved have a similar layer structure and therefore can be processed at the same time. In addition, they must all be mono work fashionably. This can be, for example, the connection of a or more lasers or to waveguide feeds to one or more Act photodiodes. In the case of particularly complex optical ones Components that have a complex layer structure or are designed multimode, is a training of the field transformer advantageous according to the invention, in which the integrated optical waveguide Interface for shock coupling with another optical component, in particular an optical board. There is a butt coupling a lower coupling efficiency compared to integrated couplings, therefore but also different material combinations, for example between the expensive compound semiconductors with the cheaper silicone, silica or polymer materials. Because the area of the semiconductor material used through the necessary many process steps for the production of integrated Circuits with optoelectronic elements (OEIC) such as lasers and  Photodetectors are "valuable", and these process steps may not with the process steps to manufacture the optical circuit network are identical, a planar-hybrid integration can in many cases be economically cheaper than a completely monolithic solution. The OEICs, the ultra-compact photonic crystal devices with the tapers of present invention included as discrete chips no longer would be mechanically grasped, are then upside down ("up-side-down") in flip-chip technology in mechanical guides on the optical board inserted, if necessary when making electrical contact actively adjusted to the integrated optical waveguide and until the end of Formation of the flip-chip connection mechanically fixed. This technology can be seen in analogy to the microelectronic multi-chip module technology, at which also houses certain functions in a monolithic chip and these chips are then placed on a motherboard form a planar hybrid integrated unit, which is then coupled to the outside world becomes.

Between the two waveguides to be adapted in the invention Field width transformer must be used when dimensioning the taper area Condition of single mode must be met. When using Waveguide networking using interferometric effects (e.g. used in directional couplers or multimode interference couplers) is one single-mode design required. For example, for the feeder Waveguide to photodiodes can, however, according to a next embodiment the field width transformer according to the invention can be advantageously provided, that the integrated optical waveguide is connected to the taper area has a run-out area in which the geometric dimensioning abandoned the condition of single mode and allowed multi-mode is. The configuration according to the invention is achieved by such a configuration Span width transformer of a special versatility that through the different adapter designs are already very large.  

Photonic crystals can also have multiple parallel defect waveguides or have branched defect waveguides. According to another invention embodiment of the invention, it is therefore advantageous if the field trans formator according to the invention with further field transformers of the same type parallel to different defect waveguides of a photonic crystal is integrated monolithically integrated. So every defect waveguide is with one own field transformer according to the invention monolithically integrated. The branching can be performance-dependent or wavelength-selective via a appropriate switch (or unifier). To the individual defect Waveguides can then be integrated using optical waveguides monolithically integrated optoelectronic components (e.g. laser or photodiodes) can be coupled.

Depending on the application, the field width transformer according to the invention or its training forms can be implemented in different layer structures. According to a next continuation of the invention, it can be provided on the one hand that the monolithically integrated layer structure in a higher refractive, in particular quaternary, III-V semiconductor connecting material as a waveguide layer and a low-refractive, in particular binary, III-V semiconductor connecting material as an optical limiting layer is trained. A common material pairing is, for example, GaInAsP with a vacuum wavelength of 1.3 µm and InP. On the other hand, it can also be advantageously provided in the invention that the monolithically integrated layer structure is formed in a higher refractive index semiconductor material, in particular silicon, as a waveguide layer and a semiconductor material which refracts from it, in particular SiO _x , as an optical limiting layer. In this way, for example, a coupling to another PIC made of a silicon-based semiconductor material (Silicon-on-Isolator SOI), which serves as an optical board for receiving III / V-PICs or -OEICs, can be realized. The connection to the fiber optic world and the optical networking circuit are then carried out on an inexpensive material system on the optical board. In the OEICs, the laser and detector functions can then be monolithically integrated with photonic crystal components in an adequate material system.

The field width transformer according to the invention is relatively easy to manufacture due to its compact construction. In particular, the vertical tapering of the height of the integrated optical waveguide can be generated by transferring a vertically tapered lacquer ramp. Epitaxial (a crystalline) growth process for the production of both lateral tapering (exposure through a stationary resist mask) and vertical tapering (exposure through a portable resist mask, compare EP 0973188 A1) for span transformers are known per se. In the double-tapered field transformer according to the invention, for example in training with a ridge waveguide, both known methods are combined. First, an epitaxial layer structure of the starting material takes place. Then the semiconductor fin is defined with a first mask (e.g. made of SiN _x material) with lateral tapering and formed in a dry etching step. To form the vertical tapering, the photoresist is then exposed for different lengths of time by means of a second mask which can be moved during the photolithographic exposure of the photoresist layer, which leads to the formation of a vertical lacquer ramp after development. In a further dry etching step, the vertical lacquer tapping is then transferred to the rib waveguide, which has already been tapered laterally, as far as possible into the buffer layer, so that it now has the desired double tapering in the desired dimensions.

