GaN基紫外垂直腔面发射激光器的量子效率调控和器件研制

原子钟是导航、定位和授时系统的核心元器件，目前正朝着小型化、集成化的光学原子钟的方向发展。垂直腔面发射激光器是光学原子钟的核心光源和关键部件。GaN基VCSEL激光器的波长范围覆盖了紫外和可见光波段，光子能量与铷原子、钙原子的多个Zeeman能级系统相对应，适合作为激光光源研制芯片尺寸的光学原子钟。本项目针对GaN基紫外垂直腔面发射激光器量子效率调控的三个关键科学问题，即InGaN紫外量子阱局域态密度低导致的有源区内量子效率下降、激光器谐振腔在紫外波段光学吸收损耗增大导致的外量子效率下降、缺乏在紫外波段具有高光学反射率的DBR反射镜，争取突破激光器材料生长和器件工艺的难题，研制出紫外波段的GaN基垂直腔面发射激光器，激射波长380±10nm，连续输出功率≥10μW，作为核心激光光源应用于光学原子钟的研制，并为我国其他领域所需的GaN基激光光源提供关键元器件支撑。

The atomic clock is the core component of the positioning, navigation, timing (PNT) system. It has been developed towards to the optical atomic clock with a miniaturization and integration tendency. The vertical-cavity surface-emitting laser (VCSEL) is the light source of optical atomic clock. The wavelength of GaN-based VCSEL covers a wide spectrum, including the visible and ultraviolet wavelength range. The corresponding photon energy matches the s series of the Zeeman energy levels of rubidium and calcium atoms. The GaN-based VCSEL can be applied to the research and development of chip-scale optical atomic clock...This proposal focuses on the material growth and device fabrication of GaN-based ultraviolet (UV) VCSEL device. There are several problems of quantum efficiency which holds back the development of this device. The indium composition of InGaN quantum wells in ultraviolet region is lower, and the density of localized state will be reduced. So the internal quantum efficiency of the multiple-quantum-well (MQW) active region is lower than that of the devices with a longer wavelength. The second question is the short wavelength and the high energy of UV light increases the optical absorption loss inside the resonant cavity as well as the reflectance lass on the facets of the cavity. The last problem is the lack of an effective distributed Bragg reflector (DBR) mirror with high optical reflectance in the ultraviolet wavelength range. ..Our efforts will be put on the possible solutions of the above-mentioned key problems in the epitaxial growth and the device processing. The goal of the project is to obtain an electrically injected GaN-based VCSEL with an ultraviolet lasing wavelength of 380±10nm and an output light power higher than 10μW under continuous operation. Such a GaN-based VCSEL device will work as the laser light source of the optical atomic clock and be applied to other related fields.