Hot electron bolometer heterodyne receiver with a 4.7-THz quantum cascade laser as a local oscillator

TL;DR

This paper presents a heterodyne receiver for astrophysical observations at 4.7448 THz, utilizing a quantum cascade laser as a local oscillator and a superconducting bolometer mixer, achieving near-quantum-limited noise performance.

Contribution

It introduces a heterodyne receiver operating at 4.7448 THz with a quantum cascade laser LO and superconducting bolometer, demonstrating effective performance for astrophysical applications.

Findings

Recorded a receiver noise temperature of 815 K, about 7 times the quantum limit.

Achieved an Allan variance time of 15 seconds at 18 MHz bandwidth.

Confirmed heterodyne performance with methanol line spectrum measurement.

Abstract

We report on a heterodyne receiver designed to observe the astrophysically important neutral atomic oxygen [OI] line at 4.7448 THz. The local oscillator is a third-order distributed feedback Quantum Cascade Laser operating in continuous wave mode at 4.741 THz. A quasi-optical, superconducting NbN hot electron bolometer is used as the mixer. We recorded a double sideband receiver noise temperature (T^DSB_rec) of 815 K, which is ~7 times the quantum noise limit (h{\nu}/2k_B) and an Allan variance time of 15 s at an effective noise fluctuation bandwidth of 18 MHz. Heterodyne performance was confirmed by measuring a methanol line spectrum.