Photoacoustic spectroscopy and the effect of amplified spontaneous emission

Amplified spontaneous emission (ASE), which results from dye fluorescence, causes pulsed dye lasers to produce an output that is spectrally impure. The effect of such an output can create inaccurate analytical information, particularly in absorption and photothermal spectroscopies. The spectral output of laser dye LD-466 has been characterized. ASE was shown to have a broad-band spectral output, 445-495 nm, and was most Intense when lasing was inefficient, on the edges of the dye gain curve. A 10^-3 M Pr³⁺ solution produced similar photoacoustic waveforms from lasing and ASE. Linear calbration curves were generated with the laser tuned to 468 and 495 nm. At 495 nm Pr³⁺ has no absorbance and the photoacoustic signals were produced from ASE.