Experimental study of photonic crystal fibers

Photonic crystal fibers (PCF) have been the focus of increasing scientific interest since the first workings in 1996. Although similar to a conventional optical fiber, PCF have a unique microstructure, consisting of an array of microscopic holes that runs along the entire length of the fiber. Such a structure is optically an excellent approximation of a two-dimensional photonic crystal. These holes suitably arranged can trap and guide light with in a central core (either hollow or made of solid glass). PCF supports two guidance mechanisms: total internal reflection (as a conventional optical fiber) when the core has a higher average refractive index than the holey cladding, and a two-dimensional photonic bandgap, when the core is hollow or filled with suitable material. The large design flexibility of the PCF allows to produce unusual optical properties. For example the guiding of light in a hollow core, the creation of highly nonlinear solid cores with anomalous dispersion in the visible, the generation of a broadband supercontinuum and the design of endlessly single-mode fibers. The optics of these structures have not yet been fully explored and also the possibilities of app lications in diverse areas (especially nonlinear optics, sensors, new fiber devices). We are studying experimentally some very interesting properties of the PCF guided modes for possible new sensors.