Short-wave infrared InP-based photonic crystal surface emitting laser

Abstract

The invention discloses a short-wave infrared InP-based photonic crystal surface emitting laser, and relates to the technical field of lasers. The laser comprises an n-type InP substrate, an n-type coating layer, a multi-quantum well layer, an electron blocking layer, a photonic crystal layer, a p-type coating layer and a metal distributed Bragg reflection layer which are sequentially arranged in the stacking direction. The photonic crystal layer is formed by periodically arranging a plurality of tri-lattice units, and a surrounding distributed Bragg reflection structure is arranged around the photonic crystal layer; at least two lattice points in the tri-lattice unit have lateral and longitudinal offsets with respect to another lattice point. Planar light leakage is suppressed through the peripheral distributed Bragg reflection structure, and in combination with active regulation and control of tri-lattice micro-offset on planar coupling and vertical radiation proportion, and through the synergistic effect of the planar coupling and the vertical radiation proportion, the simulation result shows that the slope efficiency is improved to 0.18 W / A and the vertical radiation loss proportion is improved to 45% while low threshold gain (26cm <-1 >) is kept, and the performance of the device is improved. Unification of low threshold and high efficiency is achieved, and the method is suitable for the fields of optical communication, laser radar and the like.

Description

Short-wave infrared InP-based photonic crystal surface-emitting laser Technical Field

[0001] This invention relates to the field of semiconductor laser technology, and more specifically to an InP-based photonic crystal surface-emitting laser in the short-wave infrared band (particularly 1.55 μm). Background Technology

[0002] Short-wave infrared lasers, especially semiconductor lasers operating in the 1.55μm band, have shown continuously growing application demand in high-tech fields such as optical communication, precision sensing, and lidar due to their outstanding advantages of low fiber transmission loss and eye safety. They have become an important development direction for high-reliability light source platforms. For short-wave infrared light sources with high brightness and good beam quality, traditional edge-emitting lasers and distributed feedback lasers, while possessing mature manufacturing processes and stable operating performance, have inherent structural limitations in achieving device array integration, obtaining low divergence angle output, and improving overall brightness, making it difficult to meet the stringent performance requirements of next-generation optoelectronic devices. In contrast, InP-based vertical-cavity surface-emitting lasers (VCSELs), while capable of vertical surface emission and two-dimensional array integration, are limited by the inherently low refractive index contrast of the InP material system. This requires the growth of dozens of distributed Bragg mirrors to achieve sufficiently high reflectivity, which not only significantly increases the thickness of the epitaxial structure and introduces additional optical transmission loss but also brings severe thermal management problems, thus seriously restricting the device's performance in high power output and high slope efficiency.

[0003] The emergence of photonic crystal surface-emitting lasers (SSELS) provides another feasible technological path for high-performance light sources in the short-wave infrared band. SSELS utilize the Bragg diffraction effect of two-dimensional photonic crystals to create optical field feedback within the chip plane to achieve lasing. Simultaneously, the periodic modulation of the photonic crystal structure couples a portion of the light into the vertical direction to achieve surface emission. Theoretically, it has the potential to achieve near-diffraction-limited low divergence angle output, single-mode operation, narrow linewidth, and high power, thus being considered a strong candidate for realizing high-brightness short-wave infrared light sources. However, current research and development of InP-based photonic crystal surface-emitting lasers in the 1.55μm band faces a significant challenge in achieving both low threshold gain and high slope efficiency: On the one hand, low threshold lasing typically relies on enhancing the 180° coupling strength of the photonic crystal in the plane to ensure sufficient feedback gain in the horizontal direction. However, this strong coupling mechanism significantly suppresses the vertical radiation efficiency, resulting in most of the light energy being confined within the plane and unable to be effectively emitted. On the other hand, achieving high slope efficiency requires increasing the proportion of vertical radiation loss in the total loss. This necessitates designing the photonic crystal structure to offset the electric field center from the centroid of the photonic crystal's refractive index. However, this offset weakens the in-plane optical feedback strength, thereby increasing the device's threshold gain. This inherent design trade-off makes it difficult for traditional photonic crystal surface-emitting lasers to achieve ideal output efficiency while maintaining low threshold lasing.

