CN117878717B - Femtosecond laser direct writing waveguide coupled monolithic integrated light emitting chip - Google Patents

Abstract

The invention provides a monolithic integrated light emitting chip coupled with a femtosecond laser direct writing waveguide, which relates to the technical field of optical device integration and comprises the following components: the silicon substrate, the silicon dioxide oxygen-buried layer and the silicon dioxide embedding layer grow sequentially from bottom to top; the silicon waveguide layer is arranged on the silicon dioxide buried oxide layer and is positioned inside the silicon dioxide buried oxide layer; the silicon dioxide embedding layer comprises a first area, a second area and a third area, wherein the first area comprises a quantum dot laser array, the second area comprises a modulator array, the third area comprises an optical waveguide array, the quantum dot laser array, the modulator array and the optical waveguide array are arranged in the same direction, the height of the output end face of the quantum dot laser array is different from the height of the input end face of the modulator array, and each group of quantum dot laser arrays is correspondingly connected with the modulator array through the optical waveguide array. The invention can solve the problems of matching the size of the die spot and space alignment between the quantum dot laser and the modulator, and better realizes photoelectric monolithic integration.

Description

Femtosecond laser direct writing waveguide coupled monolithic integrated light emitting chip

Technical Field

The invention relates to the technical field of optical device integration, and in particular to a femtosecond laser direct writing waveguide coupled monolithic integrated light emitting chip.

Background technique

With the explosion of Internet traffic data, facing the development needs of high-speed information flow such as 5G applications, Internet, Internet of Things, artificial intelligence, etc., the traditional electrical interconnection integrated architecture has encountered technical application bottlenecks in terms of speed, power consumption, and integration. With the advantages of low power consumption, high speed, and high integration of photonic devices, it is possible to break through the limitations of Moore's Law in electricity. Therefore, the development of optoelectronic integration technology has become a very promising solution.

On the complementary metal oxide semiconductor compatible (CMOS) process platform, silicon photonic devices have the advantage of high integration and can be integrated with electrical devices in a monolithic interconnection, so they have become a popular cutting-edge technology in recent years. However, since silicon materials are indirect bandgap semiconductors and cannot form efficient light sources, it is necessary to integrate high-power lasers based on III-V materials and other materials through epitaxial growth on the silicon photonic platform in a heterogeneous form to achieve monolithic integration of light sources and silicon photonic devices. Quantum dot lasers are a potential solution. However, in the prior art, there are two matching difficulties between the optical signal output of the epitaxially grown quantum dot laser and the optical signal input of the modulator. The first point is that the mode spot size of the two is matched, making it difficult to achieve low-loss coupling; the second point is the spatial alignment of the two on the SOI common substrate. Since the heterogeneous integration of the laser is difficult to use the same process as the silicon platform modulator, it is difficult to achieve precise pre-docking of the optical signal output of the active region with the modulator optical waveguide layer.

Therefore, how to solve the problem of mode spot size matching and spatial alignment between quantum dot lasers and modulators to better realize the monolithic integration of silicon photonic devices and electronic devices is an extremely challenging task.

Summary of the invention

In view of the above problems, the present invention provides a femtosecond laser direct writing waveguide coupled monolithic integrated light emitting chip to solve the problem of mode spot size matching and spatial alignment between quantum dot laser and modulator.

The invention provides a femtosecond laser direct writing waveguide coupled monolithic integrated light emitting chip, comprising: a silicon substrate; a silicon dioxide buried oxide layer, arranged on the silicon substrate; a silicon dioxide buried oxide layer, arranged on the silicon dioxide buried oxide layer; a silicon waveguide layer, arranged on the silicon dioxide buried oxide layer and located inside the silicon dioxide buried oxide layer; the silicon dioxide buried oxide layer comprises a first region, a second region and a third region, the first region comprises a quantum dot laser array, the second region comprises a modulator array, the third region comprises an optical waveguide array, the quantum dot laser array, the modulator array and the optical waveguide array are arranged in the same direction, the height of the output end face of the quantum dot laser array is different from the height of the input end face of the modulator array, and each group of the quantum dot laser array and the modulator array are correspondingly connected through the optical waveguide array.

