Photobiological effects of semiconductor laser radiation in the near infrared

An investigation was made of the effects of radiation from a pulsed gallium arsenide (λ = 890 nm, pulse repetition frequency 666 and 3480 Hz, intensity 12 mW/m²) on the rate of growth of E. coli bacteria. It was found that the growth of a culture was accelerated by radiation doses 0.1–1.5 J/m² and the maximum effect (when ratio of the number of cells in the irradiated and unirradiated cultures amounted to about 1.7) was observed for doses 0.5–0.8 J/m². The effect was independent of the pulse repetition frequency, provided the other parameters of laser radiation (intensity, dose) were constant.