A narrow linewidth coherent light vcse1 array chip

Abstract

The application discloses a narrow linewidth coherent light VCSEL array chip, and the array size is 1*2; the array chip comprises a first laser emission unit and a second laser emission unit which are symmetrical; the first laser emission unit and the second laser emission unit each comprise a first reflector, an oxidation limiting layer, an active layer, a second reflector and a substrate layer which are sequentially arranged from top to bottom; the middle of the oxidation limiting layer of the first laser emission unit and the second laser emission unit is provided with a water drop type light transmission hole, and the end surface of the first laser emission unit and the second laser emission unit is provided with a water drop type light emission hole; the two water drop type light transmission holes and the two water drop type light emission holes are symmetrically arranged and the hole spacing is less than the lasing wavelength. The two lasers of the application oscillate and propagate between the first reflector and the second reflector, are emitted in the surface direction perpendicularly to the oxidation limiting layer in the form of evanescent waves in the light transmission hole, and the evanescent waves emitted by the two laser emission units are coupled near the water drop tip to emit coherent light.

Description

Technical Field

[0001] This invention relates to the field of laser technology, and more specifically to a narrow-linewidth coherent optical VCSEL array chip. Background Technology

[0002] With continuous technological development and breakthroughs, semiconductor lasers are evolving towards higher power, smaller size, two-dimensional integration, longer lifespan, and higher beam quality to meet the needs of various applications, resulting in an increasingly diverse range of products. Semiconductor lasers, leveraging their numerous technological advantages, are widely used in 3D printing, lidar, military, medical imaging, and industrial processing. Furthermore, high-power direct semiconductor lasers, coupled into optical fibers for transmission, are widely used in cutting and welding.

[0003] VCSELs, due to their advantages such as high beam quality, single longitudinal mode, low threshold, ease of on-chip testing, and low production cost, have been increasingly widely used in data transmission, sensing, optical interconnects, laser printing, and optical signal processing. Initially, VCSELs achieved high power output by increasing the output aperture. Because VCSELs are easily fabricated into two-dimensional arrays, high power output can also be achieved through two-dimensional integration. However, with technological advancements, the demand for high-power lasers with high beam quality, high brightness, narrow linewidth, and high coherence is constantly growing in various fields. Generally, the light emitted by each emitting unit in a laser array is incoherent, and there is no definite phase relationship between the units. When such arrays are focused by lenses, the light field distribution on the focal plane of the lens is an incoherent superposition of the light emitting units. This superposition method cannot improve beam quality and laser brightness. In industrial processing, laser ignition, military long-range target practice, and navigation, there are high requirements for laser brightness and beam quality, which incoherent VCSEL arrays often cannot meet.

[0004] The coherent superposition of in-phase light-emitting units in a VCSEL array concentrates energy at the axial center. Therefore, for VCSEL arrays, coherent coupling can yield laser chips with better beam quality, enabling applications in fields requiring high-brightness light sources, such as military long-range target practice and image processing. VCSEL arrays exhibit high longitudinal mode selectivity due to their short resonant cavities; however, transverse mode competition within the device significantly reduces their coherence. Typical VCSEL arrays lack coherence because they cannot achieve photon injection between individual light-emitting units in a linear array. This results in a wide linewidth, poor mode characteristics, large far-field divergence angle, and low brightness, limiting their applications. Furthermore, the poor coherence between the emitted beams of a VCSEL array, involving multiple lasers, fails to meet practical requirements.

[0005] Therefore, it is necessary to develop a coherent laser array chip with a narrow linewidth output to achieve the characteristics of narrow linewidth and high coherence. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a narrow-linewidth coherent optical VCSEL array chip.

