6533b871fe1ef96bd12d18f3

RESEARCH PRODUCT

Improvement of solid state Er:YAG pulse laser performance for use in medicine

subject

description

The large quadratic electro-optic effect of PLZT ceramics allows to design small size modulators for the solid state infrared Er:YAG laser (lasing at (lambda) equals 2.94 micrometers - the most pronounced absorption band of water), which has found application in medicine for efficient ablation of hard and soft tissues. In the free-running mode, the Er:YAG laser emits spikes that form the pulse envelope with duration of 150 - 800 microsecond(s) . An extracavity PLZT 8.5/65/35 ceramics modulator (aperture of 4 X 6 mm2 and length of 18 mm) was used to obtain (Pi) -shaped segments with the rise and decay times less than 5 microsecond(s) . That allows to reduce considerably the fraction of the pulse energy below the ablation threshold so avoiding undesirable heating of tissues. The halfwave voltage of such modulator was 1350 V with an additional DC bias of 300V. The contrast ration K > 15:1. The Q-switching technique was applied to obtain high intensity small duration monopulses using modulators of the same PLZT 8.5/65/35 ceramics. PLZT ceramics Q-switches (tested in two schemes - as a (lambda) /4 switch placed perpendicular to the beam with a length of 6mm without antireflection coatings; and as a (lambda) /2 switch with a length of 3 mm placed at the Brewster angle) allowed to obtain monopulses with the energy of 5 - 8 mJ and with a pulse width of 150 ns.