[0004] To address the aforementioned technical challenges, researchers have attempted to propose improvement solutions from different perspectives. For example, US Patent 8861564B2 discloses a distributed feedback surface-emitting laser, which places a second photonic crystal region generating out-of-plane light diffraction between multiple first photonic crystal regions that cause laser oscillation, and places a light absorber that absorbs light of a specific wavelength above the second photonic crystal region. Furthermore, the emissivity of the first photonic crystal region is configured to be smaller than that of the second photonic crystal region. This solution mainly focuses on reducing the input of leakage light between adjacent light-emitting units and reducing the occurrence of reflected feedback light, thereby achieving stable oscillation characteristics and solving the problem of optical crosstalk between different units in the laser array. However, it does not involve the active control of the intrinsic radiation ratio of the photonic crystal, nor does it propose how to overcome the performance trade-off between low threshold and high efficiency through fine structural design. Another US patent, US8130808B2, discloses a two-dimensional photonic crystal surface-emitting laser. Its stacked structure has a multi-refractive-index layer, comprising a central region composed of a high-refractive-index medium and a peripheral region composed of a low-refractive-index medium. This structure utilizes the refractive index difference to achieve lateral light confinement in the in-plane direction, suppressing light leakage to the outside of the two-dimensional photonic crystal in the in-plane direction. Simultaneously, it reduces the active layer absorption loss caused by the peripheral region acting as an absorption layer due to the lack of injected charge carriers. While this approach improves light utilization efficiency to some extent, it lacks a synergistic control mechanism between the peripheral confinement structure and the core photonic crystal region, failing to achieve independent adjustment of the in-plane coupling strength and vertical radiation ratio. Therefore, it still cannot fundamentally resolve the contradiction between low threshold and high efficiency.

[0005] Therefore, how to significantly improve the slope efficiency of photonic crystal surface-emitting lasers while maintaining their low threshold gain advantage remains a key technical challenge that needs to be overcome in this field. Summary of the Invention

[0006] The technical problem to be solved by this invention is to overcome the technical contradiction in the design of existing short-wave infrared InP-based photonic crystal surface-emitting lasers, in which it is difficult to achieve both low threshold gain and high slope efficiency, and to provide a novel photonic crystal surface-emitting laser structure that can significantly improve slope efficiency while maintaining a low threshold gain.

[0007] To address the aforementioned problems, this invention provides a short-wave infrared InP-based photonic crystal surface-emitting laser, comprising an n-type InP substrate, an n-type cladding layer, a multiple quantum well layer, an electron blocking layer, a photonic crystal layer, a p-type cladding layer, and a metal distributed Bragg reflector layer arranged sequentially along the stacking direction, as well as an n-electrode and a p-electrode.

[0008] The n-electrode is disposed in the peripheral region of the n-type InP substrate on the side away from the n-type cladding layer and is in ohmic contact with the n-type InP substrate; the p-electrode is disposed on the side of the metal distributed Bragg reflector layer away from the p-type cladding layer and is electrically connected to the metal distributed Bragg reflector layer.

[0009] The photonic crystal layer is composed of multiple three-lattice units arranged periodically in a plane perpendicular to the stacking direction, and a peripheral distributed Bragg reflection structure is provided around the photonic crystal layer.

[0010] At least two lattice points in the three-lattice unit have lateral and longitudinal offsets relative to another lattice point in the plane.

[0011] Furthermore, the n-type coating layer is n-In. 0.53 Al 0.47 As layer;

[0012] The electron blocking layer is p-In 0.53 Al 0.47 As layer;

[0013] The photonic crystal layer is In. 0.53 Al 0.31 Ga 0.16 As layer;

[0014] The p-type coating layer is a p-InP layer;

[0015] The peripheral distributed Bragg reflection structure is formed by alternating InP layers and InGaAsP layers.

[0016] Furthermore, the multiple quantum well layer is formed by alternating InGaAlAs barrier layers and InGaAs quantum well layers, and the number of quantum well layers in the multiple quantum well layer is 7.

[0017] Furthermore, the photonic crystal layer is formed in In 0.53 Al 0.31 Ga 0.16 A three-lattice photonic crystal layer formed by etching in the As layer.

[0018] Furthermore, each of the three lattice units includes a first lattice point A, a second lattice point B, and a third lattice point C;

[0019] The second lattice point B and the third lattice point C are respectively offset relative to the first lattice point A.

[0020] Furthermore, the lateral offset and longitudinal offset of the three lattice units are both 0.05a, where a is a lattice constant.

[0021] Furthermore, the lattice constant a is 480 nm.

