The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

http://ieeexplore.ieee.org/iel5/6354/16969/00781867.pdf

Photonic crystals

Sensing technology has been widely investigated and utilized for gas detection. Due to the different applicability and inherent limitations of different gas sensing technologies, researchers have been working on different scenarios with enhanced gas sensor calibration. This paper reviews the descriptions, evaluation, comparison and recent developments in existing gas sensing technologies. A classification of sensing technologies is given, based on the variation of electrical and other properties. Detailed introduction to sensing methods based on electrical variation is discussed through further classification according to sensing materials, including metal oxide semiconductors, polymers, carbon nanotubes, and moisture absorbing materials. Methods based on other kinds of variations such as optical, calorimetric, acoustic and gas-chromatographic, are presented in a general way. Several suggestions related to future development are also discussed. Furthermore, this paper focuses on sensitivity and selectivity for performance indicators to compare different sensing technologies, analyzes the factors that influence these two indicators, and lists several corresponding improved approaches.

A Survey on Gas Sensing Technology

Infrared spectroscopy in the 3-20 μm spectral window has evolved from a routine laboratory technique into a state-of-the-art spectroscopy and sensing tool by benefitting from recent progress in increasingly sophisticated spectra acquisition techniques and advanced materials for generating, guiding, and detecting mid-infrared (MIR) radiation. Today, MIR spectroscopy provides molecular information with trace to ultratrace sensitivity, fast data acquisition rates, and high spectral resolution catering to demanding applications in bioanalytics, for example, and to improved routine analysis. In addition to advances in miniaturized device technology without sacrificing analytical performance, selected innovative applications for MIR spectroscopy ranging from process analysis to biotechnology and medical diagnostics are highlighted in this review.

Advances in Mid-Infrared Spectroscopy for Chemical Analysis.

Volatile organic compound (VOC) detection is a topic of growing interest with applications in diverse fields, ranging from environmental uses to the food or chemical industries. Optical fiber VOC sensors offering new and interesting properties which overcame some of the inconveniences found on traditional gas sensors appeared over two decades ago. Thanks to its minimum invasive nature and the advantages that optical fiber offers such as light weight, passive nature, low attenuation and the possibility of multiplexing, among others, these sensors are a real alternative to electronic ones in electrically noisy environments where electronic sensors cannot operate correctly. In the present work, a classification of these devices has been made according to the sensing mechanism and taking also into account the sensing materials or the different methods of fabrication. In addition, some solutions already implemented for the detection of VOCs using optical fiber sensors will be described with detail.

/pdf/volatile-organic-compound-optical-fiber-sensors-a-review-3tvel5h6fs.pdf

Volatile Organic Compound Optical Fiber Sensors: A Review

In general, in one aspect, the invention features systems, including a photonic crystal fiber including a core extending along a waveguide axis and a dielectric confinement region surrounding the core, the dielectric confinement region being configured to guide radiation along the waveguide axis from an input end to an output end of the photonic crystal fiber. The systems also includes a handpiece attached to the photonic crystal fiber, wherein the handpiece allows an operator to control the orientation of the output end to direct the radiation to a target location of a patient.

Photonic crystal fibers and medical systems including photonic crystal fibers

An integrated midinfrared sensing system for trace level (ppb) gas analysis combining a quantum cascade laser with an emission frequency of 10.3μm with a frequency matched photonic band-gap hollow core waveguide has been developed, demonstrating the sensing application of photonic band-gap fibers. The photonic band-gap fiber simultaneously acts as a wavelength selective waveguide and miniaturized gas cell. The laser emission wavelength corresponds to the vibrational C–H stretch band of ethyl chloride gas. This sensing system enabled the detection of ethyl chloride at concentration levels of 30ppb (v∕v) with a response time of 8s probing a sample volume of only 1.5mL in a transmission absorption measurement within the photonic band-gap hollow core waveguide, which corresponds to a sensitivity improvement by three orders of magnitude compared to previously reported results obtained with conventional hollow waveguides.

Midinfrared sensors meet nanotechnology: Trace gas sensing with quantum cascade lasers inside photonic band-gap hollow waveguides

Laser cutting of human bone and tissue is one of the oldest and most widespread applications of biophotonics. Due to the unique absorption of different kinds of tissue, choosing an appropriate laser wavelength allows selective ablation of tissue. Consequently, a large variety of laser sources with different emission wavelengths have been successfully applied to an equally large variety of medical indications. However, only a limited set of successful tissue-interaction experiments have translated into standard minimally-invasive procedures. One of the main reasons for this discrepancy between medical research and clinical practice is the lack of a commercially viable, flexible, and easy-to-use fiber optic beam delivery systems for wavelengths longer than 2 μm. In this paper, we will show how OmniGuide fibers, a new type of photonic bandgap fibers, could solve this problem. Recent performance data will be presented for both straight and bent fibers, including losses and power capacity, for delivery of CO2 lasers. We will also highlight medical procedures where these fibers could find first applications.

Photonic bandgap fibers exploiting omnidirectional reflectivity enable flexible delivery of infrared lasers for tissue cutting

In general, in one aspect, the invention features methods that include guiding radiation at a first wavelength, λ 1 , through a core of a photonic crystal fiber and guiding radiation at a second wavelength, λ 2 , through the photonic crystal fiber, wherein |λ 1 −λ 2 |>100 nm.

Photonic crystal fibers and systems using photonic crystal fibers

In general, in one aspect, the disclosure features a system that includes a flexible waveguide having a hollow core extending along a waveguide axis and a region surrounding the core, the region being configured to guide radiation from the CO2 laser along the waveguide axis from an input end to an output end of the waveguide. The system also includes a handpiece attached to the waveguide, wherein the handpiece allows an operator to control the orientation of the output end to direct the radiation to a target location of a patient and the handpiece includes a tip extending past the output end that provides a minimum standoff distance between the output end and the target location.

Gregor Dellemann

Papers

Photonic crystal fibers and medical systems including photonic crystal fibers

Midinfrared sensors meet nanotechnology: Trace gas sensing with quantum cascade lasers inside photonic band-gap hollow waveguides

Photonic bandgap fibers exploiting omnidirectional reflectivity enable flexible delivery of infrared lasers for tissue cutting

Photonic crystal fibers and systems using photonic crystal fibers

Medical system including a flexible waveguide mechanically coupled to an actuator