CN218828414U

CN218828414U - Double-ridge semiconductor optical amplifier with high coupling efficiency

Info

Publication number: CN218828414U
Application number: CN202223317693.6U
Authority: CN
Inventors: 蔡俊原; 顾千澜; 费俊娇
Original assignee: Xiamen Hengguangxinrui Technology Co ltd
Current assignee: Xiamen Hengguangxinrui Technology Co ltd
Priority date: 2022-12-12
Filing date: 2022-12-12
Publication date: 2023-04-07
Anticipated expiration: 2032-12-12

Abstract

The utility model discloses a high coupling efficiency's double flute ridge type semiconductor optical amplifier, semiconductor optical amplifier main part and optic fibre including mutual coupling, semiconductor optical amplifier main part includes from supreme substrate, buffer layer, lower waveguide layer, quantum well layer, upper waveguide layer and the upper cover layer that sets gradually down, the utility model discloses the active area comprises quantum well and upper and lower waveguide layer, and quantum well figure is less, and upper and lower waveguide layer thickness broad constitutes great optical cavity structure, and the light wave can expand in big optical cavity, and narrower ridge waveguide structure has restrained the high-order transverse mode, and most high-order transverse mode can be restrained to the slot width that is not less than 3 mu m, and nearly circular shape light beam output can be realized to double flute ridge waveguide structure, has slowed down the difference of size in X and Y direction for semiconductor optical amplifier exports the mode field and the optic fibre phase-match, has effectively improved coupling efficiency between them.

Description

Double-ridge semiconductor optical amplifier with high coupling efficiency

Technical Field

The utility model relates to a semiconductor optoelectronic device technical field specifically is a high coupling efficiency's two ditch ridge type semiconductor optical amplifier.

Background

Semiconductor optical amplifiers are widely used in optical communications, and can be used for amplifying optical signals and processing optical signals. In the field of optical communication, the amplification effect of a semiconductor optical amplifier is mainly applied to three aspects: (1) Power amplification is used to increase the laser power used as a transmitter; (2) The in-line amplifier is used for compensating the transmission loss of the long-distance connection of the optical fiber and other transmission media; and (3) the signal is used as a preamplifier to improve the sensitivity of the receiver. In addition to the application of optical amplification, the nonlinearity of semiconductor optical amplifiers is also used in cross gain modulation (XGM), cross phase modulation (XPM), self Phase Modulation (SPM), quad mixing (FWM) to achieve wavelength conversion, and high speed Wavelength Division Multiplexing (WDM) and Time Division Multiplexing (TDM) networks to achieve high speed all optical switching.

In the prior art, a semiconductor optical amplifier mostly adopts a buried heterostructure, and a waveguide generally adopts modes of an inclined waveguide or a bent waveguide and the like to reduce noise. The structure has the problems of low gain efficiency, large vertical divergence angle and the like, the waveguide structure of the optical fiber is a symmetrical cylindrical structure, so that the eigenmode field of the optical fiber is a symmetrical circular light spot, and the eigenmode field of the existing semiconductor optical amplifier is an elliptical light spot. Thus, the difference in the size and shape of the eigenmode field results in a large mode mismatch between the two, very low coupling efficiency, and small alignment tolerances. Furthermore, since the conventional semiconductor optical amplifier cannot suppress transverse high-order transverse mode lasing, the optical amplifier is characterized in that a far-field optical field pattern is a multi-lobe light spot, so that the optical amplifier is difficult to couple with a single-mode optical fiber. Therefore, the conventional semiconductor optical amplifier cannot meet the requirement of optical fiber communication on the semiconductor optical amplifier with high coupling efficiency.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide a double-groove ridge type semiconductor optical amplifier of high coupling efficiency, quantum well layer structure has improved semiconductor optical amplifier's gain, has reduced threshold current, converts semiconductor optical amplifier's oval facula into the circular facula of approximate symmetry, combines the toper waveguide structure, has improved the coupling efficiency of semiconductor optical amplifier and optic fibre, has improved its alignment tolerance again, has reduced the coupling encapsulation technology degree of difficulty and cost to solve the problem that proposes in the above-mentioned background art.

