Yasui Takeshi, Hayashi Kenta, Ichikawa Ryuji, Cahyadi Harsono, Hsieh Yi-Da, Mizutani Yasuhiro, Yamamoto Hirotsugu, Iwata Tetsuo, Inaba Hajime, Minoshima Kaoru
Opt Express. 2015 May 4;23(9):11367-77. doi: 10.1364/OE.23.011367.
Real-time measurement of the absolute frequency of continuous-wave terahertz (CW-THz) radiation is required for characterization and frequency calibration of practical CW-THz sources. We proposed a method for real-time monitoring of the absolute frequency of CW-THz radiation involving temporally parallel, i.e., simultaneous, measurement of two pairs of beat frequencies and laser repetition frequencies based on dual THz combs of photocarriers (PC-THz combs) with different frequency spacings. To demonstrate the method, THz-comb-referenced spectrum analyzers were constructed with a dual configuration based on dual femtosecond lasers. Regardless of the presence or absence of frequency control in the PC-THz combs, a frequency precision of 10(-11) was achieved at a measurement rate of 100 Hz. Furthermore, large fluctuation of the CW-THz frequencies, crossing several modes of the PC-THz combs, was correctly monitored in real time. The proposed method will be a powerful tool for the research and development of practical CW-THz sources, and other applications.
实际连续波太赫兹（CW-THz）源的特性表征和频率校准需要对连续波太赫兹辐射的绝对频率进行实时测量。我们提出了一种实时监测连续波太赫兹辐射绝对频率的方法，该方法基于具有不同频率间隔的光载流子双太赫兹梳（PC-THz梳），涉及对两对拍频和激光重复频率进行时间上并行（即同时）测量。为了演示该方法，基于双飞秒激光器构建了具有双配置的太赫兹梳参考光谱分析仪。无论PC-THz梳中是否存在频率控制，在100 Hz的测量速率下都实现了10^(-11)的频率精度。此外，还实时正确监测了连续波太赫兹频率跨越PC-THz梳多个模式的大幅波动。所提出的方法将成为实际连续波太赫兹源研发及其他应用的有力工具。
