EXPERIMENTAL AND THEORETICAL INVESTIGATION OF PHOTOACOUSTIC-SIGNAL GENERATION BY WAVELENGTH-MODULATED DIODE-LASERS

The dependence of photoacoustic spectra on different experimental para meters was investigated by both theoretical and experimental means. Th e experiments were carried out with an inexpensive resonant optoacoust ic system based on near-infrared laser diodes, which allowed photoacou stic and direct absorption spectra to be recorded simultaneously. The experimental observations were compared to theoretical predictions. It was also demonstrated that source-frequency (wavelength) modulation a t the resonance frequency of the cell provides superior signal to nois e ratio compared to amplitude modulation and eliminates background dri fts and fluctuations.