Binary Dispersion Formulations of Mid-Infrared Lossless Dielectric Contrast Gratings

The Zero Contrast Grating (ZCG) is a promising candidate for moded and dispersive mid-infrared (MIR) photonics for its broadband transmittance and reflectance greater than 99.9%. The optimal grating design including refractive index and grating parameters is investigated, and is compared to its analogue the High Contrast Grating (HCG). This study provides insights on how ZCG can manipulate the electromagnetic waves within the low refractive index dielectric bars. The foundations following its near-perfect transmittance and reflectance due to phase matching are described from the perspective of diffraction orders and dispersion relations. Both 0th and 1st order diffraction contribute to construction or destruction of interferences that occur at the output plane, which is a significant finding in differentiating ZCG and HCG. Applications for the ZCG can be found in selective bandpass windows, beam splitters, broadband reflectors, and narrowband thermal emitters.