Parallel-coupled self-imaging external-cavity coherent array semiconductor laser and preparation method thereof

Abstract

The application discloses a kind of parallel coupling self-imaging external cavity coherent array semiconductor laser, comprising: semiconductor laser chip array, light transmission dielectric layer and external cavity reflection layer;Semiconductor laser chip array includes multiple light emitting units, light transmission dielectric layer and external cavity reflection layer form laser self-imaging external cavity;The non-light emitting area of semiconductor laser chip array light emitting surface is coated with high reflection film, and the feedback light that cannot be injected into the light emitting unit due to incomplete self-imaging at the edge of semiconductor laser chip array can oscillate in self-imaging external cavity multiple times to reform the self-imaging that can be completely injected into the light emitting unit.The application improves the injection of laser outside the light emitting area, can efficiently parallel coupling all light emitting units including edge in chip array, eliminate the edge effect of chip array generated by self-imaging external cavity feedback, enhance the feedback efficiency of self-imaging external cavity, obtain the coherent array laser output of high parallel coupling efficiency, high efficiency optical mutual injection.

Description

Technical Field

[0001] This invention relates to the field of semiconductor laser technology, specifically to an enhanced parallel-coupled self-imaging external cavity coherent array semiconductor laser and its fabrication method. Background Technology

[0002] Coherent combining technology is an important method for achieving high-power, high-beam-quality laser output. It achieves phase locking by controlling the wavelength and phase of the output beams from each sub-unit of a multi-aperture laser chip array, forming a coherently combined laser chip array laser. For m laser beams that are close together and have the same intensity, the greater the intensity obtained after their coherent overlap in the far field, the better. If the laser beams are one-dimensionally distributed and incoherent, their superimposed intensity in the far field is m times the intensity of a single laser beam; if the laser beams are coherent, their superimposed intensity in the far field is m times the intensity of a single laser beam. 2 The output of a laser can be greatly enhanced by several times; therefore, it is of great significance to design coherent semiconductor lasers and their self-imaging external cavity structures.

[0003] With the continuous advancement of coherent technology, various application fields have placed higher demands on the device performance of coherent array semiconductor lasers, especially on their output light intensity and beam quality, requiring high-brightness semiconductor coherent chip array lasers. However, in reality, since objects are not infinitely long periodic objects under ideal conditions, the self-imaging external cavity phase-locked loop technology will deviate from the actual situation of finite lengths, which is the non-ideal coupling situation of the self-imaging external cavity. Especially at the edge of the semiconductor laser chip array, due to increased diffraction loss, the far-field light intensity distribution at the edge is weaker, a phenomenon known as the edge effect. This will have a certain impact on the output light intensity of the semiconductor laser chip array, making it impossible to achieve coherent output with high coupling efficiency between the light-emitting unit of the semiconductor laser chip array and the laser self-imaging external cavity. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides an enhanced parallel-coupled self-imaging external cavity coherent array semiconductor laser and its fabrication method. A high-reflectivity film is deposited on the non-emitting area of ​​the semiconductor laser chip array's emitting surface. This allows laser light that cannot be injected into the emitting unit due to incomplete self-imaging at the edge of the feedback laser chip array to oscillate multiple times in the self-imaging external cavity. During the oscillation process in the self-imaging external cavity, a new self-image is formed and injected into the chip's emitting unit, ultimately resulting in complete injection into the emitting unit. This method improves the injection of laser light outside the emitting region, efficiently couples all emitting units in the chip array, including the edges, eliminates the chip array edge effect caused by self-imaging external cavity feedback, enhances the self-imaging external cavity feedback efficiency, and obtains coherent array laser output with high parallel coupling efficiency and efficient optical mutual injection.

[0005] This invention discloses a parallel-coupled self-imaging external cavity coherent array semiconductor laser, comprising: a semiconductor laser chip array, a light-transmitting dielectric layer, and an external cavity reflective layer arranged sequentially from bottom to top;

[0006] The semiconductor laser chip array includes multiple light-emitting units, and the light-transmitting dielectric layer and the external cavity reflective layer constitute a laser self-imaging external cavity; the laser emitted by the light-emitting units of the semiconductor laser chip array is reflected by the laser self-imaging external cavity to form a self-imaging injection into the light-emitting units, realizing feedback light mutual injection and forming coherent light output;

[0007] The non-light-emitting area of ​​the light-emitting surface of the semiconductor laser chip array is coated with a high-reflectivity film. The high-reflectivity film allows the feedback light that cannot be injected into the light-emitting unit due to incomplete self-imaging at the edge of the semiconductor laser chip array to oscillate multiple times in the self-imaging outer cavity, so as to re-form a self-image that can be completely injected into the light-emitting unit.

