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Cr:ZnSe crystal newly grown by Bridgman method was investigated as an active material for laser coherently pumped either by flashlamp-pumped Er:YAP (wavelength 1.66 µm) or by diode pumped Tm:YAP (wavelength 1.97 µm) laser radiations. The maximal Cr:ZnSe laser output pulse energy, for the case of flashlamp Er:YAP laser pumping, was 14 mJ (slope efficiency 66%) with the length of pulse 120 µs. The generated laser radiation was tunable from 2.15 µm to 2.60 µm with only 2.5 times drop in laser energy. In the case of diodepumped Tm:YAP laser pumping the maximal obtained Cr:ZnSe laser output power in cw regime was 195 mW for the absorbed pump power 300 mW (slope efficiency 66%). The generated laser radiation was tunable from 2.12 µm up to 2.38 µm.

Abstract:The study describes the preclinical experience with laser-activated bleaching agent for discolored teeth. Extracted human upper central incisors were selected and in a bleaching experiment 35% hydrogen peroxide was used. Three different laser systems and halogen-light unit for activation of the bleaching agent were used: alexandrite laser (wavelength 750 nm and SHG -375 nm), Nd:YAG laser (wavelength 1.064 µm), and Er:YAG laser (wavelength 2.94 µm). The halogen light unit was used in a standard regime. The enamel surface was analyzed in the scanning electron microscope. The method of chemical oxidation results in a 2-3 shade change in one treatment. The halogen-light unit received the same effect with shorter time of bleaching process (from 630 s to 300 s). Alexandrite laser (750 nm) and bleaching agent helped to reach the desired color shade after shorter time (400 s). Alexandrite laser (375 nm) and Nd:YAG laser had no effect on the longevity of the process of bleaching. Overheating of chemical bleaching agent was visible after Er:YAG laser activation (195 s). This effect was only local, no crack or essential surface modifications were observed.The enamel surface after the irradiation of Er:YAG laser (2.94 µm) and bleaching agent application (magnification 2000x)

Compact broadly tunable Cr:ZnSe laser was constructed and described. Cr:ZnSe bulk crystal was grown by the Bridgman technique. In our best knowledge the bulk Cr:ZnSe prism was utilized as laser active media and simultaneously as an intra-cavity dispersive element for the first time. The maximal output pulse energy was 20 mJ. The generated radiation was tunable from 2000 up to 2750 nm. The repetition-rate was 1 Hz. The generated radiation beam spatial structure was close to TEM00.

The room-temperature laser-oscillation properties of lead thiogallate crystals doped with dysprosium ions PbGa(2)S(4):Dy(3+) without additional codoping and codoped with potassium ion for excessive charge compensation were investigated. A slope efficiency of 1% was obtained for the codoped crystal. YAP:Er -1.66 microm laser resonant pumping of PbGa(2)S(4):Dy(3+) laser was compared with YAG:Nd -1.32 microm nonresonant pumping. The maximum energy obtained was 57 microJ with the negligible influence of the atmosphere.