Fourier-transform Spectroscopic Technique for Multi-spectral Nonlinear Microscopy Using a 5-fs Broadband Light Source

Abstract

We propose nonlinear Fourier-transform spectroscopy using a broadband pulse, which can discriminate the origin in Four-wave mixing (FWM) process. By taking account of the response function of a sample in the third-order interferometric autocorrelation (IAC) signal, we theoretically analyze FWM-FTS using a broadband pulse. The discrimination of the origin is achieved by taking advantage of the FWM power spectrum obtained by the Fourier-transform of the IAC signal. In the FWM power spectrum, there are frequency components, which indicate the effects of the two-photon electronic resonance and the Raman resonance. By focusing into the frequency components, the origin in FWM process is identified. Based on the theoretical analysis, we experimentally demonstrate nonlinear FTS employing the tightly focused pulse with a pulse duration of 5 fs and measure the Raman and two-photon electronic spectra in FWM process.