Pump-probe multi-species CARS in a hollow-core PCF with a 20 ppm detection limit under ambient conditions

Opt Lett. 2019 May 15;44(10):2486-2489. doi: 10.1364/OL.44.002486.

Abstract

We report coherent anti-Stokes Raman spectroscopy (CARS) in a gas-filled single-ring hollow-core photonic crystal fiber (SR-PCF) using a pump-probe configuration. The long collinear path length offered by an SR-PCF strongly enhances the efficiency of the Raman interactions. Pressure tuning the zero-dispersion wavelength (ZDW) of the SR-PCF allows the Raman coherence prepared by seeded pumping at 515 nm to be used in the visible for phase-matched generation of an anti-Stokes signal from a probe in the ultraviolet. The unique dispersion profile in the vicinity of the ZDW enables simultaneous phase matching of all known Raman transitions. We demonstrate that simultaneous multi-species CARS with a detection limit of 20 ppm is possible with only 20 kW of peak pump power delivered by a single laser source.