Fiber delivered two-color picosecond source for coherent Raman scattering imaging

Abstract

We demonstrate two-color, fiber delivered picosecond source for coherent Raman scattering (CRS) imaging. The wavelength tunable picosecond pump is generated through nonlinear spectral compression of a prechirped femtosecond pulse from a mode-locked femtosecond Titanium:Sapphire (Ti:S) laser. The 1064 nm Stokes pulse is generated by an allfiber time-lens source that is synchronized to the Ti:S laser. The pump and Stokes are combined in an optical fiber coupler, which serves not only as the delivery fiber for the two-color picosecond source but also as the nonlinear medium for spectral compression of the femtosecond Ti:S pulse. The temporal overlap of the two pulses is electronically adjusted without any mechanical optical delay line, greatly facilitating the temporal alignment of the excitation beams for CRS. CARS imaging of mouse skin at CH2 stretching frequency (2845 cm-1) are performed to demonstrate the practicality of this source. The combination of the all-fiber time-lens source and the nonlinear spectral compression of a femtosecond source in an optical fiber has the potential to make CRS imaging practical to any researcher with a wavelength tunable femtosecond source.