Coupled external cavity narrow linewidth vertical cavity surface emitting laser based on compact bonding

Abstract

The invention relates to the technical field of vertical cavity surface emitting lasers, and discloses a coupling outer cavity narrow linewidth vertical cavity surface emitting laser based on compact bonding, which comprises a bottom substrate and an n-type DBR (Distributed Bragg Reflector) mirror grown on the bottom substrate, the cavity length extension layer, the active region, the p-type optical limiting layer and oxide layer, the p-type DBR reflector, the bonding middle layer, the outer cavity feedback structure and the laser output surface are located on the surface, away from the bottom substrate, of the n-type DBR reflector and are sequentially arranged; the external cavity feedback structure comprises an optical spacing layer and a feedback mirror, is attached to the upper surface of the p-type DBR reflector through a bonding intermediate layer in a bonding manner, and is prefabricated on an independent chip or a film before bonding. The external cavity module is directly bonded to the surface of the main cavity VCSEL to construct an integrated composite resonant cavity system, deep compression of the line width of the laser is realized on the premise of not sacrificing the chip size and the process compatibility, and the laser has good single-mode characteristics, wavelength tuning capability and system integration adaptability.

Description

Technical Field

[0001] This invention relates to the field of vertical cavity surface-emitting laser technology, and particularly to a narrow-linewidth vertical cavity surface-emitting laser based on compact bonding coupled external cavity. Background Technology

[0002] Vertical-cavity surface-emitting lasers (VCSELs), due to their unique vertical emission structure, have become key devices in optical communication, 3D sensing, lidar, chip-level optical interconnects, atomic clocks, and quantum sensing over the past few decades. Compared to edge-emitting lasers (EELs), VCSELs offer advantages such as smaller beam divergence angles, lower power consumption, lower threshold current, ease of fabrication into two-dimensional arrays, and higher integration capabilities. For applications requiring high coherence and high frequency stability, such as compact atomic clocks (CPT atomic clocks), magneto-optically pumped atomic magnetometers, and optical inertial navigation systems, stringent requirements are placed on the spectral purity and linewidth of the laser. Typically, the laser linewidth needs to be below 1 MHz, and sometimes even below 100 kHz. Due to their short cavity length (typically less than 2 μm) and low cold cavity quality factor Q, VCSELs have a wide intrinsic linewidth. Without external structures, their linewidth is typically in the tens of MHz range or even wider, making it difficult to meet the requirements of high-precision quantum measurement and sensing. To achieve linewidth compression, existing technologies mainly adopt the following strategies: Cavity optimization schemes: By increasing the cavity length, adopting cavity mode selection structures (such as selective absorption layer, GCL reflective layer), and high reflectivity mirror design, the cavity quality factor can be improved, thereby reducing the cold cavity linewidth; for example, by introducing an extension layer in an n-type DBR, the effective cavity length can be increased to about 2μm, and the fundamental mode output can be achieved by combining small oxide hole confinement, and the linewidth can be compressed to the 2MHz level. External cavity feedback scheme: Introduce part of the optical feedback path at the laser output end, such as Fresnel mirror, fiber ring external cavity, thin film filter, etc. to form a delayed feedback external cavity, increase the effective cavity length and reduce phase noise; A typical example in the market is the external cavity VCSEL (EC-VCSEL), whose linewidth can be compressed to <1MHz. However, due to the need for precise alignment, complex feedback control systems, poor disturbance rejection performance, and large size, it is not conducive to chip-level integration and large-scale applications. Therefore, the biggest challenge at present is how to achieve a compact, interference-resistant, and easily integrated laser architecture while ensuring narrow linewidth output. Especially in atomic chips and integrated sensor arrays, a laser structure that can achieve external cavity feedback and be compactly integrated into the chip platform is needed. Summary of the Invention

[0003] This invention provides a compactly bonded coupled external cavity narrow linewidth vertical cavity surface emitter laser. By directly bonding a high-Q, low-loss external cavity module to the surface of the main cavity VCSEL, an integrated composite resonant cavity system is constructed. Without sacrificing chip size and process compatibility, the laser linewidth is deeply compressed, and it has good single-mode characteristics, wavelength tuning capability and system integration adaptability.

