CN-122026221-A - Surface-emitting laser with photonic crystal cladding with gradually changed structure

Abstract

The invention discloses a surface-emitting laser with a photonic crystal cladding with a gradual change structure, and relates to the technical field of semiconductor lasers. The surface emitting laser comprises a substrate, a lower distributed Bragg reflector, an n-type cladding layer, an active region, a p-type spacing layer, a photonic crystal layer, a p-contact layer and an upper electrode. The photonic crystal layer includes a two-dimensional periodic array of holes that is divided in-plane into a central radiation region, a transition region, and a peripheral in-plane confinement region. The structure of the invention can simultaneously realize controllable radiation coupling of a central area and low-loss strong in-plane restraint of a peripheral area, effectively inhibit interface scattering and mode competition and improve single-mode stability, threshold performance and manufacturing tolerance of the small-size surface-emitting laser.

Inventors

• LI HUI
• LU JINLONG
• LI NANNAN
• Pan Shaochi
• QIU ZHENHUAN
• WANG BIN
• ZHANG KE
• FENG JIAN
• DENG SHUPENG
• DING SHIHAO
• ZHONG CHUYU

Assignees

• 深圳技术大学

Dates

Publication Date

20260512

Application Date

20260211

Claims (10)

1. 1. The surface emitting laser with the photonic crystal cladding layer with the structure gradient is characterized by comprising a lower electrode (520), a substrate (490), a lower distributed Bragg reflector (480), an n-type cladding layer (470), an active region (440), a p-type spacer layer (430), a photonic crystal layer (420), a p-contact layer (410) and an upper electrode (510) which are sequentially arranged from bottom to top, wherein the photonic crystal layer (420) comprises a two-dimensional periodic hole array which is divided into a central radiation region (100), a transition region (200) and a peripheral in-plane limiting region (300) in a plane, a plurality of holes are formed in a unit cell of the two-dimensional periodic hole array, a unit cell of the central radiation region (100) adopts a first displacement parameter d L , a unit cell of the peripheral in-plane limiting region (300) adopts a second displacement parameter d H , and d L ≠d H , and the displacement parameter d of a unit cell of the transition region (200) continuously changes from the first displacement parameter d L to the second displacement parameter d H .
2. 2. The surface-emitting laser with graded photonic crystal cladding layer according to claim 1, wherein the cell comprises four holes, the center of the cell is taken as a reference point, the four holes are arranged at equal intervals along the circumference of the reference point, and the distances from the centers of the four holes to the reference point are all D, wherein 0< d < a/2, a is the lattice constant of the two-dimensional periodic array of holes.
3. 3. The surface emitting laser with graded photonic crystal cladding according to claim 2, wherein the second displacement parameter d H has a value ranging from 0.48a to 0.52a, and the first displacement parameter d L has a value ranging from 0.40a to 0.47a.
4. 4. The surface emitting laser with structured graded photonic crystal cladding according to claim 1, wherein the aperture r of the two-dimensional periodic array of holes is kept constant or the variation ratio is less than 10% in the central radiation region (100), the transition region (200) and the peripheral in-plane confinement region (300).
5. 5. The surface emitting laser with a structured graded photonic crystal cladding according to claim 1, wherein the transition region (200) has a width of 3a to 20a.
6. 6. The surface emitting laser with a structured graded photonic crystal cladding according to claim 1, wherein the continuous variation of the displacement parameter d in the transition region (200) follows a linear function, a piecewise linear function, a cosine function, a hyperbolic tangent function or a gaussian function.
7. 7. The surface emitting laser with a graded photonic crystal cladding layer according to claim 1, further comprising an n-type spacer layer (450) and a current confinement layer (460) disposed between the n-type cladding layer (470) and the active region (440), the n-type spacer layer (450) being located above the current confinement layer (460).
8. 8. The surface emitting laser with graded photonic crystal cladding according to claim 7, wherein the current confinement layer (460) is an oxidation confinement layer, an ion implantation confinement layer or a tunneling junction confinement layer.
9. 9. The surface emitting laser with a graded photonic crystal cladding according to claim 1, wherein the two-dimensional periodic hole array is formed in the photonic crystal layer (420) by a surface etching or buried etching process.
10. 10. The surface emitting laser with graded photonic crystal cladding according to claim 1, wherein the shape of the central radiation region (100) is circular, square, rectangular or elliptical, and the peripheral in-plane confinement region (300) is a single ring or multiple ring structure surrounding the central radiation region (100).

