Advisory Committee Chair
Sergey B Mirov
Advisory Committee Members
Renato Camata
Vladimir Fedorov
Eugenia Kharlampieva
Patrick R Leclair
Document Type
Dissertation
Date of Award
2013
Degree Name by School
Doctor of Philosophy (PhD) College of Arts and Sciences
Abstract
Transition metal doped II-VI mid-IR lasers feature a broad (50% of the central wavelength) tuning range, high (tens of Watts) output power, close to theoretical limit quantum efficiency of lasing, and are capable to operate at room temperature over 1.8-6.1µm spectral range. However, these lasers work only under optical excitation. The goal of the research is to study physical processes and elements of technology essential for TM:II-VI lasing under direct electrical excitation. Gamma-irradiation of II-VI crystals was studied as a possible way to produce electrical conductivity in these media. It was found that color centers can be formed in gamma-irradiated II-VI crystals, however, they feature poor thermal stability at room temperature and don't enable conductivity. It was also demonstrated that the valence state of Cr2+ is stable under gamma-irradiation and, overall, Cr2+ doped ZnS and ZnSe laser crystals feature unprecedented (up to 2x108rad) resistance to ionizing irradiation. An effective energy transfer from carriers to transition metal (TM) impurities is needed for achieving mid-IR electroluminescence and lasing in TM:II-VI crystals. TM doped II-VI quantum dots (where quantum confinement can enable a more efficient than in the bulk medium energy transfer) were fabricated and studied. A strong quenching of visible photoluminescence of II-VI quantum dots was detected, indicating success with Cr doping. A mid-IR luminescence was also detected. Annealing with zinc is another well-known method to produce conductive ZnS and ZnSe crystals. Study of doped ZnSe crystals annealed in Zn vapor showed a strong bleaching of Cr2+ and Fe2+ ions, which cannot be explained by ionization of the TM to Cr3+, Cr4+, Cr+, Fe3+ valence states. ZnSe and Cr:ZnSe thin films and bulk samples were used for electroluminescence studies. Optically induced conductivity in Cr:ZnSe studies showed that the conductivity of illuminated part of the sample is two orders of magnitude bigger that of not illuminated part. Technology of fabrication of high optical quality conductive Al:ZnSe and Al:Cr:ZnSe crystals was developed. A strong mid-IR electroluminescence was detected in 0.5 mm thick single Cr:ZnSe crystal at potential difference and the current across the sample of 575 V and 200 mA, respectively.
Recommended Citation
Konak, Tetyana, "Optical And Electrical Characterization Of Transition Metal Doped Ii-Vi Mid-Ir Laser Materials" (2013). All ETDs from UAB. 2173.
https://digitalcommons.library.uab.edu/etd-collection/2173