All ETDs from UAB

Advisory Committee Chair

Sergey B Mirov

Advisory Committee Members

Vladimir V Fedorov

Renato P Camata

Kenneth L Schepler

Patrick Kung

Document Type

Dissertation

Date of Award

2016

Degree Name by School

Doctor of Philosophy (PhD) College of Arts and Sciences

Abstract

The middle infrared (mid-IR) spectral range of 2-15 μm possesses characteristics that make it interesting for a number of applications such as spectroscopy, free-space communication, remote detection of organic compounds, materials processing and medical diagnosis. Many organic molecules exhibit strong absorption in this spectral range, rendering their detection and identification possible. There also exist bands of atmospheric transmission which can allow free-space propagation of mid-IR light over considerable distances within the atmosphere. Because of these, there is an increasing demand for broadly tunable laser sources operating in this spectral range. II-VI wide bandgap semiconductor hosts doped with transition metal (TM) impurities such as Fe2+, Co2+, and Cr2+ exhibit favorable characteristics for mid-IR laser applications. Cr2+:II-VI materials function as saturable absorbers for the passive Q-switching of lasers operating in the 1.5-2 µm range and can produce broadly tunable laser oscillation over the 2-3 µm spectral range [1]. Minimal temperature quenching of fluorescence lifetime provides long room temperature (RT) lifetime, which has allowed the production of laser systems in continuous wave (CW), free running (FR), gain-switched, and mode locked regimes of operation even at RT [1]. Laser systems based on Fe2+:II-VI gain media can produce broadly tunable laser oscillation over the 3-6 μm spectral range in all regimes of operation and despite strong temperature quenching of Fe2+ lifetime can operate in pulsed regimes even at RT [1]. However, there are still issues to be addressed that can improve the utility of these TM2+:II-VI mid-IR lasers. The work outlined in this dissertation is divided into three major goals: 1) To fill the spectral tunability gap between Cr2+:II-VI and Fe2+:II-VI through the study of Co2+:II-VI materials as potential gain media, 2) To study the energy transfer processes from Co2+ to Fe2+ ions in co-doped II-VI crystals with the goal of extending the range of available pump sources for Fe2+:II-VI lasers, and 3) The study of Cr2+:II-VI under excitation by visible radiation into the charge transfer band to extend available excitation methods of the gain media as well as to better understand interaction of active ions with charge carriers to advance progress toward obtaining laser oscillation under electrical excitation.

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