There is a special reason for reviewing this book at this time: it is the 50th edition of a compendium that is known and used frequently in most chemical and physical laboratories in many parts of the world. Surely, a publication that has been published for 56 years, withstanding the vagaries of science in this century, must have had something to offer. There is another reason: while the book is a standard fixture in most chemical and physical laboratories, including those in medical centers, it is not as frequently seen in the laboratories of physician's offices (those either in solo or group practice). I believe that the Handbook can be useful in those laboratories. One of the reasons, among others, is that the various basic items of information it offers may be helpful in new tests, either physical or chemical, which are continuously being published. The basic information may relate

Handbook of Chemistry and Physics

A topical review of numerical and experimental studies of supercontinuum generation in photonic crystal fiber is presented over the full range of experimentally reported parameters, from the femtosecond to the continuous-wave regime. Results from numerical simulations are used to discuss the temporal and spectral characteristics of the supercontinuum, and to interpret the physics of the underlying spectral broadening processes. Particular attention is given to the case of supercontinuum generation seeded by femtosecond pulses in the anomalous group velocity dispersion regime of photonic crystal fiber, where the processes of soliton fission, stimulated Raman scattering, and dispersive wave generation are reviewed in detail. The corresponding intensity and phase stability properties of the supercontinuum spectra generated under different conditions are also discussed.

Supercontinuum generation, photonic crystal fiber

A review on recent advances in the applications of surface-enhanced Raman scattering in analytical chemistry

We describe the history, guiding mechanism, recent advances, applications, and future prospects for hollow-core negative curvature fibers. We first review one-dimensional slab waveguides, two-dimensional annular core fibers, and negative curvature tube lattice fibers to illustrate the inhibited coupling guiding mechanism. Antiresonance in the glass at the core boundary and a wavenumber mismatch between the core and cladding modes inhibit coupling between the modes and have led to remarkably low loss in negative curvature fibers. We also summarize recent advances in negative curvature fibers that improve the performance of the fibers, including negative curvature that increases confinement, gaps between tubes that increase confinement and bandwidth, additional tubes that decrease mode coupling, tube structures that suppress higher-order modes, nested tubes that increase guidance, and tube parameters that decrease bend loss. Recent applications of negative curvature fibers are also presented, including mid-infrared fiber lasers, micromachining, and surgical procedures. At the end, we discuss the future prospects for negative curvature fibers.

Negative curvature fibers

This review presents an overview of “Lab on Fiber” technologies and devices with special focus on the design and development of advanced fiber optic nanoprobes for biological applications. Depending on the specific location where functional materials at micro and nanoscale are integrated, “Lab on Fiber Technology” is classified into three main paradigms: Lab on Tip (where functional materials are integrated onto the optical fiber tip), Lab around Fiber (where functional materials are integrated on the outer surface of optical fibers), and Lab in Fiber (where functional materials are integrated within the holey structure of specialty optical fibers).

This work reviews the strategies, the main achievements and related devices developed in the “Lab on Fiber” roadmap, discussing perspectives and challenges that lie ahead, with special focus on biological sensing applications.

Lab on Fiber Technology for biological sensing applications

We report the first extruded tellurite antiresonant hollow core fibers (HC-ARFs) aimed at the delivery of mid-infrared (Mid-IR) laser radiation. The preform extrusion fabrication process allowed us to obtain preforms with non-touching capillaries in a single step, hence minimizing thermal cycles. The fibers were fabricated from in-house synthetized tellurite glass (containing Zn, Ba and K oxides) and co-drawn with a fluorinated ethylene propylene (FEP) polymer outer layer to improve their mechanical properties and protect the glass from humidity. The fabricated HC-ARFs transmit in the Mid-IR spectral range from 4.9 to 6 µm. We measured losses of ∼8.2, 4.8 and 6.4 dB/m at 5 µm, 5.6 µm and 5.8 µm, respectively in two different fibers. These losses, which are dominated by leakage mostly arising from a non-uniform membrane thickness, represent the lowest attenuation reported for a tellurite-based HC-ARF to date. The fibers present good beam quality and an M2 factor of 1.2. Modelling suggests that by improving the uniformity in the capillary membrane thickness losses down to 0.05 dB/m at 5.4 µm should be possible, making this solution attractive, for example, for beam delivery from a CO laser.

