Three-photon excitation of an upconversion random laser in ZnO-on-Si nanostructured films

We report the first observation, to our knowledge, of ultraviolet upconversion random laser (RL) emission from ZnO films excited by three near-infrared photons in the femtosecond regime. The nanostructured films of ZnO were fabricated on a silicon substrate using the Plasma Immersion Ion Implantation and Deposition method. The band-to-band excitation process led to RL emission with incoherent feedback, emitting light at approximate to 390 nm. RL emissions excited by one and two photons were also verified using the same pump geometry. The results are discussed and a comparison with previous studies is presented. (C) 2014 Optical Society of America