Point defects in Sc2O3 thin films by ion beam sputtering.

We show that the concentration of oxygen interstitials trapped in Sc2O3 films by ion beam sputtering from metal targets can be controlled by modifying deposition conditions. We have identified point defects in the form of oxygen interstitials that are present in Sc2O3 films, in significantly high concentrations, i.e., ∼10(18) cm(-3). These results show a correlation between the increase of oxygen interstitials and the increase in stress and optical absorption in the films. Sc2O3 films with the lowest stress and optical absorption loss at 1 µm wavelength were obtained when using a low oxygen partial pressure and low beam voltage.

Quasi-phase-matched second-harmonic generation of 532 nm radiation in 25 degrees -rotated, x-cut, near-stoichiometric, lithium tantalate fabricated by vapor transport equilibration.

Quasi-phase-matched second-harmonic generation of 532 nm radiation in 25 degrees -rotated, x-cut, near-stoichiometric lithium tantalate has been performed. Using a face-normal topology for frequency conversion applications allows scalable surface area to avoid surface and volume damage in high-power interactions. First-order, quasi-phase-matched second-harmonic generation was achieved using near-stoichiometric lithium tantalate fabricated by vapor transport equilibration. These crystals supported 1 J of 1064 nm radiation and generated 21 mJ of 532 nm radiation from a 7 ns, Q-switched Nd:YAG laser within a factor of 4.2 of expectation.

Vapor-transport equilibrated near-stoichiometric lithium tantalate for frequency-conversion applications.

Near-stoichiometric lithium tantalate (SLT) crystals were produced from congruent lithium tantalate by a vapor-transport equilibration process. Because of the resultant increase in photoconductivity and reduction in photogalvanism, the crystals showed no observable photorefractive damage at 514.5 nm up to the highest intensity used, 2 MW/cm2. The crystals also exhibited low green-induced infrared absorption, a Curie temperature of 693 degrees C, and a coercive field of 80 V/mm. The SLT samples were periodically poled with an 8-microm-period grating, permitting first-order quasi-phase-matched second-harmonic generation of 532-nm radiation at 43 degrees C. A 17-mm-long sample generated 1.6 W of continuous-wave output power at 532 nm for 50 h. With 150-ns pulses at a 100-kHz repetition rate in the same sample, 5-W average-power, 532-nm radiation was generated for 1000 h. No damage to the crystal and no aging effects were observed during these experiments.

Light-emitting diodes: a novel light source for phototherapy.

High intensity light-emitting diodes (LEDs) are being studied as possible light sources for the phototherapy of hyperbilirubinemic neonates. These power-efficient, low heat-producing light sources have the potential to deliver high intensity light of narrow wavelength band in the blue-green portion of the visible light spectrum, which overlaps the absorption spectrum of bilirubin (BR). We compared the efficacy between single LEDs of different color and then constructed a prototype phototherapy device using 300 blue LEDs. The efficacy of this device was compared with that of conventional phototherapy devices by measuring the in vitro photodegradation of BR in human serum albumin. When blue, blue-green, green, and white LEDs were compared, the blue light was the most effective in degrading BR by 28% of dark control, followed by blue-green (18% of control), and then white light (14% of control). Green light was the least effective (11% of control). The prototype device with three focused arrays, each with 100 blue LEDs, generated greater irradiance (> 200 microW.cm-2.nm-1) than any of the conventional devices tested. It also supported the greatest rate of BR photodegradation. We conclude that light from LEDs should be considered a more effective treatment for hyperbilirubinemia than light from presently used phototherapy devices. Furthermore, the unique characteristics of this light source may make it especially suitable for use in safe and lightweight home phototherapy devices.

Generation of tunable 187.9-196-nm radiation in beta-BaB(2)O(4): errata.

In Ref. 1, the first full sentence in the right-hand column of p. 1608 should read as: 'Although BBO is phase matchable down to 187 nm and shorter in this configuration without a very large (2-4 degrees ) change in theta (and hence in d(eff)), and B2 is also suitable to accommodate the phase matching, tunability below 187.9 nm becomes limited by the exponential increase in crystal absorption.'

Generation of tunable 187.9-196-nm radiation in beta-Ba(2)BO(4).

Tunable 187.9-196-nm vacuum-ultraviolet radiation was generated at room temperature in a beta barium borate crystal by sum-frequency mixing of Nd:YAG laser radiation and the second harmonic of a dye laser pumped by the second harmonic of the same Nd:YAG laser. By use of the advantageous noncollinear phase-matching configuration, a peak power of 1.3 kW was obtained at 194 nm with input power densities as low as 79MW/cm(2) for 1064-nm and 0.65MW/cm(2) for 237.3-nm radiation.

Mid-IR absorption in AgGaSe(2) optical parametric oscillator crystals.

We report new experimental results on the spectral, thermal, and orientational characteristics of stoichiometry-dependent mid-IR absorption in AgGaSe(2) crystals. In currently available material, this absorption poses an obstacle to the power scaling of the 2-µm-pumped AgGaSe(2) optical parametric oscillator (OPO). Preliminary experiments have indicated that this absorption could be substantially reduced by optimization of the process parameters during crystal growth and annealing. OPO output powers approaching 10 W may be achievable by using optimized material.

6.5-W, 532-nm radiation by cw resonant external-cavity second-harmonic generation of an 18-W Nd:YAG laser in LiB(3)O(5).

We report 6.5 W of TEM(00) cw 532-nm radiation generated by external resonant doubling in a LiB(3)O(5) crystal. An 18-W, cw, injection-locked single-frequency Nd:YAG laser was used to generate 532-nm second-harmonic output with a 3-dB heterodyne linewidth of 15 kHz.