[0007] This invention discloses a narrow-linewidth coherent optical VCSEL array chip, comprising: a symmetrical first laser emitting unit and a second laser emitting unit;

[0008] The first laser emitting unit and the second laser emitting unit each include a first reflector, an oxide confinement layer, an active layer, a second reflector and a substrate layer arranged sequentially from top to bottom, and the laser oscillates and propagates between the first reflector and the second reflector;

[0009] The first laser emitting unit and the second laser emitting unit have a teardrop-shaped light-passing hole in the middle of their oxide confinement layers, and teardrop-shaped light-emitting holes on their end faces. The two teardrop-shaped light-passing holes are symmetrically arranged with their tips facing each other, and the distance between the tips of the light-passing holes is less than the lasing wavelength. The two teardrop-shaped light-emitting holes are symmetrically arranged with their tips facing each other, and the distance between the tips of the light-emitting holes is less than the lasing wavelength, so that the laser emitted by the first laser emitting unit and the second laser emitting unit are coupled in the form of evanescent waves to emit coherent light.

[0010] As a further improvement of the present invention, the first laser emitting unit and the second laser emitting unit are provided with a P electrode on the light-emitting end face and an N electrode on the back side; a first passivation layer is provided on the first laser emitting unit or the second laser emitting unit at a position that does not contact the P electrode, and a second passivation layer is provided on the first laser emitting unit or the second laser emitting unit at a position that does not contact the first reflector.

[0011] As a further improvement of the present invention, both the first laser emitting unit and the second laser emitting unit have an anti-reflection coating added to the first reflector.

[0012] As a further improvement of the present invention, both the two teardrop-shaped light-passing holes and the two teardrop-shaped light-emitting holes are tip-to-tip, and the distance between the tips of the two teardrops is less than the laser wavelength.

[0013] As a further improvement of the present invention, the first reflector is Al. x Ga (1-x) As / Al y Ga (1-y) As a double-layer structure, the P-type distributed Bragg reflector has a reflectivity of 99%-99.5%.

[0014] As a further improvement of the present invention, the number of pairs of the first reflector is 5 to 20.

[0015] As a further improvement of the present invention, the second reflector is Al. x Ga (1-x) As / Al y Ga (1-y) As a double-layer structure, the N-type distributed Bragg reflector has a reflectivity of 99%-99.5%.

[0016] As a further improvement of the present invention, the number of pairs of the second reflector is 5 to 20.

[0017] As a further improvement of the present invention, the material of the substrate layer includes GaAs, InP, GaN or Si.

[0018] As a further improvement of the present invention, the narrow-linewidth coherent optical VCSEL array chip is used in the fabrication of narrow-linewidth coherent lasers.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] This invention designs a teardrop-shaped light-transmitting hole at the position of the oxide confinement layer of the laser emitting unit, and the teardrop-shaped light-transmitting holes of the two laser emitting units are symmetrically arranged. The distance between the tips of the teardrops is less than the lasing wavelength. The laser oscillates and propagates between the first and second reflectors. The laser from the first laser emitting unit leaks the laser to the second laser emitting unit through an evanescent wave, and the laser from the second laser emitting unit also leaks the laser to the first laser emitting unit through an evanescent wave. The evanescent waves emitted by the two laser emitting units are coupled near the tips of the teardrops, emitting coherent light, which makes the coherence between the emitted light better. Attached Figure Description

[0021] Figure 1 This is a front view of a narrow-linewidth coherent optical VCSEL array chip according to the present invention;

[0022] Figure 2 This is a partial three-dimensional perspective view of a narrow-linewidth coherent optical VCSEL array chip according to the present invention.

[0023] Figure 3 This is a cross-sectional view of a narrow-linewidth coherent optical VCSEL array chip according to the present invention.

[0024] Figure 4 This is a schematic diagram of the oxide confinement layer of a narrow-linewidth coherent optical VCSEL array chip according to the present invention;

[0025] Figures 5-1 to 5-10 This is a schematic diagram illustrating the fabrication process of a narrow-linewidth coherent optical VCSEL array chip according to the present invention.

[0026] Figure 6 This is a schematic diagram illustrating the principle of a narrow-linewidth coherent optical VCSEL array chip according to the present invention.

[0027] Figure 7 This is a physical diagram of a narrow-linewidth coherent optical VCSEL array chip according to the present invention.

[0028] Figure 8 This is a device linewidth test diagram of a narrow-linewidth coherent optical VCSEL array chip according to the present invention.