[0004] This invention provides a compactly bonded coupled external cavity narrow linewidth vertical cavity surface-emitting laser, comprising: A bottom substrate and an n-type DBR mirror grown on the bottom substrate; Located on the surface of the n-type DBR mirror away from the bottom substrate, and arranged sequentially are the cavity length extension layer, the active region, the p-type optical confinement layer and oxide layer, the p-type DBR mirror, the bonding intermediate layer, the external cavity feedback structure, and the laser output surface; The main cavity is composed of an n-type DBR mirror, an active region, a p-type optical confinement layer and an oxide layer, and a p-type DBR mirror, with the main cavity emission wavelength set at 894.6 nm. The external cavity feedback structure includes an optical spacer layer and a feedback mirror. The feedback mirror is a DBR mirror composed of 10 pairs of stacked Ta2O5 / SiO2. The thickness of the external cavity feedback structure ranges from 10 to 100 μm, forming an effective external cavity feedback channel with controllable cavity length. It is attached to the upper surface of the p-type DBR mirror by bonding through the bonding intermediate layer, with a bonding thickness of <1 μm. It is prefabricated on an independent chip or thin film before bonding.

[0005] Furthermore, the bottom substrate serves as a physical support layer and is configured as n-type GaAs or InP according to the emission wavelength region; The n-type DBR mirror is 36 pairs of n-type Al0.9Ga0.1As / Al0 grown on the bottom substrate. 12 Ga0. 88 As the DBR layer, used to reflect the downward excitation light, the doping concentration is 2×10⁻⁶. 18 cm⁻³, each pair of Al0.9Ga0.1As / Al0. 12 Ga0. 88 As the thickness of the DBR layer is λ / 4 of the lasing wavelength, it is used to construct a high-reflectivity resonant mirror. A superlattice layer, which is AlGaAs / InGaAs, is also disposed between the bottom substrate layer and the n-type DBR mirror to enhance lateral thermal conduction and improve the thermal uniformity of the laser array.

[0006] Furthermore, the cavity length extension layer uses a high-aluminum composition material Al0.9Ga0.1As to extend the effective cavity length to a set length.

[0007] Furthermore, the active region is located in an InGaAs / AlGaAs multi-quantum-well structure with 3 pairs of quantum wells and a thickness of λ / 2. The active region is arranged at the antinode of a standing wave and designed to match the wavelength of 894.6 nm.

[0008] Furthermore, the p-type optical confinement layer and oxide layer include p-type AlO. 98 Ga0. 02 The As material layer is laterally oxidized to form an Al2O3 insulator, creating a current-limiting hole with a diameter of 2-4 μm.

[0009] Furthermore, the p-type DBR mirror consists of 22 pairs of Al0.9Ga0.1As / Al0. 12 Ga0. 88 The structure consists of As stacks, with a doping concentration of 3 × 10⁻⁶. 18 cm⁻³.

[0010] Furthermore, the thickness of the bonding intermediate layer is <1μm, and it is an oxide intermediate layer, a polymer bonding material, or directly bonded through plasma surface activation. The oxide intermediate layer uses SiO2 or Al2O3 as a passive medium, and the polymer bonding material is BCB.

[0011] Furthermore, the external cavity feedback structure also includes a tuning unit, which is a liquid crystal layer, an electro-optic modulator, or a piezoelectric micro-driver, used for feedback phase fine-tuning to achieve wavelength adjustment in the range of 5-10 GHz.

[0012] Furthermore, the laser output surface is used to emit light vertically from the top mirror of the external cavity feedback structure, with the beam exhibiting a Gaussian distribution.

