A Raman spectroscopy system is disclosed which includes a sub-wavelength resonant grating filter and a photodiode with integrated sub-wavelength resonant grating filter are disclosed. The resonant grating filter comprises an array of diffraction elements having a periodic spacing that is less than the wavelength of radiation to be filtered and which are formed over a waveguide layer. The filter, which can reject a specific wavelength of radiation, can be placed between a Raman sample and a Raman detector in order to filter radiation that is elastically scattered from the sample while transmitting other wavelengths. The wavelength rejected by the filter can be selected by tilting the filter with respect to the radiation incident upon the filter.