Description

Surface-emitting laser with photonic crystal cladding with gradually changed structure Technical Field The invention relates to the technical field of semiconductor lasers, in particular to a surface-emitting laser with a photonic crystal cladding with a gradual change structure. Background The Photonic Crystal Surface Emitting Laser (PCSEL) is a surface emitting semiconductor laser which utilizes a two-dimensional photonic crystal to realize in-plane relative oscillation and diffract to a vertical direction, can realize single-mode oscillation, narrow divergence angle, high power and high coherence on a large area, and has wide application prospect in the fields of laser radar, optical communication, display and the like. However, as device dimensions shrink, in-plane loss increases dramatically, edge scattering is significant, leading to threshold rise, lasing difficulties, limiting PCSEL miniaturization and high speed performance. In the prior art, a 'two-photon crystal structure' is often adopted to enhance the in-plane feedback of the small-size PCSEL, namely, a band gap photon crystal reflection ring is introduced at the periphery of a central oscillation area. But this approach forms heterostructures by varying pore size, fill factor, or period, often introducing abrupt band structure changes between the central and cladding regions. Such abrupt changes result in interface scattering and interface states, resulting in mode distortion and far field quality degradation. Meanwhile, the band gap center frequency of the center region and the band gap center frequency of the cladding region are not easy to match accurately, mode competition and frequency drift are easy to cause, the band gap center frequency is very sensitive to manufacturing errors, and the yield is reduced. In addition, when a strong in-plane confinement is pursued, it is often difficult to achieve low out-of-plane radiation loss, and there is a contradiction in performance trade-off. Therefore, there is an urgent need for a new photonic crystal heterostructure design that can enhance in-plane confinement and mode selection capabilities while minimizing interface effects and synergistically optimizing out-of-plane radiation characteristics to improve performance and manufacturing tolerances of small-sized PCSELs. Disclosure of Invention The invention aims to provide a surface-emitting laser with a photonic crystal cladding with a gradual structural change, so as to solve the problems in the prior art. The invention provides a surface emitting laser with a structure graded photonic crystal cladding, which comprises a lower electrode, a substrate, a lower distributed Bragg reflector, an n-type cladding layer, an active region, a p-type spacing layer, a photonic crystal layer, a p-contact layer and an upper electrode which are sequentially arranged from bottom to top, wherein the photonic crystal layer comprises a two-dimensional periodic hole array which is divided into a central radiation region, a transition region and a peripheral in-plane limiting region in a plane, a plurality of holes are formed in a cell of the two-dimensional periodic hole array, the displacement parameter of the inner hole of the cell is defined as d, the cell of the central radiation region adopts a first displacement parameter d L, the cell of the peripheral in-plane limiting region adopts a second displacement parameter d H and d L≠dH, and the displacement parameter d of the cell of the transition region is continuously changed from the first displacement parameter d L to the second displacement parameter d H. Preferably, the unit cell comprises four holes, the center of the unit cell is taken as a reference point, the four holes are arranged at equal intervals along the circumferential direction of the reference point, and the distances from the center of the four holes to the reference point are allD, wherein 0< d < a/2, a is the lattice constant of the two-dimensional periodic array of holes. Preferably, the value of the second displacement parameter d H ranges from 0.48a to 0.52a, and the value of the first displacement parameter d L ranges from 0.40a to 0.47a. Preferably, the aperture r of the two-dimensional periodic array of holes remains constant or varies less than 10% in the central radiation zone, transition zone and peripheral in-plane confinement zone. Preferably, the transition zone has a width of 3a to 20a. Preferably, the continuous variation of the displacement parameter d in the transition zone follows a linear function, a piecewise linear function, a cosine function, a hyperbolic tangent function or a gaussian function. Preferably, the semiconductor device further comprises an n-type spacer layer and a current limiting layer, wherein the n-type spacer layer and the current limiting layer are arranged between the n-type cladding layer and the active region, and the n-type spacer layer is positioned above the current limiting layer. Preferably,