Forms of the invention are described below with reference to schematic figures, for better viewing in some strong distorted scaling are shown, explained in more detail. It shows:  

Fig. 1 a perspective view of the transformer of the span lengths according to the invention,

Fig. 2 is a diagram for field adjustment by the double tape tion of the field width transformer,

Fig. 3 shows a dual adapter for coupling a defect waveguide having a glass fiber,

Fig. 4 shows another dual adapter for coupling a defect waveguide having a glass fiber,

Fig. 5 shows a multiple adapter for producing a network of photonic crystals,

Fig. 6 is a parallel connection of a photonic crystal to various optoelectronic devices,

Fig. 7 is a performance-based connection of a photonic crystal to various optoelectronic components, and

Fig. 8 is a wavelength dependent connectivity of a photonic crystal in various optoelectronic devices.

Fig. 1 shows an integrated optical field width transformer 1 for adiabatic single-mode field matching between a photonic crystal 2 and an integrated optical waveguide 3, both of which are monolithically formed in a waveguide layer 4. Below the waveguide layer 4 is a layer structure of at least two buffer layers 5 , 6 and a conductive layer 7 on a substrate 8 . In the selected exemplary embodiment, the waveguide 3 is designed as a rib waveguide 9 . The photonic crystal 2 as a component island with size dimensions in the submicron range has a periodic hole arrangement 10 . The resulting refractive index is changed in this area by the hole-like deep etching 11 , which extends into the upper buffer layer 5 , in such a way that a band gap for the light wave arises.

This can only spread in a defect waveguide 12 , which is structured by the elimination of the deep etching.

The field width transformer 1 has a taper area 13 , in which the rib waveguide 9 is double-tapered. On the one hand, a vertical taper 14 of the height H of the rib 16 extends from the defect waveguide 12 in the direction of the rib waveguide 9 . On the other hand, the vertical taper 14 runs counter to a lateral taper 15 of the width B of the rib 16 (indicated by corresponding arrows in FIG. 1). The double, opposing tapering makes the rib 16 of the rib waveguide 9 ever narrower and higher in the direction of the photonic crystal 2 . The cross-sectional course depends on two criteria. First, 13 single-mode must be guaranteed in the entire taper area (see FIG. 2). In addition, in order to produce as large a field overlap as possible, an at least vertical alignment of the centers of gravity of the optical fields of defect waveguide 12 and rib waveguide 9 must be achieved (see FIG. 3). For this purpose, depending on the effectiveness of the selected semiconductor material combination, it may be necessary to let the vertical taper 14 run into the upper buffer layer 5 (shown in the selected exemplary embodiment in FIG. 1). As a result, the height H as a measure of the vertical tapering 14 is a parameter which can be set by controlled deep etching for the field overlap and thus for the coupling efficiency to be achieved of less than -1 dB of the field width transformer 1 according to the invention.

In FIG. 2 is a diagram for determining the correct ratio of height H to width B of the light-guiding waveguide layer 4, the ridge waveguide 9 shown in the chosen embodiment of the rib 16. The hexagonal hole pattern has a hole spacing (lattice constant) of 0.4 µm. This corresponds to a material fill factor of 0.6. The optical field width is 0.6 µm. The corresponding rib cross sections in the taper area 13 are assigned for clarification. The simulation was created with an applicant's own computer program (the same simulation can be carried out, for example, with the commercially available program "FullWAVE" from RSOFT), which offers a two-dimensional method of finite differences for TE and TM modes. Depending on the height H of the rib 16 and its width B, the propagation fields are calculated separately for the TE mode and the TM mode. The TE mode propagation image is shown for a quaternary waveguide layer 4 with a vacuum wavelength equivalent to the energy gap of 1.3 μm (Q-1.3 μm GaInAsP) on a binary buffer layer 5 (InP). In the calculation, the dimensions are chosen such that no secondary modes occur in the rib 16 and maximum field overlaps are achieved at the beginning and end of the taper region 13 . At the transition to the photonic crystal 2 , the rib 16 has a height H which extends into the buffer layer 5 . The diagram also shows that the relationship between height H and width B is inversely proportional in a large section.