[0013] Furthermore, the total cavity length L of the laser composite cavity total =L vcsel +L ext , where L vcsel The length of the main cavity, L ext The length of the external cavity; quality factor Q ∝ L total Increasing the effective cavity length can multiply the Q value; the linewidth Δν∝1 / Q indicates that the linewidth is inversely proportional to the Q value; when Q increases from 10³ to 10 6 At that time, the linewidth was compressed from 10MHz to <0.5MHz.

[0014] The beneficial effects of this invention are as follows: Compared with existing technologies, this invention has advantages in several aspects, including structural design, integration capabilities, and performance indicators, specifically in the following aspects: 1. Significantly reduced laser linewidth: By introducing a compact coupled external cavity structure, the effective cavity length of the laser is extended from the micrometer level of traditional VCSELs to tens or even hundreds of micrometers; the quality factor Q of the resonant cavity is increased by 1-3 orders of magnitude, so that the intrinsic linewidth is reduced from tens of MHz to <0.5 MHz, meeting the high coherence requirements of atomic clocks, quantum measurement and other applications.

[0015] 2. Compact structure facilitates system integration: The external cavity is achieved through chip-level bonding, resulting in a compact and planar design of the overall device structure. It eliminates the need for large-volume fiber optic reflector cavities or mechanical reflector systems, greatly reducing device size and system complexity, making it suitable for space-constrained scenarios such as atomic chips and photonic integration platforms.

[0016] 3. Strong anti-interference capability and high stability: The external cavity feedback structure is integrated with the main cavity, avoiding the feedback phase instability problem caused by external disturbances (vibration, thermal drift, mechanical displacement) in conventional EC-VCSEL structures; it supports package-level co-thermal drift design, improving the stability of laser wavelength and power.

[0017] 4. Excellent single-mode control capability: External cavity feedback can enhance the fundamental mode and suppress the side modes, achieving mode-selective excitation through feedback regulation; combined with a small oxide hole design (2-4μm), it further improves the transverse mode suppression ratio, avoids mode jumps, and improves spectral purity.

[0018] 5. High-precision wavelength tuning capability: The introduction of thermal tuning, piezoelectric adjustment or liquid crystal control mechanism in the external cavity can realize dynamic wavelength adjustment at the 5-10GHz level; it supports continuous tuning and mode skipping avoidance design to meet the wavelength matching requirements of different applications (such as cesium atom D1 line 894.6nm).

[0019] 6. Compatible with existing VCSEL manufacturing processes and capable of mass production: The main cavity part maintains the standard VCSEL preparation process, with only the addition of bonding process steps on the light-emitting surface; the external cavity module can be prepared and bonded separately in batches, suitable for wafer-level manufacturing and automated packaging production lines.

[0020] 7. Suitable for a variety of high-end applications, including compact atomic clocks, quantum sensing arrays, integrated gyroscopes, chip-level magnetometers, spectrum analyzers, lidar, and low phase noise light sources.

[0021] In summary, this invention not only achieves a breakthrough improvement in laser performance indicators, but also has comprehensive advantages in structural design, system integration and manufacturing process, and has broad prospects for engineering promotion and industrialization. Attached Figure Description

[0022] Figure 1 This is a schematic cross-sectional view of the present invention, which is a narrow-linewidth vertical cavity surface-emitting laser based on compact bonding coupled external cavity.

[0023] Figure 2 This is a schematic diagram of the electrical performance curves of the laser structure of the present invention.

[0024] Figure 3 This is a reflection spectrum of the laser structure of the present invention.

[0025] Figure 4 This is the gain spectrum of the active region quantum well of the laser structure of the present invention at room temperature.

[0026] In the attached diagram, 1 is an n-type GaAs substrate, 2 is an n-type DBR mirror, 3 is a quantum well active region, 4 is a p-type DBR mirror, 5 is a bonding intermediate layer, 6 is the bottom DBR of the external cavity feedback structure, 7 is the resonant cavity of the external cavity feedback structure, and 8 is the top DBR of the external cavity feedback structure.