[0022] Furthermore, the peripheral distributed Bragg reflection structure consists of 35 pairs of InP / InGaAsP periodic layers;

[0023] Each pair of InP / InGaAsP periodic layers includes an InP layer with a thickness of 0.095 μm and an InGaAsP layer with a thickness of 0.137 μm.

[0024] Furthermore, the metal distributed Bragg reflector layer comprises a SiO2 layer, a TiO2 layer, and an Au layer;

[0025] The SiO2 layer consists of three layers, each with a thickness of 0.277 μm, the TiO2 layer has a thickness of 0.116 μm, and the Au layer has a thickness of 0.1 μm.

[0026] Furthermore, the thickness of the n-type InP substrate is 1.45 μm;

[0027] The thickness of the n-type coating layer is 0.025 μm;

[0028] The thickness of the InGaAlAs barrier layer is 0.007 μm;

[0029] The thickness of the InGaAs quantum well layer is 0.005 μm;

[0030] The thickness of the electron blocking layer is 0.07 μm;

[0031] The thickness of the photonic crystal layer is 0.40 μm;

[0032] The thickness of the p-type coating layer is 1.60 μm.

[0033] Compared with existing technologies, this invention overcomes the technical bottleneck of traditional photonic crystal surface-emitting lasers, which struggle to achieve both low threshold gain and high slope efficiency, through the synergistic design of a four-sided distributed Bragg mirror and a three-lattice micro-offset, thus significantly improving the overall performance of the device. The InP / InGaAsP distributed Bragg mirrors positioned around the photonic crystal layer effectively suppress in-plane light leakage loss, recoupling plane waves overflowing from the edge of the photonic crystal region back into the resonant cavity. This design not only avoids unnecessary loss of valuable optical energy but, more importantly, increases the total optical field intensity participating in oscillation within the cavity, laying a solid foundation for increasing the vertical radiation ratio. Secondly, by precisely micro-offsetting the three-lattice structure laterally and longitudinally, active control of the in-plane coupling strength and the vertical radiation ratio is achieved. This micro-offset design moderately weakens excessive in-plane coupling to prevent excessive light confinement, while effectively enhancing the diffraction efficiency in the vertical direction, achieving an optimal balance between in-plane oscillation and vertical emission of photons.

[0034] More importantly, the two techniques mentioned above are not simply a functional superposition, but rather produce a significant synergistic effect. The light recovery effect provided by the peripheral distributed Bragg reflection structure increases the total tunable light field, which amplifies the control effect of the three-lattice micro-offset. The three-lattice micro-offset ensures that the recovered light can be coupled to the vertical direction in the optimal proportion. The organic combination of the two enables the device to significantly improve the vertical radiation efficiency while maintaining a low threshold gain.

[0035] Simulation results show that the vertical radiation loss ratio of the photonic crystal surface-emitting laser structure optimized by this invention is significantly improved from the initial 5% to 45%, while the threshold gain is stably maintained at 26 cm⁻¹. -1 The threshold efficiency was reduced from a low level, while the slope efficiency was significantly improved from 0.02 W / A to 0.18 W / A, achieving a balance between low threshold and high efficiency. This technological breakthrough not only provides an effective technical route for the structural design of high-performance short-wave infrared photonic crystal surface-emitting lasers, but also provides an ideal solution for the application requirements of high brightness, low power consumption, and high-quality beam sources in fields such as optical communication and lidar. Attached Figure Description

[0036] Figure 1 is a schematic diagram of the epitaxial cross-sectional structure of the short-wave infrared InP-based photonic crystal surface-emitting laser according to an embodiment of the present invention;

[0037] Figure 2 is a top view of the Bragg reflection structure distributed around the photonic crystal layer in an embodiment of the present invention.

[0038] Figure 3 is a schematic diagram of the design parameters of the photonic crystal three-lattice lateral and longitudinal offset structure in an embodiment of the present invention;

[0039] Figure 4 is a pseudo-color diagram showing the influence of lateral and longitudinal offsets on the core performance indicators of the photonic crystal surface-emitting laser in an embodiment of the present invention, in which:

[0040] Figure 4(a) shows the distribution of threshold gain as a function of offset;

[0041] Figure 4(b) shows the distribution of slope efficiency as a function of offset.

[0042] Figure 4(c) shows the distribution of vertical loss percentage as a function of offset.

