Fast thermal relaxation in cavity-coupled graphene bolometers with a Johnson noise read-out

TL;DR

This paper presents a graphene-based hot-electron bolometer with a Johnson noise readout that achieves ultrafast thermal relaxation, high sensitivity, and operation at room temperature, promising advancements in high-bandwidth photodetection.

Contribution

It introduces a novel graphene bolometer with Johnson noise readout and photonic nanocavity coupling, demonstrating ultrafast thermal relaxation and high sensitivity at room temperature.

Findings

Thermal relaxation time {} < 34 ps

Noise equivalent power NEP < 5 pW/Hz^{1/2}

Enhanced light absorption by a factor of ~3

Abstract

Since the invention of the bolometer, its main design principles relied on efficient light absorption into a low-heat-capacity material and its exceptional thermal isolation from the environment. While the reduced thermal coupling to its surroundings allows for an enhanced thermal response, it in turn strongly reduces the thermal time constant and dramatically lowers the detector's bandwidth. With its unique combination of a record small electronic heat capacity and a weak electron-phonon coupling, graphene has emerged as an extreme bolometric medium that allows for both, high sensitivity and high bandwidths. Here, we introduce a hot-electron bolometer based on a novel Johnson noise readout of the electron gas in graphene, which is critically coupled to incident radiation through a photonic nanocavity. This proof-of-concept operates in the telecom spectrum, achieves an enhanced bolometric response at charge neutrality with a noise equivalent power NEP < 5pW/ Sqrt(Hz), a thermal relaxation time of {\tau} < 34ps, an improved light absorption by a factor ~3, and an operation temperature up to T=300K.