Optionally, the end face size of one end of the optical waveguide array connected to the quantum dot laser matches the mode spot size of the output end face of the quantum dot laser, and the end face size of one end of the optical waveguide array connected to the modulator matches the mode spot size of the input end face of the modulator.

Optionally, the optical waveguide array is a device formed by femtosecond laser direct writing technology.

Optionally, each optical waveguide in the optical waveguide array is a curved waveguide.

Optionally, the modulator array is a Mach-Zehnder modulator or a micro-ring modulator.

Optionally, the quantum dot laser array is a device formed by epitaxially growing III-V group materials on the silicon substrate or the silicon waveguide layer.

Optionally, a GaAs epitaxial layer is pre-grown between the silicon substrate and the quantum dot laser array.

Optionally, the refractive index of the optical waveguide array is greater than the refractive index of the silica embedding layer.

Optionally, the mode spot size of each optical waveguide end face in the optical waveguide array is 2-10 μm.

Optionally, the length of each optical waveguide in the optical waveguide array is 0.1-10 mm.

At least one of the above technical solutions adopted in the embodiments of the present invention can achieve the following beneficial effects:

1. The present invention is based on a CMOS-compatible SOI platform process, which realizes the monolithic heterogeneous integration of light sources and modulators. Further extension to the optoelectronic fusion process platform can truly realize the fusion integration of monolithic all-optoelectronic devices including light sources, achieving high integration while having a commercial application foundation and prospects;

2. The optical waveguide generated by the femtosecond laser direct writing technology of the present invention can realize on-chip coupling between the laser and the modulator. The path and size of the optical waveguide can be matched according to the end face mode spot size of the laser and the modulator, thereby realizing high-precision alignment and low-loss coupling between the laser and the modulator;

3. The optical waveguide generated by the present invention using femtosecond laser direct writing technology can avoid the problems of fatigue and performance degradation existing in the optical waveguide generated based on photonic wire (PWB) technology, and has high reliability.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and its advantages, reference will now be made to the following description taken in conjunction with the accompanying drawings, in which:

FIG1 schematically shows a schematic diagram of a three-dimensional structure of a femtosecond laser direct writing waveguide coupled laser and a Mach-Zehnder modulator monolithic 8-channel array integrated according to an embodiment of the present invention;

FIG2 schematically shows a cross-sectional view of a single channel of a femtosecond laser direct writing waveguide coupled laser and a Mach-Zehnder modulator provided by an embodiment of the present invention;

FIG3 schematically shows a schematic diagram of a mode spot transformation method of an end face of an optical waveguide provided by an embodiment of the present invention;

FIG4 schematically shows a schematic diagram of a three-dimensional structure of a femtosecond laser direct writing waveguide coupled laser and a micro-ring modulator monolithic 4-channel array integrated according to an embodiment of the present invention.

Figure numerals: 1-silicon substrate; 2-silicon dioxide embedding layer; 21-first region; 22-second region; 23-third region; 3-quantum dot laser array; 4-modulator array; 41-micro-ring modulator array; 5-optical waveguide array; 51-first section of optical waveguide; 52-second section of optical waveguide; 53-third section of optical waveguide.

Detailed ways

Below, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of embodiments of the present invention. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of concepts of the present invention.

The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and/or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

FIG1 schematically shows a schematic diagram of a three-dimensional structure of a femtosecond laser direct writing waveguide coupled laser and a Mach-Zehnder modulator monolithic 8-channel array integrated according to an embodiment of the present invention.

