All-in-fibre Rayleigh-rejection filter for raman spectroscopy

An in-line Rayleigh-rejection filter for Raman spectroscopy is demonstrated. The device is based on a solid-core photonic crystal fibre infiltrated with a high-index liquid. At room temperature, the filter exhibits a full width at half maximum bandwidth of 143 nm and an insertion loss of 0.3 dB. A shift of 32 nm of the central wavelength is demonstrated by increasing the temperature from 22 to 70 C. FEM simulations of the spectra at different temperatures showed good agreement with experimental results. The device was successfully employed to perform Raman spectroscopy of a sample of cyclohexane and allowed for a fourfold attenuation of the Rayleigh scattered light.