Tunable ultra-high quality factor graphene absorber based on semicylindrical silica array and distributed Bragg reflector structure

Abstract

We propose a tunable narrowband absorber by utilizing a graphene monolayer placed between a dielectric semicylindrical array and a multilayer silica/silicon distributed Bragg reflector (DBR) structure. The multi-band perfect absorption can be achieved due to the excitation of multiple resonant modes in the absorber, including the guided mode resonance of the dielectric silica array and BR-based guided mode resonance in the DBR structure. The ultra-high quality factor (Q) is mainly attributed to the low external leakage loss of the resonator and the low intrinsic loss of the graphene monolayer. Moreover, the Q-factor of absorption peaks can be tuned by electrically controlling the Fermi energy of graphene. The sensitivity of a spectral wavelength shift for the refractive index change of the resonator is up to 730 nm/RIU, and the figure of merit is 1043. The proposed graphene-based metamaterial offers potential applications for photodetectors, optical modulators, and sensors in the near infrared frequency regime.

Towards Mirror-Less Graphene-Based Perfect Absorbers

“…In this section, we briefly introduce a few optoelectronic applications of GPA structures using external mirrors. Figure 12a indicates the schematic depiction of the possible applications, such as high-efficiency modulators [14,15,36,[93][94][95], photodetectors [12,13,16], tunable polarizers [96][97][98], switches [99][100][101][102][103], and sensors [104][105][106].…”

“…In particular, the GPAs based on dielectric resonant structures have the potential for sensing or switching applications because they can minimize the undesired ohmic loss in metals, and even ultra-narrow (Q > 10,000) graphene perfect absorption can be achieved [28,33,102,103]. For example, in 2020, Tang et al [103] numerically demonstrated a GPA structure with a record-breaking Q-factor (up to 10 5 ), which is one or two orders of magnitude larger than that of the conventional GPAs.…”