Tunable mid-infrared filter based on the superposition of subwavelength gratings

In 2010, the existence of a zero of transmission at high wavelengths different from the Rayleigh Wood anomaly was highlighted when two identical subwavelength gratings are brought close enough. We recently revealed the origin of this transmission extinction and the mechanism is recalled here. Furthermore, we present an experimental setup to measure the amplitude of this extinction and study its spectral behavior when changing geometrical parameters which represent a real technological challenge. This way a new generation of tunable filters in the mid-infrared with perfect spectral shape control and high rejection efficiency can be designed with practical use to gas sensing applications.