The authors have studied the diffusion of carriers in GaN by photoluminescence and pump-probe spectroscopy in an InGaN∕GaN single quantum well sample at 300K. The sample was designed with the quantum well buried beneath a thick (240nm) GaN layer. When pumping above the GaN band gap, the carriers that are excited in the GaN layer diffuse to the InGaN quantum well before recombining radiatively. The hole diffusion coefficient was determined from the rise time of the quantum well photoluminescence, together with pump-probe experiments. A value of 2.0±0.4cm2∕s is found for the diffusion coefficient.

Zn-Ni-TiO 2 nanocomposites with various amounts of TiO 2 were successfully prepared by electroplating method on copper substrates using an acidic solution with TiO nanoparticles in 2 suspension. The composition and morphology of the composite coatings were characterised respectively using of scanning electron microscope (SEM), energy dispersive spectrometer and elemental mapping analysis system. The microhardness of the nanocomposite coatings was investigated. The antibacterial activity of Zn-Ni-TiO 2 nanocomposites films was studied against Gram positive (Staphylococcus aureus) and Gram negative (Escherichia coli) bacteria. Antimicrobial property increased upon the increase in the TiO 2 concentration. In addition, the antimicrobial property was more pronounced with the positive bacteria than the negative one. These results demonstrated the microbiocidal property of TiO 2 , so Zn-Ni-TiO 2 coatings have great potential applications in reducing biofouling formation in devices that suffer from biofouling problems.

We report on two pulse, degenerate four-wave mixing ͑DFWM͒ measurements on shallow In x Ga 1−x N / GaN multiquantum wells ͑MQWs͒ grown on sapphire substrates. These reveal pulse length limited signal decays. We have found a 10:1 resonant enhancement of the DFWM signal at the excitonic transition frequencies which thereby give a sharp discrimination of the discrete excitonic contributions within the featureless distribution seen in absorption spectra. The exciton resonances have peak positions, which yield good overall agreement with a full k · p model calculation for the quantum well ͑QW͒ energy levels and optical transition matrix elements. In x Ga 1−x N / GaN MQWs generally exhibit strongly inhomogeneously broadened excitation spectra due to indium fluctuation effects; this approach therefore affords a practical method to extract information on the excited excitonic states not available previously.

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For the first time, to the best of our knowledge, a green (520 nm) and amber (592 nm) light emitting diode-pumped Nd:YAG laser is reported. The laser oscillator is a stable semi-planar resonator with a total length of 140 mm. The green (amber) light emitting diode-pumped laser produced a 107 (52) µJ laser energy, at 2.6 (0.7) J electrical pump energy. The oscillator operated at a low repetition rate (about 0.1 Hz) in free-running mode, where the laser spikes were initiated about 210-280 µs after the leading edge of the pump pulse. Moreover, the transverse mode profiles of the resonator, pump absorption efficiency, and optical gain have been studied in some detail.