Toward all-fiber coherent anti-Stokes Raman scattering in the gas phase

The available fiber lasers, photonic-crystal fiber (PCF) frequency converters, and hollow-core PCFs are shown to offer realistic practical solutions for an all-fiber format of coherent anti-Stokes Raman scattering (CARS) in the gas phase. In view of the substantial enhancement of CARS in the guided modes of hollow-core PCFs, a broad class of compact ytterbium and erbium fiber laser sources become suitable for the CARS analysis of gas media. The quantum limit of the signal-to-noise ratio, S/N, in all-fiber CARS is shown to scale as λα-1a-2 with radiation wavelength λ, fiber loss α, and the fiber core radius,aleading, in the case of a hollow-PCF gas cell, to a dramatic improvement of S/N relative to CARS in the regime of tight focusing.