Green semiconductor laser based on hybrid integration

Abstract

The invention relates to a green semiconductor laser based on hybrid integration, and belongs to the technical field of optoelectronic integration. The laser comprises a silicon nitride chip and a gallium nitride chip which are bonded through a BCB bonding layer, wherein the gallium nitride chip is used for generating laser and coupling the laser into the silicon nitride chip. A receiving unit, a mode selection unit and a reflection output unit are arranged in the silicon nitride chip. The receiving unit is used for receiving the laser coupled by the gallium nitride chip; the mode selection unit is used for realizing longitudinal mode selection and narrowing of laser; and the reflection output unit is used for realizing reflection enhancement of the laser and outputting the laser subjected to mode selection and line width narrowing. According to the invention, the high-quality green light semiconductor laser based on hybrid integration can be realized, the difficult problems of high gallium nitride waveguide preparation difficulty, narrow laser line width, difficulty in integration with a silicon-based photon chip and the like can be avoided, and a green light semiconductor laser realization scheme is provided for application of biological monitoring, visible light communication and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of optoelectronic integration and relates to a green light semiconductor laser structure based on hybrid integration. Background Art

[0002] In the field of optoelectronic integrated technology, green semiconductor lasers have important applications in display, storage, military, and medical fields due to their unique wavelength (510-560 nanometers) and high energy characteristics. Gallium nitride is a semiconductor material with a wide bandgap, high critical electric field strength, and high electron saturation velocity. These characteristics make it an ideal material for manufacturing green semiconductor lasers. Gallium nitride can cover the wavelength range from ultraviolet to green light, can operate at high energy, can withstand high current density and high-speed modulation, and is a good material for realizing green semiconductor lasers. However, gallium nitride has stable chemical properties, and the etching and waveguide preparation in the laser preparation process face great challenges, especially the high-precision gratings and high-verticality waveguides required for narrow linewidth lasers are difficult to achieve. Summary of the invention

[0003] In view of this, the purpose of the present invention is to provide a green light semiconductor laser based on hybrid integration, by efficiently coupling the light field of a gallium nitride light source with a silicon nitride waveguide, preparing equivalent end faces on a gallium nitride chip, and preparing a mode selection unit and a reflection unit on a silicon nitride chip, together forming a hybrid integrated green light semiconductor laser that can achieve high-quality light beams, thereby solving the problems of difficult waveguide etching and difficult control of laser beam quality in the existing gallium nitride material system.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] A green light semiconductor laser based on hybrid integration includes a silicon nitride chip and a gallium nitride chip bonded by a BCB bonding layer, wherein the gallium nitride chip is used to generate laser light and couple into the silicon nitride chip. A receiving unit, a mode selection unit and a reflection output unit are provided in the silicon nitride chip. The receiving unit is used to receive the laser light coupled into the gallium nitride chip; the mode selection unit is used to achieve longitudinal mode selection and narrowing of the laser light; the reflection output unit is used to achieve reflection enhancement of the laser light and output the laser light after mode selection and line width narrowing.

[0006] Furthermore, the gallium nitride chip includes a P-type gallium nitride layer, a gallium nitride multi-quantum well layer, an N-type gallium nitride layer and a reflective layer stacked in sequence from bottom to top, and also includes a P-type electrode and an N-type electrode arranged on the surface of the reflective layer.

[0007] Furthermore, the receiving unit includes a silicon nitride grating and an inverted cone waveguide connected to the silicon nitride grating. The silicon nitride grating is in a relative position to the gallium nitride chip to better receive the laser output by the gallium nitride chip. The duty cycle and period of the silicon nitride grating are determined according to the emission wavelength of the gallium nitride chip to achieve maximum coupling efficiency; the inverted cone waveguide realizes single-mode adiabatic transmission and converges the light coupled into the silicon nitride layer into the single-mode waveguide.

