Time-delay fourier transform spectrometer for high-speed spectral measurement

Abstract

In the field of optics, there exist numerous chaotic processes like dissipative soliton dynamics, random laser generation, and laser scattering. It's very challenging to accurately capture the dynamics of these stochastic processes from the wavelength perspective with traditional spectrometers due to their slow signal integration speeds. Here, we propose a new approach, named time-delay Fourier transform spectrometer (TDFTS), to characterize the spectra of laser pulses with durations ranging from fs to ns with high speeds. Based on a fiber array with different lengths to impose frequency-dependent time delay, TDFTS efficiently maps the spectral distribution of light pulses to the temporal domain, and the spectrum can thus be detected with a photodiode and an oscilloscope. In experimental operation, the TDFTS provides spectral acquisition speeds up to 56 MHz frame rates and a bandwidth of tens of nanometers, while keeping comparable fidelity to traditional grating-scan spectrometers. While its spectral resolution of the current configuration is ∼0.1 nm, it can be further improved to 0.001 nm through optimizing the system. Based on its high speed, high spectral resolution, broad-bandwidth coverage, and compact configuration, TDFTS can be used to monitor nanosecond-scale spectral dynamics of non-repetitive optical processes.