Martin Fibrich

Ceramic Bracket Debonding by Tm:YAP Laser Irradiation

OBJECTIVE The aim of this study was to prepare a simple and reliable method for ceramic bracket debonding, ensuring minimal changes in the enamel structure and an acceptable temperature rise in the pulp. BACKGROUND DATA Ceramic bracket debonding is based on the principle of degrading the strength of adhesive resin between the tooth and ceramic bracket. The search for a safe and efficient method of adhesive resin removal following debonding has resulted in the introduction of a wide range of instruments and procedures, among which proper use of laser irradiation can be promising. METHODS The debonding of two types of ceramic brackets utilized a diode-pumped Thulium:Ytterbium-Aluminium-Perovskite (Tm:YAP) microchip laser generating irradiation at a wavelength of 1998 nm (spot size 3 mm; focused by lens), with two power settings (1-2 W). Loss of enamel and residual resin on teeth, as well as rise in temperature inside the tooth were subsequently investigated in detail. RESULTS A 1W power of irradiation during a 60-sec period resulted in a temperature rise from 3 to 4°C in the approximate root location. This power is also suitable for debracketing from the point of view of damage to enamel lying below the bracket. Only a slight damage to the enamel was registered by SEM compared to conventional bracket removal. CONCLUSIONS Use of a Tm:YAP laser (wavelength 1998 nm, power 1 W, irradiance 14 W/cm(2), interacting time 60 sec) which is at the same time compact and small enough to be used in the dental practice, together with moderate cooling, could be an efficient tool for debracketing.

Continuous-wave blue generation of intracavity frequency-doubled Pr:YAP laser

We report the cw blue generation of Pr:YAP laser emission at room temperature, which has been achieved by intracavity frequency doubling of the near-IR-emitting Pr:YAP laser operating at a fundamental wavelength of 747 nm. For active medium pumping, a GaN laser diode providing up to 1 W of output power at approximately 448 nm was used. With beta barium borate crystal employed as a nonlinear medium, 12.3 mW of output power at 373.5 nm has been obtained.

Pr:YAlO 3 microchip laser

A cw Pr:YAlO(3) microchip-laser operation in the near-IR spectral region is reported. A microchip resonator was formed by dielectric mirrors directly deposited on the Pr:YAlO(3) crystal surfaces. For active medium pumping, a GaN laser diode providing up to 1W of output power at approximately 448 nm was used. 139mW of laser radiation at 747nm wavelength has been extracted from the microchip-laser system. Slope efficiency related to the incident pumping power was approximately 25%.

HiLASE cryogenically-cooled diode-pumped laser prototype for inertial fusion energy

We present the design parameters of a diode-pumped 100J-class multi-slab Yb:YAG laser at 10 Hz scalable to the kJ regime. Results of detailed energetics and thermo-optical modeling confirm the viability of cryogenic helium-gas cooling approach to drastically reduce thermally-induced distortions in the laser slabs. In addition, a comparison of spectral measurements from laser-diode stacks and Yb:YAG crystals validates the feasibility of highly efficient diode-pumped solid-state lasers at cryogenic temperatures.

Pr:YAlO 3 laser generation in the green spectral range

A continuous-wave 37 mW Pr:YAlO<subYAlO₃ laser operating at 547 nm wavelength is reported. Microchip resonator geometry in connection with 1 W InGaN laser diode-pumped, cryogenically cooled active medium was employed to achieve green laser emission.

Flash-lamp pumped Pr:YAP laser operated at wavelengths of 747 nm and 662 nm

Successful room-temperature generation of Pr:YAP laser radiation at wavelengths of 747 nm and 662 nm was demonstrated. A flash-lamp pumped Pr:YAP laser was operated in free-running pulsed regime at room temperature. Permanent laser action was reached by means of a special UV color glass plate filter placed directly into the laser cavity. The maximum output energy and pulse length reached at wavelengths of 747 nm and 662 nm were 102 mJ, 92 μs and 6.1 mJ, 47.5 μs, respectively. The laser beam parameter M2 ~ 1.5 was measured when the 662 nm wavelength was generated. In the case of 747 nm wavelength generation, M2 ~ 1.2 was reached with a diaphragm inside the resonator. For different pumped energy values, the line shape and linewidth remained stable for both cases.

Multiline generation capabilities of diode-pumped Nd:YAP and Nd:YAG lasers

Multiline generation capabilities of diode-pumped Nd:YAP and Nd:YAG lasers within 1.3?1.5??m wavelength range at room temperature are reported. Two optical resonators designed for 1.3 and 1.4??m laser operation have been realized. Using a single quartz plate as a tuning element, six single emission lines within the 1.3?1.5??m spectral range for both Nd:YAG and Nd:YAP lasers have been reached. Moreover, as also demonstrated, it was possible to obtain Nd:YAG/YAP dual frequency regime operation for some line combinations.

Tunable eye-safe Er:YAG laser

Er:YAG crystal was investigated as the gain medium in a diode (1452 nm) pumped tunable laser. The tunability was reached in an eye-safe region by an intracavity birefringent filter. The four tuning bands were obtained peaking at wavelengths 1616, 1632, 1645, and 1656 nm. The broadest continuous tunability was 6 nm wide peaking at 1616 nm. The laser was operating in a pulsed regime (10 ms pulse length, 10 Hz repetition rate). The maximum mean output power was 26.5 mW at 1645 nm. The constructed system demonstrated the tunability of a resonantly diode-pumped Er:YAG laser which could be useful in the development of compact diode-pumped lasers for spectroscopic applications.

Four micron radiation generated by dysprosium doped lead thiogallate laser

The lead thiogallate (Dy:PbGa2S4) crystal doped with trivalent dysprosium ions was used as a laser active medium for obtaining radiation in mid-IR spectral region. To prove in-band pumping, the Er:YAP laser generating 1.66 μm radiation was used. This radiation was focused by CaF2 lens (f = 100 mm) on the investigated Dy:PbGa2S4 crystal placed inside the resonator formed by an in-coupling flat-dichroic mirror with low reflectivity at pumping wavelength and with high reflectivity within the 4-5 μm spectral range, and by an out-coupling concave mirror (500 mm curvature) with reflectances of 86%, 88%, 89%, and 93% at 4325 nm. Three Dy:PbGa2S4 active crystals were investigated. The Dy:PbGa2S4 laser was working at room temperature without any cooling. The maximal reached output energy was as high as 275 μJ for the optimal mirror reflectance and the best Dy:PbGa2S4 crystal. The incident pumping energy was 132 mJ. The measured output radiation wavelength was 4332 nm with the spectral width of 62 nm. From the point of efficiency it was recognized that the in-band pumping directly into 6H11/2 level results in decrease of lasing threshold and increase of slope efficiency.

Influence of temperature on Pr:YAlO3 laser operation in the orange and near-infrared spectral range

Continuous wave Pr:YAlO3 laser behavior in the orange (622 nm) and near-infrared (747 nm) spectral range down to cryogenic temperature is reported. To minimize resonator losses, dielectric films were deposited on the crystal facets to form a microchip geometry. More than 300 mW of output power at 747 nm wavelength with a slope efficiency close to the quantum limit is demonstrated. Furthermore, the first diode-pumped Pr:YAlO3 orange laser is described, as we believe.