Tunable Antenna-Coupled Intersubband Terahertz (TACIT) Mixer: Frequency-agile THz Heterodyne Detector Based on Intersubband Transitions in Single GaAs/AlGaAs Quantum Wells

The Tunable Antenna-Coupled Intersubband Terahertz (TACIT) mixer is a novel THz heterodyne detector based on intersubband transitions in single GaAs/AlGaAs quantum-well heterostructures. With the ability to operate at higher temperatures (up to 60 K) and wide in-situ frequency tunability (2-5 THz), TACIT mixers have potential for a low-noise (with $\mathrm{T}_{\mathrm{SSB}} \sim 2,000 \mathrm{~K}$) operation with a low (~1μW) required local-oscillator power. These properties offer both flexibility in detection frequency and multi-pixel array capability, making TACIT mixers an attractive THz heterodyne mixer technology for high-resolution spectroscopy in space applications. Here, we report on the recent development of 2.52 THz TACIT mixers fabricated from single, modulation-doped, 40-nm wide, rectangular GaAs/AlGaAs quantum wells for 2.52 THz operation. Direct detection results at 20 K show that the detection frequency of a single TACIT device is widely tunable from 2.52 THz to 4.25 THz. We also present the heterodyne detection results at 2.52 THz at 10 K.