We report on ZnGeP2 and AgGaS2 crystal growth and improvement of optical transparency by annealing. Good optical
quality single-crystal samples with size up to 5×5×20 mm3 were cut from our ingots, allowing to demonstrate efficient
optical parametric oscillation with ZnGeP2 and to carry out first difference-frequency generation experiments with
AgGaS2.
The use of ZnO template layers grown Pulsed Laser Deposition (PLD) has been seen to produce dramatic improvements in the surface morphology, crystallographic quality and optical properties of ZnO layers grown on c-sapphire substrates by Metal Organic Chemical Vapor Deposition. This paper provides complementary details on the PLD-grown ZnO template properties.
We report on the development of a compact laser source devoted to airborne countermeasures. Several spectral lines are
emitted simultaneously by the use of optical parametric oscillators (OPOs) pumped by a high repetition rate near-IR
pulsed laser. The general architecture of the source is designed to locate the pump laser inside the aircraft while the
conversion stages are positioned close to the orientation turret. In this purpose, OPOs whose typical volume is less than
100 cm3 are optimized to produce the required average power under high repetition rate pumping and the emitted output
beam quality is typically 1.5 diffraction limited. The selection of the proper nonlinear material for each OPO is also a
critical issue. ZnGeP2 (ZGP) is currently the material of choice to operate where conventional nonlinear materials
strongly absorb. In this context, the ZGP crystal growth has been investigated. The first samples with a good optical
quality have been obtained and the preliminary results are discussed. In addition to countermeasure applications, we also
discuss other Defence & Security issues that can be addressed by miniature OPOs such as biological and chemical
detection.
The incorporation and electrical activity of nitrogen as an acceptor in ZnO has been investigated. Low temperature Metalorganic Vapor Phase Epitaxy (MOVPE) growth, using diallylamine as nitrogen precursor, yields to incorporation of nitrogen in the range 1016-1021 cm-3. The electrical activity of nitrogen is demonstrated through the increased compensation of the natural donors with doping level. Close Space Vapor transport (CSVT) and Chemical Vapor Transport (CVT) are found to be less efficient for nitrogen incorporation. This suggests that the use of high temperature growth is a limiting factor for nitrogen incorporation in ZnO. Ex-situ techniques have been tried for both electrical activation and nitrogen incorporation in ZnO. High pressure annealing under oxygen pressure shows a conversion to p-type on nitrogen doped samples grown by MOVPE. Finally, diffusion of nitrogen was carried out on undoped MOVPE layers under high pressure conditions stemming from the decomposition of NH4NO3. Conversion to p-type conductivity was observed in a systematic way with measured hole concentrations up to 6.5.1017 cm-3. These results suggest that ex-situ treatment can be a practical way to realize p-type ZnO layers.
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