RESUMO
We perform a transmission experiment on a ZnO nanowire waveguide to study its transmission characteristics under nonlinear femtosecond-pulse excitation. We find that both the second harmonic and the photoluminescence couple into low-order waveguide modes of the nanowires but with distinctly different efficiencies. We measure the transmission spectrum of a single ZnO nanowire waveguide for near-UV light generated by interband recombination processes. The transmission spectrum allows us to determine the absorption edge of the excited nanowire and to study the temperature profile of the nanowire under femtosecond-pulse excitation.
Assuntos
Análise de Falha de Equipamento/métodos , Lasers , Teste de Materiais/métodos , Nanoestruturas/química , Nanotecnologia/instrumentação , Óxido de Zinco/química , Óxido de Zinco/efeitos da radiação , Análise de Falha de Equipamento/instrumentação , Teste de Materiais/instrumentação , Nanoestruturas/ultraestrutura , Nanotecnologia/métodos , Dispositivos Ópticos , Tamanho da Partícula , TemperaturaRESUMO
Silica nanowires provide strong mode confinement in a cylindrical silica-core/air-cladding geometry and serve a model system for studying nonlinear propagation of short optical pulses inside fibers. We report on the fiber diameter dependence of the supercontinuum generated by femtosecond laser pulses in silica fiber tapers with average diameters in the range of 200 nm to 1200 nm. We observe a strong diameter-dependence of the spectral broadening, which can be attributed to the fiber's diameter-dependent dispersion and nonlinearity. The short interaction length (less than 20 mm) and the low energy threshold for supercontinuum generation (about 1 nJ) make tapered fibers with diameters between 400 nm and 800 nm an ideal source of coherent white-light source in nanophotonics.
RESUMO
We use tapered silica fibers to inject laser light into ZnO nanowires with diameters around 250 nm to study their waveguiding properties. We find that high-order waveguide modes are frequently excited and carry significant intensity at the wire surface. Numerical simulations reproduce the experimental observations and indicate a coupling efficiency between silica and ZnO nanowires of 50%. Experimentally, we find an emission angle from the ZnO nanowires of about 90 degrees , which is in agreement with the simulations.