[0008] As a further improvement of the present invention, each light-emitting unit of the semiconductor laser chip array includes, from bottom to top, the following: an N-electrode layer, a substrate layer, a space waveguide layer, an active region, and a P-electrode layer, wherein the high-reflectivity film is deposited on the P-electrode layer of the light-emitting unit; a specific embodiment is as follows: from bottom to top, the following are arranged in sequence: an N-electrode layer, a substrate layer, an N-DBR layer, an active layer, an oxide confinement layer, a P-DBR layer, and a P-electrode layer, with laser output from the top P-electrode layer side.

[0009] As a further improvement of the present invention, the substrate layer includes one of GaAs, lnP, GaN and SiC substrates, the electrode material of the N-electrode layer or P-electrode layer includes one or more metals formed by alloying Al, Ti, Pt, Pb, Au, Cu, Ni and Ge, and the semiconductor laser chip array selectively emits ultraviolet to infrared lasers.

[0010] As a further improvement of the present invention, the semiconductor laser chip array forms a self-image after oscillating for one cycle in the laser self-imaging external cavity, so that the feedback laser is injected back into the light-emitting unit of the chip; the laser self-imaging external cavity can be a Fourier external cavity or a Talbot external cavity, or other external cavity structures that can form a self-image.

[0011] As a further improvement of the present invention, the material of the laser self-imaging outer cavity can be amorphous silicon dioxide, quartz glass or silicon nitride, etc., which are laser transmission materials. The light-emitting unit of the semiconductor laser chip array realizes coherent light output through feedback from the laser self-imaging outer cavity. The outermost layer of the self-imaging outer cavity is coated with an outer cavity reflective layer, and the reflectivity can be selected from 50% to 99.9% according to the actual optical design.

[0012] As a further improvement of the present invention, the high-reflectivity film is a multilayer optical reflective film system. The multilayer optical reflective film system is a film system in which high-refractive-index film layers and low-refractive-index film layers with an optical thickness of lasing wavelength λ0 / 4 are alternately deposited. The reflectivity of the multilayer optical reflective film system is 50%-99.9%, which can enhance the reflection of edge lasers.

[0013] As a further improvement of the present invention, the laser self-imaging outer cavity and the inner cavity of the semiconductor laser chip array together constitute a composite resonant cavity. The mutual injection coupling mechanism between the chip light-emitting units is established through the feedback coupling of the laser self-imaging outer cavity, so that the beam can effectively form a self-image and be injected back into the chip light-emitting unit, reducing the diffraction loss of the chip array, reducing the edge effect, realizing the passive phase-locking of the chip array, and obtaining laser output with high spatial coherence.

[0014] As a further improvement of the present invention, the semiconductor laser chip array and the laser self-imaging external cavity are connected by heterogeneous direct bonding. The heterogeneous direct bonding can be achieved by vacuum surface activation, ultraviolet light activation, Ar / O2 / N2 plasma activation or wet chemical activation.

[0015] As a further improvement of the present invention, the light-emitting units of the semiconductor laser chip array are arranged in a one-dimensional or two-dimensional periodic pattern. The one-dimensional chip array is arranged in a periodic linear pattern, and the two-dimensional chip array is arranged in one of the following ways: a two-dimensional square chip array, a two-dimensional oblique chip array, a circular chip array, and a two-dimensional hexagonal chip array.

[0016] The present invention also provides a method for fabricating a parallel-coupled self-imaging external cavity coherent array semiconductor laser, comprising:

[0017] Construct a periodically distributed array of semiconductor laser chips;

[0018] A high-reflectivity film is deposited on the non-light-emitting area of ​​the light-emitting surface of the semiconductor laser chip array;

[0019] A light-transmitting dielectric layer is bonded onto the high-reflectivity film of the semiconductor laser chip array;

[0020] An external cavity reflective layer is deposited at the output end of the light-transmitting medium layer to form a laser self-imaging external cavity;

[0021] Encapsulation of semiconductor laser chip arrays and laser self-imaging external cavities.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] This invention eliminates the edge effect present in the self-imaging external cavity feedback of a parallel-coupled self-imaging external cavity coherent array semiconductor laser by coating a high-reflectivity film on the non-emitting area of ​​the light-emitting surface of the semiconductor laser chip array, and couples all light-emitting units in the chip array, including the edges. At the same time, it achieves passive phase locking, improves the optical feedback efficiency of the self-imaging external cavity coherent array semiconductor laser, and is conducive to achieving efficient parallel coupling of light and obtaining coherent array laser output with high beam quality. Attached Figure Description

