Laser array modulated using unidirectional light injection

Abstract

The present invention relates to the field of silicon-based optoelectronics technology and provides a laser array using unidirectional light injection modulation, comprising: a plurality of laser units arranged in an array, each laser unit comprising: a waveguide grating coupler, a master laser, and a slave laser; the waveguide grating coupler comprising: a grating unit, a waveguide unit, and an oxidation unit; wherein the grating unit comprises a first grating and a second grating, the first and second gratings being connected to the bottom sides of the waveguide unit, respectively, and the oxidation unit being located on the upper surface of the waveguide unit; the master laser being located below the first grating, the slave laser being located obliquely below the second grating, and the horizontal projection of the light output area of ​​the slave laser not overlapping with the horizontal projection of the second grating. The present invention can achieve unidirectional injection of waveguide light using a simple process and structure.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon-based optoelectronics, and in particular to a laser array using unidirectional light injection modulation. Background Art

[0002] Silicon-based optoelectronics is one of the most important disciplines in the optoelectronics field. Through continuous development and innovation, its current application range has expanded significantly, encompassing optoelectronic devices such as optical switches, filters, and wavelength division multiplexers. Waveguide gratings are widely used in silicon-based optoelectronics due to their small size and low sensitivity to mechanical disturbances and external temperature. Among them, waveguide grating couplers are a device structure that accepts light input and then outputs light under certain conditions. Compared to other coupling devices, such as prism couplers, they offer significant advantages such as small size and high coupling efficiency.

[0003] Limited by the damage threshold of the cavity surface of the Vertical-Cavity Surface-Emitting Laser (VCSEL), the output power of a single VCSEL can only reach the watt level. The VCSEL array developed by taking advantage of two-dimensional integration can increase the output power of the VCSEL array to the kilowatt level, giving it a wider application space in lidar and long-distance optical communications. With the expansion of application areas, higher requirements are placed on the output power, spectral width, polarization and other characteristics of the VCSEL array. The most commonly used method is to use coupling technology to impose perturbations on the VCSEL array so that the output light of different units on the array has the same characteristics, ultimately making the light output of the array have higher beam quality.

[0004] This goal can be achieved by using a special grating structure. Using a grating, the light of one unit is coupled into another light-emitting unit through the grating. The unit that emits light is called the master laser, and the other unit where the injected light is modulated is called the slave laser. After the light is injected, the light output parameters of the slave laser, such as frequency and polarization, are generally consistent with the parameters of the injected light beam. In general, the light output quality of the master laser is relatively excellent, and the output power of the slave laser is relatively large, so that a unit with a smaller light output power can modulate a high-power unit. However, the existing light injection system that can achieve unidirectional injection of waveguide light is very complex and difficult to meet the requirements of future applications. Summary of the Invention

[0005] The present invention provides a laser array using unidirectional light injection modulation to solve the defect that the light injection system capable of realizing unidirectional injection of waveguide light in the prior art is very complex and difficult to meet the requirements of subsequent applications, and achieves the purpose of realizing unidirectional injection of waveguide light using a simple process and structure.

[0006] The present invention provides a laser array using unidirectional light injection modulation, comprising: a plurality of laser units arranged in an array, each laser unit comprising: a waveguide grating coupler, a master laser and a slave laser;

[0007] The waveguide grating coupler comprises: a grating unit, a waveguide unit and an oxidation unit; wherein the grating unit comprises a first grating and a second grating, the lower sides of the waveguide unit are respectively connected to the first grating and the second grating, and the oxidation unit is located on the upper surface of the waveguide unit;

[0008] The master laser is located below the first grating, the slave laser is located obliquely below the second grating, and the horizontal projection of the light emitting area of ​​the slave laser does not overlap with the horizontal projection of the second grating.

[0009] According to a laser array using unidirectional light injection modulation provided by the present invention, each grating period and each duty cycle of the first grating are the same, and the grating period of the first grating is associated with the duty cycle of the first grating.

[0010] According to a laser array using unidirectional light injection modulation provided by the present invention, the grating periods and duty cycles of the second grating are the same, the grating period of the second grating is associated with the emission angle and the duty cycle of the second grating, and the emission angle is the angle between the direction of the emitted light of the second grating and the plane normal direction of the second grating.

