Precise dynamic characterization of microcombs assisted by an RF spectrum analyzer with THz bandwidth and MHz resolution
Precise dynamic characterization of microcombs assisted by an RF spectrum analyzer with THz bandwidth and MHz resolution
复制标题
借助具有太赫兹带宽和兆赫兹分辨率的射频频谱分析仪对微梳进行精确的动态表征
DOI：
10.1364/oe.415933
复制
发表时间：
2021
期刊：
影响因子：
3.8
通讯作者：
Zhang Xinliang
中科院分区：
文献类型：
--
作者：
Wang Ruolan;Chen Liao;Hu Hao;Zhao Yanjing;Zhang Chi;Zhang Wenfu;Zhang Xinliang
微梳的射频频谱可以用来评价其相位噪声特性和微梳齿间的相干性。由于微梳具有重复频率高、线宽窄、动态演化快等特点，对射频测量系统的带宽、分辨率和帧率都有严格的要求。本文提出了一种1.8 thz带宽、7.5 mhz频谱分辨率、100 hz帧率的微型梳子射频频谱测量方案，该方案采用基于交叉相位调制和Fabry Perot （FP）光谱仪的全光射频频谱分析仪，即FP辅助光强频谱分析仪（FP-assisted light intensity spectrum analyzer， LISA）。然而，放大微梳所引入的额外色散会使被测射频频谱的带宽性能下降。通过监测fp辅助LISA测量的色散曲线，补偿额外的色散后，测量出更精确的微梳射频光谱。然后，利用该系统测量了微梳在2s时间窗内的噪声边带和线形演变，其中射频梳在不同谐波频率下的动态变化。在调制不稳定（MI）状态和孤子状态下，首先记录到1.96 THz。因此，fp辅助LISA的带宽和分辨率的提高使射频频谱的测量更加精确，为研究微梳的物理机制铺平了可靠的道路。
The radio frequency (RF) spectrum of microcombs can be used to evaluate its phase noise features and coherence between microcomb teeth. Since microcombs possess characteristics such as high repetition rate, narrow linewidth and ultrafast dynamical evolution, there exists strict requirement on the bandwidth, resolution and frame rate of RF measurement system. In this work, a scheme with 1.8-THz bandwidth, 7.5-MHz spectral resolution, and 100-Hz frame rate is presented for RF spectrum measurement of microcombs by using an all-optical RF spectrum analyzer based on cross-phase modulation and Fabry Perot (FP) spectrometer, namely FP-assisted light intensity spectrum analyzer (FP-assisted LISA). However, extra dispersion introduced by amplifying the microcombs will deteriorate the bandwidth performance of measured RF spectrum. After compensating the extra dispersion through monitoring the dispersion curves measured by FP-assisted LISA, the more precise RF spectra of microcombs are measured. Then, the system is used to measure the noise sidebands and line shape evolution of microcombs within 2s temporal window, in which dynamic RF combs variation at different harmonic frequencies up.to 1.96 THz in modulation instability (MI) state and soliton state are recorded firstly. Therefore, the improved bandwidth and resolution of FP-assisted LISA enable more precise measurement of RF spectrum, paving a reliable way for researches on physical mechanism of microcombs.