When femtosecond laser pulses are focused tightly into a transparent material, the intensity in the focal volume can become high enough to cause nonlinear absorption of laser energy. The absorption, in turn, can lead to permanent structural or chemical changes. Such changes can be used for micromachining bulk transparent materials. Applications include data storage and the writing of waveguides and waveguide splitters in bulk glass, fabrication of micromechanical devices in polymers, and subcellular photodisruption inside single cells.
Silica nanowires are a model system for the propagation of light at the nanoscale. Because of the tight confinement of light provided by these nanowires, nonlinear effects can be observed with pulse energies in the picojoule range, opening the door to a new class of nanophotonic devices. In addition, silica nanowires permit convenient coupling between macroscale and nanoscale. We will show how silica nanowires can be used to study waveguiding, mode propagation, and nonlinear effects in single ZnO nanowires.