Yang, HuiXu, S. J.Li, Q.Zhang, Jie2015-12-032015-12-0300036951http://hdl.handle.net/1885/16990At room temperature, by using a tuable broadband femtosecond laser as excitation source we observed second-harmonic generation (SHG) and nonlinear photoluminescence (NPL) in GaN film grown on sapphire simultaneously or individually. In addition to the observation of the resonance effect of the nonlinear response when the SHG is tuned to coincide with the near-band-edge emission, we carefully measured dependence of the SHG and NPL signals on polarization of the excitation light The results reveal that the reabsorptioo of the SHG photons with energies higher than the fundamental gap of GaN significantly contributes to generation of the efficient NPL signal.The work was supported by Competitive Earmarked Research Grant, Research Grants Council of HKSAR under Contract No. HKU-7036/03P and Research Grants of University of Hong Kong under Contract No. 10205780.4 pages© 2006 American Institute of Physics Publishing. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. The following article appeared in Applied Physics Letters and may be found at http://doi.org/10.1063/1.2197310 http://publishing.aip.org/authors/copyright-reuse http://www.sherpa.ac.uk/romeo/issn/0003-6951 Author can archive publisher's version/PDF (Sherpa/Romeo as of 3/12/2015).femtosecond lasertuable broadbandsecond-harmonic generation (SHG)GaN filmsapphirenonlinear photoluminescence (NPL)200610.1063/1.2197310