[0024] Figure 1 A schematic diagram of a parallel-coupled self-imaging external cavity coherent array laser provided by the present invention;

[0025] Figure 2a This is a schematic diagram of the original quadrilateral array light spot disclosed in one embodiment of the present invention;

[0026] Figure 2b This is a schematic diagram of the edge feedback light spot of a quadrilateral array disclosed in one embodiment of the present invention (the edge light spot is relatively large);

[0027] Figure 2c This is a schematic diagram of the original hexagonal array light spot disclosed in one embodiment of the present invention;

[0028] Figure 2d This is a schematic diagram of the edge feedback light spot of the hexagonal array disclosed in one embodiment of the present invention (the edge light spot is relatively large);

[0029] Figure 2e This is a schematic diagram of the original light spot of a linear array disclosed in one embodiment of the present invention;

[0030] Figure 2f This is a schematic diagram of the edge feedback light spot of a linear array disclosed in one embodiment of the present invention (the edge light spot is relatively large);

[0031] Figure 3 A flowchart of a method for fabricating a parallel-coupled self-imaging external cavity coherent array semiconductor laser provided by the present invention;

[0032] Figure 4 This is a schematic diagram of the light intensity distribution of a 30×1 VCSEL chip array with an external cavity 3-layer reflective film (without an edge reflective film) disclosed in an embodiment of the present invention.

[0033] Figure 5 This is a schematic diagram of the light intensity distribution of a 30×1 VCSEL chip array with 3 layers of external cavity reflective film and 4 layers of edge reflective film disclosed in an embodiment of the present invention.

[0034] In the picture:

[0035] 1. Semiconductor laser chip array; 2. High reflectivity film; 3. Light-transmitting dielectric layer; 4. External cavity reflective layer. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] The present invention will now be described in further detail with reference to the accompanying drawings:

[0038] like Figure 1 As shown, this invention provides a parallel-coupled self-imaging external cavity coherent array semiconductor laser, comprising: a semiconductor laser chip array 1, a light-transmitting dielectric layer 3, and an external cavity reflective layer 4 arranged sequentially from bottom to top; wherein, the semiconductor laser chip array 1 includes multiple light-emitting units, and the light-transmitting dielectric layer 3 and the external cavity reflective layer 4 constitute a laser self-imaging external cavity; the laser emitted by the light-emitting units of the semiconductor laser chip array 1 is reflected by the laser self-imaging external cavity to form a self-imaging injection into the light-emitting units, realizing feedback light mutual injection and forming coherent light output; wherein, the initial light spot of the laser chip array arranged in quadrilaterals, hexagons, and one-dimensional periodic arrangements is as follows. Figure 2a , 2c As shown in Figure 2e; the light field distribution of laser chip arrays arranged in quadrilaterals, hexagons, and one-dimensional periodicities after feedback from a self-imaging external cavity is as follows. Figure 2b , 2d As shown in 2f;

[0039] To solve Figure 2b , 2d As shown in 2f, the present invention coats a high-reflectivity film 2 on the non-light-emitting area of ​​the light-emitting surface of the semiconductor laser chip array 1. The high-reflectivity film 2 allows the feedback light that cannot be injected into the light-emitting unit due to incomplete self-imaging at the edge of the semiconductor laser chip array to oscillate multiple times in the self-imaging external cavity, so as to re-form a self-image that can be completely injected into the light-emitting unit. It improves the injection of laser outside the light-emitting area, can efficiently couple all light-emitting units in the chip array, including the edge, eliminate the chip array edge effect caused by the feedback of the self-imaging external cavity, enhance the feedback efficiency of the self-imaging external cavity, and obtain coherent array laser output with high parallel coupling efficiency and efficient light mutual injection.

[0040] Furthermore, each light-emitting unit of the semiconductor laser chip array includes, from bottom to top, an N-electrode layer, a substrate layer, a space waveguide layer, an active region, and a P-electrode layer, with a high-reflectivity film deposited on the P-electrode layer of the light-emitting unit; in a specific embodiment, the following layers are arranged from bottom to top: an N-electrode layer, a substrate layer, an N-DBR layer, an active layer, an oxide confinement layer, a P-DBR layer, and a P-electrode layer, with laser output from the top P-electrode layer side.

