A surgical laser musthave the ability to cut and coagulate tissue; these actions requirethe vaporization of tissue with heat. The physical characteristicsof the laser irradiation strongly influence the efficiency of theconversion of laser (light) energy to thermal energy in tissue.Many laser devices cannot be used in surgery for reasons ofwavelengthor low power output. Five types of lasers are more or lesscapable of surgical application I46 (Table 1).Pulsed lasers are not desirable for general surgical applications,since their pulses last only a fraction of a second (less than1 millisecond) and are separated by long intervals. Before comparingthe performance of the three continuous wave lasers, wewill examine the specifics of the laser beam-tissue interactionand establish the desired effects thereof.When radiation strikes any material substance (incident radiationis referred to as irradiation), it will be reflected by the surface,absorbed in the material and/or transmitted through the
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