[0008] Furthermore, the mode selection unit is used to select the longitudinal mode of the laser and select the single mode based on the vernier caliper effect. The mode selection unit is a double micro-ring structure, which includes three parallel straight waveguides and two annular waveguides spaced between the straight waveguides. One of the straight waveguides is connected to the inverted cone waveguide in the receiving unit, the other straight waveguide is connected to the adjustable reflection waveguide ring in the reflection output unit, and the other straight waveguide is located between the two annular waveguides for light transmission between the two annular waveguides.

[0009] Furthermore, the reflection output unit includes an adjustable reflection waveguide ring and an output waveguide. The adjustable reflection waveguide ring is provided with an opening, one end of which is connected to the mode selection unit, and the other end of which is connected to the output waveguide. The adjustable reflection waveguide ring realizes the reflection and output of the optical power, and the sum of the normalized power reflected back to the chip loop and passing through the output waveguide is 1.

[0010] Furthermore, the silicon nitride chip also includes a silicon substrate and a silicon dioxide cladding layer located on the surface of the silicon substrate, wherein the silicon dioxide cladding layer serves as a low refractive index material to limit the light field in the silicon nitride chip.

[0011] Furthermore, the receiving unit, the mode selection unit and the reflection output unit are all arranged in the silicon dioxide cladding layer, wherein the silicon nitride grating in the receiving unit is spaced a certain distance from the silicon substrate and the BCB bonding layer respectively.

[0012] The beneficial effects of the present invention are as follows: the present invention designs a hybrid integrated structure of a gallium nitride chip and a silicon nitride chip, adds a reflective layer in a green light wavelength range in a gallium nitride epitaxial layer to form a reflective end face; prepares a grating in a silicon nitride waveguide layer to realize coupling of green light from the gallium nitride structure to the silicon nitride layer; adopts a double micro-ring filter structure and an adjustable reflective waveguide ring structure in the silicon nitride layer to realize green light wavelength longitudinal mode selection and reflection, thereby forming two reflective surfaces of the semiconductor laser structure together with the gallium nitride reflective layer, so as to realize a high-quality green light semiconductor laser based on hybrid integration, avoid the difficulties of difficult preparation of a gallium nitride waveguide structure, narrow laser line width, and difficulty in integration with a silicon-based photonic chip, and provide a green light semiconductor laser implementation solution for applications such as biological monitoring and visible light communication.

[0013] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0015] Figure 1 A green light semiconductor laser structure based on hybrid integration provided by one embodiment of the present invention;

[0016] Figure 2 for Figure 1 a cross-sectional view of the laser shown;

[0017] Figure 3 A top view of the silicon nitride layer structure in a green semiconductor laser structure based on hybrid integration.

[0018] Figure numerals: 101 - silicon substrate, 102 - silicon dioxide cladding, 103 - silicon nitride grating, 104 - inverted cone waveguide, 105 - double micro-ring structure, 106 - adjustable reflection waveguide ring, 107 - output waveguide, 108 - BCB bonding layer, 109 - P-type gallium nitride layer, 110 - gallium nitride multi-quantum well layer, 111 - N-type gallium nitride layer, 112 - reflection layer, 113 - P-type electrode, 114 - N-type electrode. DETAILED DESCRIPTION

[0019] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0020] like Figure 1As shown, a green light semiconductor laser based on hybrid integration is provided in one embodiment of the present invention. The laser includes, from bottom to top, a silicon substrate 101, a silicon dioxide cladding 102, a silicon nitride grating 103, an inverted cone waveguide 104, a double micro-ring structure 105, an adjustable reflection waveguide ring 106, an output waveguide 107, a BCB bonding layer 108, a P-type gallium nitride layer 109, a gallium nitride multi-quantum well layer 110, an N-type gallium nitride layer 111, a reflection layer 112, a P-type electrode 113, and an N-type electrode 114.

