Heavy Metal Fluoride Glasses for Optical Applications

Abstract

ABSTRACTGreat progress has been made in optical device technology over the past decade. This progress brings a host of new services which include voice, data and visual communications. The realization of low loss optical fibers which give rise to long distance optical communication and the growth in information processing through computer technology will lead to an accelerating growth in the utilization of light guides and light wave communication systems. Heavy metal fluoride glasses have proved to be excellent hosts for both rare earth and 3d transition metal ions. In addition, their potential as light guides is at present unexcelled. This glass is especially promising for optical display devices, laser hosts, and electroluminescence panels. Numerous defects and impurities can be incorporated in the glass which absorb or emit light. Through optical studies of rare earth ions such as Er3+, Ho3+, Nd3+ and Pr3+ it is possible to investigate the multiphonon emission rate for optical transitions in the heavy metal fluoride materials. It is found that these particular materials have a much lower multiphonon rate than oxide glasses. This makes them attractive for room temperature devices. When 3d transition metal ions are incorporated into heavy metal fluoride glasses, the optical properties are similar in many cases to those in crystals. Inhomogeneous broadening of the absorption and emission bands occurs in the glass, but the lifetimes and oscillator strengths of the transitions in glass and crystals are of the same magnitude. Radiation damage of glasses can be detrimental to long range optical communication. It is found that the heavy metal fluoride glasses damage by the photochemical mechanism which is also dominant in highly ionic materials. Optical absorption and electron spin resonance measurements have been utilized to identify the types of radiation induced defects in these materials.