[0043] In the figure: 1. n-type InP substrate; 2. n-type cladding layer; 3. Multiple quantum well layer; 4. Electron blocking layer; 5. Photonic crystal layer; 6. p-type cladding layer; 7. Metallic distributed Bragg reflector layer; 8. n-electrode; 9. p-electrode. Detailed Implementation

[0044] To make the objectives, technical solutions, and physical mechanisms of this invention clearer, the short-wave infrared InP-based photonic crystal surface-emitting laser proposed in this invention will be described in detail, thoroughly, and completely below with reference to all the above-mentioned accompanying drawings. It should be fully understood that the specific embodiments described herein are merely illustrative of the technical concept of this invention and are not intended to limit the scope of protection of this invention.

[0045] This embodiment provides a short-wave infrared InP-based photonic crystal surface-emitting laser, which is an electrically injected photonic crystal surface-emitting laser. Optionally, by setting the lateral and longitudinal offsets of the three lattice units of the photonic crystal to 0.05a (where a is a lattice constant), an ideal balance is achieved between extremely low threshold gain and extremely high slope efficiency. As shown in Figure 1, the laser's overall hardware architecture includes multiple functional film layers and peripheral auxiliary electrodes tightly coupled from top to bottom along the stacking direction. Specifically, it includes an n-type InP substrate 1, an n-type cladding layer 2, a multiple quantum well layer 3, an electron blocking layer 4, a photonic crystal layer 5, a p-type cladding layer 6, a metal distributed Bragg reflector layer 7, and n electrodes 8 and p electrodes 9 corresponding to the device's electrical injection and lead connections.

[0046] Specifically, the n-electrode 8, serving as the top-level interface for current injection, is typically made of a high-conductivity metal alloy. It is deposited and ohmically contacts the outer region of the upper surface of the underlying n-type InP substrate 1. Its core mounting position can be designed as a ring or symmetrically distributed strip, leaving sufficient optical windows in the central region to allow out-of-plane radiated laser light to smoothly penetrate and achieve upward laser emission. In other words, the n-electrode 8 is preferably located on the outer region of the n-type InP substrate 1 away from the n-type cladding layer 2, serving both as the positive electrode or one-end current introduction function of the device and minimizing obstruction of the top light emission path. Closely below the n-electrode 8 is the n-type InP substrate 1, which not only serves as the growth substrate for the entire device during molecular beam epitaxy or metal-organic chemical vapor deposition but also as the final short-wave infrared emission medium. To minimize the absorption loss of free carriers during the penetration of 1.55 μm wavelength photons through the substrate, the thickness of the n-type InP substrate 1 is optionally reduced and controlled to 1.45 μm.

[0047] On the lower surface of this n-type InP substrate 1, an n-type cladding layer 2 is grown in close contact. The material of this n-type cladding layer 2 is strictly limited to n-type doped In. 0.53 Al 0.47 As a ternary alloy, its thickness can be set to 0.025 μm. The main physical function of the n-type cladding layer 2 is to provide an efficient electron injection channel and to utilize its lower refractive index relative to the active region to achieve preliminary optical confinement of the light field in the vertical direction, preventing excessive diffusion of light field energy towards the substrate.

[0048] Continuing downwards along the path of light field and carrier transport, the lower surface of the n-type cladding layer 2 is tightly connected to the multi-quantum well layer 3. This multi-quantum well layer 3 undertakes the core task of converting injected non-equilibrium carriers (electrons and holes) into coherent photons through stimulated emission recombination. To achieve extremely high material gain and internal quantum efficiency in the 1.55 μm communication band, the multi-quantum well layer 3 employs a superlattice periodic structure formed by alternating InGaAlAs quaternary barrier layers and InGaAs ternary quantum well layers. Preferably, the multi-quantum well layer 3 contains 7 quantum well layers. The thickness of each InGaAlAs barrier layer is controlled at 0.007 μm, while the thickness of each InGaAs quantum well layer is set to 0.005 μm. This nanoscale precision bandgap engineering not only effectively suppresses the activity of nonradiative recombination centers and significantly increases the spatial overlap integral between the optical field standing wave antinodes and the gain medium, but also greatly enhances the two-dimensional confinement capability of charge carriers through quantum tunneling and quantum confinement effects. Below the region of intense stimulated emission, attached to the lower surface of the multi-quantum-well layer 3 is an extremely thin but crucial electron-blocking layer 4. This electron-blocking layer 4 can be made of wide-bandgap p-type doped In. 0.53 Al 0.47 As, its thickness is designed to be 0.07 μm. The introduction of electron blocking layer 4 is based on the complex band shift theory. Its physical mechanism is to use the huge peak potential barrier formed by the conduction band at the heterojunction interface to effectively block the leakage of high-energy hot electrons from the multi-quantum well layer 3 to the p-type region. This is particularly critical when the device is under high current injection or high temperature operating environment, thereby greatly improving the overall electro-optical conversion efficiency and long-term operating stability of the device.

