Multimaterial Fibers

Abstract

Recent progress in combining multiple materials with disparate optical, electronic, and thermomechanical properties monolithically in the same fiber drawn from a preform is paving the way to a new generation of multimaterial fibers endowed with unique functionalities delivered at optical fiber length scales and costs. A wide range of unique devices have been developed to date in fiber form‐factor using this strategy, such as transversely emitting fiber lasers, fibers that detect light, heat, or sound impinging on their external surfaces, and fibers containing crystalline semiconductor cores. Incorporating such fibers in future fabrics will lead to textiles with sophisticated functionality. Additionally, long‐standing issues in traditional applications of optical fibers have been addressed by multimaterial fibers, such as photonic bandgap guidance in hollow‐core all‐solid‐cladding fibers and imparting mechanical robustness to soft‐glass mid‐infrared fibers. We review recent progress in this nascent but rapidly growing field and highlight areas where growth is anticipated. Furthermore, the insights emerging from this research are pointing to new ways that the fiber drawing process itself may be leveraged as a fabrication methodology. In particular, we describe recent efforts directed at appropriating multimaterial‐fiber drawing for chemical synthesis and the fabrication of nanostructures such as nanowire arrays and structured nanoparticles.

Controlled Sub‐Micrometer Hierarchical Textures Engineered in Polymeric Fibers and Microchannels via Thermal Drawing

“…Recent breakthroughs in the thermal drawing process-the same technique used to fabricate conventional optical fibers-have also enabled to integrate complex materials architectures and functionalities not only locally but along the entire fiber length of tens of kilometers. [1][2][3] The thermal drawing process consists in heating above the glass transition temperature and pulling at relatively high viscosity (typically 10 4 to 10 7 Pa s) a macroscopic preform made out of a glass, typically silica, or a thermoplastic. Pulling a fiber at such a high viscosity compared to solution-based processes has the key advantage of enabling a control over the interplay between the viscosity, internal stresses, and surface tension.…”

“…More recently, this technique was shown to also enable the fabrication of multimaterial fibers that integrate polymers or glasses but also metals, inorganic semiconductors, or nanocomposites, uniformly integrated in prescribed positions along the fiber length. [1][2][3] Such advanced multimaterial fiber systems have been proposed for applications, in optics [16][17][18][19] and imaging, [20][21][22] optoelectronics, [23][24][25][26] sensing, [27,28] energy harvesting, [29,30] bioengineering, [31,32] health care or smart textiles. [21,33,34] So far however, the use of micro-and sub-micrometer surface textures to impart fibers with novel functionalities has not been exploited.…”

Hybrid Optical Fibers – An Innovative Platform for In‐Fiber Photonic Devices

“…The fi rst step in thermal drawing multimaterial HOFs (Figure 2 a) is the fabrication of the macroscopic preform, which contains the complex structure as well as the relevant materials (or their precursors). Different materials are assembled in the preform via the thin-fi lm rolling technique for cylindrical fi bers, [ 25,29,30 ] via the stack-and-draw method commonly used for MOFs, [ 15,31 ] via extrusion, [ 24,32,33 ] or by machining and assembling materials together using consolidation in a vacuum oven or in a hot press. [ 25,34,35 ] The resulting preform assembly forms a solid object that represents the macroscopic version of the targeted fi ber.…”

“…They have been extensively used in photonic crystal fi bers owing to their large refractive index [ 29,30 ] and strongly nonlinear properties. [ 24,32,108,109 ] They are also used for IR fi bers and in particular Multimaterial IR fi bers, as pure chalcogenide glasses can exhibit extremely low absorption in different parts of the IR spectrum depending on their composition. [ 109,110 ] In the visible, however, chalcogenides can be highly absorbing and materials such as Selenium can exhibit high charge (hole) mobilities in its crystalline hexagonal phase.…”

“…Other fi ber-based devices more remote from the fi eld of photonics, or looking at highly localized modifi cation on the fi ber tip for example, are discussed in other publications. [23][24][25][26] Rather than giving detailed insights into the various physical principles, [ 27,28 ] we present the different devices and their functionality with respect to the incorporated material, revealing the potential of the research fi eld of hybrid optical fi bers in general. As the entire fi eld was triggered by disruptive improvements in fabrication technology, the review begins with a brief description of the three main fabrication techniques that involve the thermal drawing of a complete fi ber device or a fi ber template post-processing using deposition or fi lling, all allowing to incorporate "nontraditional" materials into fi bers.…”