In order to achieve the above object, the utility model provides a following technical scheme: the utility model provides a high coupling efficiency's double flute ridge type semiconductor optical amplifier, includes the semiconductor optical amplifier main part and the optic fibre of intercoupling, the semiconductor optical amplifier main part includes from supreme substrate, buffer layer, lower waveguide layer, quantum well layer, upper waveguide layer and the upper cover layer that sets gradually down, the upper cover layer includes the ridge waveguide of rectangular shape and etches first slot and the second slot in ridge waveguide both sides respectively, the upper surface of semiconductor optical amplifier main part is provided with first electrode layer, the lower surface of semiconductor optical amplifier main part is provided with the second electrode layer, be equipped with two cavity faces down between waveguide layer and the upper waveguide layer, two the cavity face is light-emitting cavity face and backlight respectively, it has first antireflection coating to plate on the light-emitting cavity face, it has the second antireflection coating to plate on the backlight cavity face.

Preferably, the thickness of the upper cover layer is set to be 1.2 to 3 μm, and the first trench and the second trench are symmetrically disposed about a central axis of the upper cover layer.

Preferably, the side walls of the first groove and the second groove are both vertically arranged, the distance between the inner bottoms of the first groove and the second groove and the upper waveguide layer is T, and the value range of T is 0.2-0.5 μm.

Preferably, the width of the ridge waveguide is set to be W1, the range of W1 is 2-6 μm, the widths of the first trench and the second trench are set to be W2, and the range of W2 is 3-5 μm.

Preferably, the thicknesses of the lower waveguide layer and the upper waveguide layer are set to be 200-800nm.

Preferably, the reflectivity of the first antireflection film and the reflectivity of the second antireflection film are not higher than 0.5%.

Preferably, the first electrode layer and the second electrode layer are window regions for current injection, the first electrode layer and the second electrode layer are both arranged corresponding to the quantum well layer, the quantum well layer is covered by the area of the first electrode layer and the area of the second electrode layer, and silicon oxide insulating layers are arranged around the first electrode layer and the second electrode layer.

Compared with the prior art, the beneficial effects of the utility model are that:

1. the active region is composed of quantum wells and upper and lower waveguide layers, the number of the quantum wells is small, the thicknesses of the upper and lower waveguide layers are wide, a large optical cavity structure is formed, light waves can be expanded in a large optical cavity, the optical limit of the structure is small, the optical limit factor of the structure is not more than 2%, the internal loss of the active region is reduced due to extremely low optical limit, the thicknesses of the upper and lower waveguide layers are not more than 800 micrometers through optimized design, and high-order transverse modes generated due to over-thick waveguide layers are effectively avoided, so that the active region structure can realize low internal loss and inhibit the high-order transverse modes, and has the characteristics of high gain and high output light quality;

2. the narrow ridge waveguide structure inhibits a high-order transverse mode, and the ridge width of not more than 6 mu m ensures that the gain peak value of the high-order transverse mode is not positioned in the ridge waveguide, namely only a fundamental mode in the ridge waveguide is subjected to lasing to inhibit the high-order transverse mode. Moreover, the ridge waveguide width of not less than 2 μm keeps higher mode gain of the fundamental mode on the basis of inhibiting the high transverse mode, so that the ridge waveguide structure of the scheme can effectively inhibit the high-order transverse mode and ensure the effective gain of the fundamental transverse mode;

3. the double-groove structure inhibits a high-order transverse mode, the grooves distributed on two sides of the ridge waveguide are provided with vertical side walls, the high-order transverse mode leaks into high-refractive-index groove regions on two sides of the ridge waveguide due to the deeper etching depth, a complex waveguide mode is generated, and the high-order mode loss is increased due to the overlapping of the high-order mode and the high refractive index on two sides of the double-groove. For the same ridge width, the smaller the groove width is, the stronger the groove effect is, that is, the more the optical mode is overlapped with the high-refractive-index regions on the two sides of the double groove, the larger the high-order mode loss caused by the double groove is, and the groove width of not less than 3 μm can inhibit most of the high-order transverse modes;

4. the double-groove land waveguide structure can realize nearly circular light beam output, the difference of sizes in the X direction and the Y direction is slowed down by adopting the double-groove land waveguide structure, the output light beam is nearly circular by optimizing the ridge waveguide width W1, the groove width W2 and the distance T of the groove distance upper waveguide layer, the shape of the output light beam is changed, the mode field of the output light of the semiconductor optical amplifier is matched with the optical fiber, and the coupling efficiency of the semiconductor optical amplifier and the optical fiber is effectively improved.

Drawings

Fig. 1 is a schematic perspective view of the present invention;

FIG. 2 is a schematic view of the planar structure at the cavity surface of the present invention;

FIG. 3 is a schematic view of the top cover layer of the present invention;

fig. 4 is a schematic view of the planar structure of the upper waveguide layer of the present invention;

fig. 5 is a schematic diagram illustrating the principle of coupling the semiconductor optical amplifier main body with the optical fiber according to the present invention;

FIG. 6 is a schematic diagram of a first antireflection film and a second antireflection film on a cavity surface of the present invention;

fig. 7 is a schematic diagram of the output light spot shape of the present invention.