[0041] Furthermore, the substrate layer includes one of GaAs, lnP, GaN, and SiC substrates, and the electrode material of the N-electrode layer or P-electrode layer includes one or more metals formed by alloying Al, Ti, Pt, Pb, Au, Cu, Ni, and Ge. The semiconductor laser chip array selectively emits ultraviolet to infrared lasers.

[0042] Furthermore, the semiconductor laser chip array forms a self-image after oscillating for one cycle in the laser self-imaging external cavity, so that the feedback laser is injected back into the light-emitting unit of the chip; the laser self-imaging external cavity can be a Fourier external cavity or a Tyber external cavity, or other external cavity structures that can form a self-image.

[0043] Furthermore, the material of the laser self-imaging external cavity can be amorphous silicon dioxide, quartz glass, or silicon nitride, etc., which are laser transmission materials. The light-emitting unit of the semiconductor laser chip array achieves coherent light output through feedback from the laser self-imaging external cavity. The outermost layer of the self-imaging external cavity is coated with an external cavity reflective layer, and the reflectivity can be selected from 50% to 99.9% according to the actual optical design.

[0044] Furthermore, the high-reflectivity film is a multilayer optical reflective film system. The multilayer optical reflective film system is a film system in which high-refractive-index film layers and low-refractive-index film layers with an optical thickness of lasing wavelength λ0 / 4 are alternately deposited. The reflectivity of the multilayer optical reflective film system is 50%-99.9%, which can enhance the reflection of edge lasers.

[0045] Furthermore, the laser self-imaging external cavity and the internal cavity of the semiconductor laser chip array together form a composite resonant cavity. By establishing a mutual injection coupling mechanism between the chip light-emitting units through feedback coupling of the laser self-imaging external cavity, the beam can effectively form a self-image and be injected back into the chip light-emitting unit, reducing the diffraction loss of the chip array, reducing edge effects, realizing passive phase-locking of the chip array, and obtaining laser output with high spatial coherence.

[0046] Furthermore, the semiconductor laser chip array and the laser self-imaging external cavity are connected by heterogeneous direct bonding. The heterogeneous direct bonding can be achieved by vacuum surface activation, ultraviolet light activation, Ar / O2 / N2 plasma activation or wet chemical activation.

[0047] Furthermore, the light-emitting units of the semiconductor laser chip array are arranged in a one-dimensional or two-dimensional periodic pattern. The one-dimensional chip array is arranged in a periodic linear pattern, such as... Figure 2e As shown; the two-dimensional chip array arrangement includes two-dimensional square chip arrays (such as... Figure 2a (as shown), two-dimensional oblique-shaped chip arrays, circular chip arrays, and two-dimensional hexagonal chip arrays (such as...) Figure 2c One of them (as shown).

[0048] The self-imaging effect of one-dimensional laser arrays is an important research direction in the study of phase-locked loop (PLL) self-imaging external cavities for semiconductor laser arrays. However, in practical applications, it is difficult for one-dimensional laser arrays to achieve an infinite number of periodic cells, making it impossible for them to produce an ideal self-imaging effect, i.e., edge effects exist. This study uses FDTD Solutions software to simulate the far-field light intensity distribution of a one-dimensional linearly arranged semiconductor laser chip array after feedback through a self-imaging external cavity. By comparing this simulation with the light field distribution of a one-dimensional laser array with an edge reflective film, the effect of mitigating the edge effects is verified.

[0049] Using a 30×1 VCSEL one-dimensional linear array as a simulation example, without an edge reflective film, the array simulation parameters are as follows: the VCSEL light source is set to a Gaussian beam with a wavelength of 980 nm, the beam waist radius of the Gaussian beam is set to 2 μm, the aperture size of each VCSEL light-emitting unit is 8 μm, and the period is 10 μm; in the simulation, an air cavity is used instead of the laser self-imaging outer cavity. To enhance the feedback efficiency of the outer cavity, a λ0 / 4 film system with three alternating layers of high and low reflective films is deposited on the outermost layer of the self-imaging outer cavity. The high and low refractive indices are set to 2.34 and 1.38, respectively, and the optical thickness of the reflective films is λ0 / 4 of the lasing wavelength, i.e., 0.245 μm. The simulation results are as follows. Figure 4 As shown: it can be seen that without the addition of the edge reflective film, the light intensity distribution at the edge of the chip array is weaker, which is 12.5% ​​weaker than the light intensity distribution in the far field.

