光谱锁相检测用于高灵敏度光谱学
Spectral Lock-in Detection for High-Sensitivity Spectroscopy
- University of California, Los Angeles（加州大学洛杉矶分校）
- California NanoSystems Institute, University of California, Los Angeles（加州大学洛杉矶分校加州纳米系统研究所）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本文提出光谱锁相检测框架，将锁相噪声抑制独立扩展到每个光谱通道，在保持频率信息的同时实现超六个数量级的灵敏度增强，适用于多种光谱平台。
AI中文摘要：
在不牺牲光谱信息的情况下恢复弱信号的能力是精密光谱学的核心，然而传统的锁相检测在实现噪声抑制的同时牺牲了光谱维度，并最终在检测带宽和灵敏度之间施加了权衡。在此，我们引入光谱锁相检测，这是一个多功能的框架，将锁相噪声抑制独立地扩展到宽带光谱的每个已分辨分量。通过将编码光谱信息的快时间坐标与携带时间调制的慢时间坐标分离，测量波形在解调前先进行光谱分辨，使得每个频率通道能够被独立检测和积分。我们在理论上表明，对于光谱稳定的信号，每个光谱通道中的信号功率保持不变，而噪声功率理想情况下随积分时间每十年降低10 dB，从而使埋在瞬时噪声底下的光谱特征得以显现而不损失频率信息。我们在相位不相干的外差太赫兹光谱学和相位相干的太赫兹时域光谱学中实验验证了这一框架，展示了在光谱分辨通道中超过六个数量级的灵敏度增强。由于光谱区分是在获取的波形上以计算方式执行的，该方法既不需要顺序光谱扫描，也不需要额外的光谱选择、多通道检测或干涉硬件。因此，光谱锁相检测为跨多种光谱平台和频率范围增强灵敏度提供了一条广泛适用的途径，为跨电磁频谱的高灵敏度、信息丰富的测量开辟了新机遇。
英文摘要：
The ability to recover weak signals without sacrificing their spectral information is central to precision spectroscopy, yet conventional lock-in detection achieves noise rejection at the expense of spectral dimensionality and ultimately imposes a trade-off between detection bandwidth and sensitivity. Here, we introduce spectral lock-in detection, a versatile framework that extends lock-in noise rejection independently to every resolved component of a broadband spectrum. By separating the fast-time coordinate encoding spectral information from the slow-time coordinate carrying temporal modulation, the measured waveform is spectrally resolved before demodulation, enabling each frequency channel to be independently detected and integrated. We show analytically that, for spectrally stable signals, the signal power in each spectral channel remains invariant, while the noise power ideally decreases by 10 dB per decade of integration time, enabling spectral features buried beneath the instantaneous noise floor to emerge without loss of frequency information. We experimentally validate this framework in both phase-incoherent heterodyne terahertz spectroscopy and phase-coherent terahertz time-domain spectroscopy, demonstrating more than six orders of magnitude of sensitivity enhancement across the spectrally resolved channels. Because spectral discrimination is performed computationally on the acquired waveform, the approach requires neither sequential spectral scanning nor additional spectral-selection, multichannel-detection, or interferometric hardware. Spectral lock-in detection therefore provides a broadly applicable route to enhancing sensitivity across diverse spectroscopic platforms and frequency regimes, opening new opportunities for high-sensitivity, information-rich measurements across the electromagnetic spectrum.