[0049] Closely connected to the electron blocking layer 4 is the core structure of this embodiment, namely the photonic crystal layer 5, which enables in-plane light field manipulation and out-of-plane high-brightness radiation. This photonic crystal layer 5 employs an InP lattice that matches the InP crystal structure. 0.53 Al 0.31 Ga 0.16Made of As quaternary alloy material, its overall longitudinal thickness can be set to 0.40 μm. As shown in Figures 2 and 3, the photonic crystal layer 5 is composed of a large number of tri-lattice units arranged periodically through strict mathematical translation operations in a two-dimensional horizontal plane perpendicular to the epitaxial growth stacking direction. As shown in Figure 2, the photonic crystal hole structure does not extend aimlessly to the cutting edge of the device around the core light-emitting region of the photonic crystal layer 5. Instead, a peripheral distributed Bragg reflection structure is embedded and set in the same layer around the perimeter of the photonic crystal layer 5, surrounding the entire core light-emitting region. This peripheral distributed Bragg reflection structure is formed by alternating high-refractive-index InP layers and low-refractive-index InGaAsP layers. In this embodiment, the peripheral structure can be specifically formed by stacking 35 pairs of InP / InGaAsP periodic layers. In each pair of periodic layers radiating from the outside in, there is an InP layer with a thickness controlled at 0.095 μm and an InGaAsP layer with a thickness of 0.137 μm. This distributed Bragg reflector, constructed horizontally with alternating high and low refractive indices, forms an optical high wall. It can reflect and couple back into the core resonant cavity abruptly due to diffraction within the photonic crystal core cavity, reversing horizontal light waves that would otherwise spill outwards due to diffraction. This leakage-proof design suppresses the unavoidable in-plane edge light leakage loss in traditional photonic crystal surface-emitting lasers. This effectively increases the total photon density and optical field energy participating in steady-state oscillation within the cavity without adding extra injection current. Photons that would otherwise dissipate at the device edges as useless heat are now re-accumulated within the cavity and ultimately participate in effective out-of-plane diffraction radiation.

[0050] To achieve active, flexible, and precise control over the vertical radiation capability of the photonic crystal, the photonic crystal layer 5 in this embodiment can be fabricated using electron beam lithography and a high-precision inductively coupled plasma dry etching process on an In crystal with a thickness of 0.40 μm. 0.53 Al 0.31 Ga 0.16 A specific three-lattice photonic crystal hole structure is etched into the As material substrate. As shown in Figure 3, each of the three-lattice units, as the smallest periodic repeating unit of the photonic crystal, contains three independent circular lattice points, namely, the first lattice point A, the second lattice point B, and the third lattice point C. In this embodiment, the second lattice point B and the third lattice point C are not placed arbitrarily, but are physically offset relative to the first lattice point A in a specific direction and with a specific value. Specifically, assuming we establish a rectangular coordinate system in this two-dimensional plane, and define the lower left corner of a complete square unit cell (whose lattice constant is denoted as a) as the origin of the reference coordinate system. In this unit cell, the geometric center coordinates of the first lattice point A are defined as... In traditional highly symmetrical photonic crystal designs, the second lattice point B and the third lattice point C should ideally be in absolutely symmetrical positions within the unit cell. However, in the asymmetric design of this embodiment, the geometric center coordinates of the second lattice point B have undergone lateral and longitudinal displacements, changing to... Meanwhile, the geometric center coordinates of the third lattice point C also underwent a composite displacement, changing to... The lateral and longitudinal offsets satisfy a strict mathematical equality relationship in spatial geometry: ,and More importantly, the ratio of the area of ​​air voids etched out within the unit cell of a photonic crystal to the total area of ​​the unit cell is the fill factor parameter of the photonic crystal. Satisfying the given relation: (in (where is the etching radius of the circular hole).