As shown in FIG1 , the present invention provides a femtosecond laser direct writing waveguide coupled monolithic integrated light emitting chip, comprising: a silicon substrate 1; a silicon dioxide buried oxide layer, arranged on the silicon substrate 1; a silicon dioxide buried layer 2, arranged on the silicon dioxide buried oxide layer; a silicon waveguide layer, arranged on the silicon dioxide buried oxide layer, and located inside the silicon dioxide buried layer 2; the silicon dioxide buried layer 2 comprises a first region 21, a second region 22 and a third region 23, the first region 21 comprises a quantum dot laser array 3, the second region 22 comprises a modulator array 4, the third region 23 comprises an optical waveguide array 5, the quantum dot laser array 3, the modulator array 4 and the optical waveguide array 5 are arranged in the same direction, the height of the output end face of the quantum dot laser array 3 is different from the height of the input end face of the modulator array 4, and each group of quantum dot laser arrays 3 and modulator arrays 4 are correspondingly connected through the optical waveguide array 5.

In an illustrative embodiment, the silicon substrate 1 is a SOI wafer substrate, and the silicon substrate 1 has a thickness of 700 μm and a diameter of 100 mm.

In an illustrative embodiment, the silicon substrate 1 is a square substrate with a thickness of 700 μm and a side length of 100 mm.

The present invention does not impose any specific limitation on the specific size of the silicon substrate 1 , and other sizes may be set according to actual needs.

In an illustrative embodiment, the silicon dioxide buried layer 2 is deposited on the silicon substrate 1 and the optoelectronic device by chemical vapor deposition.

In an illustrative embodiment, the silicon dioxide embedded layer 2 is a wafer layer with a thickness of 5 μm and a diameter of 100 mm.

In an illustrative embodiment, the silicon dioxide embedding layer 2 is square, 5 μm thick and 100 mm long.

The present invention does not impose any specific limitation on the specific size of the silicon dioxide embedding layer 2, and other sizes may be set according to actual needs.

FIG2 schematically shows a cross-sectional view of a single channel of a femtosecond laser direct writing waveguide coupled laser and a Mach-Zehnder modulator provided by an embodiment of the present invention.

In an illustrative embodiment, as shown in FIG. 1 and FIG. 2 , the quantum dot laser array 3, the Mach-Zehnder modulator array and the optical waveguide array 5 are located inside the silicon dioxide embedding layer 2 and are disposed on the silicon substrate 1; the quantum dot laser array 3 and the Mach-Zehnder modulator array have the same number of array channels, each quantum dot laser in the quantum dot laser array 3 is connected one-to-one with each Mach-Zehnder modulator in the Mach-Zehnder modulator array, one quantum dot laser and one corresponding Mach-Zehnder modulator form a group, and each optical waveguide in the optical waveguide array 5 connects each group of quantum dot lasers with the Mach-Zehnder modulator. Among them, one end of each optical waveguide connected to the quantum dot laser is flush with the end face of the quantum dot laser, and one end of each optical waveguide connected to the Mach-Zehnder modulator is flush with the end face of the Mach-Zehnder modulator, which solves the spatial alignment problem between the quantum dot laser and the Mach-Zehnder modulator and realizes optical transmission coupling.

In an illustrative embodiment, the number of array channels of the quantum dot laser array 3 and the modulator array 4 is 8 or 4.

The present invention does not impose any specific limitation on the number of array channels of the quantum dot laser array 3 and the modulator array 4 .

In an illustrative embodiment, the modulator array 4 is a Mach-Zehnder type electro-optic modulator array, including a silicon modulator based on plasma dispersion effect realized by SOI silicon waveguide doping, or a lithium niobate modulator, a barium titanate modulator or a lead zirconate titanate modulator based on electro-optic effect realized by heterogeneous integration in a silicon-based material system. The present invention does not impose specific restrictions on the material system of the modulator.

FIG. 3 schematically shows a schematic diagram of a mode spot transformation method of an end face of an optical waveguide provided by an embodiment of the present invention.

As an optional embodiment, the end face size of one end of the optical waveguide array 5 connected to the quantum dot laser array 3 matches the mode spot size of the output end face of the quantum dot laser array 3, and the end face size of one end of the optical waveguide array 5 connected to the modulator array 4 matches the mode spot size of the input end face of the modulator array 4.

