Tunable optical filters based on silicon nitride mem-branes with subwavelength gratings

We report the use of 500 nm thick silicon nitride membrane as a high reflective broad-band filter in the orange-red spectral range. The membrane is patterned into a high contrast grating with 560 nm period to act as a high-reflectivity mirror. Using electrostatic tuning, we have achieved a tunable filter based on a Fabry-Pérot cavity architecture. By applying 9 V to the MEMs device, we observe a 13 nm wavelength shift of a peak centred at 630 nm.