[0051] In this embodiment, to satisfy the second-order Bragg diffraction resonance phase-matching condition near a wavelength of 1.55 μm, the lattice constant α can be selected as 480 nm; simultaneously, to find the optimal balance between gain and loss, the lateral and longitudinal offsets of the three lattice units (i.e., the aforementioned...) and All values ​​were set to an optimal median value of 0.05a (i.e., an absolute offset distance of 24nm). This tiny spatial offset of 0.05a precisely disrupts the highly symmetrical in-plane electric field distribution mode within the traditional photonic crystal unit, causing a sharp spatial misalignment between the center of the resonant electric field and the centroid of the effective refractive index of the photonic crystal. Under this asymmetrical microscopic physical state, the originally excessively strong 180° coupling feedback in the plane, which easily leads to photons being tightly bound within the plane, is effectively and moderately weakened; at the same time, due to the introduction of abundant first-order Fourier harmonic components due to the symmetry breaking, the perpendicular diffraction coupling coefficient in the out-of-plane direction is significantly enhanced.

[0052] Directly beneath the photonic crystal layer 5, which has undergone complex optical field manipulation, a thick p-type cladding layer 6 is densely grown. This p-type cladding layer 6 is made of heavily doped p-InP material, with an overall thickness of up to 1.60 μm. This p-type cladding layer 6 not only provides a wide channel for the injection of hole carriers from below into the multi-quantum well layer 3 above, but also possesses an extremely low optical refractive index, thus serving as an excellent optical confinement layer at the bottom. Together with the n-type cladding layer 2 above, they tightly confine the lasing light field within the vertical waveguide core region. At the very bottom of the p-type cladding layer 6, which is also the substrate surface of the entire epitaxial growth structure, a high-reflectivity metal distributed Bragg reflector layer 7 is deposited using magnetron sputtering or electron beam evaporation. This metal distributed Bragg reflector layer 7 is actually a highly composite dielectric-metal hybrid reflector system, its structure comprising a SiO2 layer and a TiO2 layer for the dielectric phase, and a final sealing layer of Au metal. Specifically, the SiO2 layer can be provided in three layers, each with a calibrated thickness of 0.277 μm; the TiO2 layer interspersed between the SiO2 layers can have a thickness of 0.116 μm; and the Au layer, which serves as the conductive ohmic contact interface and the ultimate broadband reflective surface on the outermost side of the entire reflector, can have a thickness of 0.1 μm.

[0053] Because the photonic crystal diffraction results in both upward-emitting and downward-propagating radiation beams, the downward-propagating light undergoes high reflection and phase change at the reflection interface when it reaches the bottom metal distributed Bragg reflector layer 7. This changes the propagation direction and propagates upward again, coherently superimposing with the original upward-radiating beam, thus forming a stronger laser emission on the n-type InP substrate 1 side.

[0054] On the bottom surface of the Au layer of the metal distributed Bragg reflector layer 7, which is the very bottom of the entire device, a p electrode 9 is also provided. This p electrode 9 is electrically connected to the metal distributed Bragg reflector layer 7 to provide an electrical access path for the other end of the device; at the same time, its large-area metal contact can also facilitate the rapid conduction of Joule heat generated by the device in continuous wave operation mode to the external heat sink or packaging substrate.

[0055] To verify the effectiveness of the above structure and obtain device performance indicators, this embodiment uses numerical simulation to model and calculate the designed photonic crystal surface-emitting laser. Specifically, the reflection characteristics of the bottom metal distributed Bragg reflector layer and the surrounding distributed Bragg reflector structure, including reflectivity and reflection phase, can be calculated and verified using the transfer matrix method (TMM). For core indicators such as the mode characteristics of the photonic crystal layer and the overall device, the near-field distribution of the electromagnetic field, and the ratio of vertical loss to in-plane loss, simulations can be performed using three-dimensional coupled-wave theory (3D-CWT) combined with analytical methods. The confinement factors of the photonic crystal layer and the active layer can be obtained by integrating the longitudinal optical field distribution at the target resonant wavelength of 1.55 μm.

[0056] In a preferred simulation model, the lateral dimension of the overall light-emitting region of the device can be set to 50μm × 50μm; the lattice constant α of the three-lattice photonic crystal layer can be set to 480nm, and the fill factor... The thickness can be set to 400 nm and the horizontal and vertical offsets can be set to [-0.1a, 0.1a], with the horizontal and vertical offsets preferably both being 0.05a. To simulate the physical effects of the surrounding distributed Bragg reflection structure, specific reflectivity boundary conditions can be set around the photonic crystal layer in the 3D-CWT simulation space. Under a preferred condition, the equivalent reflectivity parameter ρ of the four boundaries can be taken as 0.92, and the reflection phase φ can be taken as 2.06 rad. The bottom reflection boundary conditions can be set according to the incident angle of 0°-5° and the wavelength of 1500nm-1600nm in TE mode light to provide a reflectivity greater than 97%.

