Ultra-high quality graphene perfect absorbers for high performance switching manipulation.

Abstract

Wavelength-selective light absorption and the related switching operations are highly desired in optical devices. Herein, we report the approach for ultra-high quality (Q) graphene perfect optical absorption, which possesses impressive performance in switching manipulation. A record-breaking Q-factor (up to 105) is observed, suggesting one or two orders of magnitude larger than that of the conventional graphene absorbers. The ultra-low external leakage loss rate of quasi-bound states in the continuum (BIC) resonator and the ultra-low intrinsic absorption loss rate in the resonant mode volume are the main contributions for the ultra-high Q perfect absorption. By introducing a Kerr nonlinear medium, spectral relative intensity can be changed from 0 to 100% when an ultra-low pump light with the intensity of only 5 kW cm-2 is used. After a rather slight tuning of the refractive index (Δn = 5×10-4) for the resonators, the absorption contrast ratio reaches 31 dB. The switching related spectral wavelength shift sensitivity is up to 915 nm/RIU and the figure of merit (FOM) is 50 833. These features confirm the ultra-high tunability and switching manipulation. It is believed that the ultra-high Q-factor absorption offered by all-dielectric configuration provides plentiful potential applications for graphene-based devices in the all-optical switch, modulator, notch filter, etc.