Abstract
An electro-optically Q-switched high-energy Er:YAG laser with two polarizers is proposed. By using two Al(2)O(3) polarizing plates and a LiNbO(3) crystal with Brewster angle, the polarization efficiency is significantly improved. As a result, 226 mJ pulse energy with 62 ns pulse width is achieved at the repetition rate of 3 Hz, the corresponding peak power is 3.6 MW. To our knowledge, such a high peak power has not been reported in literature. With our designed laser, in-vitro teeth were irradiated under Q-switched and free-running modes. Results of a laser ablation experiment on hard dental tissue with the high-peak-power laser demonstrates that the Q-switched Er:YAG laser has higher ablation precision and less thermal damage than the free-running Er:YAG laser.
Highlights
Erbium:yttrium-aluminum-garnet (Er:YAG) laser crystals can be used to produce a laser radiation at 2.94 μm, which is closed to the infrared absorption peaks of water and hydroxyapatite
The results demonstrate that the Q-switched Er:YAG laser exhibits higher ablation precision and less thermal damage to the surrounding tissues than the free-running Er:YAG laser
If we assume that about 30% pulse energy is used to heat the dentine, the results will be in good agreement with the simulated data in in dental tissues irradiated with Er,Cr:YSGG laser
Summary
Erbium:yttrium-aluminum-garnet (Er:YAG) laser crystals can be used to produce a laser radiation at 2.94 μm, which is closed to the infrared absorption peaks of water and hydroxyapatite. The free-running Er:YAG laser designed for clinical use typically has a pulse width of a few hundred microseconds When such a long-pulsed radiation is applied to the affected areas, the excess heat diffuses into the surrounding healthy tissues, causing damage or necrosis [6, 7]. Zajac et al used LN as a Q-switch in a flashlamp-pumped Er:YAG laser, 137 mJ pulse energy with 91.2 ns pulse width was obtained at the repetition rate of 3 Hz, the corresponding peak power was 1.5 MW [11]. Jelínkova et al observed obvious thermal damage when a free-running erbium laser with a pulse energy of 75 mJ and a pulse width of 200 μs was applied to ablate the hard dental tissues [14]. This study provides a basis for further investigation on the biological effects of high-energy and high-peak-power Q-switched Er:YAG laser, especially for hard tissue ablation experiments
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