[0029] Figure 9 This is a simulated near-field coherence diagram of a narrow-linewidth coherent optical VCSEL array chip according to the present invention.

[0030] In the picture:

[0031] 101. Substrate layer; 102. First reflector; 103. Second reflector; 104. Active layer; 105. Oxide confinement layer; 106. First passivation layer; 107. Second passivation layer; 108. P electrode; 109. N electrode; 110. Antireflection coating; 111. First laser emitting unit; 112. Second laser emitting unit. Detailed Implementation

[0032] 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.

[0033] This invention provides a narrow-linewidth coherent optical VCSEL array chip with an array size of 12. It includes: a symmetrical first laser emitting unit and a second laser emitting unit; each of the first and second laser emitting units includes, from top to bottom, a first reflector, an oxide confinement layer, an active layer, a second reflector, and a substrate layer; a teardrop-shaped light-passing aperture is provided in the middle of the oxide confinement layer of the first and second laser emitting units, and a teardrop-shaped light-exiting aperture is provided on the end face of the first and second laser emitting units; the two teardrop-shaped light-passing apertures are symmetrically arranged with their tips facing each other, and the distance between the tips of the light-passing apertures is less than the lasing wavelength; the two teardrop-shaped light-exiting apertures are also symmetrically arranged with their tips facing each other, and the distance between the tips of the light-exiting apertures is less than the lasing wavelength. The two lasers of this invention oscillate and propagate between the first and second reflectors, and are emitted perpendicularly to the surface direction of the oxide confinement layer in the form of evanescent waves within the light-passing apertures. The evanescent waves emitted by the two laser emitting units couple near the tips of the teardrops, emitting coherent light.

[0034] The present invention will now be described in further detail with reference to the accompanying drawings:

[0035] like Figure 1-3 As shown, this invention provides a narrow-linewidth coherent optical VCSEL array chip with an array size of 12. Specifically, it includes a symmetrical first laser emitting unit 111 and a second laser emitting unit 112, both fabricated on the same substrate. Each laser emitting unit includes, from top to bottom, a first reflector 102, an oxide confinement layer 105, an active layer 104, a second reflector 103, and a substrate layer 101. The generated laser light oscillates and propagates between the first and second reflectors 102 and 103. A teardrop-shaped light-passing hole is provided in the middle of the oxide confinement layer 105 of the first and second laser emitting units 111 and 112, with the oxide confinement layer 105 surrounding the teardrop. The teardrop-shaped light-passing holes are symmetrically arranged with their tips facing each other, and the distance between the tips is less than the lasing wavelength. Figure 4 As shown; based on this, the laser is emitted perpendicularly to the oxide confinement layer towards the surface in the form of an evanescent wave within the light-transmitting aperture. The end faces of the first and second laser emitting units are provided with teardrop-shaped light-emitting apertures. The two teardrop-shaped light-emitting apertures are symmetrically arranged with their tips facing each other, and the distance between the aperture tips is less than the lasing wavelength, such as... Figure 2 As shown, the laser emitted from the first and second emitting units is coupled in the form of an evanescent wave to emit coherent light.

[0036] like Figure 1 As shown, the first laser emitting unit 111 and the second laser emitting unit 112 of the present invention have a P electrode 108 on the light-emitting end face (first reflector 102 side) and an N electrode 109 on the back side (substrate layer 101 side); a first passivation layer 106 is provided on the first laser emitting unit 111 or the second laser emitting unit 112 at a position that does not contact the P electrode 108, and a second passivation layer 107 is provided on the first laser emitting unit 111 or the second laser emitting unit 112 at a position that does not contact the first reflector 102; an antireflection film 110 is added to both the first laser emitting unit 111 and the second laser emitting unit 112 on the first reflector 102.

