Dynamically tunable reflecting near-infrared bandpass filter based on a hybrid graphene–nanometallic structure

Abstract

A dynamically tunable reflecting near-infrared bandpass filter based on a hybrid graphene–nanometallic structure is demonstrated by numerical simulation. The proposed filter is constructed by unit cells with a graphene monolayer embedded into the nanometallic grating structure. The gradual transition of the graphene monolayer from a very thin metal to dielectric plays the key role in tuning the reflection spectrum of the structure. Spectral analysis clearly shows a passband blueshift with increasing graphene Fermi energy. The filter parameters are investigated by varying graphene Fermi energy through external voltage gates. The modulation depth, center frequency, bandwidth, and quality factor of the filter could be tuned. We achieved stable modulation depth as high as 0.735, and a quality factor as high as 3.4. The center frequency can be tuned in a broad range from 210 to 230 THz and with bandwidth tuning from 60 to 95 THz. The effect of the nanogap size and environment refractive index is also numerically investigated. These results are very promising for future use and integration of the proposed filters as a key element of optical communication systems and infrared sensing.