Recent progress in the theory and applications of optical microfibers

Abstract

Recent progress in the understanding of the transmission properties of optical microfibers and their applications in photonics are reviewed. An optical microfiber (MF) is usually fabricated from a standard telecom optical fiber by drawing and has a diameter of ~ 1 micron. The interest in photonic devices fabricated of MFs is basically caused by two advantages of MFs compared to lithographically-fabricated waveguides: significantly smaller losses for a given index contrast and the potential ability of micro-assemblage in 3D. Eventually, these properties could make possible the creation of MF devices, which are significantly more compact than those fabricated lithographically. Furthermore, some MF-based devices possess functionalities, which are not possible or much harder to achieve by other means. The first part of this paper discusses methods of fabrication and transmission properties of MFs. The effects of microdeformations (in particular, the frozen-in microdeformations) and the adiabatically slow deformations of an MF are considered. The recently developed theory of adiabatic MF tapers is presented and applied to the investigation of transmission loss and evanescent field structure of MF tapers. The second part of the paper considers applications of MFs in photonics. Generally, MF devices and circuits can be created by the macro- and micromanipulation (bending, looping, coiling, twisting, crossing, etc.) of uniform and tapered MFs. The most straightforward application of an MF is using a regular MF taper as a sensor of an ambient medium. More advanced applications of MFs include MF loop resonators and MF circuits assembled by wrapping an MF around a cylindrical rod. It is believed that further exploration of MF properties and possible applications will give rise to the invention and practical realization of innovative MF photonic devices with unique functionalities.