[0037] Furthermore, the first reflecting mirror 102 of the present invention is Al. x Ga (1-x) As / Al y Ga (1-y) As a double-layered P-type distributed Bragg reflector, the reflectivity is 99%-99.5%. The first reflector 102 has 5 to 20 pairs. The first reflector 102 is a semi-reflective mirror, and an anti-reflective coating is added below it to achieve a reflectivity of 99.9%. The second reflector 103 is made of Al.x Ga (1-x) As / Al y Ga (1-y) The As double-layer N-type distributed Bragg reflector has a reflectivity of 99%-99.5%. The second reflector 103 has 5 to 20 pairs. The second reflector 103 is a semi-reflective mirror, and an anti-reflective coating is added above the corresponding position of the second reflector 103 to achieve a reflectivity of 99.9%. The substrate layer 101 is made of materials including GaAs, InP, GaN, or Si.

[0038] Furthermore, the narrow-linewidth coherent optical VCSEL array chip of the present invention is suitable for light in the 450nm-2µm wavelength band, and it can be applied to the fabrication of narrow-linewidth coherent lasers.

[0039] like Figures 5-1 to 5-10 As shown, this invention provides a method for fabricating a narrow-linewidth coherent optical VCSEL array chip, comprising:

[0040] Step 1: Epitaxially grow a VCSEL laser chip using plasma-enhanced chemical vapor deposition (PECVD). Clean the VCSEL laser chip according to RCA standards. After cleaning, dry the VCSEL laser chip under high-purity nitrogen protection. Then, heat-dry the VCSEL laser chip for later use. The structure of the VCSEL laser chip is as follows: Figure 5-1 As shown;

[0041] Step 2: Deposit or sputter a SiO2 mask of a certain thickness on the VCSEL laser chip to be processed; then, use photolithography and etching techniques to etch the laser emitting unit array structure on the VCSEL laser chip, forming the first laser emitting unit 111 and the second laser emitting unit 112; remove excess SiO2 with chemical etching and clean the VCSEL laser chip. After cleaning, blow-dry the VCSEL laser chip under protection with high-purity nitrogen gas, and then heat-dry the chip for later use; Figure 5-2 As shown;

[0042] Step 3: Using wet selective oxidation technology, by controlling the nitrogen flow rate and oxidation time, a droplet-shaped unoxidized region is formed, resulting in an oxidation confinement layer 105 within the annular structure of each laser emitting unit; for example... Figure 5-3 As shown;

[0043] Step 4: Deposit or sputter a transparent insulating material of a certain thickness on the VCSEL laser chip as a passivation layer; such as... Figure 5-4 As shown;

[0044] Step 5: Using photolithography and etching techniques, expose electrodes on the VCSEL laser chip to form the first passivation layer 106 and the second passivation layer 107; as shown... Figure 5-5 As shown;

[0045] Step 6: Coat the VCSEL laser chip with photoresist, fabricate the electrode pattern through photolithography and development, sputter metal, and peel off to form the P electrode 108; as shown Figure 5-6 As shown;

[0046] Step 7: Thin the substrate 101 of the VCSEL laser chip to less than 50µm using CMP (chemical mechanical polishing) technology; Figure 5-7 As shown;

[0047] Step 8: Sputter metal onto substrate 101 and peel it off to form N-electrode 109; as shown Figure 5-8 As shown;

[0048] Step 9: Deposit an antireflection film 110 on the surface of the VCSEL laser chip; as shown Figure 5-9 As shown;

[0049] Step 10: Expose the P-electrode on the surface of the VCSEL laser chip using photolithography and etching techniques to complete the fabrication of the coherent optical VCSEL array chip; such as Figure 5-10 As shown.

[0050] The principle of coherent light VCSEL array chips emitting laser light in the form of evanescent waves to generate coupling and emit coherent light is as follows: Figure 6 As shown, the physical diagram of the coherent optical VCSEL array chip is as follows: Figure 7 As shown.

[0051] The linewidth of the present invention was measured using a YOKOGAWA AQ6370C spectrometer. Tests were performed on a single lasing unit VCSEL and 1×2 array droplet-type VCSELs, respectively. Figure 8 As shown, the test results are as follows: Under the same size and conditions, compared with a single VCSEL, the linewidth of the array VCSEL is only 0.5nm, while the linewidth of a single VCSEL is 1.5nm.

