Fabrication, microstructure and optical characterization of transparent glass ceramic

Abstract

Over the past few years, polycrystalline Nd:Y3Al5O12 (Nd-YAG) ceramic has replaced single crystal from solid state laser because of the possibility of higher at% Nd-doping and ease of fabrication. Development of transparent ceramic becomes more challenging with increase in size. The laser active Nd-ion when added in glass matrix as laser host is better in term of large size fabrication but Nd-glass has poor thermal conductivity compared to YAG crystal. Aim of the present work is to combine size advantages of Nd-glass with excellent thermal conductivity of YAG by precipitating YAG phase in glass. A suitable Nd-doped silicate glass composition based on ytterium-lithium-aluminum-silicate is fabricated having absorption coefficient 0.72 cm-1 and ~ 75 % transmission at 1061 nm wavelength. All the major transition observed in the absorption spectra are assigned based on the transition from the ground state 4I9/2 to the crystal field state as marked. Emission spectra of Nd-glass revealed a broad peak near 1061 nm when excited with 585 or 808 nm wavelength. It is observed that absorption and emission peaks are broad, which is consistent with the Nd-ions in glass matrix. The change in thickness of Nd-glass (~ 2mm) is measured to determine the thermal expansion coefficient ~ 8.0 x 10-6 /oC. Thermal treatment is given to a section of the glass sample at different temperature (900-1450 oC) in air for 1-6-hour dwell.