Virtual Journal of Laser

We present a laser architecture to obtain continuous-wave (CW) light sources at the 589 nm sodium D2 line. A 808 nm diode-pumped a Nd:YLiF4 (Nd:YLF) crystal emitting at 1053 nm. A part of the pump power was then absorbed by the Nd:YLF crystal. The remaining was used to pump a Nd:YAG crystal emitting at 1338 nm. Intracavity sum-frequency mixing at 1053 and 1338 nm was then realized in a LiB3O5 (LBO) crystal to reach the yellow-orange radiation. We obtained a CW output power of 235 mW at 589 nm with a pump laser diode emitting 17.8 W at 808 nm. (© 2010 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)

The continuous wave (CW) and passively Q-switched Nd:Gd3AlxGa5-xO12 (Nd:GAGG) laser operation at 938 nm have been realized for the first time. The maximum CW output power of 0.44 W was obtained under the absorbed pump power of 8.54 W, corresponding to the slope efficiency of 7.8% and optical-to-optical efficiency of 5.2% respectively. A V3+:YAG saturable absorber crystal with the initial transmission of 97% was used for the passive Q-switching regime. The maximum average output power of 0.19 W was achieved with the minimum pulse width of 358 ns and Q-switched repetition rate of 116 kHz. The corresponding single pulse energy and pulse peak power were determined to be 1.6 [mu] J and 4.6 W, respectively. (© 2010 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)

Laser induced autofluorescence spectroscopy of enamel and teeth at different artificial demineralization stage irradiated by 403 nm semiconductor laser were investigated. The quantitative evaluation parameter of mineral content is built on the basis of the fluorescence characteristic spectrum of 443 nm and 526 nm ratio to the total fluorescence integral. In the end, the dependence of characteristic spectrum on the excitation light power was experimentally investigated. The results reveal that at least 10 mW power is necessary to stimulate the featured spectrum. (© 2010 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)

We report on an 880 nm LD pumped passive modelocked TEM00 Nd:YVO4 laser based on a semiconductor saturable absorber mirror (SESAM) for the first time. When the incident pump power was 16 W, 4.76 W average output power of continuous-wave mode-locked laser with an optical-to-optical conversion efficiency of 30% was achieved. The repetition rate of mode-locked pulse was 80 MHz with 25 ps pulse width. The maximum pulse energy and peak power were 60 nJ and 2.4 kW, respectively. (© 2010 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)

An electrical-to-green efficiency of more than 10% was demonstrated by intracavity-frequency-doubling a Q-switched diode-side-pumped Nd:YAG laser with a type II lithium triborate (LBO) crystal in a straight plano-concave cavity. An average power of 69.2 W at 532 nm was generated when electrical input power was 666 W. The corresponding electrical-to-green conversion efficiency is 10.4%. To the best of our knowledge, this is the highest electrical-to-green efficiency of second harmonic generation laser systems with sidepumped laser modules, ever reported. At about 66 W of green output power, the power fluctuation over 4 hours was better than ±0.86%. (© 2010 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)

A high power eye-safe optical parametric oscillator driven by the LD end-pumped Nd:YAlO3 laser was demonstrated based on a non-critically phase-matched KTiOAsO4 crystal. The mode mismatch compensating resonator was adopted for efficient OPO conversion. The maximum output power of 2.3 W at 1562 nm was achieved at the pulse repetition frequency of 20 kHz. The conversion efficiency between the fundamental light and the signal light was up to 62%, which was much higher than other relative reports. (© 2010 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)

We report a high-efficiency Nd:LuVO4 laser operating at 1066 and 1343 nm, respectively, direct pumped by a diode laser at 880 nm. The maximum outputs of 10.5 and 7.0 W, at 1066 and 1343 nm, respectively, are obtained in a 8-mm-thick 0.4 at.% Nd:LuVO4 crystal with 16.9 W of absorbed pump power at 880 nm, leading to a high slope efficiency with respect to the absorbed pump power of 64.4 and 44.5%. Under traditional pumping at 809 nm, the maximum outputs of 9.8 and 6.2 W, at 1066 and 1343 nm respectively, are obtained with 19.3 W of absorbed pump power, corresponding to the slope efficiency with respect to the absorbed pump power of 54.9 and 34.9%. (© 2010 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)

Technique of delayed optical nutations is investigated from the viewpoint of possibility to measure collision relaxation rates in molecular gas by application of levels Stark switching. The numerical analysis enabled us to define the range of experimental parameters, at which the dependence of the delayed nutation signal on the duration of the Stark pulse becomes pure exponential, providing simple measuring tools. Experiments were performed at rotation transition R(4,3) of vibration band 0 [harr] 1 [nu]3 of polar gas 13CH3F by levels Stark switching method in presence of CW radiation of CO2 laser operating at 9P(32) line. Both pure 13CH3F gas and its mixtures with atomic buffers He, Ne, Ar, Kr and non-polar molecular gases N2, and CO2 were studied. The experiments revealed that the relaxation cross-section increases with a mass of collision partner, but do not exceed the cross-section in pure 13CH3F. (© 2010 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)

The aim of this study was to investigate the mechanism of cell death by photodynamic therapy (PDT) in the Rhabdomyosarcoma (RD) cell line. The present study evaluates the effects of photodynamic therapy (PDT) with 5-ALA as photosensitizer using human muscle cancer cells as experimental model. We study the photosensitizer uptake, cytotoxicity, phototoxicity, and cellular viability of the RD cells which was es-timated by means of neutral-red spectrophotometric assay. The given experiment was consisted of two steps. For the first one, RD cells were exposed to 5-ALA at concentrations of 0 up to 1000 [mu] g of ALA/ml in minimum essential medium (MEM). The optimal uptake of photosensitizer (5-ALA) in RD cells was investigated by means of spectrometric measurements. Cells viability was determined by means of neutral red assay (NRA). In the second step, 5-ALA exposed RD cells were irradiated with red light (a diode laser, [lambda] = 635 nm) at total light dose of 80 J/cm2. The influence of different incubation times and concentrations of 5-ALA, different irradiation doses and various combinations of photosensitizer and light doses on the viability of RD cells were investigated.

The performance of laser-diode end-pumped Yb:LuAG microchip lasers has been investigated at ambient temperature without active cooling of the gain media. Efficient laser oscillation of Yb:LuAG crystals with different thickness and output couplings was achieved at 1030 and 1047 nm with slope efficiencies of 72 and 54%, correspondingly. The thermal population distribution at the terminated laser level of Yb:LuAG crystal plays an important role in the laser performance. The effects of the thickness of Yb:LuAG crystal and the transmission of output couplers on the laser oscillating wavelength and central wavelength shift were investigated by taking account into the reabsorption loss at lasing wavelength and intracavity laser intensity. (© 2010 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)