Development and Applications of Infrared Fiber Sensors

Dear Colleagues

Middle infrared (mid-IR) radiation in the spectral range 2–30μm has been used for sensing and treatment purposes in numerous fields of industry, scientific research, medicine, and environment monitoring. Sensing applications include pyrometry, thermal imaging for thermography, medical diagnostics, night vision, and IR-astronomy. In addition to the natural mid-IR radiation emitted by any objects above absolute zero (0°K) many artificial sources have been developed to generate more intensive radiation at selected wavelengths: mid-IR gaseous, solid-state lasers and quantum cascade lasers (QCL), mid-IR LED, plus high-temperature sources for broad IR-emittance spectra. These sources are used either for direct treatment in medicine or industry (like mid and high power IR-lasers) or, at low power, for mid-IR vibrational spectroscopy – the most informative for molecular analysis of various liquid and gaseous media used in chemical, petrochemical, pharma and food industry, biotechnologies, environment monitoring, medical diagnostics, scientific research, and more. In all these fields there is a mid-IR system that performs a measurement or sensing, and quite often it will be beneficial to incorporate it in mid-IR transmitting optical fiber to enable remote IR-sensing in situ and in real-time (and in vivo – in medicine).

Common fibers based on soft or silica-based glasses are opaque in the mid-IR, while there are many IR-materials used for fabrication of the several families of mid-IR waveguides: (1) Chalcogenide glass fibers, made of sulfide glass (e.g., As₂S₃), selenide glass (As₂Se₃), and based on the other chalcogen compositions; (2) fluoride glass fibers, made for example from ZBLAN (ZrF₄-BaF₂-LaFe₃-AlF₃-NaF); (3) polycrystalline fibers, made by extrusion from silver halides and their solid solutions (e.g., AgCl, AgBr, or AgClBr) or from thallium halides solid solutions (e.g., TlCl, TlBr, and TlI). In addition, there is a variety of flexible hollow waveguides of different types that also transmit mid-IR radiation, but for a much smaller numerical aperture (compared to IR-fibers) and transmission is lost quickly under bending.

Mid-IR fibers enable remote non-contact IR-imaging. Ordered bundles of mid-IR fibers can be used for IR-endoscopes, night vision, and mid-IR astronomy and industrial thermovision. Mid-IR fibers connected to spectrometers or tunable QCL lasers can carry out measurements in situ, in a remote location, and in real-time. This would be useful for the analysis of various materials at a distance. This would make it possible to perform reaction monitoring and process control in industry, perform studies of biological tissues and cells, perform medical diagnosis during operations, to carry out food composition analysis, to perform on-line monitoring of pollutions in water and air, to detect hazardous chemicals, and to run many other promising applications.

The goal of this Special Issue is to collect original manuscripts dealing with mid-IR fiberoptic sensors. These manuscripts may deal with new or improved mid-IR fibers plus a broad variety of mid-IR fiberoptic devices or systems. They may be focused on mid-IR fiber sensing in research and development for various pragmatic applications in the areas mentioned above and in other areas.

Research and developments in the following areas will be covered:

• Novel and improved mid-IR fibers for sensor applications.
• Novel and improved mid-IR-fiber-optic (F/O) sensor systems, including more sensitive, cheaper, and portable systems.
• Applications of mid-IR-F/O systems in pyrometry and thermal imaging, including endoscopic medical imaging.
• Applications of mid-IR-F/O spectral systems for chemical, petrochemical, pharma, and food industry in process control applications
• Application of spectroscopic mid-IR-F/O systems for on-line monitoring of water and air pollutions, for soil contamination in agriculture, etc.
• Applications of mid-IR-F/O systems for medical diagnosis of diseases, such as cancer, for biomedical research and in biotechnologies
• Applications of mid-IR-F/O systems in the military: chemical hazards

Prof. Abraham Katzir
Dr. Viacheslav Artyushenko
Guest Editors

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