Optoelectronic application of graphene nanoribbon for mid-infrared bandpass filtering

In this study, an ultra-compact optoelectronic bandpass filter is proposed. A single piece of graphene nanoribbon (GNR) is placed between two input-output GNRs to form a Fabry-Perot-like cavity. The GNR, as a mid-infrared surface waveguide, enhances the compatibility with complementary metal oxide-semiconductor processing technologies. The transmission characteristics of the bandpass filter are tuned by the modulation of surface charge carrier density simply through changing the bias voltage applied on the GNR cavity, and thus a tunable filter at room temperature is achieved. It is found that increasing the gate voltage and the silica substrate thickness or middle GNR width alters the max peak of transmission spectra of the filter toward smaller wavelengths. In contrast, increasing the middle GNR length redshifts max peak of the filter toward longer wavelengths. The finite different time domain (FDTD) inhouse code has been employed to verify the designs.