Jan Šulc

Efficient diode-pumped passively Q-switched Raman laser on barium tungstate crystal

Abstract An efficient all-solid-state diode-pumped intracavity Raman laser was constructed. This laser was based on three-mirror linear cavity with triangular Brewster-angle-cut Nd:YAG slab crystal pumped by 300-W quasi-CW diode Q-switched by Cr 4+ :YAG saturable absorber operated at 1064 nm. BaWO 4 (barium tungstate) crystal was used as a Raman converter. After the Raman laser optimisation for the first Stokes (1180 nm) the reproducible conversion efficiency was about 40% with respect to the Q-switched laser operation at the fundamental frequency. The corresponding output energy and pulse duration was 1.46 mJ and 3.5 ns, respectively. The top reached Raman laser output energy was 2.3 mJ with the conversion efficiency of 55%.

Diode-pumped Er:CaF 2 ceramic 2.7 μm tunable laser

Spectroscopic and laser properties of a newly developed high optical quality Er:CaF2 hot-formed ceramic were investigated. Under pulsed 968 nm laser diode pumping, the mid-infrared (2.7 μm) radiation was obtained with a slope efficiency of 3%. Laser tunability was reached using a birefringent filter and the laser tuning range of 118 nm, from 2687 up to 2805 nm, was demonstrated. The maximal output energy reached was 0.48 mJ at 2730 nm for the absorbed pumping energy 34 mJ.

Endodontic Treatment with Application of Er:YAG Laser Waveguide Radiation Disinfection

OBJECTIVE The objective of this study is to examine the ability of Er:YAG laser radiation. Using a movable waveguide helps to obtain an antibacterial effect, not only in root canal walls but also in the surrounding tissues. BACKGROUND DATA Conventional endodontic treatment is not fully effective due to microbial colonization of root canal walls dentin in premolars and molars. Various laser systems seem to be effective to kill the remaining microbial content in the root canal. The problem is in the flexibility of laser system tips. MATERIALS AND METHODS The Er:YAG laser system was designed with a fluorocarbon polymer-coated silver hollow glass waveguide. Root canal systems of 44 premolars and molars were treated endodontically, using a step-back technique; 10 teeth were then treated with calcium hydroxide paste, and 22 teeth were irradiated by a movable waveguide. Before and after treatment, the colony-forming units were counted to determine 21 various microorganisms. RESULTS Classical enlargement and shaping of the root canal is effective in 60%. Application of calcium hydroxide prepares sterile root canal in 80%. Er:YAG laser irradiation via movable waveguide (energy of 100 mJ, 30 pulses, repetition rate 4 Hz) can ensure residual disinfection of the root canal. CONCLUSION Application of Er:YAG laser radiation through a flexible waveguide helps to attain antibacterial effect, not only in the root canal walls, but also in the surrounding tissues. Therapeutic doses of laser radiation guarantee one-step disinfection, including of anaerobic microorganisms.

Erbium:YAG laser lithotripsy by use of a flexible hollow waveguide with an end-scaling cap.

An Er:YAG laser light delivery system composed of a polymer-coated silver hollow waveguide and a quartz sealing cap has been developed for calculus fragmentation. Sealing caps with various distal-end geometries were fabricated, and the focusing effects of these caps for Er:YAG laser light were measured both in air and in water. Owing to the high power capability of the quartz a beam of sealing caps, Er:YAG laser light with an output energy of 200 mJ and a repetition rate of 10 Hz was successfully transmitted in saline solution by use of the system. Calculus fragmentation experiments conducted in vitro showed that the delivery system is suitable for medical applications in lithotripsy. We also found that the cap with a focusing effect is more effective in cutting calculi. The deterioration of the sealing caps after calculus fragmentation is also discussed.

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.

1444-nm Q-switched pulse generator based on Nd:YAG/V:YAG microchip laser

Q-switched microchip laser emitting radiation at eye-safe wavelength 1444 nm was designed and realized. This laser was based on composite crystal which consists of 4 mm long Nd:YAG active medium diffusion bonded with 1 mm long V:YAG saturable absorber. The diameter of the composite crystal was 5 mm. The initial transmission of the V:YAG part was T0 = 94% @ 1440 nm. The microchip resonator consists of dielectric mirrors, directly deposited onto the composite crystal surfaces. These mirrors were specially designed to ensure desired emission at 1444 nm and to prevent parasitic lasing at other Nd3+ transmissions. The output coupler with reflectivity 94% for the generated wavelength 1444 nm was placed on the V3+-doped part. The laser was operating under pulsed pumping for the duty-cycle up to 50%. With increasing value of mean pumping power a strong decrease of generated pulse length was observed. The shortest generated pulses were 4.2 ns long (FWHM). Stable pulses with energy 34 μJ were generated with repetition rate up to 1.5 kHz. Corresponding pulse peak power was 8.2 kW. The wavelength of linearly polarized TEM00 laser mode was fixed to 1444 nm.

High-power Nd:YAG laser picosecond pulse delivery by a polymer-coated silver hollow-glass waveguide

An oscillator-amplifier high-power Nd:YAG laser system was used for transmission of a single 50-ps-long pulse or a train of pulses through a cyclic olefin polymer-coated silver hollow-glass waveguide. The maximum energy that was transmitted was 150 mJ for the train of pulses and 40 mJ for the single pulse, from which followed a delivered power of 100 GW/cm(2) . The characteristics that were obtained make these waveguides promising for the delivery of high-power laser pulses in medical as well as other applications.

Dysprosium-doped PbGa2S4 laser excited by diode-pumped Nd:YAG laser.

We realized a compact mid-IR room temperature operating Dy(3+):PbGa(2)S(4) laser, excited by a diode-pumped Nd:YAG laser at a wavelength of 1318 nm. The pumping laser was operating in pulsed mode with a pulse length of 4 ms and repetition rate of 20 Hz. Maximum pumping energy at a wavelength of 1318 nm was 15 mJ. Energy up to 90 μJ and mean output power of 1.8 mW was obtained at a wavelength of 4290 nm with a slope efficiency with respect to absorbed pumping energy better than 3%.

Resonantly pumped, high peak power Er:YAG laser

The high peak power hybrid Er:YAG laser, resonantly pumped at the wavelength of 1532 nm was developed. The fused silica acousto-optic modulator driven by 10 W of RF power was deployed as the Q-switch for such a laser. For the best case of Q-switching regime the pulses of 110 kW peak power (4 mJ, 37 ns) were reached at the pump power of 7.8 W and the repetition rate of 500 Hz.

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.