Coherent anti-Stokes Raman scattering microspectroscopy based on a compact Er:fiber laser

Abstract

A two branch Er:fiber laser was developed for coherent anti-Stokes Raman scattering (CARS) microspectroscopy. The compact and highly stable light source allows for fast single-frequency CARS microspectroscopy with a wide tuning range from 1150 cm -1 up to 3800 cm -1 . Single-pass frequency conversion enables easy tunability. The spectral selectivity of the system is shown using polymer beads. Imaging of biological samples is demonstrated on C. elegans and yeast cells. Modification of the light source allows for broadband background-free CARS microspectroscopy. Impulsive excitation of molecular resonances is achieved using an 11 fs pulse at 1210 nm. Broadband excitation gives access to molecular resonances from 0 cm -1 up to 4000 cm -1 . Time-delayed narrowband probing at 775 nm enables sensitive and high-speed spectral detection of the CARS signal, free of nonresonant background with a resolution of 10 cm -1 .