In the figure: 10. a substrate; 20. a buffer layer; 30. a lower waveguide layer; 40. a quantum well layer; 50. an upper waveguide layer; 60. an upper cover layer; 61. a ridge waveguide; 62. a first trench; 63. a second trench; 70. a first electrode layer; 80. a second electrode layer; 90. a cavity surface; 91. a first antireflection film; 92. a second antireflection film; 100. a semiconductor optical amplifier main body; 110. an optical fiber.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.

Referring to fig. 1-7, the present invention provides a technical solution: a double-groove ridge type semiconductor optical amplifier with high coupling efficiency comprises a semiconductor optical amplifier main body 100 and an optical fiber 110 which are mutually coupled, wherein the semiconductor optical amplifier main body 100 comprises a substrate 10, a buffer layer 20, a lower waveguide layer 30, a quantum well layer 40, an upper waveguide layer 50 and an upper cover layer 60 which are sequentially arranged from bottom to top, the upper cover layer 60 comprises a long-strip-shaped ridge waveguide 61, a first groove 62 and a second groove 63 which are respectively etched on two sides of the ridge waveguide 61, the upper surface of the semiconductor optical amplifier main body 100 is provided with a first electrode layer 70, the lower surface of the semiconductor optical amplifier main body 100 is provided with a second electrode layer 80, two cavity surfaces 90 are arranged between the lower waveguide layer 30 and the upper waveguide layer 50, the two cavity surfaces 90 are respectively a light-emitting cavity surface and a backlight cavity surface, a first antireflection film 91 is plated on the light-emitting cavity surface, and a second antireflection film 92 is plated on the backlight cavity surface.

The quantum well layer 40 is used for generating optical gain, and the quantum well layer 40 includes a well region of a quantum well and a barrier layer of the quantum well, and is located above the lower waveguide layer 30. The quantum well layer 40 has a multi-quantum well structure with compressive strain, and is designed to improve the gain of the semiconductor optical amplifier and reduce noise.

The thickness of the upper cover layer 60 is set to 1.2-3 μm, and the first and

second trenches

62 and 63 are symmetrically disposed about a central axis of the upper cover layer 60.

The side walls of the first groove 62 and the second groove 63 are both vertically arranged, the distance between the inner bottoms of the first groove 62 and the second groove 63 and the upper waveguide layer 50 is T, and the value range of T is 0.2-0.5 μm.

The width of the ridge waveguide 61 is set as W1, the range of W1 is 2-6 μm, the widths of the first trench 62 and the second trench 63 are set as W2, and the range of W2 is 3-5 μm. The ridge width of not more than 6 μm ensures that the gain peak of the high-order transverse mode is not in the ridge waveguide, i.e. only the fundamental mode is lasing in the ridge waveguide and the high-order transverse mode is suppressed. And, the ridge waveguide width of not less than 2 μm maintains a higher mode gain of the fundamental mode while suppressing the high transverse mode. The high-order mode loss is increased due to the overlap of the high refractive index on both sides of the high-order mode and the double trench. For the same ridge width, the smaller the trench width, the stronger the trench effect. That is, the more the optical mode overlaps the high refractive index regions on both sides of the double trench, the larger the high-order mode loss caused by the double trench, and the trench width of not less than 3 μm can suppress most of the high-order transverse mode.

In a conventional semiconductor optical amplifier, two directions X and Y perpendicular to a PN junction and a parallel PN junction are arranged in an active region, and the size difference between X and Y is very large, wherein the size in the Y direction of the parallel PN junction is small, so that output light has different sizes in the X and Y directions, that is, the output light beam is elliptical. Particularly, some high-gain semiconductor optical amplifiers adopt a wide-face or conical waveguide structure, so that the non-uniformity of output light beams is aggravated.

The narrow ridge waveguide 61 inhibits high-order transverse modes, the first grooves 62 and the second grooves 63 distributed on two sides of the ridge waveguide 61 have vertical side walls, the high-order transverse modes are leaked to the areas of the first grooves 62 and the second grooves 63 with high refractive indexes on two sides of the ridge waveguide 61 due to deep etching, the difference of the sizes in the X direction and the Y direction is relieved by adopting a double-groove ridge waveguide structure, and the output light beam is in a nearly circular shape by optimizing the width W1 of the ridge waveguide 61, the width W2 of the first grooves 62 and the second grooves 63 and the distance T between the first grooves 62 and the second grooves 63 and the upper waveguide layer 50.