[0050] Taking a one-dimensional linear periodic array as an example, such as Figure 4 As shown, when there is no edge-reflective film, the light field intensity distribution of the semiconductor chip array exhibits an edge effect.

[0051] With the addition of an edge-reflecting film, the edge effect of the self-imaging optical field distribution of a one-dimensional laser array after feedback from the self-imaging external cavity is significantly reduced, such as... Figure 5 As shown, the far-field light intensity distribution at the edge of the chip array is enhanced, and its far-field light intensity distribution is relatively uniform. Therefore, adding an edge reflective film can effectively eliminate the edge effect.

[0052] Simulation results show that adding a high-reflectivity film can effectively reduce edge effects.

[0053] The present invention also provides a method for fabricating a parallel-coupled self-imaging external cavity coherent array semiconductor laser, comprising:

[0054] Construct a periodically distributed array of semiconductor laser chips;

[0055] A high-reflectivity film is deposited on the non-light-emitting area of ​​the light-emitting surface of a semiconductor laser chip array;

[0056] A light-transmitting dielectric layer is bonded onto the high-reflectivity film of a semiconductor laser chip array;

[0057] An external cavity reflective layer is deposited at the output end of the light-transmitting dielectric layer to form a laser self-imaging external cavity;

[0058] Encapsulation of semiconductor laser chip arrays and laser self-imaging external cavities.

[0059] Example 1:

[0060] like Figure 1 As shown, this invention provides an enhanced parallel-coupled self-imaging external cavity coherent surface-emitting laser; comprising: a surface-emitting semiconductor laser chip array 1, a light-transmitting dielectric layer 3, and an external cavity reflective layer 4 arranged sequentially from bottom to top; wherein:

[0061] The surface-emitting semiconductor laser chip array 1 in this embodiment is as follows: Figure 2a The quadrilateral top-emitting surface-emitting semiconductor laser chip array shown has at least four light sources, with n equal to at least two light sources per row or column. The horizontal and vertical periods are both T = 5–1000 μm, used to generate a spatially periodically distributed light field. The substrate can be GaAs-based to achieve lasing wavelengths of 850 / 940 / 980 nm, lnP-based to achieve lasing wavelengths of 1300 / 1550 nm, GaN-based to achieve lasing wavelengths of 400–565 nm, or SiC-based to achieve lasing wavelengths of 200 nm, emitting laser light in the ultraviolet to infrared range. The substrate of the surface-emitting semiconductor laser chip array has an N-DBR layer composed of Al. x Ga 1-x As provides a reflectivity of over 99.5%; the N-DBR layer is topped by an active layer, which in turn is topped by an oxide confinement layer, and finally by a P-DBR layer, composed of Al. x Ga 1-x As provides a reflectivity of less than 99.5%; the substrate layer is thinned, and the non-planar electrodes are prepared by metal evaporation, with the laser output from the top P-electrode layer side.

[0062] The surface-emitting semiconductor laser chip array 1 has a P-electrode layer with a high-reflectivity film 2 deposited on its P-DBR layer output end. A light-transmitting dielectric layer 3 is located outside the P-electrode layer, and a laser self-imaging external cavity reflective layer 4 is located at the output end of the light-transmitting dielectric layer 3. To increase the reflectivity of the output end, the reflectivity of the self-imaging external cavity reflective layer 4 in this invention is above 50%. To achieve heterogeneous direct bonding, the P-electrode layer with the high-reflectivity film, the light-transmitting dielectric layer 3, and the self-imaging external cavity reflective layer 4 are arranged parallel to the light-emitting surface of the surface-emitting semiconductor laser chip array 1, and their surfaces are all ground and polished to achieve a flatness with a uniformity of less than 5 nm. Furthermore, a heat dissipation structure can be provided under the substrate layer of the surface-emitting semiconductor laser chip array 1.

[0063] In this embodiment, the light-transmitting dielectric layer 3 is used to transmit the light beam emitted from the surface-emitting semiconductor laser chip array and obtain the diffraction light field distribution.

[0064] This invention provides a method for fabricating the above-mentioned enhanced parallel-coupled self-imaging external cavity coherent chip array surface-emitting laser, comprising:

[0065] S1. Prepare a periodically distributed surface-emitting semiconductor laser chip array 1;

[0066] Specifically, this involves arranging top-emitting lasers with more than four units according to... Figure 2a The chip array shown is arranged in a quadrilateral shape, with the spacing between the surface-emitting laser light-emitting units being 5–1000 μm, and the device is fabricated accordingly.