[0027] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0028] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0029] This invention provides a compactly bonded coupled external cavity narrow linewidth vertical cavity surface-emitting laser, comprising: A bottom substrate and an n-type DBR mirror grown on the bottom substrate are located on the surface of the n-type DBR mirror away from the bottom substrate, and are arranged sequentially as follows: cavity length extension layer, active region, p-type optical confinement layer and oxide layer, p-type DBR mirror, bonding intermediate layer, external cavity feedback structure, and laser output surface. This forms a structure as follows: Figure 1 The overall cross-sectional structure shown is in Figure 1 In the diagram, each number represents: n-type GaAs substrate 1, n-type DBR mirror 2, quantum well active region 3, p-type DBR mirror 4, bonding intermediate layer 5, bottom DBR of external cavity feedback structure 6, resonant cavity of external cavity feedback structure 7, and top DBR of external cavity feedback structure 8. n-type GaAs substrate 1 is the bottom substrate, and the bottom DBR 6, resonant cavity 7, and top DBR 8 of external cavity feedback structure constitute the external cavity feedback structure.

[0030] The main cavity is composed of an n-type DBR mirror, an active region, a p-type optical confinement layer and an oxide layer, and a p-type DBR mirror, with the main cavity emission wavelength set at 894.6 nm. The external cavity feedback structure includes an optical spacer layer and a feedback mirror. The feedback mirror is a DBR mirror composed of 10 pairs of stacked Ta2O5 / SiO2. The thickness of the external cavity feedback structure ranges from 10 to 100 μm, forming an effective external cavity feedback channel with controllable cavity length. It is attached to the upper surface of the p-type DBR mirror by bonding through the bonding intermediate layer, with a bonding thickness of <1 μm. It is prefabricated on an independent chip or thin film before bonding.

[0031] The present invention provides a compactly bonded coupled external cavity narrow linewidth vertical cavity surface-emitting laser, which includes the following key functional layers from bottom to top: (1) Bottom substrate and n-type DBR mirror The bottom substrate serves as the physical support layer, typically n-type GaAs or InP (the specific type depends on the emission wavelength region), on which 36 pairs of n-type Al0.9Ga0.1As / Al0 are grown. 12 Ga0. 88 As the DBR layer, used to reflect the downward excitation light, the doping concentration is 2×10⁻⁶. 18 cm⁻³, each pair of Al0.9Ga0.1As / Al0. 12 Ga0. 88 As the thickness of the DBR layer is λ / 4 of the lasing wavelength, it is used to construct a high-reflectivity resonant mirror (reflectivity > 99.9%).

[0032] In addition, a superlattice layer, which is AlGaAs / InGaAs, is disposed between the bottom substrate layer and the n-type DBR mirror to enhance lateral thermal conduction and improve the thermal uniformity of the laser array.

[0033] (2) Cavity extension layer The cavity length extension layer is also an optical spacer layer, located at the top of the n-type DBR mirror. It uses a high-aluminum composition material Al0.9Ga0.1As to extend the effective cavity length to a set length (unit: micrometer). By adjusting the thickness of this layer (e.g., 1.5μm), the standing wave optical path of the main cavity is extended while ensuring low absorption, thus improving the quality factor Q.

[0034] (3) Active region (multiple quantum well MQW) The active region is located in an InGaAs / AlGaAs multi-quantum-well structure with 3 pairs of quantum wells and a thickness of λ / 2. The active region is arranged at the antinode of the standing wave to optimize photon-electron coupling and improve photo-to-electric conversion efficiency. The wavelength is designed to match 894.6nm (to match the D1 line of cesium atoms).

[0035] (4) p-type optical confinement layer and oxide layer The p-type optical confinement layer and oxide layer include p-type AlO. 98 Ga0. 02 The As material layer is laterally oxidized to form an Al2O3 insulator, which forms a current-limiting hole with a diameter of 2-4 μm. This effectively limits the carrier injection region and achieves lateral mode confinement, which is beneficial for fundamental mode output and low threshold operation.

