Composite wavelength tuning for precision Raman resonance in soliton self-frequency shift-based coherent anti-Stokes Raman scattering

Abstract

Composite wavelength tuning is proposed and demonstrated in a soliton self-frequency shift (SSFS)-based coherent anti-Stokes Raman scattering (CARS) system in order to realize a fast and precision measurement of the Raman spectrum. The Stokes wavelength can be continuously tuned over 300 nm, corresponding to a molecular vibrational range of approximately 3600 cm−1. The CARS three-dimensional spectrogram of cyclohexane around 2900 cm−1 has been measured and the corresponding Raman spectrum was recovered with 25 cm−1 spectral resolution. The composite wavelength tuning method strikes a balance between wavelength scanning speed and tuning precision during the measurement of the Raman spectrum in the SSFS-based CARS system, which can effectively solve the larger wavelength tuning step problem caused by the min-repeatable optical power adjustment.