Nonlinear optics in optical slot-microfiber

Optical microfibers (MFs) are fabricated by adiabatically stretchingconventional optical fiber thus preserving the original optical fiberdimensions at their input/output pigtails, allowing ready splicing tostandard fibers. MFs diameters, close to the wavelength of propagatinglight, are of interest for a range of emerging fiber optic applications sincethey offer a number of enabling optical and mechanical propertiesincluding large evanescent fields, high nonlinearity, extreme flexibilityand configurability, low-loss interconnection to other optical fibers andfiberized components. However, its application will still be limitedbecause MFs are generally circular symmetric. Here we review one kindof novel MF with non-circular symmetric geometry, the fiberized slotwaveguides (FSW) or slot-microfiber (slot-MF), which is a highlybirefringent engineered MF with nano-scale slots where light field can beconfined and enhanced. The slot-MF has the advantages of both a MFand a slot waveguide. Taking advantage of the unique and flexiblegeometry, a number of significant linear and nonlinear characteristics canbe realized including high birefringence, ultra-flattened and lowdispersion profiles, and strong surface second-order nonlinearity.