FIG. 3 shows a dual adapter 20 which is used to couple the defect waveguide 12 to an optical glass fiber 21 . With the field width transformer 1 for coupling the defect waveguide 12 to the ribbed waveguide 9 , a further field transformer 22 is monolithically integrated, which serves to couple a ribbed waveguide 23 to the glass fiber 21 . Such a field width transformer 22 is known from EP 0890121 and has vertical tapering with variable inclination. FIG. 4 also shows a dual adapter 30 for coupling to an optical glass fiber 31 with a similar further field width transformer 32 , which is known from the paper [VI] cited above and has only a lateral tapering in its rib waveguide 33 . the known field width transformer 32 is used to expand the optical field of a typical GaInAsP / InP chip waveguide for the wavelength of 1.5 μm (eg rib width: 2 μm; rib and layer material: GaInAsP material with an energy gap equivalent Vacuum wavelength of 1.3 µm (short: Q-1.3); Q-1.3 thickness: 1 µm; rib height: 0.3 µm; Q-1.3 guiding layer below the rib waveguide) onto the optical field of a standard singlemode glass fiber. The monolithically integrated photonic crystal 2 uses the same Q-1.3 layer to produce the vertical guide. The effect of the two field width transformers 22 , 32 is identical, in both the light wave is pushed down. Which embodiment is chosen depends on the materials used and the installation conditions.

Combinations of the field width transformer according to the Invention with another field width transformer for coupling a photonic circuit or with an identical field width trans formator according to the invention for coupling to a further defect waveguide of another photonic crystal possible. For connecting The field width transformer can also directly integrate non-integrated components have a joint at the end of its taper area. There can also be a Section of an integrated optical waveguide can be provided in which Connection of a multi-mode component the condition of Single mode has been abandoned and several modes are in parallel can spread.

In the previous figures, adapters with two interfaces have been shown. In FIG. 5, a multiple adapter 40 is shown with three interfaces in monolithic integrated construction, with the aid of an optical network 41 from a plurality of photonic crystals 42, 43, can be prepared ment islands as Bauele 44th The coupling to their defect waveguides 45 , 46 , 47 takes place via a plurality of field width transformers 1 , 48 , 49 according to the invention (indicated in the figure by a symbol with a double, opposing tapering), which are connected via a rib waveguide 9 in a Y shape and can have different dimensions, each adapted to the photonic crystals 42 , 43 , 44 to be coupled. A 3 dB division of the paths in the Y is shown, other divisions, in particular with a power-maintaining coupling arrangement, are possible. The advantage of such an arrangement is its small space requirement and the good integration of the very small photonic crystals. Such a monolithically integrated adapter with a plurality of output interfaces can also be designed for coupling a plurality of glass fibers, integrated optical components or other optical components for coupling to one or more defect waveguides of photonic crystals.

In FIGS. 6, 7 and 8, a parallel use of a plurality of field lengths is shown transformers according to the invention, which are coupled to a plurality of monolithically integrated defect waveguide. In FIG. 6, 50 four parallel defect waveguide 51 are integrated into the photonic crystals. Each defect waveguide 51 is connected via a field width transformer 52 according to the invention with an integrated optical waveguide 53 with an optoelectronic component 54 . , , 57 connected. This can be, for example, laser or photodiodes. The photonic crystal 60 in FIG. 7 shows a defect waveguide 61 , which is divided into two defect waveguides 62 , 63 via an integrated Y-switch as a 3 dB coupler. These are connected via two field width transformers 64 , 65 to two integrated optical waveguides 66 , 67 , which lead to two monolithically integrated optoelectronic components 68 , 69 . Finally, in FIG. 8, a photonic crystal 70 shows a defect waveguide 71 which , depending on the wavelength, conducts the light signals to two defect waveguides 72 , 73 via an integrated wavelength-selective switch, which can also function as a bidirectional component as a wavelength-selective combiner. These are in turn connected to two field width transformers 74 , 75 according to the invention via two integrated optical waveguides 76 , 77 with two monolithically integrated optoelectronic components 78 , 79 .

LIST OF REFERENCE NUMBERS

1

Field width transformer according to the invention

2

photonic crystal

3

integrated optical waveguide

4

Waveguide layer

5

upper buffer layer

6

lower buffer layer

7

conductive layer

8th

substratum

9

Ridge waveguide

10

periodic hole arrangement

11

hole-like deep etching

12

Defect waveguide

13

Taperbereich

14

vertical tapering

15

lateral tapering

16

rib

20

dual adapter

21

optical fiber

22

additional field transformer

23

Ridge waveguide

30

dual adapter

31

optical fiber

32

additional field transformer

33

Ridge waveguide

40

multiple adapter

41

optical network

42

.

43

.

44

photonic crystal

45

.

46

.

47

Defect waveguide

48

.