In an illustrative embodiment, as shown in FIG3 , the optical waveguide includes a first section of optical waveguide 51, a second section of optical waveguide 52 and a third section of optical waveguide 53. The first section of optical waveguide 51 is connected to the quantum dot laser array 3 and is an inverted cone structure. The end face size of the first section of optical waveguide 51 connected to the quantum dot laser array 3 is the same as the end face size of the quantum dot laser array 3. The end face size of the first section of optical waveguide 51 not connected to the quantum dot laser array 3 is smaller than the end face size of the first section of optical waveguide 51 connected to the quantum dot laser array 3. The second section of optical waveguide 52 is connected to the modulator array 4 and is an inverted cone structure. The end face mode spot size of the second section of optical waveguide 52 connected to the modulator array 4 is the same as the end face mode spot size of the modulator array 4. The end face mode spot size of the second section of optical waveguide 52 not connected to the modulator array 4 is smaller than the end face mode spot size of the second section of optical waveguide 52 connected to the modulator array 4. The first section of optical waveguide 51 is connected to the second section of optical waveguide 52 via the third section of optical waveguide 53 , and the third section of optical waveguide 53 realizes the gradual change of mode spot, thereby ensuring the optical coupling between the quantum dot laser array 3 and the modulator array 4 .

As an optional embodiment, the optical waveguide array 5 is a device formed by femtosecond laser direct writing technology.

Femtosecond laser direct writing technology can customize the generation of optical waveguides in hard glass materials through the silicon dioxide embedding layer 2.

The above-mentioned “customization” means that due to the difference in size between the quantum dot laser array 3 and the modulator array 4, it is difficult to achieve spatial alignment between the two on the same horizontal plane, and there is a height difference. Therefore, the femtosecond laser energy and alignment position can be controlled according to the end face height and end face size of the quantum dot laser array 3 and the modulator array 4 to generate an optical waveguide path to achieve effective optical transmission coupling.

As an optional embodiment, the refractive index of the optical waveguide array 5 is greater than the refractive index of the silicon dioxide embedding layer 2 .

In an illustrative embodiment, a high-energy pulsed femtosecond laser is used to perform ultra-fine focusing processing on the inside of the silicon dioxide embedding layer 2, generating local high temperature and high pressure, forming shock waves and material densification, and forming a processing path with a refractive index higher than that of silicon dioxide, thereby forming a 3D optical waveguide array 5 that can bind the optical signal mode field, and the end face of the optical waveguide array 5 is aligned and flush with the end faces of the laser array 3 and the modulator array 4. The size of the optical waveguide array 5 and the end face mode spot size are adjustable according to the femtosecond laser processing technology capability.

As an optional embodiment, each optical waveguide in the optical waveguide array 5 is a curved waveguide to achieve a gradual change in the mode spot of the optical signal in the optical waveguide, thereby achieving low-loss optical coupling.

As an optional embodiment, the mode spot size of each optical waveguide end face in the optical waveguide array 5 is 2-10 μm.

As an optional embodiment, the length of each optical waveguide in the optical waveguide array 5 is 0.1-10 mm.

FIG4 schematically shows a schematic diagram of a three-dimensional structure of a femtosecond laser direct writing waveguide coupled quantum dot laser array 3 and a micro-ring modulator array 41 provided in an embodiment of the present invention as a monolithic 4-channel array integration.

As an optional embodiment, as shown in FIG. 3 and FIG. 4 , the modulator array 4 is a Mach-Zehnder type or a micro-ring type modulator.

As an optional embodiment, the quantum dot laser array 3 is a device formed by epitaxially growing III-V group materials on the silicon substrate 1 or the silicon waveguide layer.

As an illustrative embodiment, the III-V material epitaxially grown on the silicon substrate 1 or the silicon waveguide layer is InAs/GaAs or InAs/InP.

As an optional embodiment, a GaAs epitaxial layer is pre-grown between the silicon substrate 1 and the quantum dot laser array 3 .

In an exemplary embodiment, the thickness of the GaAs epitaxial layer is 100 nm.

In an illustrative embodiment, the number of array channels of the optical waveguide array 5 is 4 or 8. The present invention does not impose any specific limitation on the number of array channels of the optical waveguide array 5 .

