ORCID

https://orcid.org/0009-0004-4428-7602

Keywords

Mode-Locked Laser Diodes; Optical Frequency Combs; AlGaInAs/InP Multi-Quantum-Well Lasers; Hybrid and Passive Mode Locking; Multi-Tone Injection Locking; Proton Radiation Effects on Semiconductor Lasers

Abstract

This dissertation presents the design, fabrication, and characterization of three-section AlGaInAs/InP multi-quantum-well mode-locked laser diodes (MLLDs) operating near 1.55 µm for optical frequency-comb generation and control in space communication systems. The devices integrate gain, saturable-absorber, and modulation sections, enabling both passive and hybrid mode-locking with precise tunability through independent bias control. Under hybrid mode-locking, the MLLD achieved 1.32 ps pulses with a 5.87 nm optical bandwidth and a 35 dB improvement in RF side-mode suppression compared with passive operation, demonstrating enhanced timing stability and reduced phase noise. Fixed-point analysis established a framework for evaluating dispersion and frequency drift, while the concept of fixed-point equivalent impedance unified repetition-rate and carrier-envelope-offset frequency stability. Multi-tone optical injection locking demonstrated coherent comb recovery, reducing RF linewidth from 3.6 MHz to 200 kHz and revealing blue-side-favored asymmetric locking that defines a mode-locked linewidth-enhancement factor (αML).

For the first time, proton-radiation effects on mode-locked semiconductor lasers were experimentally demonstrated using 1.8 MeV protons at a fluence of 1×10¹² H⁺/cm², confirming stable mode-locking and enhanced comb coherence despite radiation-induced degradation. This work establishes a compact, electrically tunable, and radiation-hard platform for stable optical frequency-comb generation in deep-space communication systems.

Completion Date

2025

Semester

Fall

Committee Chair

Peter J. Delfyett

Degree

Doctor of Philosophy (Ph.D.)

College

College of Optics and Photonics

Department

CREOL

Format

PDF

Identifier

DP0029840

Document Type

Thesis

Campus Location

Orlando (Main) Campus

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