49

Field width transformer according to the invention

50

photonic crystal

51

Defect waveguide

52

Field width transformer according to the invention

53

integrated optical waveguide

54

, , ,

57

optoelectronic component

60

photonic crystal

61

.

62

.

63

Defect waveguide

64

.

65

Field width transformer according to the invention

66

.

67

integrated optical waveguide

68

.

69

optoelectronic component

70

photonic crystal

71

.

72

.

73

Defect waveguide

74

.

75

Field width transformer according to the invention

76

.

77

integrated optical waveguide

78

.

79

optoelectronic component
B waveguide width
H waveguide height
TE vertical fashion component
TM horizontal fashion component

Claims (16)

1. Integrated optical field transformer ( 1 ) for adiabatic, monomode field adaptation between an optical component and an integrated optical waveguide ( 3 ) belonging to a planar waveguide circuit, which in a taper area ( 13 ) has a continuous, at least one between waveguide layer ( 4 ) and guide layer ( 7 ) arranged buffer layer ( 5 ) vertical tapering ( 14 ) of the waveguide height (H), characterized in that the optical component is a photonic crystal ( 2 ) with at least one defect waveguide generated in a periodic hole arrangement ( 10 ) ( 12 ), from which the vertical tapering ( 14 ) extends in the direction of the integrated optical waveguide ( 3 ), and that the integrated optical waveguide ( 3 ) is continuously opposite to the vertical tapering ( 14 ) of the waveguide height (H) has lateral tapering ( 15 ) of the waveguide width (B). 2. Integrated optical field width transformer according to claim 1, characterized in that the vertical tapering ( 14 ) of the waveguide height (H) extends into the buffer layer ( 5 ). 3. Integrated-optical field transformer according to claim 1 or 2, characterized in that the vertical and the lateral tapering ( 14 , 15 ) of the integrated-optical waveguide ( 3 ) run with changing inclinations. 4. Integrated-optical field transformer according to one of claims 1 to 3, characterized in that the integrated optical waveguide ( 3 ) is a rib waveguide ( 9 ) which the vertical and lateral tapering ( 14 , 15 ) in the region of its rib ( 16 ) having. 5. Integrated-optical field transformer according to one of claims 1 to 4, characterized in that the integrated optical waveguide ( 3 ) with at least one further integrated-optical waveguide of a further field transformer ( 22 ; 32 ; 48 , 49 ) is connected monolithically integrated. 6. Integrated-optical field transformer according to claim 5, characterized in that the at least one further field transformer ( 48 , 49 ) for field adaptation to a further defect waveguide ( 46 , 47 ) is formed in a photonic crystal ( 43 , 44 ). 7. Integrated optical field transformer according to claim 5, characterized in that the at least one further field transformer ( 22 ; 32 ) is designed for field adaptation to a monomode optical glass fiber ( 21 ; 31 ). 8. Integrated-optical field transformer according to claim 5, characterized in that the at least one further field transformer ( 48 , 49 ) is designed for field adaptation to a photonic circuit. 9. Integrated-optical field transformer according to one of claims 1 to 4, characterized in that the integrated optical waveguide ( 3 ) has an interface for shock coupling with another optical component. 10. Integrated-optical field transformer according to one of claims 1 to 9, characterized in that the integrated optical waveguide ( 3 ) following the taper area ( 13 ) has an outlet area in which the condition of the mono-mode and multimode are given up in the geometric dimensioning is allowed. 11. Integrated optical field transformer according to one of claims 1 to 10, characterized in that it with additional field transformers ( 52 ; 64 , 65 ; 74 , 75 ) of the same type in parallel to different defect waveguides ( 51 ; 62 , 63 ; 72 , 73 ) a photonic crystal ( 50 ; 60 ; 70 ) is integrated in a monolithic manner. 12. Integrated optical field transformer according to one of claims 1 to 11. characterized in that the monolithically integrated layer structure in a higher refractive III-V Semiconductor connection material as a waveguide layer and one in comparison and III-V semiconductor connecting material that breaks down as optical Boundary layer is formed.   13. Integrated optical field transformer according to one of claims 1 to 11. characterized in that the monolithically integrated layer structure in a higher refractive index Semiconductor material as a waveguide layer and one in comparison low-index semiconductor material as an optical confinement layer is trained. 14. Integrated optical field transformer according to claim 9, characterized in that the other optical component is an optical board. 15. Integrated optical field transformer according to claim 12, characterized in that the higher refractive index III-V semiconductor connecting material is quaternary and that in Comparison to this low-index III-V semiconductor interconnect material is binary. 16. Integrated optical field transformer according to claim 13, characterized in that the higher refractive index semiconductor material is silicon and the low refractive index semiconductor material is SiO _x .