[0057] With the aforementioned mesh size and boundary conditions fixed, a convergent solution for performance parameters such as threshold gain, slope efficiency, and vertical radiation loss ratio can be obtained through a two-dimensional parameter space scan composed of lateral and longitudinal offsets, thus providing a basis for the 26cm solution in this embodiment. -1 Performance data such as 0.18W / A and 45% provide the basis for calculations.

[0058] To clearly and intuitively demonstrate the improvements in the epitaxial structure of this embodiment and the resulting gains, data from Tables 1 and 2 can be used for illustration. For a conventional and unoptimized epitaxial structure of a photonic crystal surface-emitting laser, the material and thickness parameters of each film layer are shown in Table 1. It can be clearly seen that the conventional structure lacks optical confinement protection measures around the photonic crystal layer 5, and also lacks a strong metal-dielectric hybrid total internal reflection mirror at the bottom.

[0059] Table 1: Materials and parameters of the epitaxial structure of the photonic crystal surface-emitting laser before optimization

[0060]

[0061] After comprehensive and systematic improvements in this embodiment, the composition of each film layer material and its absolute thickness parameters of the optimized epitaxial structure are detailed in Table 2 below.

[0062] Table 2: Optimized epitaxial structure materials and parameters for photonic crystal surface-emitting lasers

[0063]

[0064] Figure 4 shows a pseudo-color diagram illustrating the impact of lateral and longitudinal offsets on the core performance indicators of the photonic crystal surface-emitting laser in this embodiment, illustrating the following pattern: when the offsets of apertures B and C are close to 0, the threshold gain is at a low level; as the aperture offset increases, the threshold gain gradually increases overall, reaching a maximum of nearly 55 cm⁻¹. -1 The slope efficiency also increases significantly with the increase of the offset, rising from approximately 0.02 W / A to a higher level, while the vertical radiation loss ratio gradually increases from the low central region to the high peripheral region. In this embodiment, when the lattice offset is precisely controlled at 0.05a, the distributed Bragg reflection structure composed of 35 pairs of InP / InGaAsP around the perimeter acts like a wall, reflecting and coupling the in-plane diffracted plane waves that escape from the edge of the device back into the main resonant cavity. At the same time, this leakage prevention mechanism is superimposed on the intrinsic vertical radiation enhancement effect caused by the lattice offset of 0.05a, thereby increasing the vertical radiation loss ratio, which was originally low in the traditional symmetrical three-lattice structure, from an initial low value to 45%.

[0065] From a mechanistic perspective, the minute offset of the three-pore unit cell disrupts the ideal symmetric resonance condition of the three-lattice photonic crystal, moderately weakening the 180° planar coupling between the fundamental waves, thus preventing the optical field energy from being excessively confined within the plane. Simultaneously, the minute aperture offset also breaks the coincidence between the electric field center and the geometric center node, allowing some of the electromagnetic field energy that originally circulated within the plane to be more effectively guided to radiate in the vertical direction. Furthermore, the aperture offset changes the 180° and 90° coupling coefficients, leading to changes in the coefficients of the coupled wave equation, causing a phase shift in the field distribution, thereby disrupting the cancellation effect between the upper and lower radiated light, ultimately significantly enhancing vertical radiation. This mechanism directly explains the physical source of the improved slope efficiency and demonstrates that this embodiment does not simply pursue an extreme value for a certain parameter, but rather establishes an adjustable and optimizable balance between low threshold gain and high slope efficiency.

[0066] In summary, this specific structural parameter configuration enables the device to maintain a low threshold gain while significantly improving the slope efficiency, which determines the device's power conversion capability, and effectively increasing the proportion of vertical radiation loss in the total loss. Preferably, with both lateral and vertical offsets of 0.05a, a lattice constant a of 480nm, and in conjunction with a peripheral distributed Bragg reflector structure and a bottom metallic distributed Bragg reflector layer, the device can achieve a length of approximately 26cm. -1 The threshold gain is high, the slope efficiency is approximately 0.18 W / A, and the vertical radiation loss is approximately 45%. This synergistic design breaks the traditional compromise between low threshold gain and high slope efficiency in photonic crystal surface-emitting lasers, providing a practical structural design solution for high-power, high-brightness, and low-power high-performance short-wave infrared light sources.