[0011] According to a laser array using unidirectional light injection modulation provided by the present invention, the first grating and the second grating have the same depth and different grating periods.

[0012] According to a laser array using unidirectional light injection modulation provided by the present invention, the projection of the first grating on the horizontal plane overlaps with the projection of the light emitting area of ​​the master laser on the horizontal plane.

[0013] According to a laser array using unidirectional light injection modulation provided by the present invention, the waveguide grating coupler is not in contact with the upper surfaces of the master laser and the slave laser respectively.

[0014] According to a laser array using unidirectional light injection modulation provided by the present invention, the first grating and the second grating are both diffraction gratings, the diffraction gratings include alternately distributed grating teeth and etched holes, and the grating teeth are rectangular in shape.

[0015] According to a laser array using unidirectional light injection modulation provided by the present invention, the grating unit is a sub-wavelength grating structure formed by etching the lower surface of the waveguide layer, and the etched waveguide layer includes the grating unit and the waveguide unit.

[0016] According to a laser array using unidirectional light injection modulation provided by the present invention, the materials of the waveguide unit and the grating unit are both silicon nitride.

[0017] According to a laser array using unidirectional light injection modulation provided by the present invention, the material of the oxidation unit is silicon dioxide.

[0018] The present invention provides a laser array using unidirectional light injection modulation, comprising: a plurality of laser units arranged in an array, each laser unit comprising: a waveguide grating coupler, a master laser, and a slave laser; the waveguide grating coupler comprising: a grating unit, a waveguide unit, and an oxidation unit; wherein the grating unit comprises a first grating and a second grating, the lower sides of the waveguide unit being connected to the first and second gratings respectively, and the oxidation unit being located on the upper surface of the waveguide unit; since the master laser is located below the first grating, the first grating can couple the output light of the master laser into the interior of the waveguide unit; the slave laser is located obliquely below the second grating, and the horizontal projection of the light output area of ​​the slave laser does not overlap with the horizontal projection of the second grating; the second grating directs the output light coupled into the interior of the waveguide unit to the slave laser at a certain output angle, so that the output light of the slave laser is vertically emitted without passing through the second grating, so that the output light of the slave laser is no longer coupled into the interior of the waveguide unit, thereby achieving unidirectional injection of waveguide light, and the process and structure are relatively simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 1 is a schematic structural diagram of a laser unit in a laser array using unidirectional light injection modulation provided by an embodiment of the present invention;

[0021] Figure 2 Schematic diagram of the working principle of a laser unit in a laser array using unidirectional light injection modulation provided by an embodiment of the present invention;

[0022] Figure 3 It is a flow chart of a method for manufacturing a waveguide grating coupler array provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0023] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0024] The following combination Figures 1 to 2 A laser array using unidirectional light injection modulation according to an embodiment of the present invention is described.

[0025] Please refer to Figure 1 , Figure 1 The structure diagram of the laser unit in the laser array using unidirectional light injection modulation provided by the embodiment of the present invention. The laser array using unidirectional light injection modulation includes: a plurality of laser units arranged in an array. Figure 1 As shown, each laser unit includes a waveguide grating coupler 1 , a master laser 2 and a slave laser 3 . The waveguide grating coupler 1 includes a grating unit 10 , a waveguide unit 20 and an oxidation unit 30 .

[0026] The grating unit 10 includes a first grating 101 and a second grating 102. The lower sides of the waveguide unit 20 are connected to the first grating 101 and the second grating 102, respectively. Optionally, the grating unit 10 is a sub-wavelength grating structure formed by etching the lower surface of a waveguide layer. The etched waveguide layer includes the grating unit 10 and the waveguide unit 20. Specifically, the thickness of the waveguide layer can range from 0.25 μm to 0.4 μm. For example, the thickness of the waveguide layer can be 400 nm, and the etching depth can be 272 nm. This embodiment is not limited to this.

[0027] The oxidation unit 30 is located on the upper surface of the waveguide unit 20 , and the thickness of the oxidation unit 30 does not affect the coupling of light.

[0028] The master laser 2 is located below the first grating 101. Preferably, the projection of the first grating 101 on the horizontal plane overlaps with the projection of the light emitting area of ​​the master laser 1 on the horizontal plane. Figure 2 As shown, the first grating 101 can couple the output light of the master laser 2 into the interior of the waveguide unit 20 .

