Universität zu Köln

Mertens, Marc Ruben ORCID: 0000-0002-4903-9542 (2023). On-Chip Frequency Control in THz Quantum Cascade Lasers. PhD thesis, Universität zu Köln.

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Abstract

Several attempts have been made to build terahertz Quantum Cascade Lasers with the capability for frequency tuning exceeding the range accessible by variation of temperature and current, but so far, no technique has been widely adopted. This work investigates a novel approach based on mechanical manipulation of the resonator length. This on-chip approach requires no external optics and could be implemented in a compact setup with micromechanical actuators. A combination of a classical metal-metal QCL with attached waveguide structures based on a benzocyclobutene substrate allows the construction of a movable reflector. In the course of the thesis, lasers are initially designed and simulated using a computer model. After fabrication, the real-world performance is evaluated and compared to simulation results. It is shown that this technique is generally feasible with the best performing device achieving a full free spectral range of continuous tuning (25 GHz) plus another 5 GHz accessible by current tuning. Possible points of improvement are identified, and a second generation of lasers is designed and fabricated. Unfortunately, the second-generation devices suffer from unexpected laser modes that prevent tuning. Nevertheless, in the course of this thesis, the possibility of translating mechanical resonator tuning - usually seen in much larger lasers - to the chip level of semiconductor devices is successfully demonstrated.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code Mertens, Marc Ruben mertens@ph1.uni-koeln.de https://orcid.org/0000-0002-4903-9542 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-700449
Date:	2023
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Physics > Institute of Physics I
Subjects:	Physics
Uncontrolled Keywords:	Keywords Language Terahertz English Quantum Cascade Laser English Submillimeter Astronomy English
Date of oral exam:	23 February 2023
Referee:	Name Academic Title Stutzki, Jürgen Prof. Dr. Grüninger, Markus Prof. Dr.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/70044