Multiphoton absorption induced amplified spontaneous emission from biocatalyst-synthesized ZnO nanorods

Multiphoton absorption-induced photoluminescence and amplified spontaneous emission (ASE) have been observed from ZnO nanorod arrays upon near-infrared excitation (lambda(exc)similar to 800 nm). A low threshold of similar to 12 mJ/cm(2) was demonstrated for the ASE process. The ultraviolet emission can be attributed to the recombination of carriers coexcited by the processes of three-photon and off-resonant two-photon absorption, which was confirmed by the excitation wavelength-dependent experiments. Additionally, it has been observed that the processes of ASE and second harmonic generation in ZnO nanorods appear to enhance each other when the excitation wavelength approaches the resonant wavelength for two-photon absorption. (c) 2008 American Institute of Physics.