[0029] The slave laser 3 is located obliquely below the second grating 102, and the horizontal projection of the light emitting area of ​​the slave laser 3 does not overlap with the horizontal projection of the second grating 102. In addition, the second grating 102 needs to be as far away from the light emitting area of ​​the slave laser 3 as possible within the range allowed by the process device structure. For example, the offset length between the slave laser and the second grating along the light emitting offset direction is 10μm. Figure 2 As shown, the second grating 102 irradiates the outgoing light coupled into the interior of the waveguide unit to the laser 3 at a certain output angle, and the outgoing light from the laser 3 is vertically emitted without passing through the second grating 102, so that the outgoing light from the laser is no longer coupled into the interior of the waveguide unit, thereby realizing unidirectional injection of the waveguide light.

[0030] In this embodiment, a laser array using unidirectional light injection modulation includes: a plurality of laser units arranged in an array, each laser unit including: a waveguide grating coupler, a master laser, and a slave laser; the waveguide grating coupler includes: a grating unit, a waveguide unit, and an oxidation unit; wherein the grating unit includes a first grating and a second grating, the first and second gratings being connected to the lower sides of the waveguide unit, respectively, and the oxidation unit being located on the upper surface of the waveguide unit; since the master laser is located below the first grating, the first grating can couple the output light of the master laser into the interior of the waveguide unit; the slave laser is located obliquely below the second grating, and the horizontal projection of the light output area of ​​the slave laser does not overlap with the horizontal projection of the second grating; the second grating directs the output light coupled into the interior of the waveguide unit to the slave laser at a certain output angle, so that the output light of the slave laser is vertically emitted without passing through the second grating, so that the output light of the slave laser is no longer coupled into the interior of the waveguide unit, thereby achieving unidirectional injection of waveguide light, and the process and structure are relatively simple.

[0031] Optionally, the grating unit 10 and the waveguide unit 20 are both made of silicon nitride. This embodiment is not limited thereto, and other materials with different effective refractive indices for the TE mode may also be used. Using silicon nitride, a material with low dispersion, adjustable refractive index, and stable properties, to manufacture the grating unit 10 provides the advantages of low insertion loss, good thermal stability, wide manufacturing tolerances, and high relative error tolerance.

[0032] Alternatively, the oxidation unit 30 may be made of silicon dioxide, but the present embodiment is not limited thereto. Using silicon dioxide to make the oxidation unit 30 can form a protective film on the upper surface of the waveguide unit 20 to protect the surface and interior of the device.

[0033] Alternatively, as Figure 1As shown, the grating periods and duty cycles of the first grating 101 are the same. The grating period of the first grating 101 is associated with the duty cycle of the first grating 101. To achieve the highest coupling efficiency, the grating period and duty cycle are numerically optimized using simulation software to determine specific values.

[0034] For example, each grating period of the first grating 101 is 768 nm, each duty cycle of the first grating 101 is 0.5, and the total number of periods of the first grating 101 may be 13, but the embodiment is not limited thereto.

[0035] In this embodiment, the grating periods and duty cycles of the first grating are the same, and the grating period of the first grating is associated with the duty cycle of the first grating. That is, the structure and process of the first grating are relatively simple.

[0036] Alternatively, as Figure 1 As shown, the grating periods and duty cycles of the second grating 102 are the same. The grating period of the second grating 102 is associated with the emission angle and the duty cycle of the second grating 102. The emission angle is the angle between the direction of the emitted light of the second grating 102 and the plane normal direction of the second grating 102.

[0037] For example, each grating period of the second grating 102 is 805 nm, each duty cycle of the second grating 102 is 0.75, and the total number of periods of the second grating 102 may be 13, but the embodiment is not limited thereto.

[0038] In this embodiment, the grating periods and duty cycles of the second grating are the same, and the grating period of the second grating is associated with the emission angle and the duty cycle of the second grating. That is, the structure and process of the second grating are relatively simple.

