Variable pulse width laser and method of use

Abstract

A laser for medical includes an optically pumped laser medium, and the output of the laser is directed through an optical fiber delivery system to a tissue target. The flashlamp is driven by a pulsed power signal that is selectively variable to produce laser pulses of predetermined temporal width and pulse energy, and these values can be selected in accordance with the type of tissue being treated and the tissue effect desired. The laser may be operated to produce relatively brief pulses of high energy, which create a localized plasma at the surface of the target tissue. The plasma effect blocks any significant penetration of the laser beam into the tissue, and each laser pulse causes the ablation of a small portion of the tissue target. Thus thermal necrosis of adjacent and underlying tissue minimized. At the opposite extreme, the laser may be operated to produce relatively long pulses of low or moderate energy, so that the laser beam penetrates the tissue to create such effects as deep coagulation, deep thermal heating and necrosis, and the like. In a further aspect, the laser is provided with an automatic system to control the temporal width of the laser pulses. A photodetector apparatus is optimized to detect the optical radiation from the plasma created at the tissue target and transmitted retrograde through the optical fiber delivery system to the laser. The pulse generating circuitry of the laser terminates the laser pulse in response to the plasma signal. The laser produces tissue effects comparable to a wide range of prior art medical lasers.