All ETDs from UAB

Advisory Committee Chair

Sergey B Mirov

Advisory Committee Members

Vladimir V Fedorov

Mary E Zvanut

Shane A Catledge

Muhammad Maqbool

Patrick Kung

Document Type

Dissertation

Date of Award

2021

Degree Name by School

Doctor of Philosophy (PhD) College of Arts and Sciences

Abstract

Diamond has been gaining a lot of interest in the field of photonics such as quantum optics, nano-photonics, quantum computation, magnetometry, sensing, laser development, and color center physics as it provides a remarkable platform to combine its non-linear optical properties in conjunction with the unique optical and spin properties of its color centers. Besides that, energetic pulsed lasers operating in the visible to near IR spectral range are mostly obtained from non-linear frequency conversion which is less efficient, expensive, and requires nonlinear crystal with excellent optical quality, a special cut to meet the perfect phase-matching condition. Another alternative is dye lasers but these are less common due to less tunability, the toxicity of the gain medium, and the requirement of high maintenance. Because of the wide band gap and compactness of its crystal structure, diamond serves as a host for several hundreds of color centers. Some of them exhibit excellent optical properties such as stable photoluminescence, long lifetime, high transition cross-section, broad tunability range, and most importantly the photo-thermal and chemical stability. Furthermore, the diamond itself is an unrivaled host with the highest thermal conductivity of any bulk material known. Some of the color centers are very promising for laser applications and lasers based on those centers could span the whole visible to the near-infrared spectral range. Nitrogen-Vacancy (NV) color centers in diamond are one of the most widely studied solid-state defects, which have received attention in recent years due to their impressive optical and spin characteristics. One of the major challenges for many applications is the photoionization processes of NV centers between negative and neutral charge states. The rate of photoionization depends on the intensity and wavelength of the pump photon. However, there is still no clear understanding of several aspects of these photoionization processes. In addition to spectroscopic characterization, non-linear absorption properties and extent of saturation with pump intensities were studied. The temporal dynamics of saturation and photoionization were examined at different wavelengths using the pump-probe technique and a model describing the photoionization processes was developed. Another promising color center for laser application is GR1, which is one of the most common but poorly studied centers in diamond. Passive Q-switching of Ruby laser was demonstrated using these centers but a detailed understanding of spectroscopic and laser properties of GR1 in diamond color center crystals is not available. These centers are strongly luminescent, photo-thermo stable, feature broad absorption, and emission bands, and can serve as laser active optical centers and saturable absorbers for passive Q-switching of popular Alexandrite and Ti:Sapphire laser cavities. A detailed study and analysis of spectroscopic and laser properties of these centers were carried out in this work. Diamond has outstanding Raman properties in comparison to other commonly used Raman gain media. Diamond Raman lasers (DRLs) are highly efficient and the average output of multi-tens of watts in pulsed and kilowatt range in CW regime have been reported. Mostly, DRL are demonstrated in simple intra-cavity and external cavity configurations with the major focus on power scaling. Different unconventional geometries like backscattering, and distributed feedback gain, could result in even higher efficiencies and output energies. Stimulated Raman scattering often results in pulse shortening. Raman lasing of pure synthetic diamond was studied under single frequency 532 nm pump radiation to compare efficiency and pump pulse shortening capabilities in several cavities that allow single, double pass, and multi-pass Stokes amplification.

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