Fano resonance membrane reflectors from mid-infrared to far-infrared

Compact broadband reflectors (BBRs) are of great importance for optoelectronic devices and photonic integrated circuits like lasers, photodetectors, solar cells, and sensors, etc. Traditionally, they can be realized by using metal films or stacked dielectric thin films. Metal films can offer larger reflection bandwidth but are limited by their intrinsic absorption losses. Stacked dielectric thin films can achieve very low losses. But they typically require many individual layers with stringent refractive index and thickness tolerances for each layer. It becomes more of an engineering challenge to realize extremely high reflection DBRs at longer wavelengths, including mid-IR, far-IR, and THz frequencies, due to the scaling of quarter-wavelength stack dielectrics.