A 3.5-THz, x6-Harmonic, Single-Ended Schottky Diode Mixer for Frequency Stabilization of Quantum-Cascade Lasers

TL;DR

This paper introduces a room-temperature 3.5-THz Schottky diode mixer with harmonic operation, enabling efficient frequency stabilization of quantum-cascade lasers for terahertz applications.

Contribution

The paper presents a novel integrated, single-ended Schottky diode mixer operating at 3.5 THz with high harmonic conversion and room-temperature functionality, advancing terahertz source stabilization.

Findings

Achieved 59 dB conversion loss at 200 MHz IF

Demonstrated 40 dB SNR for phase locking quantum-cascade laser

Validated results with electromagnetic simulations

Abstract

Efficient and compact frequency converters are essential for frequency stabilization of terahertz sources. In this paper, we present a 3.5-THz, x6-harmonic, integrated Schottky diode mixer operating at room temperature. The designed frequency converter is based on a single-ended, planar Schottky diode with a sub-micron anode contact area defined on a suspended 2-$\mu$m ultra-thin GaAs substrate. The dc-grounded anode pad was combined with the radio frequency E-plane probe, which resulted in an electrically compact circuit. At 200 MHz intermediate frequency, a mixer conversion loss of about 59 dB is measured and resulting in a 40 dB signal-to-noise ratio for phase locking 3.5-THz quantum-cascade laser. Using a quasi-static diode model combined with electromagnetic simulations, good agreement with the measured results was obtained. Harmonic frequency converters without the need of cryogenic cooling will help in the realization of highly sensitive space and air-borne heterodyne receivers.