Recent developments in wavelength to time conversion for low intensity Raman spectroscopy

We have been able to observe wavelength to time conversion in a 121 core fibre at the single-photon level. Due to dispersion, photons of different wavelengths experience different delays and arrive at the single-photon sensitive detector at different pre-defined arrival times. The arrival times of the photons are measured via Time-Correlated Single-Photon Counting (TCSPC) techniques.

Such an instrument can be very useful for applications where only a low photon intensity is available and a large accessible wavelength range is desired. An example for an application with these requirements is Raman Spectroscopy of waterborne pathogens. Here we present our recent developments towards an optical instrument for the rapid detection of Cryptosporidium in drinking water using TCSPC techniques. We are able to detect single-photons within a wavelength range in excess of 100nm with nanometre resolution.