Carbon dioxide laser-induced fast signals from silicon photodiodes

The present investigation is concerned with the observation of fast reproducible electrical signals from silicon photodiodes when exposed to high-power CO2 laser radiation. Levels of laser power which might have produced damage in the diodes were avoided. A hybrid Transversely Excited Atmospheric (TEA) low pressure double-discharge CO2 laser was employed in the experiment. This device produces smooth 60-nsec single-longitudinal mode CO2 laser pulses with an amplitude fluctuation of + or - 5 percent. The laser pulse was directed onto a reverse-biased silicon photodiode without focusing. Two commercially available photodiodes were used in the experiments. Photodiode signal magnitudes as a function of laser intensity are presented in a graph. One of the possible applications of the observed fast electrical responses of the photodiode to the laser pulse is related to the detection of CO2 laser radiation density.