Mode-locked THz QC-VECSELs

锁模太赫兹 QC-VECSEL

• 批准号: 2041165
• 负责人: Benjamin Williams
• 金额: $ 38.49万
• 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: 2021
• 资助国家: 美国
• 起止时间: 2021-03-15 至 2024-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2041165&HistoricalAwards=false
• 关键词: Mode; locked; THz; QC; VECSELs

This research addresses the challenge of making terahertz semiconductor laser sources that emit electromagnetic waves with frequencies between 2 and 5 THz (i.e. wavelengths between 60 and 150 microns). The terahertz frequency range is relatively underdeveloped part of the electromagnetic spectrum, which resides between the infrared and microwave. In past research, this team demonstrated a new laser architecture that addressed the challenge of how to generate high power THz light simultaneously with high beam quality, known as the THz quantum-cascade vertical-external-cavity surface-emitting-laser. The goal of this research is how to adapt this laser architecture to create a so-called “mode-locked” terahertz laser. In such a laser, instead of emitting steady continuous light, the laser would emit a series of extremely short high-intensity light pulses at regular intervals. While mode-locked lasers are ubiquitous in the visible and infrared wavelengths, they have proven very difficult to implement for terahertz lasers. Work will focus on several approaches to adapt the vertical-external-cavity surface-emitting-laser approach, including coaxing the laser to emit many wavelengths at once, controlling the speed of propagation of all of these various wavelengths within the laser cavity, and introducing a fast “saturable absorber” switch into the laser cavity to encourage these various wavelengths to travel in lock-step so that they all constructively interfere to create a short pulse. If successful, this research would result in a new terahertz source for applications in the fields of astrophysics, atmospheric science, biological and medical sciences, security screening, illicit material detection, combustion science, antiquities, waste-sorting, next-generation wireless communications, and non-destructive evaluation. As a part of the project, the research will train graduate and undergraduate students, and will support recruitment and retention of underrepresented minorities to engineering through participation in a targeted research project course.Technical descriptionThe research goal of this proposal is the development of active and passive mode-locked terahertz quantum-cascade lasers that emit picosecond pulses based upon the metasurface vertical-external-cavity surface-emitting-laser (VECSEL) concept. Two primary schemes will be investigated: active mode-locking in which the gain metasurface is modulated via radiofrequency (RF) electrical injection at the round trip frequency, and passive/hybrid mode-locking where a fast saturable absorber is used with optional RF loss modulation. The enabling component of the VECSEL is a reflectarray metasurface made up of sub-wavelength antenna-coupled microcavities loaded with laser gain material; this creates an active amplifying mirror which serves as one mirror in an open cavity. The intellectual merit in the proposed work lies in the use of the metasurface VECSEL architecture to investigate mode-locked terahertz lasers. Such a configuration gives the possible of engineering the metasurface to achieve broadband gain and dispersion compensation; furthermore the external cavity allows power combining for high-power output along with control of the cavity repetition rate. Additionally, the external cavity will allow integration of a fast saturable absorber, which can be separately optimized to have a fast recovery time while the quantum-cascade active material is optimized to have a long gain recovery time. The broader impacts are addressed at several levels including undergraduate and graduate research experiences, dissemination of results, technology advancement, and outreach to underrepresented minorities. Outreach will specifically occur through development of research projects for a course designed for the recruitment and retention of underrepresented minority first-year engineering students.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

这项研究解决了制造太赫兹半导体激光源的挑战，该源发射频率在2到5太赫兹之间（即波长在60到150微米之间）的电磁波。太赫兹频率范围是电磁波谱中相对不发达的部分，位于红外和微波之间。在过去的研究中，该团队展示了一种新的激光架构，解决了如何同时产生高功率太赫兹光和高光束质量的挑战，称为太赫兹量子级联垂直外腔表面发射激光器。这项研究的目标是如何调整这种激光结构来创建所谓的“锁模”太赫兹激光器。在这种激光器中，激光不是发射稳定连续的光，而是以一定的间隔发射一系列极短的高强度光脉冲。虽然锁模激光器在可见光和红外波长中无处不在，但它们已被证明很难用于太赫兹激光器。工作将集中在几种方法上，以适应垂直外腔表面发射激光的方法，包括诱导激光一次发射多个波长，控制激光腔内所有这些不同波长的传播速度，并在激光腔中引入一个快速的“饱和吸收器”开关，以鼓励这些不同波长的锁步行进，以便它们都建设性地相互干扰，产生短脉冲。如果成功，这项研究将产生一种新的太赫兹源，应用于天体物理学、大气科学、生物和医学科学、安全筛查、非法材料检测、燃烧科学、文物、废物分类、下一代无线通信和非破坏性评估等领域。作为该项目的一部分，该研究将培训研究生和本科生，并将通过参与有针对性的研究项目课程，支持招募和留住代表性不足的少数族裔。技术描述本提案的研究目标是基于超表面垂直外腔表面发射激光器（VECSEL）概念，开发发射皮秒脉冲的主动和被动锁模太赫兹量子级联激光器。将研究两种主要方案：主动锁模，其中通过射频（RF）电注入在往返频率上调制增益超表面；被动/混合锁模，其中使用快速饱和吸收器和可选的RF损耗调制。VECSEL的使能组件是由载有激光增益材料的亚波长天线耦合微腔组成的反射超表面；这创造了一个主动放大镜，作为一个开放腔镜。这项工作的智力优势在于使用超表面VECSEL架构来研究锁模太赫兹激光器。这种结构为设计超表面以实现宽带增益和色散补偿提供了可能；此外，外部腔体允许功率组合用于高功率输出以及腔体重复率的控制。此外，外腔将允许集成快速饱和吸收器，可以单独优化以具有快速恢复时间，而量子级联活性材料则被优化为具有长增益恢复时间。更广泛的影响涉及几个层面，包括本科生和研究生的研究经验、成果的传播、技术进步和向未被充分代表的少数民族的推广。具体地说，外联活动将通过为一门课程开发研究项目来开展，该课程旨在招募和留住代表性不足的一年级少数族裔工程专业学生。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Multi-mode lasing in terahertz metasurface quantum-cascade VECSELs

太赫兹超表面量子级联 VECSEL 中的多模激光

• DOI: 10.1063/5.0061391
• 发表时间: 2021
• 期刊: Applied Physics Letters
• 影响因子: 4
• 作者: Wu, Yu;Addamane, Sadhvikas;Reno, John L.;Williams, Benjamin S.
• 通讯作者: Williams, Benjamin S.

Continuous wave operation of terahertz metasurface quantum-cascade VECSEL with a long intra-cryostat cavity

具有长低温恒温器腔的太赫兹超表面量子级联 VECSEL 的连续波操作

• DOI: 10.1063/5.0107667
• 发表时间: 2022
• 期刊: Applied Physics Letters
• 影响因子: 4
• 作者: Wu, Yu;Curwen, Christopher A.;Hayton, Darren J.;Reno, John L.;Williams, Benjamin S.
• 通讯作者: Williams, Benjamin S.