Borohydride anion exchange resin stabilization of flash-lamp-pumped coumarin dye lasers

Abstract

The operation of flash-lamp-pumped Coumarin 460 and 480 dye laser with ethanol solvent produced acetaldehyde; its production paralleled the increase in the optical density of the dye solution at the dye lasing wavelength and the decrease in the output intensity of the dye laser. The yield of acetaldehyde was shown to be higher with higher light intensity and with the presence of molecular oxygen. Acetaldehyde formation was further enhanced by simultaneous excitation of the singlet-singlet and triplet-triplet absorption bands of Coumarin 460. The formation of acetaldehyde and other material which interferes with stimulated emission is discussed in terms of upper triplet state energy transfer from the dye to the solvent. The concentrations of acetaldehyde and material absorbing at the lasing wavelength of the dye were controlled in real time by introducing a cartridge containing a borohydride anion exchange resin in the dye steam to reduce carbonyl functional groups to less absorbing alcohol functional groups as they were formed photochemically. The presence of the resin increased the initial output power of the dye laser and substantially improved its output stability. © 1991.