Solar surgery: remote fiber optic irradiation with highly concentrated sunlight in lieu of lasers

Highly concentrated sunlight has the power density required by many laser fiber optic surgical procedures. Thanks to recent progress in optical design, the means now exist to concentrate solar radiation in dielectrics to levels that exceed those at the surface of the sun, and to efficiently deliver it remotely. Since surgical power requirements are typically only several watts, the solar collection unit can be miniaturized. Although generating uncollimated radiation, solar surgery can serve as a low-cost alternative to laser fiber optic systems in treatments where wide-angle emissions are preferable. Even nominally monochromatic treatments such as photodynamic therapy can use highly concentrated sunlight because the power density within a typical wavelength window for these treatments (around 0.004 mu m) is adequate to the task. Scheduling of solar surgery should not pose difficulties in clear climates. Solar concentration is performed in two stages: a paraboloidal reflector dish and a second-stage nonimaging concentrator. Concentrated irradiation would be transported via low-attenuation silica optical fibers to the operating room. With power delivery typically emanating from a disk of diameter 0.6 mm, the dish diameter would be in the vicinity of 200 mm with an even smaller system depth. The system could deliver a flux density as high as 70 W mm(-2) for contact surgery and 30 W mm(-2) for noncontact surgery. Aside from lasers, sunlight is uniquely suited to the task, in contrast to today's available light sources, (C) 1998 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(98)01610-9].