可重构太赫兹多谐波双光梳
Reconfigurable Terahertz Multi-Harmonic Dual-Combs
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中文总结 AI 辅助
研究人员在单个自探测太赫兹量子级联激光器平台上实现可重构多谐波双光梳系统，可切换多种配置，拓展了双光梳运行自由度，简化了系统架构，为紧凑太赫兹应用提供新机遇。
中文摘要 AI 辅助
双光梳光谱技术由两个重复频率略有差异的频率梳构建而成，无需机械扫描即可实现实时高精度测量。在太赫兹（THz）光谱范围内，双光梳技术为高分辨率快速光谱学提供了强大工具。量子级联激光器（QCL）因体积紧凑、尺寸、重量和功耗特性优良，已成为THz双光梳系统的理想光源。在QCL频率梳中，通过本征四波混频产生的重复频率通常等于腔往返频率，对应基频梳；尽管该重复频率可通过电流和温度控制调谐，但可调范围有限。近来，重复频率为腔往返频率整数倍的谐波频率梳受到越来越多关注，其可提升单条谱线的信噪比，还能直接洞察QCL的强非线性。本文展示了在单个自探测THz QCL平台上实现的可重构多谐波双光梳系统，通过精确控制驱动电流和热条件，实现并切换多种双光梳配置，包括基频-基频、基频-二次谐波、二次谐波-二次谐波、二次谐波-三次谐波双光梳。这些结果确立了谐波阶次为单激光器系统内双光梳运行的额外自由度，所展示的平台可实现高分辨率、高灵敏度测量，同时大幅简化系统架构，这种基于单个QCL的可重构多波段双光梳方法为紧凑THz光谱学和频率计量学开辟了新机遇。
英文摘要
Dual-comb spectroscopy, constructed from two frequency combs with slightly different repetition frequencies, enables real-time and high-precision measurements without mechanical scanning. In the terahertz spectral range, dual-comb techniques provide a powerful tool for high-resolution and rapid spectroscopy. Quantum cascade lasers (QCLs), owing to their compact footprint and favorable size, weight, and power, have emerged as promising sources for THz dual-comb systems. In QCL frequency combs, the repetition frequency generated through intrinsic four-wave mixing is typically equal to the cavity round-trip frequency, corresponding to the fundamental comb. Although this repetition frequency can be tuned via current and temperature control, the accessible tuning range remains limited. Recently, harmonic frequency combs, whose repetition frequencies are integer multiples of the cavity round-trip frequency, have attracted increasing attention, offering enhanced single-line signal-to-noise ratios and providing direct insight into the strong nonlinearity of QCLs. Here, we demonstrate a reconfigurable multi-harmonic dual-comb system realized on a single self-detected THz QCL platform. By precisely controlling the driving current and thermal conditions, we achieve and switch between multiple dual-comb configurations, including fundamental-fundamental, fundamental-second-harmonic, second-harmonic-second-harmonic, and second-harmonic-third-harmonic dual-combs. These results establish harmonic order as an additional degree of freedom for dual-comb operation within a single laser system. The demonstrated platform enables high-resolution and high-sensitivity measurements while significantly simplifying the system architecture. This reconfigurable multi-band dual-comb approach based on a single QCL opens new opportunities for compact THz spectroscopy and frequency metrology.
