【Diamond Heat Dissipation】Characteristics and research status of vertical cavity surface emitting semiconductor lasers...
17:08 13-10-2020 reading
Document Management-Modification (Status: Released, ID: 34764) Column Home-Abrasives-09-10 Special Topic*Title [Diamond Heat Dissipation] Characteristics and Research Status of Vertical Cavity Surface Emitting Semiconductor Laser Turn to Link Full Title Keyword Description author: Liyu Jiao Zong Nan, Penzin Army Institute of Physics, Chinese Academy of Sciences, Chinese Academy of laser technology laboratory of solid State University, Chinese Academy of introduction semiconductor laser with a small size, light weight, high efficiency, wide wavelength range, easy integration, high reliability, batch Chemical production, etc...The author defaults to Shengdie 1 Shengdie 2 Shengdie 3 Shengdie 4 Shengdie 5 Shengdie 6 Shengdie 7 Doris Shengkun 100 million macro 100 million macro 2 Shengkun English Shengdie English release time 2020 -08-12T09:50:53 to attribute priority 0 color bold italic source 01_abrasives_superhard materials network_wang Xinhui address: http://www.idacn.org/news/41017.html title image address /uploads/1/image/public/202009/20200910181115_u5xo9nnwlj.png Width 180 Height 120 Compression is not in proportion to the original image Watermark text Ueditor Editor.md doc import function is provided in the commercial version-
Abstract author: Liyu Jiao Zong Nan, Penzin Army Institute of Physics, Chinese Academy of Sciences, Chinese Academy of Laser Technology Laboratory of Solid State University, Chinese Academy of introduction semiconductor laser with a small size, light weight, high efficiency, wide wavelength range, easy integration, high reliability, Mass production, etc...
Author: Liyu Jiao Zong Nan, Penzin army
Key Laboratory of Solid State Laser, Chinese Academy of Sciences, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences
Semiconductor laser has the advantages of small size, light weight, high efficiency, wide wavelength range, easy integration, high reliability, and mass production. Since the continuous operation at room temperature in the early 1970s, it has become an important device in the field of optoelectronic technology. . Traditional edge-emitting semiconductor lasers have achieved higher power output, but their output spot is elliptical, and the worst aspect ratio of the spot can reach 100… 1. In some applications, additional beam shaping systems are required.
In 1979, Soda et al. proposed the concept of a vertical cavity surface emitting laser (VCSEL), which is different from the traditional edge emitting laser in that its laser emission direction is perpendicular to the surface of the substrate, and a circular spot can be obtained. Since the length of the resonant cavity is close to the wavelength, the dynamic single-mode performance is relatively good, and it is expected to show its talents in the fields of optical communication, optical interconnection, optical storage, laser display, and lighting. At present, Princeton Optronics has obtained the highest continuous output power of a single VCSEL tube of 5.5 W. However, because the resonant cavity of the VCSEL is composed of a top Bragg reflector (DBR) and a bottom Bragg reflector, the cavity length is of the same order as the wavelength, resulting in a large divergence angle of the device (the half-angle width is about 15°). In order to obtain a smaller divergence angle, a vertical external cavity surface emitting laser (VECSEL) came into being. Due to the external cavity structure, the cavity length is increased from the wavelength level to the millimeter to the centimeter level, which effectively improves the beam quality, and the theoretical limit reaches M2~1.
