▎ 摘　　要

In this article, a widely tunable graphene-liquid crystal photodetector is proposed and numerically investigated. The photodetector is composed of a single graphene layer on top of a silicon grating. Tunability is achieved by employing a liquid crystal layer which acts as a Fabry-Perot filter, yielding frequency selectivity. Detection mechanism is internal photoemission rising from Si/graphene Schottky junction. In the structure, Si grating determines the operation band, which can be tuned from less than 1.5 mu m to more than 1.7 mu m. For any specific Si grating, liquid crystal voltage controls the detection wavelength. It is shown that this tuning range can be as wide as 50 nm. Graphene fermi energy on the other hand, controls the absorption efficiency and detection linewidth. This independent separation of roles is a main advantage of the proposed structure, which makes the design process straightforward. Based on these functionalities, a tunable photodetector is designed at which the detection wavelength can be tuned from less than 1530 nm to more than 1570 nm covering the entire C communications band. For this tuning to take place, liquid crystal voltage is varied between 1.1 V and 4.2 V (RMS). Detection linewidth is as low as 2 nm making the photodetector ideal for optical communications, and the responsivity and quantum efficiency are 0.25 A/W and 20% respectively. Dependency of the photodetector characteristics on graphene fermi energy, liquid crystal voltage and Si grating parameters are fully discussed in the article.