Design and characterisation of terahertz Schottky diode harmonic mixers
Licentiate thesis, 2021

Efficient, compact, and reliable terahertz frequency converters preferably operating at ambient temperature are crucial for stabilising far-infrared optical sources. This thesis focuses on the design and characterisation of terahertz Schottky diode harmonic mixers for frequency stabilisation of quantum-cascade lasers.
First, the influence of idler terminations on harmonic mixer performance and diode embedding impedance at radio and local oscillator frequencies was
studied. Based on this, a 3.5-THz, ×6-harmonic mixer was designed. A planar, single-ended Schottky diode with a sub-µm contact area was realised on a
2-µm suspended GaAs substrate. The integrated mixer circuit was assembled in an E-plane split-block with the aid of beam leads. The Schottky diode anode pad was designed to act as a radio frequency E-plane probe and extended as a beamlead to provide dc ground, resulting in an electrically compact circuit. The design was validated by conducting a sensitivity analysis of critical parameters that are susceptible to fabrication tolerances. Two integrated circuits with Schottky contact areas of 0.11 and 0.14 µm2 were assembled on mixer modules and dc/RF characterisation was carried out. Both harmonic
mixers exhibited a conversion loss of about 60 dB at an intermediate frequency of 200 MHz. When evaluated in a phase-locked loop, it resulted in a
signal-to-noise ratio of 40 dB, which was more than sufficient to phase lock the quantum-cascade lasers.
This work presents uncooled, efficient THz harmonic mixers for stabilising THz optical sources. It opens up many opportunities for building a THz heterodyne spectrometer with a high spectral resolution to detect gas species such as hydroxyl radical and atomic oxygen in the frequency range of 3-5 THz.

Frequency stabilisation

Heterodyne receivers

Terahertz electronics

Phase locking

Schottky diodes

Harmonic mixers

Frequency converters

Kollektorn A423
Opponent: Dr. Jeffrey Hesler, CTO, Virginia Diodes Inc. (VDI), USA (Passcode for zoom: 587413)

Author

Divya Jayasankar

RISE Research Institutes of Sweden

Chalmers, Microtechnology and Nanoscience (MC2), Terahertz and Millimetre Wave Laboratory

GigaHertz Centre

Effect of idler terminations on the conversion loss for THz Schottky diode harmonic mixers

International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz,; Vol. 2019-September(2019)

Paper in proceeding

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

IEEE Transactions on Terahertz Science and Technology,; Vol. 11(2021)p. 684-694

Journal article

Development of Supra-THz Schottky Diode Harmonic Mixers

International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz,; (2021)

Paper in proceeding

THz Schottky diode mixers for high resolution FIR spectroscopy

Swedish National Space Board, 2018-01-01 -- 2019-12-31.

Swedish National Space Board (170/17), 2018-01-01 -- 2019-12-31.

Areas of Advance

Information and Communication Technology

Infrastructure

Kollberg Laboratory

Nanofabrication Laboratory

Subject Categories

Electrical Engineering, Electronic Engineering, Information Engineering

Publisher

Chalmers University of Technology

Kollektorn A423

Online

Opponent: Dr. Jeffrey Hesler, CTO, Virginia Diodes Inc. (VDI), USA (Passcode for zoom: 587413)

More information

Latest update

12/11/2021