The early vertical external cavity surface emitting lasers still use the electrical pumping (EP) method. Currently, the EP-VECSEL single tube has obtained a continuous output of more than 9 W. However, both electrically pumped VCSELs and VECSELs are due to uneven current injection and thermal accumulation of series resistors, so high power output is limited in single-transverse mode operation. In 1997, Kuznetsov et al. proposed an optically pumped vertical external cavity surface emitting laser (OP-VECSEL), also known as a semiconductor disk laser (SDL). It combines the advantages of high beam quality vertical cavity surface emitting lasers and high power laser diode-pumped solid-state lasers, which can simultaneously obtain high power and high beam quality laser output, covering a wide range of wavelengths from deep ultraviolet to mid-infrared. In the ultraviolet and blue-violet light bands, the semiconductor gain medium is mainly InGaN-GaN material system, and multiple InGaN quantum wells are grown on the GaN base material. In the red to near-infrared wavelength range, semiconductor gain media mainly adopt InGaP-AlGaInP, GaAs-AlGaAs, InGaAs-GaAsP and GaInNAs-GaAs quantum wells grown on GaAs substrates. The wavelength around 1.5 μm is mainly achieved by growing AlGaInAs-InP quantum wells on InP substrates, and 2~3 μm is realized by growing GaInAsSb-GaSb material systems on GaSb substrates. For the longer 4~5 μm band, the substrate material is mostly BaF2, and the gain medium material is PbSe-PbEuTe or PbTe-PbEuTe system. At the same time, thanks to the existence of its external cavity, it can be easily mode-locked to obtain ultra-short pulse output; it can also achieve high-efficiency laser cavity frequency-frequency conversion, expanding the output wavelength range.
In addition, OP-VECSEL is unique in that the semiconductor gain chip has a simple structure, no p-n junction, and no electrical contact, which greatly simplifies its growth process, improves the reliability of the gain chip, and eliminates the thermal effect on the additional resistor; The wavelength can be selectively designed; the wavelength tuning range of hundreds of nanometers can be obtained; the pumping spot on the semiconductor gain chip is larger, and the possibility of optical damage is reduced at high power; the laser is compact, convenient to carry, and has a high degree of practicality. In practical applications, it can be conveniently used as a supporting light source for instruments and microscopes. At present, the continuous output power of single-tube OP-VECSEL has reached 106 W.
This article introduces the principles and characteristics of VCSEL, EP-VECSEL and OP-VECSEL, and summarizes its latest research progress, main applications and development prospects.
As shown in Figure 1, a typical VCSEL includes top-emitting and bottom-emitting structures. Generally speaking, early typical devices were grown on N-type GaAs substrates by metal organic chemical vapor deposition (MOCVD) technology. The DBR is mainly used as the laser cavity mirror. The quantum well active region (MQWs) is sandwiched between n-DBR and p-DBR. Due to the small thickness of the quantum well, the single-pass gain is small, so the reflectivity of the mirror is high. Generally, the reflectivity of the total-reflective cavity mirror is> 99.9%, and the output cavity mirror reflectivity is set to the best coupling output rate (> 99%) through theoretical calculation. Then, a metal contact layer is made on the outer surface of the substrate and the p-DBR. By making a circular light-emitting window on p-DBR or n-DBR, a circular beam is obtained, the diameter of the window is from a few microns to a hundred microns, and then it is bonded with a heat sink with good thermal conductivity to improve the heat dissipation performance of the chip. Since GaAs substrates have strong absorption of light near 800 nm, devices in this band usually adopt a top-emitting structure. The bottom emission structure can be used to generate 976 nm and 1064 nm bands. In order to reduce the absorption loss of the substrate, the substrate is usually thinned to less than 150 μm, and then an antireflection film is grown to improve the quality of the laser beam. Finally, the gain chip is installed On the heat sink, it is closer to the active area, so the heat dissipation is better.
The EP-VECSEL chip includes an electrical injection structure, an active area and a DBR. Compared with the traditional VCSEL, the external cavity structure introduced increases the cavity length, as shown in Figure 2. The resonant cavity includes three mirrors: p-DBR, n-DBR and external cavity mirror. It is a coupled resonant cavity composed of two sub-cavities. The resonant cavity composed of p-DBR, n-DBR and the active region sandwiched on the laser chip is an active cavity, which provides the gain required for lasing; the resonant cavity composed of p-DBR and external cavity mirror can By controlling the loss of different transmission modes, suppress high-order transverse modes, thereby improving beam quality.
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