High rejection bandpass optical filters based on sub-wavelength metal patch arrays.

We report the study of a resonant bandpass filter made of a very thin subwavelength metal patch array coupled to a high index dielectric waveguide. The spectral properties of those filters can easily be tuned by playing on the lateral dimensions of the grating. They exhibit high and narrow transmission peaks together with very good rejection of light out of the pass-band and low angular dependance. An experimental demonstration using standard large scale silicon microelectronics processes is presented in the mid infrared spectral range. This concept of filters can easily be scaled throughout the optical spectrum, and can be integrated within focal plane arrays of various imaging technologies, down to visible wavelengths.