[0052] Figure 9 This is a simulation diagram of a narrow-linewidth coherent optical VCSEL array chip according to the present invention. FDTD simulation shows that there is coupling between the two laser emitting units, enabling the emission of coherent light; wherein... Figure 9 The values ​​shown decrease sequentially from the center of the light-emitting aperture outwards.

[0053] The advantages of this invention are:

[0054] This invention designs a teardrop-shaped light-transmitting hole at the position of the oxide confinement layer of the laser emitting unit, and the teardrop-shaped light-transmitting holes of the two laser emitting units are symmetrically arranged. The distance between the tips of the teardrops is less than the lasing wavelength. The laser oscillates and propagates between the first and second reflecting mirrors. The laser from the first laser emitting unit leaks the laser to the second laser emitting unit through an evanescent wave, and the laser from the second laser emitting unit also leaks the laser to the first laser emitting unit through an evanescent wave. The evanescent waves emitted by the two laser emitting units are coupled near the tips of the teardrops, emitting coherent light, which makes the coherence between the emitted light better.

[0055] In the test results of this invention, under the same size and conditions, compared with a single VCSEL, the linewidth of the array VCSEL is only 0.5nm, while the linewidth of a single VCSEL is 1.5nm.

[0056] 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 narrow-linewidth coherent optical VCSEL array chip, characterized in that, include: The first laser emitting unit and the second laser emitting unit are symmetrical; The first laser emitting unit and the second laser emitting unit each include a first reflector, an oxide confinement layer, an active layer, a second reflector and a substrate layer arranged sequentially from top to bottom, and the laser oscillates and propagates between the first reflector and the second reflector; The first laser emitting unit and the second laser emitting unit have a teardrop-shaped light-passing hole in the middle of their oxide confinement layers, and teardrop-shaped light-emitting holes on their end faces. The two teardrop-shaped light-passing holes are symmetrically arranged with their tips facing each other, and the distance between the tips of the light-passing holes is less than the lasing wavelength. The two teardrop-shaped light-emitting holes are symmetrically arranged with their tips facing each other, and the distance between the tips of the light-emitting holes is less than the lasing wavelength, so that the laser emitted by the first laser emitting unit and the second laser emitting unit are coupled in the form of evanescent waves to emit coherent light.

2. The narrow-linewidth coherent optical VCSEL array chip as described in claim 1, characterized in that, The first laser emitting unit and the second laser emitting unit are provided with a P electrode on the light-emitting end face and an N electrode on the back side; a first passivation layer is provided on the first laser emitting unit or the second laser emitting unit at a position that does not contact the P electrode, and a second passivation layer is provided on the first laser emitting unit or the second laser emitting unit at a position that does not contact the first reflector.

3. The narrow-linewidth coherent optical VCSEL array chip as described in claim 1, characterized in that, Both the first laser emitting unit and the second laser emitting unit have an anti-reflection coating added to the first reflector.

4. The narrow-linewidth coherent optical VCSEL array chip as described in any one of claims 1 to 3, characterized in that, The first reflector is Al x Ga (1-x) As / Al y Ga (1-y) As a double-layer structure, the P-type distributed Bragg reflector has a reflectivity of 99%-99.5%.

5. The narrow-linewidth coherent optical VCSEL array chip as described in claim 4, characterized in that, The number of pairs of the first reflector is 5 to 20.

6. The narrow-linewidth coherent optical VCSEL array chip as described in any one of claims 1 to 3, characterized in that, The second reflector is Al x Ga (1-x) As / Al y Ga (1-y) As a double-layer structure, the N-type distributed Bragg reflector has a reflectivity of 99%-99.5%.

7. The narrow-linewidth coherent optical VCSEL array chip as described in claim 6, characterized in that, The number of pairs of the second reflector is 5 to 20.

8. The narrow-linewidth coherent optical VCSEL array chip as described in any one of claims 1 to 3, characterized in that, The substrate layer is made of materials including GaAs, InP, GaN, or Si.

9. The narrow-linewidth coherent optical VCSEL array chip as described in any one of claims 1 to 3, characterized in that, The narrow-linewidth coherent optical VCSEL array chip is used in the fabrication of narrow-linewidth coherent lasers.

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