Femtosecond Pulse Temporal Overlap Estimation and Adjustment in SSFS-Based CARS System

We present and verify a residual-pump-based temporal overlap estimation method in soliton self-frequency shift-based coherent anti-Stokes Raman scattering system. The residual pump light, output by a highly nonlinear photonic crystal fiber, acts as a crucial link between the pump and Stokes pulses during the temporal overlap estimation. The wavelength-dependent optical delay is estimated to be 0.141 ps/nm when the Stokes wavelength is 900 nm ~1050 nm according to the temporal overlap estimation method. The actual measurement result is 0.138 ps/nm based on the nonresonant signal from a microscope slide, which is very close to the estimated result. In addition, the Raman resonant signals of liquid cyclohexane at 2853 cm
^-1
, 2923 cm
^-1
and 2938 cm
^-1
have also been successfully detected at the predicted optical delays 427.27 ps and 428.17 ps.