[0067] S2. Deposit a high-reflectivity film 2 on the P-electrode layer of the surface-emitting semiconductor laser chip array 1;

[0068] Specifically, a P-electrode layer is sputtered on the top layer of the epitaxial layer using magnetron sputtering. The metal materials and thicknesses used are as follows: Ti metal 20nm-30nm, Pt metal 20nm-30nm, and Au metal 130nm-150nm. A set of multilayer optical reflective films with uniform thickness is then deposited on the P-electrode layer using chemical vapor deposition (CVD).

[0069] S3. Bond the self-imaging external cavity onto the high-reflectivity film layer 2;

[0070] Specifically:

[0071] Heterogeneous direct bonding is performed using a surface vacuum activation method in a high vacuum environment (<10). -5Pa) utilizes high-speed argon atoms or argon ions to bombard the wafer surface, removing the surface oxide film and other contaminants. Then, a certain pressure is applied to bring the two oxide-removed surfaces into close contact in a high-vacuum environment. Relying on the chemical bonds, the surface energy is lowered, achieving a strong bond at the atomic scale. Good bond strength can be achieved at room temperature (approximately 25°C), completing the bonding without subsequent annealing.

[0072] Alternatively, heterogeneous bonding can be achieved using plasma-activated bonding. After cleaning with RCA solution, the wafer surface is irradiated with O2, N, H ratio or Ar plasma, and then pre-bonded together at room temperature. After low-temperature annealing at 200-400°C, a sufficiently high bonding strength is achieved.

[0073] Alternatively, wet chemical cleaning and activation can be used to achieve direct heterogeneous bonding. After surface cleaning, activation, and hydrophilic pretreatment, bonding is carried out at room temperature, followed by high-temperature annealing at around 450°C to achieve the final bonding strength.

[0074] S4. An external cavity reflective layer 4 is fabricated on the output end of the self-imaging external cavity structure;

[0075] Specifically, a set of multilayer optical reflective films of uniform thickness is deposited on a light-transmitting medium layer using chemical vapor deposition (CVD).

[0076] S5, packaging;

[0077] Specifically, gold-tin electrodes are prefabricated on the surface of a ceramic substrate, the prepared surface-emitting laser chip is flip-chip bonded to the gold-tin electrodes, the ceramic substrate is fixed on a water-cooled heat sink, and the encapsulation is completed.

[0078] Example 2

[0079] like Figure 1 and Figure 2e As shown, this invention provides a one-dimensional coherent array side-emitting laser structure and fabrication method, comprising: a side-emitting semiconductor laser chip array 1, a light-transmitting dielectric layer 3, and an external cavity reflective layer 4; wherein:

[0080] Side-emitting lasers with more than 4 units are arranged according to Figure 2e The chip array shown is arranged in a one-dimensional linear configuration. The number of light sources in the edge-emitting semiconductor laser chip array 1 is greater than or equal to two. The spacing between the light-emitting units of the edge-emitting lasers is 5–1000 μm, and the period is T = 5–1000 μm, used to generate a spatially periodically distributed light field. The substrate can be GaAs-based to achieve lasing wavelengths of 850 / 940 / 980 nm, lnP-based to achieve lasing wavelengths of 1300 / 1550 nm, GaN-based to achieve lasing wavelengths of 400–565 nm, or SiC-based to achieve lasing wavelengths of 200 nm, emitting lasers in the ultraviolet to infrared laser band.

[0081] The edge-emitting laser structure includes: a substrate, an N-face electrode, a semiconductor epitaxial structure, and a P-face electrode. The semiconductor epitaxial structure includes an N-type confinement layer, an N-type waveguide layer, an active region, a P-type waveguide layer, a P-type confinement layer, a highly doped layer, and an electrically insulating layer. The N-waveguide layer on the edge-emitting laser substrate is composed of Al. x Ga x As; the N-waveguide layer is the active layer, and the P-waveguide layer is above the active layer, composed of Al. x Ga x As shown in the figure, a one-dimensional chip array seed region and a lossless laser transmission waveguide are set on the surface of the epitaxial layer of the edge-emitting semiconductor laser chip. The one-dimensional chip array seed region is a one-dimensional chip array waveguide, which can be a narrow ridge waveguide, a DBR ridge waveguide, or a surface DFB ridge waveguide. The dimensions of the one-dimensional chip array waveguide are: length 500μm~2000μm, width 3μm~5μm, spacing 3μm~5μm, and depth 0.7μm~1μm. The substrate layer is thinned, and non-planar electrodes are prepared by metal evaporation. Metal P-electrodes and metal N-electrodes are fabricated in the semiconductor epitaxial structure. Two parallel cleaved cavity surfaces are obtained by cleaving the two sides of the semiconductor epitaxial structure. Anti-reflection and anti-reflection films are deposited on them respectively to obtain an edge-emitting semiconductor laser. The laser is output from the waveguide spacer layer above and below the active layer at the edge.