In summary, the present invention can realize heterogeneous integration of quantum dot lasers and modulators on a CMOS-compatible process platform, use femtosecond direct writing optical waveguide technology to achieve on-chip low-loss optical signal transmission coupling, and extend this technology to a monolithic fusion optoelectronic process platform, which can further realize monolithic optoelectronic fusion integration including light sources, and has practical commercial application prospects.

It will be appreciated by those skilled in the art that the features described in the various embodiments of the present invention may be combined and/or combined in various ways, even if such combinations and/or combinations are not explicitly described in the present invention. In particular, without departing from the spirit and teachings of the present invention, the features described in the various embodiments of the present invention may be combined and/or combined in various ways. All of these combinations and/or combinations fall within the scope of the present invention.

Although the present invention has been shown and described with reference to specific exemplary embodiments of the present invention, it will be appreciated by those skilled in the art that various changes in form and detail may be made to the present invention without departing from the spirit and scope of the present invention. Therefore, the scope of the present invention should not be limited to the above-described embodiments.

Claims (10)

1. A femtosecond laser direct-write waveguide coupled monolithically integrated light emitting chip comprising:

A silicon substrate (1);

The silicon dioxide oxygen burying layer is arranged on the silicon substrate (1);

a silicon dioxide embedding layer (2) arranged on the silicon dioxide oxygen burying layer;

the silicon waveguide layer is arranged on the silicon dioxide buried oxide layer and is positioned inside the silicon dioxide buried oxide layer (2);

The silicon dioxide buried layer (2) comprises a first area (21), a second area (22) and a third area (23), wherein the first area (21) comprises a quantum dot laser array (3), the second area (22) comprises a modulator array (4), the third area (23) comprises an optical waveguide array (5), the quantum dot laser array (3) and the modulator array (4) are arranged in the same direction with the optical waveguide array (5), the height of an output end face of the quantum dot laser array (3) is different from the height of an input end face of the modulator array (4), and each group of the quantum dot laser arrays (3) and the modulator array (4) are correspondingly connected through the optical waveguide array (5).

2. The femtosecond laser direct write waveguide coupled monolithic integrated light emitting chip according to claim 1, wherein an end face size of the optical waveguide array (5) connected to the quantum dot laser array (3) is matched with a mode spot size of an output end face of the quantum dot laser array (3), and an end face size of the optical waveguide array (5) connected to the modulator array (4) is matched with a mode spot size of an input end face of the modulator array (4).

3. The femtosecond laser direct write waveguide coupled monolithically integrated light emitting chip of claim 1, wherein the optical waveguide array (5) is a device formed by a femtosecond laser direct write technique.

4. The femtosecond laser direct write waveguide coupled monolithically integrated light emitting chip of claim 1, wherein each optical waveguide of the array of optical waveguides (5) is a curved waveguide.

5. The femtosecond laser direct write waveguide coupled monolithically integrated light emitting chip of claim 1, wherein the modulator array (4) is a mach-zehnder type or micro-ring type modulator.

6. The femtosecond laser direct write waveguide coupled monolithically integrated light emitting chip according to claim 1, wherein the quantum dot laser array (3) is a device formed by epitaxially growing a group III-V material on the silicon substrate (1) or the silicon waveguide layer.

7. The femtosecond laser direct write waveguide coupled monolithically integrated light emitting chip according to claim 6, wherein a GaAs epitaxial layer is pre-grown between the silicon substrate (1) and the quantum dot laser array (3).

8. The femtosecond laser direct write waveguide coupled monolithically integrated light emitting chip according to claim 1, wherein the refractive index of the optical waveguide array (5) is larger than the refractive index of the silica embedding layer (2).

9. The femtosecond laser direct write waveguide coupled monolithic integrated light emitting chip according to claim 1, wherein the size of each optical waveguide end face spot in the optical waveguide array (5) is 2-10 μm.

10. The femtosecond laser direct write waveguide coupled monolithic integrated light emitting chip according to claim 1, wherein the length of each optical waveguide in the optical waveguide array (5) is 0.1-10 mm.