Angle and polarization tolerant midinfrared dielectric filter designed by genetic algorithm optimization

We report a dielectric frequency selective surface filter with an angularly tolerant, polarization independent stop band designed at a midinfrared wavelength of 3.0 μm. The structure, consisting of a doubly-periodic amorphous silicon grating supported by a polyimide membrane, was optimized using a genetic algorithm to have a transmission stop band with a 3.33% 10 dB bandwidth for incidence angles as large as 10° from normal. The measured properties of the fabricated filter were within 1% of theoretical predictions. This strategy provides a practical and efficient approach to creating advanced dielectric filters for highly customized infrared optical device and coating applications.