[0036] (5) p-type DBR reflector The p-type DBR mirror consists of 22 pairs of Al0.9Ga0.1As / Al0. 12 Ga0. 88 Composed of As stacks, the reflectivity is close to 99.5%; the doping concentration is 3×10⁻⁶. 18 cm⁻³, but the logarithmic design is slightly less than that of an n-type DBR mirror, in order to reduce series resistance and improve PCE.

[0037] (6) Bonding Layer The external cavity structure is attached to the upper surface of the p-type DBR through thin film bonding technology. The intermediate layer can be: an oxide intermediate layer (such as SiO2, Al2O3 passive dielectric), a polymer bonding material (such as BCB), or direct bonding by plasma surface activation. The thickness of the bonding intermediate layer is <1μm to ensure low optical loss and tight coupling.

[0038] (7) External Resonator Stack The overall thickness of the external cavity feedback structure is approximately 10-100 μm, and the cavity length is controllable, forming an effective external cavity feedback channel. It includes the following substructures: a. Optical spacer layer: used to control the optical path between the main cavity and the feedback mirror, and can be integrated with a thermal control / piezoelectric adjustment module; b. External DBR (Dual Mirror): Composed of 10 pairs of high-refractive-index Ta₂O₅ / SiO₂ mirrors, with a reflectivity of 99.9%; c. Tuning unit: can be a liquid crystal layer, an electro-optic modulator or a piezoelectric micro-actuator, to achieve wavelength fine-tuning (5-10 GHz range).

[0039] (8) Laser output surface Light is emitted vertically from the top mirror of the external cavity, and the beam has a Gaussian distribution, which is suitable for collimation or coupling to a micro-optical system.

[0040] The present invention provides a compactly bonded coupled external cavity narrow linewidth vertical cavity surface-emitting laser with the following innovative structural features: 1. Main cavity VCSEL structure The main cavity is a typical oxide-confined VCSEL structure with an emission wavelength of 894.6 nm (fitted to the Cs D1 line). The active region adopts an InGaAs / AlGaAs multi-quantum-well structure with 3 pairs of quantum wells. The thickness is designed at λ / 2 and arranged at the antinodes of the standing wave. The upper and lower Bragg mirrors (p-DBR and n-DBR) are 22 pairs and 36 pairs of Al0.9Ga0.1As / Al0. 12 Ga0. 88 As, an optical thickness of λ / 4 is employed, and a refractive index gradient transition layer is inserted to reduce series resistance; lateral optics and current confinement are achieved using Al. 0.98 Ga 0.02 The As oxide layer is implemented with an oxide pore diameter of 3 μm to ensure low threshold and fundamental mode emission.

[0041] 2. External cavity feedback structure The outer cavity consists of a separately fabricated optical feedback structure, which is integrated onto the main cavity via bonding. The outer cavity DBR mirror is made of low-loss, high-reflectivity stacked materials (such as 10 pairs of Ta2O5 / SiO2). The length of the outer cavity is designed to be between 10-100 μm, which is achieved by controlling the interlayer thickness or introducing a spacer layer (SiO2). Tuning structures, such as thermally induced expansion and contraction dielectric layers, MEMS piezoelectric modulators, liquid crystals, etc., can be added for feedback phase fine-tuning. The overall structure of the outer cavity is prefabricated on an independent chip or thin film before bonding.

[0042] 3. Bonding method between the main cavity and the outer cavity To achieve a coupling interface with low loss and high mechanical stability, the following integration technologies are adopted: the intermediate layer bonding uses passive dielectric thin layers such as Al2O3 and SiO2 as a transition; surface activated plasma bonding (PAB) is suitable for low-temperature (<200℃) wafer-level processes, and the bonding thickness is controlled to <1 μm to ensure that the output light from the main cavity can effectively enter the external cavity to form feedback.

