Novel dual wavelength and multi-wavelength DFB/DBR lasers for MMW/THz generation

Fan, Yizhe (2025) Novel dual wavelength and multi-wavelength DFB/DBR lasers for MMW/THz generation. PhD thesis, University of Glasgow.

Abstract

Millimeter-wave (MMW) and terahertz (THz) and sources have gained significant attention due to their wide-ranging applications in high-speed wireless communications, high resolution imaging, and advanced sensing technologies. In this thesis, I propose and experimentally demonstrate a series of innovative DFB and DBR semiconductor lasers based on multiple quantum well (MQW) structures operating at 1550 nm for MMW/THz generation.

Three novel findings are reported in the work. Firstly, I demonstrate a dual-wavelength DFB laser array employing a four-phase-shifted sampled Bragg grating (4PS-SBG), which enhances coupling efficiency by approximately 2.83 times compared to conventional designs. The device exhibits stable dual-mode operation with frequency spacings ranging from 320 GHz to 1 THz, achieving an output power of 23.6 mW when integrated with semiconductor optical amplifiers (SOAs). Photomixing in a photoconductive antenna (PCA) result in THz signal generation with a measured power of 12.8 μW. Secondly, I introduce a dual-wavelength DFB laser using a four-phase-shifted sampled Moiré grating (4PS-SMG) with distinct sampling periods on each ridge waveguide side, equivalently introducing two π-phase shifts within the cavity. The device exhibits high stability across a broad injection current range, maintaining a power difference below 2 dB between primary modes. This laser generates a high-purity RF signal at 39.4 GHz with a linewidth of approximately 5.0 MHz. Lastly, I propose mode-locked DBR and DFB lasers employing multiple phase-shift gratings (MPSGs) for high-frequency THz generation. The mode-locked DBR laser achieves stable operation at 150 GHz, 400 GHz, 800 GHz, and 1.2 THz, validated through second harmonic generation measurements. A 200 GHz mode-locked DFB laser, amplified via an erbium-doped fiber amplifier (EDFA) and injected into a PCA, delivers a THz output power of 19.6 μW. Design, fabrication and characterization of these semiconductor lasers are introduced in detail in this thesis.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: T Technology > T Technology (General)
• Colleges/Schools: College of Science and Engineering > School of Engineering
• Supervisor's Name: Hou, Professor Lianping
• Date of Award: 2025
• Depositing User: Theses Team
• Unique ID: glathesis:2025-85378
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 12 Aug 2025 09:09
• Last Modified: 12 Aug 2025 09:11
• Thesis DOI: 10.5525/gla.thesis.85378
• URI: https://theses.gla.ac.uk/id/eprint/85378

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