  We demonstrate sensitive high-resolution stimulated Raman measurements of
hydrogen using a hollow-core photonic crystal fiber (HC-PCF). The Raman
transition is pumped by a narrow linewidth (<50 kHz) 1064 nm continuous-wave
(CW) fiber laser. The probe light is produced by a homebuilt CW optical
parametric oscillator (OPO), tunable from around 800 nm to 1300 nm (linewidth ~
5 MHz). These narrow linewidth lasers allow for an excellent spectral
resolution of approximately 10^-4 cm^(-1). The setup employs a differential
measurement technique for noise rejection in the probe beam, which also
eliminates background signals from the fiber. With the high sensitivity
obtained, Raman signals were observed with only a few mW of optical power in
both the pump and probe beams. This demonstration allows for high resolution
Raman identification of molecules and quantification of Raman signal strengths.
