Free-space Terahertz Spectrum Analysis with an Optoelectronic Hybrid System

• Published in: IEEE transactions on terahertz science and technology Vol. 13; no. 6; pp. 1 - 11
• Main Authors: Theis, Alexander, Kocybik, Michael, Freymann, Georg von, Friederich, Fabian
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 01.11.2023; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Bandwidth; Continuous radiation; CW photoconductive antennas; EO-detection; GaAs photomixers; Gallium arsenide; hybrid system; Hybrid systems; Laser feedback; Laser stability; Laser theory; Measurement by laser beam; Millimeter waves; Optical attenuators; optoelectronic; Optoelectronics; phase-locking; Semiconductor lasers; Spectrum analysis; Synchronism; Terahertz frequencies; terahertz radiation
• ISSN: 2156-342X; 2156-3446
• DOI: 10.1109/TTHZ.2023.3301450

We present an optoelectronic hybrid system to perform high-resolution spectrum analysis in the terahertz regime. The concept is based on phase-locking of the difference frequencies of at least three continuous-wave (CW) distributed-feedback diode lasers by mixing the laser light with the radiation from a high-power electronic narrow-band source. Unlike for state-of-the-art spectrum analysis, no additional frequency extenders are required, keeping the system less complex and more cost-effective. Following our concept, we can generate laser difference frequencies from 0 to more than 1 THz with several Hz precision, which can be easily expanded to even higher frequencies, e.g., by cascading more lasers within our synchronization scheme. We demonstrate the systems frequency resolution and stability by measuring the first five harmonics of an electronic W-band source, and the first three of an active multiplier chain millimeter-wave source, using a CW GaAs photoconductive antenna as a receiver.