[0039] Specifically, the grating period of the first grating 101 and the grating period of the second grating 102 can be calculated using the Bragg grating formula. The Bragg grating formula is as follows:

[0040]

[0041] Among them, n t represents the ambient refractive index, which can be the air refractive index in this embodiment and has a value of 1; n eff represents the effective refractive index of the grating, which can be calculated from the refractive index of the material used for the grating (such as silicon nitride) and the duty cycle of the grating; θ represents the output angle, that is, the angle between the direction of the output light of the grating and the plane normal direction of the grating; Λ represents the grating period of the grating; λ represents the wavelength of the coupled light corresponding to the grating; and m represents the diffraction order of the output light.

[0042] With respect to the grating period of first grating 101, since the ambient refractive index of first grating 101, the refractive index of the grating material, the exit angle, and the diffraction order of the exiting light are all fixed, the only parameter affecting the grating period of first grating 101 is the duty cycle of first grating 101. Based on experimental data, the duty cycle of first grating 101 corresponding to the optimal coupling efficiency was selected, and then the grating period of first grating 101 was calculated using the Bragg grating formula.

[0043] As for the grating period of second grating 102, since the ambient refractive index of second grating 102, the refractive index of the grating material used, and the diffraction order of the emitted light are all fixed, the only parameters affecting the grating period of second grating 102 are its duty cycle and the emission angle. Based on experimental data, the duty cycle and emission angle corresponding to the optimal coupling efficiency are selected. The emission angle is generally controlled within a range of 8°-10°. The grating period of second grating 102 is then calculated using the Bragg grating formula.

[0044] Optionally, the first grating 101 and the second grating 102 have the same depth and different grating periods. For example, the grating period of the first grating 101 is 768 nm, the grating period of the second grating 102 is 805 nm, and the depths of the first grating 101 and the second grating 102 are both 272 nm. This embodiment is not limited thereto.

[0045] Optionally, the waveguide grating coupler 1 does not contact the upper surface of the master laser 2 and the slave laser 3. That is, there is a certain distance between the waveguide grating coupler 1 and the upper surface of the laser, for example, 63 μm, but this embodiment is not limited thereto.

[0046] In this embodiment, since the waveguide grating coupler does not contact the upper surfaces of the master laser and the slave laser, the light emitted by the master laser is irradiated onto the first grating through a certain distance, and the light emitted by the second grating is irradiated onto the slave laser through a certain distance. Optionally, the light source is a Gaussian light source.

[0047] Optionally, both the first grating 101 and the second grating 102 are diffraction gratings, and the diffraction gratings include alternately distributed grating teeth and etched holes, and the grating teeth are rectangular in shape.

[0048] In this embodiment, since both the first grating and the second grating include alternately distributed grating teeth and etched holes, and the grating teeth are rectangular in shape, the structures and processes of the first grating and the second grating are relatively simple.

[0049] The following is a detailed description of the method for manufacturing the waveguide grating coupler array in the above laser array.

[0050] Please refer to Figure 3 , Figure 3FIG. 1 is a flow chart of a method for manufacturing a waveguide grating coupler array according to an embodiment of the present invention. Figure 3 As shown, the process flow of the waveguide grating coupler array may include:

[0051] Step 301: growing a silicon nitride layer on a silicon dioxide substrate;

[0052] Step 302: Cleaning the surface of the silicon nitride layer and drying the cleaned silicon nitride layer;

[0053] Step 303: spin-coating a photoresist layer on the lower surface of the silicon nitride layer at a preset rotation speed, and drying the photoresist layer;

[0054] Step 304: exposing the surface of the photoresist layer to form a waveguide pattern;

[0055] Step 305: Etching the silicon nitride layer using the waveguide pattern to form a waveguide layer;

[0056] Step 306: Continue exposing the surface of the photoresist layer to form a grating pattern;

[0057] Step 307: Etching the waveguide layer using the grating pattern to form a plurality of grating units arranged in an array, each grating unit including a first grating and a second grating;

[0058] Step 308 : remove the remaining photoresist layer and perform cleaning to form a waveguide grating coupler array.

[0059] In step 301, a silicon nitride layer may be grown on a silicon dioxide substrate by using a plasma enhanced chemical vapor deposition (PECVD) method.

[0060] In step 303 , a photoresist layer may be spin-coated on the lower surface of the silicon nitride layer in a spin coater at a preset rotation speed. The preset rotation speed may be 2000-5000 rpm, but the embodiment is not limited thereto.