Claims

1. A short-wave infrared InP-based photonic crystal surface-emitting laser, characterized in that, The system includes an n-type InP substrate (1), an n-type cladding layer (2), a multiple quantum well layer (3), an electron blocking layer (4), a photonic crystal layer (5), a p-type cladding layer (6), and a metal distributed Bragg reflector layer (7) arranged sequentially along the stacking direction, as well as an n-electrode (8) and a p-electrode (9). The n-electrode (8) is disposed in the peripheral region of the n-type InP substrate (1) away from the n-type cladding layer (2) and is in ohmic contact with the n-type InP substrate (1). The p-electrode (9) is disposed in the metal distributed Bragg reflector layer (7) away from the p-type cladding layer (6) and is electrically connected to the metal distributed Bragg reflector layer (7). The photonic crystal layer (5) is composed of a plurality of three-lattice units arranged periodically in a plane perpendicular to the stacking direction, and a peripheral distributed Bragg reflector structure is provided around the photonic crystal layer (5). At least two lattice points in the three-lattice units have lateral and longitudinal offsets relative to another lattice point in the plane.

2. The short-wave infrared InP-based photonic crystal surface-emitting laser according to claim 1, characterized in that: The n-type coating layer (2) is n-In 0.53 Al 0.47 As layer; the electron blocking layer (4) is p-In 0.53 Al 0.47 As layer; the photonic crystal layer (5) is In 0.53 Al 0.31 Ga 0.16 As layer; the p-type cladding layer (6) is a p-InP layer; the peripheral distributed Bragg reflection structure is formed by alternating InP layer and InGaAsP layer.

3. The short-wave infrared InP-based photonic crystal surface-emitting laser according to claim 2, characterized in that: The multi-quantum well layer (3) is formed by alternating InGaAlAs barrier layers and InGaAs quantum well layers, and the number of quantum well layers in the multi-quantum well layer (3) is 7.

4. The short-wave infrared InP-based photonic crystal surface-emitting laser according to claim 2, characterized in that: The photonic crystal layer (5) is in In 0.53 Al 0.31 Ga 0.16 (5) A three-lattice photonic crystal layer formed by etching in the As layer.

5. The short-wave infrared InP-based photonic crystal surface-emitting laser according to claim 1, characterized in that: Each of the three lattice units includes a first lattice point A, a second lattice point B, and a third lattice point C; the second lattice point B and the third lattice point C are respectively offset relative to the first lattice point A.

6. The short-wave infrared InP-based photonic crystal surface-emitting laser according to claim 5, characterized in that: The lateral and longitudinal offsets of the three lattice units are both 0.05a, where a is a lattice constant.

7. The short-wave infrared InP-based photonic crystal surface-emitting laser according to claim 6, characterized in that: The lattice constant a is 480 nm.

8. The short-wave infrared InP-based photonic crystal surface-emitting laser according to claim 2, characterized in that: The peripheral distributed Bragg reflection structure consists of 35 pairs of InP / InGaAsP periodic layers; each pair of InP / InGaAsP periodic layers includes an InP layer with a thickness of 0.095 μm and an InGaAsP layer with a thickness of 0.137 μm.

9. The short-wave infrared InP-based photonic crystal surface-emitting laser according to claim 1, characterized in that: The metal distributed Bragg reflector layer (7) includes a SiO2 layer, a TiO2 layer and an Au layer; wherein, the SiO2 layer consists of 3 layers, each with a thickness of 0.277 μm, the TiO2 layer has a thickness of 0.116 μm, and the Au layer has a thickness of 0.1 μm.

10. The short-wave infrared InP-based photonic crystal surface-emitting laser according to claim 3, characterized in that: The thickness of the n-type InP substrate (1) is 1.45 μm; the thickness of the n-type cladding layer (2) is 0.025 μm; the thickness of the InGaAlAs barrier layer is 0.007 μm; the thickness of the InGaAs quantum well layer is 0.005 μm; the thickness of the electron blocking layer (4) is 0.07 μm; the thickness of the photonic crystal layer (5) is 0.40 μm; and the thickness of the p-type cladding layer (6) is 1.60 μm.

Images