Abstract
Photonic crystal fibers (PCFs) are a special class of optical fibers with a periodic arrangement of microstructured holes located in the fiber’s cladding. Light confinement is achieved by means of either index-guiding, or the photonic bandgap effect in a low-index core. Ever since PCFs were first demonstrated in 1995, their special characteristics, such as potentially high birefringence, very small or high nonlinearity, low propagation losses, and controllable dispersion parameters, have rendered them unique for many applications, such as sensors, high-power pulse transmission, and biomedical studies. When the holes of PCFs are filled with solids, liquids or gases, unprecedented opportunities for applications emerge. These include, but are not limited in, supercontinuum generation, propulsion of atoms through a hollow fiber core, fiber-loaded Bose–Einstein condensates, as well as enhanced sensing and measurement devices. For this reason, infiltrated PCF have been the focus of intensive research in recent years. In this review, the fundamentals and fabrication of PCF infiltrated with different materials are discussed. In addition, potential applications of infiltrated PCF sensors are reviewed, identifying the challenges and limitations to scale up and commercialize this novel technology.
Highlights
Over the past several decades, the advances in optical fiber technology have undoubtedly improved and reshaped the field of telecommunication technologies [1,2,3,4]
The microcapillaries in the Photonic crystal fibers (PCFs) cladding provide a natural platform for their full or selective infiltration with optical liquids, which extends by far the degrees of freedom in terms of engineering the fiber’s key properties
One can design liquid-infiltrated PCF (LI-PCF) bend sensors based on the same physical principles, e.g., the bent-sensitive coupling between core mode and a single-capillary in a LI-PCF, which showed a linear sensitivity response of −1.2 nm/m−1 for a bend-radius up to 10.7 −1, albeit with high thermal sensitivity [137]
Summary
Over the past several decades, the advances in optical fiber technology have undoubtedly improved and reshaped the field of telecommunication technologies [1,2,3,4]. A hollow-core PCF was reported, which provides a combination of low losses (3.5 dB/km) and wide bandwidth (160 nm), employed to transmit 37 × 40 Gbps channels at 0.2904 m/ns, i.e., 1.54 ns/km faster than a conventional fiber This represents the first experimental demonstration of fiber-based wavelength-division multiplexing data transmission at a speed close to (99.7%) that of light in a vacuum [25]. Thanks to the wavelength dispersion of the effective cladding index, the infiltrated material can strongly interact with guided light via evanescent-field effects in a lab-on-a-fiber platform, not achievable in all-solid optical fibers.
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