THz optical beat-note detection with a fast Hot Electron Bolometer operating up to 31 GHz

TL;DR

This paper demonstrates a hot-electron bolometer based on niobium nitride films capable of detecting THz signals up to 31 GHz, with potential for high-frequency applications.

Contribution

It presents the first measurement of a superconducting niobium nitride HEB operating at THz frequencies up to 31 GHz, including its bandwidth, response, and sensitivity.

Findings

Impulse response cut-off around 2 GHz

Detection capability observed above 30 GHz in heterodyne experiments

Optical noise equivalent power NEP of 0.8 pW/√Hz at 1 MHz

Abstract

We study the performance of an hot-electron bolometer (HEB) operating at THz frequencies based on superconducting niobium nitride films. We report on the voltage response of the detector over a large optical bandwidth carried out with different THz sources. We show that the impulse response of the fully packaged HEB at 7.5 K has a 3 dB cut-off around 2 GHz. Remarkably, detection capability is still observed above 30 GHz in an heterodyne beating experiment using a THz quantum cascade laser frequency comb. Additionally, the HEB sensitivity has been evaluated and an optical noise equivalent power NEP of 0.8 pW/sqrt(Hz) has been measured at 1 MHz.