[0061] In step 304, an electron beam exposure process may be used to expose the surface of the photoresist layer to form a waveguide pattern.

[0062] In step 305, an inductively coupled plasma process may be used to etch the silicon nitride layer using the waveguide pattern to form a waveguide layer. The thickness of the waveguide layer ranges from 0.25 μm to 0.4 μm, but the present embodiment is not limited thereto.

[0063] In step 306 , an electron beam exposure process may be used to continue exposing the surface of the photoresist layer to form a grating pattern.

[0064] In step 307, an inductively coupled plasma process can be used to etch the waveguide layer using the grating pattern to form a plurality of grating units arranged in an array, each of which includes a first grating and a second grating. Specifically, the first grating and the second grating each include alternating grating teeth and etched holes, and the grating teeth are rectangular in shape.

[0065] Optionally, the grating periods and duty cycles of the first grating are the same. For example, the grating periods of the first grating are 768 nm, the duty cycles of the first grating are 0.5, and the total number of periods of the first grating may be 13. This embodiment is not limited thereto.

[0066] The grating periods and duty cycles of the second grating are the same. For example, the grating periods of the second grating 102 are 805 nm, the duty cycles of the second grating 102 are 0.75, and the total number of periods of the second grating 102 can be 13. This embodiment is not limited thereto.

[0067] The first grating and the second grating have the same depth and different grating periods. For example, the grating period of the first grating is 768 nm, the grating period of the second grating is 805 nm, and the depths of the first grating and the second grating are both 272 nm. This embodiment is not limited thereto.

[0068] In this embodiment, the waveguide grating coupler array is manufactured by using deposition, exposure, etching and other processes. The structure and process of the waveguide grating coupler array are relatively simple.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A laser array using unidirectional light injection modulation, characterized in that: include: A plurality of laser units arranged in an array, each laser unit comprising: a waveguide grating coupler, a master laser and a slave laser; The waveguide grating coupler comprises: a grating unit, a waveguide unit and an oxidation unit; wherein the grating unit comprises a first grating and a second grating, the lower sides of the waveguide unit are respectively connected to the first grating and the second grating, and the oxidation unit is located on the upper surface of the waveguide unit; The master laser is located below the first grating, the slave laser is located obliquely below the second grating, and the horizontal projection of the light emitting area of ​​the slave laser does not overlap with the horizontal projection of the second grating.

2. The laser array using unidirectional light injection modulation according to claim 1, characterized in that: The grating periods and duty cycles of the first grating are the same, and the grating period of the first grating is associated with the duty cycle of the first grating.

3. The laser array using unidirectional light injection modulation according to claim 1, characterized in that: The grating periods and duty cycles of the second grating are the same. The grating period of the second grating is associated with an emission angle and the duty cycle of the second grating. The emission angle is the angle between the direction of the emitted light of the second grating and the plane normal direction of the second grating.

4. The laser array using unidirectional light injection modulation according to claim 1, characterized in that: The first grating and the second grating have the same depth and different grating periods.

5. The laser array using unidirectional light injection modulation according to any one of claims 1 to 4, characterized in that: The projection of the first grating on the horizontal plane overlaps with the projection of the light emitting area of ​​the master laser on the horizontal plane.

6. The laser array using unidirectional light injection modulation according to any one of claims 1 to 4, characterized in that: The waveguide grating coupler is not in contact with upper surfaces of the master laser and the slave laser, respectively.

7. The laser array using unidirectional light injection modulation according to any one of claims 1 to 4, characterized in that: The first grating and the second grating are both diffraction gratings. The diffraction gratings include alternately distributed grating teeth and etched holes. The grating teeth are rectangular in shape.

8. The laser array using unidirectional light injection modulation according to any one of claims 1 to 4, characterized in that: The grating unit is a sub-wavelength grating structure formed by etching the lower surface of the waveguide layer, and the etched waveguide layer includes the grating unit and the waveguide unit.

9. The laser array using unidirectional light injection modulation according to any one of claims 1 to 4, characterized in that: The waveguide unit and the grating unit are both made of silicon nitride.

10. The laser array using unidirectional light injection modulation according to any one of claims 1 to 4, characterized in that: The material of the oxidation unit is silicon dioxide.

Images