原子微系统用窄光谱线宽垂直腔面发射激光器研究

The project aims at the research of the key technologies and scientific question in the integrated optical external cavity narrow spectral linewidth vertical-cavity surface-emitting lasers (VCSELs). The high contrast subwavlength grating (HCG) is proposed as the reflector and integrates on the top surface of the polarization stable single fundamental mode VCSEL through the semiconductor planar process to form the planar optical external cavity. The new type HCG structure consisted of the support layer with SiO2 and the grating structure of TiO2 is designed. The HCG characteristics affected by the refractive index of SiO2, grating parameters, surface morphologies and structure of grating are simulated and analyzed. After that, the HCG with high reflectivity, larger high reflection bandwidth and larger redundancy processing is obtained. The spectral linewidth and other characteristics of the device affected by the integrated external cavity, consisted of HCG structure, is researched and the HCG fabrication technology and integration process are also researched in the project. Suitable HCG planar optical external cavity structure can design and integrate for the device and the high performance narrow linewidth VCSEL can be fabricated. This new type device using the SiO2 to support the HCG structure can solve the normal HCG preparation problem such as floating, gating protection and stress releasing. The device can adjust the device effective cavity length by control the SiO2 thickness and the advantage of the device includes larger range of narrowing the spectral linewidth, simple fabrication process and easy preparation. The research results obtained by the project will provide new approaches and techniques for developing VCSELs operating with narrow linewidth with independent intellectual property, and will meet the application requirements of the new atomic microsystem.

本项目对集成光学外腔窄线宽面发射激光器（VCSEL）的关键科学技术问题进行研究。提出采用高对比度光栅（HCG）作为光学外腔的反射镜,通过半导体平面工艺集成到偏振稳定基横模VCSEL顶部形成平面光学外腔。设计由SiO2作为支撑层，TiO2作为光栅层的新型HCG结构。模拟分析SiO2折射率、光栅参数和形貌等因素对HCG特性影响，获得具有高反射率和反射带宽，加工冗余度大的HCG结构。研究带HCG结构的集成外腔对器件光谱线宽等特性影响，研究在器件顶部进行HCG加工集成技术，制备出MHz窄光谱线宽高性能器件。这种新型HCG外腔器件用SiO2支撑HCG，解决了常规HCG悬空、光栅保护和应力释放等制备难题，通过SiO2厚度调节有效谐振腔长度，具有光谱线宽调节范围大、平面加工工艺、易于制备等优势。本研究为发展我国具有自主知识产权的窄光谱线宽VCSEL提供新思路和新技术，满足我国新型原子微系统的应用需求。

该项目主要研究采用高对比度光栅结构（HCG）与基横模高功率VCSEL集成，制备集成外腔窄光谱线宽VCSEL。在深入研究和理解集成光学外腔VCSEL光谱线宽控制理论的基础上，设计制备出基于低折射率介质层具有高反射率和反射带宽的HCG结构，并实现其与偏振稳定基横模VCSEL的集成，掌握了基于低折射率介质HCG设计、加工与器件集成关键技术。研究了集成HCG 结构后，光学外腔导致光注入对VCSEL 器件偏振、模式、阈值、出光功率和光谱线宽等特性影响，研制出性能优良的VCSEL器件。针对芯片原子钟和原子陀螺等应用对VCSEL波长、线宽、模式以及工作温度的需求，研制出阈值电流小于1 mA，偏振抑制比大于20 dB，高温工作高性能基横模894.6nm VCSEL，并送样到合作单位进行测试。在后续研究中，我们将超构表面引入到半导体激光器中，对VCSEL发射的光束实现多种调控，使常规VCSEL成为具备光束聚焦、准直和偏转等功能的激光芯片，并初步实现了可发射零阶无衍射贝塞尔光束和低阶涡旋光束的激光芯片。在项目支持下共发表10余篇高水平的学术论文，其中包括《Nature nanotechnology》论文1篇，《Photonics Research》论文1篇，《Optics Express》论文1篇，IEEE等其他期刊论文7篇，申请6项发明专利，其中2项获得授权，直接培养研究生5名，其中1人博士毕业，1人硕士毕业，3人直博。直接培养青年教师1 人。