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An Introduction to Photonic Crystal Fiber: Modal and Structural Parameters
Published in Narendra Kumar, Bhuvneshwer Suthar, Advances in Photonic Crystals and Devices, 2019
The central defect is surrounded by several air holes in a triangular/hexagonal/circular lattice (Birks et al. 1997; Knight et al. 1998). The index guiding mechanism depends on the contrast in the refractive indices between the core and the cladding, similar to conventional fibers. Air-guiding PCFs possess a periodic structure of air holes with a hollow central defect. The PBG effect occurs only when there exists a huge contrast in refractive indices between the core and the cladding of a microstructured fiber (Russell 2007). With respect to the design flexibility, hollow-core PCF provides low-loss guidance by limiting the conventional propagation technique (i.e., total internal reflection [TIR]) in a single-mode regime (Russell 2007). Similarly, solid-core PCF provides a smaller mode volume, which allows for higher effective nonlinearities and higher birefringence (Russell 2007). Moreover, irrespective of solid and hollow cores, PCFs can perform single-mode operations over a wide range of wavelengths with considerable diminution in chromatic dispersion (Aristizabal et al. 2006; Saitoh and Koshiba 2005). Due to such tunable configurational properties of PCFs, they are now implemented in multitude of sensing schemes based on the surface plasmon resonance (Figure 1.2).
Introduction to Optical Fiber Sensors
Published in Krzysztof Iniewski, Ginu Rajan, Krzysztof Iniewski, Optical Fiber Sensors, 2017
Since the first demonstration of the microstructured fiber (MOF) in 1996 (photonic crystal fiber), it has caused enormous attention and excitement in the photonics community. The unique features of the fiber such as the light guidance, dispersion properties, endlessly single-mode nature, higher birefringence, and enhanced nonlinear effects have led MOFs being applied in many fields such as in optical communications, nonlinear optics, and sensing. Unlike conventional fibers, MOFs can be optimized for a large range of applications by tailoring the size, number, and the geometry of the air holes that form the confining microstructure around the core region. This led to a large interest among researchers to exploit the advantages and use MOF-based sensors in a variety of applications. In a short span of time since the first introduction of the MOF, a variety of MOFs are reported ranging from silica to polymer for applications ranging from environmental sciences to medicine, industry, and astronomy [20]. Fascinating physics and applications of MOFs are still of great interest among researchers. Some of the sensing applications of photonic crystal fibers are presented in Chapter 6 (Figure 1.6).
Design and Fabrication of Optical and Fiber-Optic Humidity Sensors
Published in Ghenadii Korotcenkov, Handbook of Humidity Measurement, 2018
However, beyond these specific applications, a large number of new fibers is nowadays available with different materials and geometries. Some of them can be customer made. Among the available optical fibers, one can distinguish (Lecler and Meyrueis 2012): The single-mode and multimodes optical fibers, with core diameter from 5 µm to the millimeter.The polarization maintaining fibers (generally with an elliptical core).The step index fibers and the graded index ones with several index profiles.The fibers whose core and cladding are in silicate or polymer (plastic). A lot of improvements have been achieved concerning plastic fiber (Peters 2011): loss decrease, temperature resistance, homogeneity, and so on.The silica fibers with several possible doping (germanium, fluorine, alumina, erbium, etc.).The microstructured fiber in the radial direction such as the photonic crystal fibers.The Bragg grating fiber (with a periodic modulation of the RI in the longitudinal direction).
Surface plasmon resonance sensor for refractive index and temperature measurement based upon a double-sided polished microstructured fiber
Published in Instrumentation Science & Technology, 2023
Xin Yan, Yang Zhao, Tonglei Cheng, Rao Fu
The sensor was fabricated as shown in Figure 3a. The preform is stretched into microstructured fiber[13] and the double-sided polished microstructured fiber is prepared.[14] A gold film is deposited using the chemical vapor method, and the polydimethylsiloxane is cured.[15] Next, a silver film is deposited upon the lower polished plane.[16] Lastly, several techniques may be used to deposit graphene on silver surfaces.[17]