Terahertz quantum-cascade vertical external cavity surface emitting lasers

太赫兹量子级联垂直外腔表面发射激光器

• 批准号: 1407711
• 负责人: Benjamin Williams
• 金额: $ 37.8万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-08-01 至 2017-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1407711&HistoricalAwards=false
• 关键词: Terahertz; quantum; cascade; vertical; external

This research addresses the challenge of making terahertz semiconductor laser sources with high power and excellent beam quality in the 2-5 THz range. Compact sources of terahertz radiation that operate with both high output power (tens to hundreds of milliwatts or more) and excellent beam quality are sorely needed for a range of spectroscopy and imaging applications for example in the fields of astrophysics, atmospheric science, biological and medical sciences, security screening and illicit material detection, and non-destructive evaluation. The intellectual merit lies in the development of a new type of terahertz quantum-cascade (QC) laser: a vertical-external-cavity-surface-emitting-laser (THz QC-VECSEL). This new approach addresses a challenging issue for THz QC-lasers: how to operate both with high power and an excellent beam pattern. The enabling technology for this proposed laser is a so-called "active metasurface reflector", which is composed of a sparse array of antenna-coupled THz QC-laser sub-cavities locked to an external cavity mode. Each sub-cavity is designed to be an efficient radiator and have a very favorable geometry for heat removal, which allows high-power continuous-wave operation. This research will integrate and unite complementary concepts from antenna engineering and laser engineering. The broader impacts are addressed at several levels including undergraduate and graduate research experiences, dissemination of results, and technology advancement. Outreach to underrepresented minorities (URM) will specifically occur through the PI's development of research projects for a course designed for the recruitment and retention of URM engineering freshmen. The intellectual merit lies in the development of a new type of terahertz quantum-cascade (QC) laser: a vertical-external-cavity-surface-emitting-laser (THz QC-VECSEL). The enabling component is an innovative THz active metasurface reflector, which is composed of a sparse array of antenna-coupled THz QC-laser sub-cavities. The metasurface reflector forms part of the laser cavity such that many THz QC-laser sub-cavities are locked to a high-quality factor cavity mode, allowing for scalable power combining. The sparse distribution of laser material on the metasurface reduces the average power dissipation density and offers a favorable geometry for heat extraction which in turn will allow excellent continuous-wave performance of large effective area emitters. The primary goal is to achieve THz QC-lasers with directive beams (single transverse mode with divergence angle 6 degrees), with near-diffraction limited beam quality, that have scalable power of 1 W peak power in pulsed mode, and 200 mW power in continuous-wave mode. A secondary goal is the design of external THz laser cavities based upon engineered inhomogeneous metasurfaces with customized gain, spectral, phase, and polarization response for new capabilities such as beam shaping, wavefront engineering, and dynamic polarization modulation. An integrated theoretical, computational, and experimental effort is proposed to (a) design and implement low-loss and efficient amplifying reflective QC metasurfaces, (b) design and implement external cavity configurations for single-mode operation with excellent beam-quality, and (c) design and grow high-efficiency quantum-cascade active region material suitable for use in the QC-VECSEL, (d) perform thermal design and engineering

这项研究解决了制造在 2-5 THz 范围内具有高功率和出色光束质量的太赫兹半导体激光源的挑战。天体物理学、大气科学、生物和医学科学、安全筛查和非法材料检测以及无损评估等领域的光谱学和成像应用迫切需要具有高输出功率（数十至数百毫瓦或更高）和出色光束质量的紧凑型太赫兹辐射源。其智力优势在于开发了一种新型太赫兹量子级联（QC）激光器：垂直外腔表面发射激光器（THz QC-VECSEL）。这种新方法解决了太赫兹QC激光器的一个挑战性问题：如何以高功率和出色的光束模式运行。这种激光器的实现技术是所谓的“有源超表面反射器”，它由锁定到外腔模式的天线耦合太赫兹QC激光器子腔的稀疏阵列组成。每个子腔都被设计成一个高效的散热器，并具有非常有利的散热几何形状，从而允许高功率连续波运行。这项研究将整合和统一天线工程和激光工程的互补概念。更广泛的影响涉及多个层面，包括本科生和研究生的研究经验、成果传播和技术进步。 PI 将通过为招募和保留 URM 工程新生而设计的课程开发研究项目来具体开展对代表性不足的少数群体 (URM) 的外展活动。其智力优势在于开发了一种新型太赫兹量子级联（QC）激光器：垂直外腔表面发射激光器（THz QC-VECSEL）。启用组件是创新的太赫兹有源超表面反射器，它由天线耦合的太赫兹QC激光子腔的稀疏阵列组成。超表面反射器形成激光腔的一部分，使得许多太赫兹QC激光器子腔被锁定到高质量因子腔模式，从而允许可扩展的功率组合。激光材料在超表面上的稀疏分布降低了平均功率耗散密度，并为热量提取提供了有利的几何形状，这反过来又将使大有效面积发射器具有出色的连续波性能。主要目标是实现具有定向光束（发散角为 6 度的单横向模式）的太赫兹 QC 激光器，具有近衍射限制的光束质量，在脉冲模式下具有 1 W 峰值功率，在连续波模式下具有 200 mW 功率的可扩展功率。第二个目标是基于工程非均匀超表面设计外部太赫兹激光腔，具有定制的增益、光谱、相位和偏振响应，以实现光束整形、波前工程和动态偏振调制等新功能。提出了综合理论、计算和实验工作，以（a）设计和实现低损耗和高效的放大反射QC超表面，（b）设计和实现具有出色光束质量的单模操作的外腔配置，以及（c）设计和生长适用于QC-VECSEL的高效量子级联有源区材料，（d）进行热设计和工程