[0021] Among them, the silicon substrate 101 is a substrate layer of silicon nitride on an insulator, with a thickness of about 725 microns; the silicon dioxide cladding 102 has a refractive index of about 1.44, and as a low-refractive-index material, it limits the light field in the silicon nitride waveguide layer 103, and the overall thickness is about 5 microns; the duty cycle and period of the silicon nitride grating 103 are determined according to the emission wavelength of the gallium nitride chip to achieve maximum coupling efficiency, and is about 2 microns away from the silicon substrate 101 and about 3 microns away from the lower surface of the BCB bonding layer 108; the inverted cone waveguide 104 realizes single-mode adiabatic transmission, and converges the light coupled into the silicon nitride layer into the single-mode waveguide, and the cross-sectional size of the single-mode waveguide is about 150 nanometers × 800 nanometers; the double microring structure 105 realizes the longitudinal mode selection of the laser, and realizes the selection of the single mode based on the vernier caliper effect; adjustable reflection waveguide Ring 106 realizes reflection and output of optical power, and the sum of the normalized power reflected back to the chip loop and passing through the output waveguide 107 is 1; waveguide 107 outputs laser after mode selection and line width narrowing; BCB bonding layer 108 is used to realize the bonding between silicon nitride devices and gallium nitride devices, and its thickness is about 100 nanometers and it is transparent to the green light band; P-type gallium nitride layer 109, gallium nitride multi-quantum well layer 110, and N-type gallium nitride layer 111 are conventional gallium nitride epitaxial layers, and reflective layer 112 is a reflective layer specially designed according to the emission wavelength, which realizes total reflection of the green light wavelength and constitutes one of the reflection surfaces of the hybrid integrated laser; P-type electrode 113 and N-type electrode 114 are the same-plane electrode structures of the gallium nitride chip, which realize light output through electric pumping and couple into the silicon nitride chip.

[0022] In this embodiment, the gallium nitride chip is combined with the silicon nitride chip, and a reflective layer is prepared on the gallium nitride chip to form the equivalent end face of the laser. The mode selection unit and the reflective unit are constructed on the silicon nitride waveguide layer to achieve efficient coupling between the gallium nitride light source and the silicon nitride waveguide light field while achieving a narrow longitudinal mode selection pressure of the laser. This design can realize high-quality green light semiconductor lasers based on hybrid integration.

[0023] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A green light semiconductor laser based on hybrid integration, characterized in that: It comprises a silicon nitride chip and a gallium nitride chip bonded by a BCB bonding layer, wherein the gallium nitride chip is used to generate laser light and couple into the silicon nitride chip; the silicon nitride chip is provided with a receiving unit, a mode selection unit and a reflection output unit; the receiving unit is used to receive the laser light coupled into the gallium nitride chip; the mode selection unit is used to realize longitudinal mode selection and narrowing of the laser light; the reflection output unit is used to realize reflection enhancement of the laser light and output the laser light after mode selection and line width narrowing.

2. The green light semiconductor laser according to claim 1, characterized in that: The gallium nitride chip comprises a P-type gallium nitride layer, a gallium nitride multi-quantum well layer, an N-type gallium nitride layer and a reflective layer stacked in sequence from bottom to top, and also comprises a P-type electrode and an N-type electrode arranged on the surface of the reflective layer.

3. The green light semiconductor laser according to claim 1, characterized in that: The receiving unit comprises a silicon nitride grating and an inverted cone waveguide connected to the silicon nitride grating; the silicon nitride grating is opposite to the gallium nitride chip.

4. The green light semiconductor laser according to claim 1, characterized in that: The mode selection unit includes three parallel straight waveguides and two annular waveguides spaced apart between the straight waveguides; one straight waveguide is connected to the receiving unit, another straight waveguide is connected to the reflection output unit, and another straight waveguide is located between the two annular waveguides.

5. The green semiconductor laser according to claim 1, characterized in that: The reflection output unit comprises an adjustable reflection waveguide ring and an output waveguide; the adjustable reflection waveguide ring is provided with an opening, one end of the opening is connected to the mode selection unit, and the other end of the opening is connected to the output waveguide.

6. The green semiconductor laser according to claim 1, characterized in that: The silicon nitride chip also includes a silicon substrate and a silicon dioxide cladding layer located on the surface of the silicon substrate.

7. The green light semiconductor laser according to claim 6, characterized in that: The receiving unit, the mode selection unit and the reflection output unit are all arranged in the silicon dioxide cladding.

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