A spectrometer comprises a substrate and a waveguide on the substrate, the waveguide including an elongate part and a tapered input for guiding electromagnetic radiation to the elongate part. The tapered input includes an input end for receiving the electromagnetic radiation and an output end coupled to the elongate part, the input end being wider than the output end. The spectrometer may further comprise a plurality of resonators coupled to the elongate part of the waveguide.