Generation of terahertz-modulated optical signals using AlGaAs/GaAs laser diodes

Yanson, Dan Andreyevitch (2004) Generation of terahertz-modulated optical signals using AlGaAs/GaAs laser diodes. PhD thesis, University of Glasgow.

Abstract

The Thesis reports on the research activities carried out under the Semiconductor-Laser Terahertz-Frequency Converters Project at the Department of Electronics and Electrical Engineering, University of Glasgow.

The Thesis presents the work leading to the demonstration of reproducible harmonic modelocked operation from a novel design of monolithic semiconductor laser, comprising a compound cavity formed by a 1-D photonic-bandgap (PBG) mirror. Modelocking was achieved at a harmonic of the fundamental round-trip frequency with pulse repetition rates from 131 GHz up to a record-high frequency of 2.1 THz. The devices were fabricated from GaAs/AlGaAs material emitting at a wavelength of 860 nm and incorporated two gain sections with an etched PBG reflector between them, and a saturable absorber section.

Autocorrelation studies are reported, which allow the device behaviour for different modelocking frequencies, compound cavity ratios, and type and number of intra-cavity reflectors to be analyzed. The highly reflective PBG microstructures are shown to be essential for subharmonic-free modelocking operation of the high-frequency devices. It was also demonstrated that the multi-slot PBG reflector can be replaced with two separate slots with smaller reflectivity.

Some work was also done on the realisation of a dual-wavelength source using a broad-area laser diode in an external grating-loaded cavity. However, the source failed to deliver the spectrally-narrow lines required for optical heterodyning applications. Photomixer devices incorporating a terahertz antenna for optical-to microwave down-conversion were fabricated, however, no down-conversion experiments were attempted. Finally, novel device designs are proposed that exploit the remarkable spectral and modelocking properties of compound-cavity lasers.

The ultrafast laser diodes demonstrated in this Project can be developed for applications in terahertz imaging, medicine, ultrafast optical links and atmospheric sensing.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Microwave generation, terahertz, ultrafast lasers, harmonic mode-locking, mode-locked lasers, optical modulation, quantum-well lasers, semiconductor lasers, submillimeter wave generation, saturable absorber, ultrashort pulses
• Subjects: T Technology > T Technology (General); T Technology > TK Electrical engineering. Electronics Nuclear engineering
• Colleges/Schools: College of Science and Engineering > School of Engineering
• Supervisor's Name: Bryce, Prof. Catrina
• Date of Award: 2004
• Depositing User: Dr Dan Yanson
• Unique ID: glathesis:2004-2837
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 09 Sep 2011
• Last Modified: 10 Dec 2012 14:00
• URI: https://theses.gla.ac.uk/id/eprint/2837