[0043] 4. Optical feedback principle and linewidth compression mechanism Total cavity length L of laser composite cavity total =L vcsel +L ext , where L vcsel The length of the main cavity, L ext The length of the external cavity is dominant; the quality factor Q∝L total Increasing the effective cavity length can multiply the Q value; according to the Schawlow-Townes theory, the linewidth Δν ∝ 1 / Q, meaning that the linewidth is inversely proportional to the Q value. When the quality factor Q increases from 10³ to 10... 6At this time, the linewidth is compressed from 10MHz to <0.5MHz. The external cavity feedback can be designed as partial reflection, with the feedback rate controlled at 1-5% to avoid mode competition and common-mode oscillation, while ensuring stable fundamental mode output.

[0044] 5. Wavelength tuning design An embedded tuning structure in the external cavity allows for fine-tuning of the feedback phase, achieving high-precision wavelength control. Thermal tuning: A micro-heater is placed in the external cavity, and the cavity length can be adjusted to achieve 5–10 GHz tunability; Piezoelectric MEMS structure tuning: Nanoscale cavity length adjustment is achieved, with fast response and low power consumption; Liquid crystal tuning: Cavity length adjustment without mechanical parts is achieved by utilizing electrically controlled refractive index changes.

[0045] like Figure 2 As shown, IV is the voltage versus current curve, IP is the power versus current curve, and PCE is the photoelectric conversion efficiency versus current curve. It can be seen that, in terms of electrical performance, the threshold current Ith of this coupled vertical-cavity surface-emitting laser can reach 0.6 mA, the slope efficiency is 0.28 W / A, and the maximum photoelectric conversion efficiency PCE is 30%. Figure 3 The reflection spectrum of the laser structure of this invention is shown, with the troughs in the reflection spectrum corresponding to the operating wavelength of the laser. For example... Figure 4 The gain spectrum of the active region quantum well of the laser structure of the present invention is shown at room temperature.

[0046] The laser provided by this invention forms an effective composite resonant cavity by bonding a high-Q, low-loss external cavity feedback structure to the main cavity VCSEL structure, significantly compressing the laser's linewidth and improving its spectral purity. This structure includes several key layers: a substrate, providing a support platform for the device; an n-type DBR mirror, providing high reflectivity to the active region; an active region employing an InGaAs multi-quantum-well structure, designed for wavelength adaptation of 750-900 nm; an oxide confinement layer and a p-type DBR mirror, effectively limiting current and reducing series resistance, improving output power and efficiency; a bonding intermediate layer, achieving lossless and efficient bonding between the main cavity and the external cavity structure, ensuring optical coupling and mechanical stability; and an external cavity feedback structure, composed of a DBR mirror and a tuning unit, allowing dynamic wavelength tuning and mode-selective feedback. This invention, through a compact external cavity feedback structure combined with bonding technology, enables the VCSEL to possess excellent single-mode control capability, anti-interference capability, and high-precision wavelength tuning capability, meeting the stringent requirements of highly coherent applications such as quantum sensing and atomic clocks. Furthermore, the device has a compact structure, making it suitable for highly integrated optical systems and showing significant promise for industrial applications.

[0047] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, apparatus, article, or method that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, apparatus, article, or method. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, apparatus, article, or method that includes that element.

[0048] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A narrow-linewidth vertical-cavity surface-emitting laser based on compact bonding and coupled external cavity, characterized in that, include: A bottom substrate and an n-type DBR mirror grown on the bottom substrate; Located on the surface of the n-type DBR mirror away from the bottom substrate, and arranged sequentially are the cavity length extension layer, the active region, the p-type optical confinement layer and oxide layer, the p-type DBR mirror, the bonding intermediate layer, the external cavity feedback structure, and the laser output surface; The main cavity is composed of an n-type DBR mirror, an active region, a p-type optical confinement layer and an oxide layer, and a p-type DBR mirror, with the main cavity emission wavelength set at 894.6 nm. The external cavity feedback structure includes an optical spacer layer and a feedback mirror. The feedback mirror is a DBR mirror composed of 10 pairs of stacked Ta2O5 / SiO2. The thickness of the external cavity feedback structure ranges from 10 to 100 μm, forming an effective external cavity feedback channel with controllable cavity length. It is attached to the upper surface of the p-type DBR mirror by bonding through the bonding intermediate layer, with a bonding thickness of <1 μm. It is prefabricated on an independent chip or thin film before bonding.

