A simple, reliable waveguide dye laser for ophthalmological applications

Abstract

The principle of operation, construction, and performance of a compact waveguide dye laser, especially designed as a source of retinal photocoagulators, are described, The guiding effects produced by the thermal gradients induced by the pumping pulse and the use of closed resonator make the laser very reliable, simple, and with good pulse repeatibility. The construction is very simple and inexpensive. Except for flashlamps, which are commercial, no part of the laser requires sophisticated technology to be built or assembled; neither optical components have critical flatness and need careful alignment. The system does not need cooling, and slow recirculation of the solution, necessary to replace the degraded dye in the waveguide, is provided by a magnetically coupled 0.1 W electric motor. The dye cell, pump, and dye reservoir form a single component of the laser which can be easily extracted for inspection and replacement of the dye solution. The single, regular pulse emitted by the laser, its time duration (a few microseconds), the possibility to operate the laser at the absorption peaks of the ocular tissues make the laser better than the random spiking ’’passive’’ ruby laser or than the ’’explosive’’ Q−switched ruby laser for ophthalmological applications. If connected with a slit lamp, the laser should compete with the much more expensive ion gas lasers. Good retinal photocoagulations have been made in rabbits using a solution of Rhodamine 6G in ethanol. Retinal spots of rectangular shape of variable dimension but of constant energy density have veen produced by simply masking the exit window of the laser.