Mixing properties of room temperature patch-antenna receivers in a mid-infrared (9um) heterodyne system

TL;DR

This paper presents a room-temperature mid-infrared heterodyne system using quantum cascade lasers and quantum well infrared photodetectors, achieving high sensitivity and demonstrating microwave signal mixing capabilities.

Contribution

It introduces a novel room-temperature heterodyne system with optimized unipolar optoelectronic devices and demonstrates their mixing properties for the first time.

Findings

Record noise equivalent power of 30 pW at 9 um

Linear response of detectors up to high optical power

Microwave injection shifts heterodyne beat frequency

Abstract

A room-temperature mid-infrared (9 um) heterodyne system based on high-performance unipolar optoelectronic devices is presented. The local oscillator (LO) is a quantum cascade laser, while the receiver is an antenna coupled quantum well infrared photodetector optimized to operate in a microcavity configuration. Measurements of the saturation intensity show that these receivers have a linear response up to very high optical power, an essential feature for heterodyne detection. By an accurate passive stabilization of the local oscillator and minimizing the optical feed-back the system reaches, at room temperature, a record value of noise equivalent power of 30 pW at 9um. Finally, it is demonstrated that the injection of microwave signal into our receivers shifts the heterodyne beating over the bandwidth of the devices. This mixing property is a unique valuable function of these devices for signal treatment.