2. The compactly bonded coupled external cavity narrow linewidth vertical cavity surface-emitting laser according to claim 1, characterized in that, The bottom substrate serves as a physical support layer and is configured as either n-type GaAs or InP according to the emission wavelength region. The n-type DBR mirror is 36 pairs of n-type Al0.9Ga0.1As / Al0 grown on the bottom substrate. 12 Ga0. 88 The AsDBR layer, used to reflect the downward excitation light, has a doping concentration of 2×10⁻⁶. 18 cm⁻³, each pair of Al0.9Ga0.1As / Al0. 12 Ga0. 88 The thickness of the AsDBR layer is λ / 4 of the lasing wavelength, and it is used to form a high-reflectivity resonant mirror. A superlattice layer, which is AlGaAs / InGaAs, is also disposed between the bottom substrate layer and the n-type DBR mirror to enhance lateral thermal conduction and improve the thermal uniformity of the laser array.

3. The compactly bonded coupled external cavity narrow linewidth vertical cavity surface-emitting laser according to claim 1, characterized in that, The cavity length extension layer uses a high-aluminum composition material Al0.9Ga0.1As to extend the effective cavity length to a set length.

4. The compactly bonded coupled external cavity narrow linewidth vertical cavity surface-emitting laser according to claim 1, characterized in that, The active region is located in an InGaAs / AlGaAs multi-quantum-well structure with 3 pairs of quantum wells and a thickness of λ / 2. The active region is arranged at the antinode of a standing wave and designed to match the wavelength of 894.6 nm.

5. The compactly bonded coupled external cavity narrow linewidth vertical cavity surface-emitting laser according to claim 1, characterized in that, The p-type optical confinement layer and oxide layer include p-type AlO. 98 Ga0. 02 The As material layer is laterally oxidized to form an Al2O3 insulator, creating a current-limiting hole with a diameter of 2-4 μm.

6. The compactly bonded coupled external cavity narrow linewidth vertical cavity surface-emitting laser according to claim 1, characterized in that, The p-type DBR mirror consists of 22 pairs of Al0.9Ga0.1As / Al0. 12 Ga0. 88 The structure consists of As stacks, with a doping concentration of 3 × 10⁻⁶. 18 cm⁻³.

7. The compactly bonded coupled external cavity narrow linewidth vertical cavity surface-emitting laser according to claim 1, characterized in that, The thickness of the bonding intermediate layer is <1μm. It is an oxide intermediate layer, a polymer binder, or directly bonded through plasma surface activation. The oxide intermediate layer uses SiO2 or Al2O3 as a passive medium, and the polymer binder is BCB.

8. The compactly bonded coupled external cavity narrow linewidth vertical cavity surface-emitting laser according to claim 1, characterized in that, The external cavity feedback structure also includes a tuning unit, which is a liquid crystal layer, an electro-optic modulator, or a piezoelectric micro-actuator, used for feedback phase fine-tuning to achieve wavelength adjustment in the range of 5-10 GHz.

9. The compactly bonded coupled external cavity narrow linewidth vertical cavity surface-emitting laser according to claim 1, characterized in that, The laser output surface is used to emit light vertically from the top mirror of the external cavity feedback structure, with the beam having a Gaussian distribution.

10. The compactly bonded coupled external cavity narrow linewidth vertical cavity surface-emitting laser according to claim 1, characterized in that, Total cavity length L of laser composite cavity total =L vcsel +L ext , where L vcsel The length of the main cavity, L ext The length of the external cavity; quality factor Q ∝ L total Increasing the effective cavity length can multiply the Q value; the linewidth Δν∝1 / Q indicates that the linewidth is inversely proportional to the Q value; when Q increases from 10³ to 10 6 At that time, the linewidth was compressed from 10MHz to <0.5MHz.

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