Enabling Architectures and Technologies for Next-Generation Fiber Devices

In recent years, we have developed a new materials processing approach that enabled the realization of sophisticated devices in fibers. At the heart of our approach is the ability to arrange disparate materials into geometrically complex preforms which are thermally scaled to yield microscopically featured fibers at kilometer lengths. By judicious choice of materials and process conditions that mitigate surface energy effects, unprecedentedly complex cross section geometries have been realized. One of the important outcomes of our effort is the emergence of the first fiber metal-insulator-semiconductor (M-I- S) device as well as many other active and passive fiber devices. The goal of this proposed effort is to identify paths towards vastly improving the performance characteristics of these unique fiber devices. Specifically, this project will establish three important foundational capabilities in fibers. First, we will build on recent results that demonstrate the first fiber-drawn Schottky junction made of microscopic domains of a compound semiconductor ZnSe synthesized in the draw process! We will explore methods to control the chemical reaction process leading to the formation of compound semiconductors to enable novel in-fiber heterostructure junctions.

Second, guided by our acquired knowledge in multimaterial fiber drawing at low temperatures, we will draw fibers composed of high temperature materials such as silicon and GaAs. High temperature semiconductor materials are of particular interest because their electronic and optoelectronic properties surpass those of the low-temperature materials that we currently employ in fibers. We will also explore methods for doping these materials and creating in-fiber pn junctions. Third, fibers with microscopic hollow channels have recently been fabricated with electrically conducting walls, allowing for high electric fields to be established across the hollow domains. We propose to fill these channels with liquid crystals (LCs) which in turn can be switched by the electric fields. Using these microfluidic LC channels, we will create surface emitting fiber lasers that can be rapidly switched. Moreover, we will design omnidirectional fiber lasers with controlled angular emission properties that will pave the way to visible and IR emissive fabrics.