[0082] The outer surface of the light-emitting semiconductor laser chip array 1 is provided with a light-transmitting dielectric layer 3, and the output end of the light-transmitting dielectric layer 3 is provided with a laser self-imaging external cavity reflective layer 4. In order to increase the reflectivity of the output end, the reflectivity of the self-imaging external cavity reflective layer 5 in this invention is above 50%; in order to achieve heterogeneous direct bonding, the non-light-emitting region layer coated with a high-reflectivity film, the light-transmitting dielectric layer 3, and the self-imaging external cavity reflective layer 5 in this invention are arranged parallel to the light-emitting surface of the edge-emitting semiconductor laser chip array 1, and the surfaces are all ground and polished to obtain a flatness with a uniformity of less than 5nm; furthermore, a heat dissipation structure can be provided under the substrate layer of the edge-emitting semiconductor laser chip array 1.

[0083] The present invention also provides a method for fabricating the above-mentioned enhanced parallel-coupled self-imaging external cavity coherent chip array side-emitting laser, comprising:

[0084] S1. Prepare a periodically distributed edge-emitting semiconductor laser chip array 1;

[0085] Specifically, this involves arranging side-emitting lasers with more than four units according to... Figure 2e The rectangular chip array shown has a spacing of 5–1000 μm between the side-emitting laser light-emitting units, and is used to fabricate a device.

[0086] S2. A high-reflectivity film 2 is deposited on the P-electrode layer on the light-emitting surface of the edge-emitting semiconductor laser chip array 1;

[0087] Specifically, a P-electrode layer is sputtered on the top layer of the epitaxial layer using magnetron sputtering. The metal materials and thicknesses used are as follows: Ti metal 20nm-30nm, Pt metal 20nm-30nm, and Au metal 130nm-150nm. A set of multilayer optical reflective films with uniform thickness is then deposited on the P-electrode layer using chemical vapor deposition (CVD).

[0088] S3. Bond the self-imaging external cavity onto the high-reflectivity film layer 2;

[0089] Specifically:

[0090] Heterogeneous direct bonding is performed using a surface vacuum activation method in a high vacuum environment (<10). -5 Pa) utilizes high-speed argon atoms or argon ions to bombard the wafer surface, removing the surface oxide film and other contaminants. Then, a certain pressure is applied to bring the two oxide-removed surfaces into close contact in a high-vacuum environment. Relying on the chemical bonds, the surface energy is lowered, achieving a strong bond at the atomic scale. Good bond strength can be achieved at room temperature (approximately 25°C), completing the bonding without subsequent annealing.

[0091] Alternatively, heterogeneous bonding can be achieved using plasma-activated bonding. After cleaning with RCA solution, the wafer surface is irradiated with O2, N, H ratio or Ar plasma, and then pre-bonded together at room temperature. After low-temperature annealing at 200-400°C, a sufficiently high bonding strength is achieved.

[0092] Alternatively, wet chemical cleaning and activation can be used to achieve direct heterogeneous bonding. After surface cleaning, activation, and hydrophilic pretreatment, bonding is carried out at room temperature, followed by high-temperature annealing at around 450°C to achieve the final bonding strength.

[0093] S4. An external cavity reflective layer 4 is fabricated on the output end of the self-imaging external cavity structure;

[0094] Specifically, a set of multilayer optical reflective films of uniform thickness is deposited on a light-transmitting medium layer using chemical vapor deposition (CVD).

[0095] S5, packaging;

[0096] Specifically, gold-tin electrodes are prefabricated on the surface of a ceramic substrate, the prepared edge-emitting laser chip is flip-chip bonded to the gold-tin electrodes, the ceramic substrate is fixed on a water-cooled heat sink, and the encapsulation is completed.

