Raman spectroscopy system and method using a subwavelength resonant grating filter

A method for measuring by Raman spectroscopy one or more selected constituents of a chemical composition, comprising:

• irradiating with a substantially monochromatic radiation source a chemical composition comprising the one or more chemical constituents;
• directing radiation scattered and/or emitted from the chemical composition through a sub-wavelength resonant grating filter, the sub-wavelength resonant grating filter comprising a waveguide layer and an array of diffraction elements having a characteristic period and a characteristic height, and
• detecting radiation transmitted through the filter.

An integrated photodiode-filter comprising:

• a substrate, at least one photodiode comprising an active surface formed in and on the substrate;
• and
• an integrated sub-wavelength resonant grating filter, wherein the sub-wavelength resonant grating filter comprises a waveguide layer formed on the active surface and a patterned layer comprising an array of diffraction elements formed on the waveguide layer.