The thickness of the lower waveguide layer 30 and the upper waveguide layer 50 are set to 200-800nm. Through the optimized design, the thickness of the upper and lower waveguide layers is not more than 800 μm, and the generation of a high-order transverse mode due to the over-thickness of the waveguide layers is effectively avoided.

The reflectivities of the first antireflection film 91 and the second antireflection film 92 are not higher than 0.5%. Both the first antireflection film 91 and the second antireflection film 92 are plated by electron beam evaporation. The first antireflection film 91 and the second antireflection film 92, which have reflectances lower than 0.5% at the light exit facet and the backlight facet, make the gain of the semiconductor optical amplifier 100 higher and make more light waves input into the optical fiber 110.

The first electrode layer 70 and the second electrode layer 80 are window regions for current injection, the first electrode layer 70 and the second electrode layer 80 are both disposed corresponding to the quantum well layer 40, the quantum well layer 40 is covered by the areas of the first electrode layer 70 and the second electrode layer 80, and the silicon oxide insulating layers are disposed around the first electrode layer 70 and the second electrode layer 80.

Wherein, the double-groove land waveguide structure can be replaced by a flat plate coupling structure or a double-groove ridge structure; the first antireflection film 91 and the second antireflection film 92 may also be replaced with antireflection films.

The semiconductor optical amplifier has the advantages of small volume, low cost, wide bandwidth and suitability for active or passive device integration. Among them, the quantum well semiconductor optical amplifier can be used for efficient optical amplification. The quantum well semiconductor optical amplifier can more easily obtain a large saturated output power. The quantum well structure can effectively limit carriers in the well layer, and the leakage of the carriers is reduced. Therefore, the carrier injection efficiency of the quantum well SOA is higher. The strain effect reduces the valence band state density and the transparent carrier density of the quantum well, the absorption between the valence bands and the internal loss. As the transparent carrier density decreases, the effective carrier density contributing to optical gain increases, and the population inversion factor decreases accordingly. Finally, the 3dB gain bandwidth and the noise index of the semiconductor optical amplifier are reduced.

In optical communications, semiconductor optical amplifiers are generally required to maintain single-mode output, and on one hand, gain structures and grating structures are required to be optimized so that the optical amplifiers output in a single longitudinal mode. More importantly, the transverse (lateral) mode of the semiconductor optical amplifier is optimized to be coupled with the single-mode optical fiber, the main method is to limit the high-order transverse mode by using a lateral waveguide structure, and the high-order transverse mode is consumed in the optical amplification process by improving the high-order transverse mode loss. Therefore, the lateral waveguide structure of the semiconductor optical amplifier plays a crucial role in its single-mode output characteristics.

In semiconductor optical amplifiers, the most commonly used lateral waveguide structures are buried heterostructures and ridge waveguide structures. A buried heterostructure is preferred over a ridge waveguide structure because it provides a large relative refractive index difference in the active region. The buried heterostructure incorporates different structures to guide light laterally and laterally. In the lateral direction, light is guided by the relative refractive index difference between the active region and the semiconductor material of the cladding layers between which the active layer is sandwiched. In a lateral direction, light is guided by a buried heterostructure waveguide defined at least partially in a layered structure, the cladding layer and the active region forming part of the layered structure. This allows the optical waveguide to be made very narrow while maintaining a high spatial overlap between the optical fundamental mode and the active region. This provides the following advantages: low operating currents in semiconductor optical amplifiers and optical gain media.

The waveguide structure of the fiber is a symmetrical cylindrical structure, which results in a symmetrical circular spot for its eigenmode field, while the eigenmode field of the semiconductor optical amplifier is an elliptical spot. Therefore, the difference in the size and shape of the eigenmode field between the semiconductor optical amplifier and the external optical fiber results in a large mode mismatch between the semiconductor optical amplifier and the external optical fiber, the coupling efficiency between the semiconductor optical amplifier and the external optical fiber is extremely low, and the alignment tolerance is small.

