Degenerate Four-Wave Mixing-Based Light Source for CARS Microspectroscopy

A novel light source for coherent anti-Stokes Raman scattering (CARS) microspectroscopy based on degenerate four-wave mixing (DFWM) is experimentally demonstrated in a photonic crystal fiber with two adjacent zero dispersion wavelengths. When the pump pulse wavelengths are changed from 780 to 800 nm and the average input powers P
_av
are increased from 300 to 500 mW, the central wavelengths λ
_as
and λ
_s
of the generated anti-Stokes and Stokes waves are tunable from 660 to 606 nm and 953 to 1177 nm, respectively. In addition, the corresponding frequency difference between the pump and Stokes beams is in the range of 2331-4002 cm
^-1
, which covers a wide range of vibrational Raman spectra of the biological and chemical samples. The feasibility of the proposed DFWM-based light source is demonstrated through measuring the CARS spectrum of the ethanol sample.