Planar photonic crystal microspectrometers in silicon-nitride for the visible range.

We demonstrate the feasibility of forming a compact integrated photonic spectrometer for operation in the visible wavelength range using the dispersive properties of a planar photonic crystal structure fabricated in silicon nitride. High wavelength resolution and compact device sizes in these spectrometers are enabled by combining superprism effect, negative diffraction effect, and negative refraction effect in a 45 degree rotated square lattice photonic crystal. Our experimental demonstration shows 1.2 nm wavelength resolution in a 70 microm by 130 microm photonic crystal structure with better performance than alternative structures for on-chip spectroscopy, confirming the unique capability of the proposed approach to realize compact integrated spectrometers.