There are three methods for improving the coupling efficiency between the semiconductor optical amplifier and the optical fiber. The first method is to use a microlens or lensed tapered fiber, however this method only changes the spot size and not the mode field shape, resulting in mode field mismatch and coupling alignment tolerances that cannot be improved; the second method is to insert a spot conversion structure between the semiconductor optical amplifier and the optical fiber to reduce the spot size to match, which can achieve a matched mode field and higher coupling efficiency. The third method is to optimize the structure of the semiconductor optical amplifier, so that the shape of the output light beam is changed from the ellipse of the traditional semiconductor optical amplifier to the circle, and the circular output light beam can be efficiently coupled with the circular optical fiber mode field, thereby fundamentally improving the quality of the output light beam of the semiconductor optical amplifier and enabling the output light beam to be efficiently coupled with the optical fiber. Therefore, how to make the output light of the semiconductor optical amplifier become circular becomes a key issue of this method.

To sum up, the utility model discloses quantum well layer 40 has improved the gain of semiconductor optical amplifier 100, has reduced threshold current, buries heterostructure it and provides great relative refractive index difference, from side direction and horizontal guide light. In the lateral direction, the light wave is guided by the relative refractive index difference between the active region and the cladding. In the lateral direction, the optical wave is guided by a buried heterostructure waveguide defined in part in the layered structure. The above-described characteristics of the quantum well layer 40 allow the size of the optical waveguide to be small and maintain high spatial overlap between the optical fundamental mode and the active region. The longitudinal size of the near-field light spot is changed, so that the near-field light spot of the light-emitting cavity surface is matched with the mode field radius of the optical fiber, and the optical fiber has extremely high coupling efficiency. The elliptical light spots of the semiconductor optical amplifier are converted into approximately symmetrical circular light spots. Furthermore, the coupling efficiency of the semiconductor optical amplifier 100 and the optical fiber 110 is improved by combining the tapered waveguide structure, the alignment tolerance of the optical fiber is improved, and the difficulty and the cost of the coupling packaging process are reduced.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. The utility model provides a double-groove ridge type semiconductor optical amplifier of high coupling efficiency, its characterized in that, including semiconductor optical amplifier main part (100) and optic fibre (110) of mutual coupling, semiconductor optical amplifier main part (100) includes from the lower supreme substrate (10), buffer layer (20), lower waveguide layer (30), quantum well layer (40), upper waveguide layer (50) and upper cover layer (60) that set gradually down, upper cover layer (60) include rectangular shape ridge waveguide (61) and etch first slot (62) and second slot (63) in ridge waveguide (61) both sides respectively, the upper surface of semiconductor optical amplifier main part (100) is provided with first electrode layer (70), the lower surface of semiconductor optical amplifier main part (100) is provided with second electrode layer (80), be equipped with two cavity faces (90) down between waveguide layer (30) and upper waveguide layer (50), two cavity face (90) are light-emitting and cavity face backlight respectively, the light-emitting cavity face is made on the light-emitting cavity face has first antireflection coating (91), backlight is made on the light-emitting anti-reflection coating has second antireflection coating (92).

2. A high coupling efficiency double-ridge semiconductor optical amplifier as defined in claim 1, wherein: the thickness of the upper cover layer (60) is set to be 1.2-3 mu m, and the first groove (62) and the second groove (63) are symmetrically arranged about a central axis of the upper cover layer (60).

3. A high coupling efficiency double ridge semiconductor optical amplifier as defined in claim 1, wherein: the side walls of the first groove (62) and the second groove (63) are vertically arranged, the distance between the inner bottom of the first groove (62) and the second groove (63) and the upper waveguide layer (50) is T, and the value range of T is 0.2-0.5 mu m.

4. A high coupling efficiency double-ridge semiconductor optical amplifier as defined in claim 1, wherein: the width of the ridge waveguide (61) is set to be W1, the value range of W1 is 2-6 mu m, the widths of the first groove (62) and the second groove (63) are set to be W2, and the value range of W2 is 3-5 mu m.

5. A high coupling efficiency double-ridge semiconductor optical amplifier as defined in claim 1, wherein: the thickness of the lower waveguide layer (30) and the thickness of the upper waveguide layer (50) are both set to be 200-800nm.

6. A high coupling efficiency double-ridge semiconductor optical amplifier as defined in claim 1, wherein: the reflectivity of the first antireflection film (91) and the reflectivity of the second antireflection film (92) are not higher than 0.5%.

7. A high coupling efficiency double-ridge semiconductor optical amplifier as defined in claim 1, wherein: the current injection window comprises a first electrode layer (70) and a second electrode layer (80), wherein the first electrode layer (70) and the second electrode layer (80) are window regions for current injection, the first electrode layer (70) and the second electrode layer (80) are arranged corresponding to a quantum well layer (40), the quantum well layer (40) is covered by the areas of the first electrode layer (70) and the second electrode layer (80), and silicon oxide insulating layers are arranged around the first electrode layer (70) and the second electrode layer (80).