Manifestation of hexagonal-like structure in the second-order nonlinear effects in the GaN nanocrystallites |
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Authors: | I V Kityk W Gruhn B Sahraoui |
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Institution: | a Institute of Physics, University of Technology, Ul. Podchorazych 1, Krakow, Poland;b Laboratory POMA, University of Angers, UMR CNRS 6106, UFR Sciences 2, Boulevard Lavoisier, 49045, Angers Cedex 01, France |
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Abstract: | Contribution of the hexagonal-like structural components to the photoinduced second harmonic generation (SHG) in GaN large-sized nanocrystallites (with sizes about the 10–30 nm) incorporated into the polyvinylalcohol photopolymer matrices is revealed. The SHG measurements were done using pulsed Nd:YAG laser beam (λ=1.06 μm; pulse duration τ=15–50 ps, laser power about 30 MW) as a fundamental ones and a picosecond nitrogen pulsed laser (P=10 MW; λ=0.377 μm; pulse time duration τ=10–25 ps) as a photoinducing one. We have found that with increasing pumping power density the SHG output signal increases and achieves its maximum value for the power density about 2.6 GW/cm2 per pulse. The maximal output photoinduced SHG signal was achieved for parallel directions of the pumping and fundamental beam polarizations. The maximal values of the second-order nonlinear susceptibilities were equal to about 1.09 pm/V. We have observed an increase of the output SHG below 30 K and for pump-probe delaying time about 18 ps. Substantial contribution to the SHG of wurtzite-like (hexagonal) structural fragments is shown. |
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Keywords: | Second harmonic generation GaN Nanocrystals |
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