Parametric spectro-temporal analyzer based on asynchronous optical sampling

Abstract

High frame rate of a spectrometer is very important for studying rapidly changing transient phenomena. Dispersive time stretch can map spectral information in the time domain for measurement and thus have a high frame rate compared to conventional spectrometers. To measure the emission spectrum and obtain higher sensitivity, a converging time lens was introduced. The spectro-temporal analyzer realizes the Fourier transform of the incident light field at the focal dispersion position of the time lens, maps the spectral information of the signal to be measured to the time domain, and also realizes the real-time acquisition of the signal spectrum. To further improve the resolution for higher precision detection, a larger pump pulse bandwidth was used to obtain a larger time lens window. Meanwhile, the optical frequency comb with slightly different repetition frequencies is used to sample the focused signal based on four-wave mixing to reduce the sampling bandwidth requirement. On this basis, a parametric time-domain spectrometer based on asynchronous optical sampling was proposed, and the third-order dispersion of the system is compensated. After these operations, the spectral resolution was increased from 20 to 1 pm with a detection bandwidth of 24 nm and a frame rate of 1 kHz. Finally, the random lasing spectral dynamics of EDFA and the thermal drift of the resonance peak of a microring resonator were detected.