Extruded tellurite antiresonant hollow core fiber for Mid-IR operation

A high sensitivity refractive index sensor based on the combination of mechanically induced long period gratings (LPG) and fiber tapers was developed for real-time fuel quality analysis. The sensor was built in a Mach–Zehnder configuration by employing a pair of in-series gratings. In order to enhance sensor sensitivity, the region between both LPGs was tapered down from 125 to 10 µm. The system was tested by measuring water concentration in ethanol and ethanol concentration in commercial gasoline. The tapered sensor has shown an average sensitivity of 930 nm/RIU, 18 times higher than the non-tapered version. The resolution limit of the system using spectral interrogation was estimated to be 0.06% of ethanol dissolved in gasoline. For the purpose of real-time monitoring, an interrogation system based on white light interferometry (WLI) and virtual instrumentation was employed to evaluate ethanol evaporation in water, avoiding the use of spectral analysis. The WLI system, using phase tracking techniques, enabled us to record the evolution of the ethanol concentration in water with a resolution of 0.005% (v/v).

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High sensitivity LPG Mach–Zehnder sensor for real-time fuel conformity analysis

We analyze the dependence of the electromagnetic properties of wire array metamaterial media on the choice of metal, and identify promising material combinations for use in the near and mid infrared. We propose a figure of merit for the metal optical quality and consider it as a function of several parameters, such as material loss, wavelength of operation and wire diameter. Accordingly, we select promising material combinations, based on optical quality and fabrication compatibility, and simulate the loss of the quasi-TEM mode, for different wavelengths between 1 and 10 μm. We conclude that wire arrays are unlikely to deliver on their many promises at 1 μm, but should prove useful beyond 3 μm.

Metal selection for wire array metamaterials for infrared frequencies.

Mid-infrared absorption spectroscopy for gas detection is reported in this study using a quantum cascade laser (QCL) coupled with a custom-made tellurite hollow-core antiresonant fiber (HC-ARF). The HC-ARF is fabricated from tellurite glass by extrusion and subsequent fiber drawing. The QCL emitting at 5.26 µm is coupled into the 21-cm long HC-ARF. As a proof-of-concept, this spectroscopic system is demonstrated for nitric oxide (NO) detection by exploiting its strong absorption line at 1900.08 cm-1. By quickly filling gas mixtures into the HC-ARF, we first conduct direct absorption spectroscopy of NO and achieve a noise equivalent absorption (NEA) of 2.1 × 10-5 cm-1. Besides, we also conduct wavelength modulation spectroscopy to improve sensing performance. A minimum detection limit of 6 ppb NO is achieved at the integration time of 30 s, corresponding to 1.0 × 10-7 cm-1 in NEA. The HC-ARF is tested to show a response time of only 0.3 s when applying a pressure difference of 11 kPa between the two fiber ends. Such a tellurite HC-ARF-coupled QCL spectroscopic system makes it attractive for developing optical gas sensors with compact size, fast response, and high sensitivity.

Tellurite Hollow-Core Antiresonant Fiber-Coupled Quantum Cascade Laser Absorption Spectroscopy

Metamaterials for the mid-infrared spectrum require subwavelength meta-structures with dimensions of a few hundreds of nanometers. Fabrication via fiber drawing is challenging as the Plateau–Rayleigh instability caused by interfacial surface tension between the liquid metal and the dielectric during the drawing leads to fluctuation of the structure, preventing drawing of uniform wire array structures with such dimensions. Here, conventional fiber drawing technique is employed in the fabrication of wire array metamaterial fibers containing tin wires embedded in soda–lime glass. Plateau–Rayleigh instabilities ensuing detrimental deformations on submicron metallic structures are minimized through the selection of materials with favorable rheological properties and the optimization of the drawing parameters. Uniform wire array structures with wire diameter and spacing as small as 143 and 286 nm, respectively, are demonstrated. The application of this established fabrication process represents a large-volume and low-cost alternative for the production of hyperbolic metamaterials. The new metamaterial fibers achieved open up a range of exciting applications at mid-infrared frequencies, such as lifetime engineering and super-resolution imaging.

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Juliano G. Hayashi

Papers

Extruded tellurite antiresonant hollow core fiber for Mid-IR operation

High sensitivity LPG Mach–Zehnder sensor for real-time fuel conformity analysis

Metal selection for wire array metamaterials for infrared frequencies.

Tellurite Hollow-Core Antiresonant Fiber-Coupled Quantum Cascade Laser Absorption Spectroscopy

Fabrication of Soft-Glass-Based Wire Array Metamaterial Fibers for Applications at Infrared Frequencies