[0097] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A parallel-coupled self-imaging external cavity coherent array semiconductor laser, characterized in that, include: The semiconductor laser chip array, the light-transmitting dielectric layer, and the external cavity reflective layer are arranged sequentially from bottom to top. The semiconductor laser chip array includes multiple light-emitting units, and the light-transmitting dielectric layer and the external cavity reflective layer constitute a laser self-imaging external cavity; the laser emitted by the light-emitting units of the semiconductor laser chip array is reflected by the laser self-imaging external cavity to form a self-imaging injection into the light-emitting units, realizing feedback light mutual injection and forming coherent light output; The non-light-emitting area of ​​the light-emitting surface of the semiconductor laser chip array is coated with a high-reflectivity film. The high-reflectivity film allows the feedback light that cannot be injected into the light-emitting unit due to incomplete self-imaging at the edge of the semiconductor laser chip array to oscillate multiple times in the self-imaging outer cavity, so as to re-form a self-image that can be completely injected into the light-emitting unit.

2. The parallel-coupled self-imaging external cavity coherent array semiconductor laser as described in claim 1, characterized in that, Each light-emitting unit of the semiconductor laser chip array includes, from bottom to top, an N-electrode layer, a substrate layer, a space waveguide layer, an active region, and a P-electrode layer, with the high-reflectivity film deposited on the P-electrode layer of the light-emitting unit.

3. The parallel-coupled self-imaging external cavity coherent array semiconductor laser as described in claim 2, characterized in that, The substrate layer includes one of GaAs, lnP, GaN and SiC substrates, the electrode material of the N-electrode layer or P-electrode layer includes one or more metals formed by alloying Al, Ti, Pt, Pb, Au, Cu, Ni and Ge, and the semiconductor laser chip array selectively emits ultraviolet to infrared lasers.

4. The parallel-coupled self-imaging external cavity coherent array semiconductor laser as described in claim 1, characterized in that, The laser self-imaging external cavity includes one of a Fourier external cavity and a Talbot external cavity, and is used to cause the semiconductor laser chip array to oscillate in the laser self-imaging external cavity for one cycle to form a self-image.

5. The parallel-coupled self-imaging external cavity coherent array semiconductor laser as described in claim 1, characterized in that, The material selection for the light-transmitting medium layer includes laser transmission materials selected from amorphous silicon dioxide, quartz glass, and silicon nitride, and the reflectivity of the outer cavity reflective layer is 50%-99.9%.

6. The parallel-coupled self-imaging external cavity coherent array semiconductor laser as described in claim 1, characterized in that, The high-reflectivity film is a multilayer optical reflective film system, which is a film system in which high-refractive-index film layers and low-refractive-index film layers with an optical thickness of lasing wavelength λ0 / 4 are alternately deposited. The reflectivity of the multilayer optical reflective film system is 50%-99.9%.

7. The parallel-coupled self-imaging external cavity coherent array semiconductor laser as described in claim 1, characterized in that, The laser self-imaging outer cavity and the inner cavity of the semiconductor laser chip array together form a composite resonant cavity. The feedback coupling of the laser self-imaging outer cavity establishes a mutual injection coupling mechanism between the chip light-emitting units, so that the beam can effectively form a self-image and be injected back into the chip light-emitting units.

8. The parallel-coupled self-imaging external cavity coherent array semiconductor laser as described in claim 1, characterized in that, The semiconductor laser chip array is connected to the laser self-imaging external cavity by heterogeneous direct bonding. The heterogeneous direct bonding can be achieved by one of the following methods: vacuum surface activation, ultraviolet light activation, Ar / O2 / N2 plasma activation, and wet chemical activation.

9. The parallel-coupled self-imaging external cavity coherent array semiconductor laser as described in claim 1, characterized in that, The light-emitting units of the semiconductor laser chip array are arranged in a one-dimensional or two-dimensional periodic pattern. The one-dimensional chip array is arranged in a periodic linear pattern, and the two-dimensional chip array is arranged in one of the following ways: a two-dimensional square chip array, a two-dimensional oblique chip array, a circular chip array, and a two-dimensional hexagonal chip array.

10. A method for fabricating a parallel-coupled self-imaging external cavity coherent array semiconductor laser as described in any one of claims 1 to 9, characterized in that, include: Construct a periodically distributed array of semiconductor laser chips; A high-reflectivity film is deposited on the non-light-emitting area of ​​the light-emitting surface of the semiconductor laser chip array; A light-transmitting dielectric layer is bonded onto the high-reflectivity film of the semiconductor laser chip array; An external cavity reflective layer is deposited at the output end of the light-transmitting medium layer to form a laser self-imaging external cavity; Encapsulation of semiconductor laser chip arrays and laser self-imaging external cavities.

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