Praseodymium Yttrium Fluoride Lithium (Pr:Ylf) Green-Lasers And Its Excited State Absorption(Esa) Spectrum

Abstract

Solid state visible lasers have various applications in the field of color display, holographic techniques, data storage and medical treatment. So far green laser output has been obtained using methods of frequency conversion, thus increasing the cost of building the laser as well due to the low efficiency of such techniques. There are very few materials which produce visible laser radiation directly. Trivalent Praseodymium (Pr 3+ ) is one such example. It is quite interesting because of its unique energy scheme which offers multiple transitions in the visible spectrum. We are mainly interested in the energy transition from 3P0 to 3H5 which produces light in the green visible spectrum (523 nm). Green lasers are particularly useful and important in certain types of underwater communications. Sea water has low absorbance and offers relatively low scattering for green light, thus making green light one of the most effective sources for underwater communications. Excited State Absorption (ESA) is a phenomenon where absorption occurs from an occupied excited state level of the specie. This can lead to additional loss, which causes complications for lasing in the form of increased threshold power, reduced power slope efficiency, and change in lasing wavelength due to offset in the highest emission cross-section. This thesis examines the spectroscopic profile of Praseodymium-doped Yttrium Lithium Fluoride (Pr:YLF) including the ground state absorption, fluorescence, and ESA in great detail. We explore the experimental setups used, detection scheme and finally reveal the results obtained.