Single Crystal Fibers: Diversified Functional Crystal Material

Abstract

Single crystal fibers (SCF) are considered to be a combination of bulk crystals and conventional fibers, thereby possessing the stable physical and chemical properties accompanied with excellent waveguide properties. This paper gives a detailed introduction to the development history of single crystal fibers, including the evolution of the growth technique and the optimization of the growth process. Laser-heated pedestal growth (LHPG) and Micro-pulling-down (μ-PD) methods are considered to be the most widely used growth techniques for growing single crystal fibers, and the advantages of the two methods are also introduced in detail. The second part of this paper describes the characterization of single crystal fibers, including diameter fluctuation, crystal quality and optical losses. A series of cladding approaches for SCF, such as magnetron sputtering, sol-gel, liquid phase epitaxy, co-drawing LHPG, ion implantation and micro-structure cladding will be reviewed. In addition, the research status of single crystal fiber laser and single crystal fiber sensor are also summarized in view of the current research foundation.

Tough Gel-Fibers as Strain Sensors Based on Strain–Optics Conversion Induced by Anisotropic Structural Evolution

“…In addition, it is worth mentioning that a tiny -− GN Fiber 16 14 0.94 (40 mg) could even firmly lift a 500 g weight (almost 12500 times its own weight) and almost return to its initial length after weight removal (Figure 5e). As expected, the resultant GN-Fibers showed excellent elongation and stretchability in comparison to conventional silica (<1%) 10,11 or PMMA optical fiber (∼3%), 40,41 giving them great prospects as large strain sensors. Due to the densely packed and stretching induced aligned cross-linking networks, GN-Fibers displayed much higher tensile strength and modulus in comparison other gel systems or PDMS optical fibers (tensile strength ≤0.3 MPa or modulus ≤0.5 MPa) 42 (Figure 5f).…”

“…The rapid growth of wearable smart devices has resulted in a huge demand for smart flexible sensors, especially those applicable to the human body. , Particularly, fibrous strain sensors remain appealing due to their large specific surface area, good flexibility, and facile assembly properties. , So far, various efforts have been devoted toward electrical-mediated fibrous strain sensors, which respond to mechanical deformations via resistance or capacitance variations. , However, the electromagnetic interference (EMI) and electrical safety issues (such as current leakage) of such materials have restricted their further applicability . Optical mediation based fibrous sensors possess inherent immunity to EMI and intrinsic electric safety as well as excellent multiplexing capabilities, showing great prospects as wearable strain sensors. , Among them, silicon-based inorganic or amorphous isotropic plastic (such as poly­(methyl methacrylate)) optical fibers with good transparency are very common. − In combination with Bragg grating technology, such optical fibers have achieved strain sensing via shifting of the Bragg wavelength arising from the strain–optics and geometric effects. , However, they have received limited use due to some imperfections such as brittleness, only allowing for detection within a narrow range of strain (ε < 1%). In addition, polydimethylsiloxane-based elastomer optical fibers have shown a large strain range (∼200%) but seldom sustain high stress detection ( E > 1 MPa) because their amorphous isotropic structure quickly fractures upon high tensile loading .…”

All-solid anti-resonant single crystal fibers

“…As a combination of bulk crystals and traditional fibers, single crystal fibers (SCFs) inherited the advantages of crystals, including high melting points, high thermal conductivity, high laser damage threshold, and good mechanical properties. They also carried the advantages of conventional optical fibers, such as having a large aspect ratio and specific surface area, both of which remarkably improve their thermal management capabilities [1,2]. SCFs have been widely used in many fields due to their excellent comprehensive properties.…”

Fabrication and Application of Single Crystal Fiber: Review and Prospective

“…Some applications, such as the fiber laser market, have a characteristic market size over 1 trillion dollars. [ 1 ] Comprehensive review articles have been focused on the single crystal materials development, [ 2–4 ] functional crystal materials, [ 5 ] and the perspective on the fabrication of molten core optical fiber. [ 6 ] In the literature, particular interests are placed on the sapphire fiber cladding development [ 7 ] and sapphire shaped crystals.…”