Collaborative Research: Quantum cascade laser sources of high-power, coherent frequency combs

摘要标题：紧凑型，高功率半导体激光源的相干频率梳快速和有效的分子detectionAbstract：非技术：该项目的目标是紧凑型，实用，高功率半导体激光源的相干频率梳在中红外光谱范围的发展。梳状结构在频率空间中起着标尺的作用，提供了快速准确的分子振动频率读数。这些频率可以作为不同分子的唯一标识符。因此，所提出的激光源将使超宽带和快速分子光谱学，这在痕量气体环境监测，药品质量控制和生化试剂的远程检测具有广泛的应用。该项目将探索一种新的频率梳产生机制，该机制基于量子级联激光器中的相干脉动。该项目将作为哈佛和德克萨斯A M大学团队成员之间的合作努力，并与来自欧洲的世界领先的光谱学专家合作。这将为所有参与的学生和研究人员创造独特的跨学科和多文化教育，研究和推广机会。技术支持：这项合作研究的目标是开发基于连续泵浦量子级联激光器的中红外相干频率梳的高功率半导体激光源。量子级联激光锁模和频率梳领域在过去三年中迅速发展，这要归功于提出小组和其他几个小组的贡献。然而，到目前为止，宽带相位相干梳已被证明在激光器的特殊设计，在一个狭窄的时间间隔内的阈值附近的电流。超快增益弛豫是大多数锁模技术的根本障碍。提议的团队将专注于通过相干拉比振荡实现频率梳的新途径，这将导致由太赫兹频率间隔分离的模式的相位相干“超级梳”的参数生成。 由此产生的谐波锁模在时域上相当于在太赫兹频率下的幅度调制，与增益弛豫率相当。这种新的频率梳产生机制是完全相位相干的，并且本质上在阈值以上足够高地操作，从而产生每模式的高功率。该项目将采用几种策略，利用拉比机制，使用标准的高性能激光芯片产生稳定、高功率和宽带的梳齿。

Abstract title: Compact, high-power semiconductor laser sources of coherent frequency combs for fast and efficient molecular detectionAbstract:Non-technical: The objective of the project is the development of compact, practical, high-power semiconductor laser sources of coherent frequency combs in the mid-infrared spectral range. The combs work as rulers in frequency space, providing fast and accurate readings of frequencies of molecular vibrations. These frequencies can serve as unique identifiers of different molecules. Therefore, the proposed laser sources will enable ultra-broadband and fast molecular spectroscopy, which has a wide range of applications in trace gas environmental monitoring, pharmaceutical quality control and remote detection of biochemical agents. The project will explore a new mechanism of frequency comb generation, which is based on coherent pulsations in quantum cascade lasers. The project will be pursued as a collaborative effort between the team members at Harvard and Texas A&M University and in collaboration with world-leading spectroscopy experts from Europe. This will create unique inter-disciplinary and multi-cultural education, research, and outreach opportunities for all involved students and researchers. Technical: The objective of this collaborative research is to develop high-power semiconductor laser sources of coherent frequency combs in the mid-infrared based on continuously pumped quantum cascade lasers. The field of quantum cascade laser mode locking and frequency combs has seen rapid expansion over the last three years, due to contributions of the proposing team and several other groups. However, so far broadband phase-coherent combs have been demonstrated in lasers of special design in a narrow interval of currents near threshold. Ultrafast gain relaxation presents a fundamental obstacle to most mode locking techniques. The proposing team will focus on a new route to frequency combs through coherent Rabi oscillations, which result in parametric generation of a phase-coherent "supercomb" of modes separated by terahertz frequency intervals. The resulting harmonic mode locking is equivalent in time domain to amplitude modulation at terahertz frequencies comparable to the gain relaxation rate. This new mechanism of frequency comb generation is entirely phase-coherent and intrinsically operates high enough above threshold, yielding high power per mode. The project will pursue several strategies of utilizing the Rabi mechanism for generation of stable, high-power, and broadband combs using standard high-performance laser chips.