Experimental studies of the applications of the holmium laser in dentistry.

The purpose of this study is to evaluate the possibility of using a pulsed Ho:YLF laser for endodontic surgery access, preparation of cavities, etching of dental enamel, and treatment of dental caries. Specimens were irradiated with a prototype of pulsed Ho:YLF laser (2,065 microns). Laser energies in the range of 120-750 mJ per pulse were used. The study of morphological changes on enamel and dentine was conducted on light and scanning electron microscopes. Perforation of approximately 4 mm depth with homogeneous and smooth aspect of its wall surfaces was obtained. There was no carbonization. Irradiation with low energy results in melted and recrystalized surface with small and shallow pits. In accordance with our results the Ho:YLF laser produces surfaces that are white in appearance in contrast to the Nd:YAG modified enamel and dentine surfaces, that were darkened. These are indications that the holmium laser may be useful for dentistry in the future.

High-efficiency, argon-laser-pumped Nd:YLF laser system.

An Ar-ion laser was used to pump a Nd:YLF laser, in both σ and π polarizations, in a longitudinal scheme. In spite of the small absorption coefficient at the pump (~0.25 cm (-1)), a careful laser design can circumvent this problem, and efficiencies as high as those attained with semiconductor pumping schemes are reported. The laser fundamental parameters were experimentally determined. A double-pass net gain as high as 10(3) was measured, and an output power of 1 W was obtained with a pumping power of 6 W.

Mode-locking operation of a pulsed Nd:YAG laser with F(2) BF:LiF color-center crystal in a dual configuration.

Passive stable mode locking of a pulsed Nd:YAG laser was achieved with a long-decay-time saturable absorber in a coupled-cavity longitudinal scheme. In this configuration the saturable absorber (LiF:F(2) ) also behaves as an active medium in intracavity pumping and is the load for the Nd laser. This arrangement provides proper lasing conditions for the F(2) color centers so that the cavity photon lifetime of the color centers is much shorter than the cavity round-trip time of the Nd laser. In this way the Nd pulses are simultaneously Q switched and mode locked. The pulses show a stable temporal profile, with an envelope of 160 ns and a train of mode-locked pulses of less than 200-ps duration.