Within the past several years we have witnessed the emergence of a new class of materials which provide capabilities along a new dimension for the control and manipulation of light. These materials, known as `photonic crystals,' are viewed ideally as a composite of a periodic array of macroscopic dielectric scatterers in a homogeneous dielectric matrix. A photonic crystal affects the properties of a photon in much the same way that a semiconductor affects the properties of an electron. Consequently, photons in photonic crystals can have band structures, localized defect modes, surface modes, etc. This new ability to mold and guide light leads naturally to many novel applications of these materials in a variety of fields including optoelectronics, telecommunications, medicine and pharmaceuticals. An introductory survey including recent exciting developments in the field of photonic crystals is presented.

Several groups worldwide investigate hollow waveguides for IR radiation extensively. These waveguides can transmit well laser radiation however they have some serious drawbacks such as high sensitivity to bending and wavelength. A potential solution to this problem is to use the 1D photonic crystal theory, i.e. to develop a multi layer waveguide. According to this theory it is possible to get close to 100% reflectivity for large angles of incidence and for a wide interval of wavelengths. Based on this idea we have produced such a hollow glass waveguide, with four inner layers made of alternating Ag and AgI layers. Some preliminary spectral measurements have shown low attenuation for an optimized IR wavelength range, which encouraged us to pursue the research in this direction.

The glass based on the combination of the chalcogenide elements, Selenium, Tellurium and pseudo-chalcogenide Arsenic, named TAS glasses, were investigated due to their unique transparency in the infrared spectral domain. To obtain better optical quality of the glass surface, a procedure of chemical polishing using a congruent dissolution process of the glass is developed. The good performances of Te-As-Se glass fibers allow them to be used for IR evanescent wave spectroscopy analysis. The chemical polishing allows to taper TAS glass fibers which can be used as chemical sensors. The significance of the chemically tapered fiber diameter is shown in this paper. A characteristic example of biological analysis is also presented.

Amorphous Materials has developed a chalcogenide glass which can be drawn in unclad fibers continuously with diameters as low as 50 micrometers . The glass, designed C4, was used to form bundles using the stacked ribbon method. The bundles, 1 meter long and containing 4 - 5 thousand fibers, fitted with relay and objective lenses, produced images using the 3 - 5 micrometers Agema 210 camera far superior than observed at Amorphous Materials with previous bundles. Resolution and contrast were markedly improved. Further improvement was observed when a bundle was used with a much more sensitive Raytheon Radiance it 3 - 5 micrometers camera. FTIR scans showed the transmission was low in the 8 - 12 micrometers range. Images obtained using a Raytheon Palm IR were faint with low contrast. Antireflection coating on the bundles improved 3 - 5 micrometers transmission but failed to improve the 8 - 12 micrometers performance sufficiently.

A hollow fiber composed of a glass-tube substrate and an aluminum thin film coated upon the inside of the tube delivers F₂-excimer laser light with a low transmission loss. It was shown that the fiber should be pressurized with an inert gas to remove the absorption of air.

New fiber-optic applications have been demonstrated within the last years, mainly due to the unexpected progress in manufacturing of solarization-reduced fibers. In meantime, analytical systems including UV-fibers and spectrometers are in operation including the wavelength region from 200 to 250 nm.

A fabrication condition has been newly established to transmit pilot beams in cyclic olefin polymer-coated silver (COP/Ag) hollow fibers for CO₂ laser light. The COP/Ag hollow fibers show low loss properties in the visible wavelength band of 0.5 - 0.7 micrometers without affecting the loss of CO₂ laser light significantly. Bending losses of visible light with the wavelengths of 0.63 micrometers (red) and 0.53 micrometers (green) are evaluated. It is shown that both the red and green pilot beams are successfully delivered with low losses even when the fibers are bent to the angle of 360 degrees.

For delivery of powerful radiation in visible spectral region--cyclic olefin polymer-coated silver (COP/Ag) hollow glass waveguides with a length of 1 m and inner diameters of 1 mm were tested. As radiation sources--alexandrite electro- optically Q-switched laser generating tunable radiation centered at 750 nm (fundamental) or 357 nm (SHG) and two Q- switched and mode-locked Nd:YAG lasers generating wavelengths 1064 nm (fundamental) or 532 nm (SHG) were used. In every case, the output beam was coupled into the COP/Ag hollow glass waveguide. Coupling of radiation was optimized investigating several waveguide input protectors made from different materials to avoid spark generation at high radiation intensity. Transmittance/attenuation as a function of the input laser energy was measured in dependence to input radiation wavelength. The input/output time radiation characteristics and the spatial distributions of the output beams were also investigated. Transmission efficiency of the COP/Ag waveguides was found to be 80 - 95% in the spectral range from green to near infrared. In the blue region, transmittance was 66%. The measured transmission properties make COP/Ag hollow glass waveguides very promising for delivery of high-power laser pulses in medicine and also in other applications.

There are two kinds of `step-index' optical fibers with cores made of pure silica glass--high-OH and low-OH content. High-OH fibers are notable for transparency in the UV region of the spectrum and exhibit high radiation resistance while low-OH fibers are applied in IR applications. Decreasing the Cl₂-content in low-OH fibers diminishes the losses in the UV region, which expands the applications for low OH fibers to approximately 300 nm. But the task of fiber production with low OH-content along with transparency in the UV region to 200 nm with high radiation resistance requires a detailed study of the mechanisms of intrinsic and impurity defect formation.

Spectroscopic sensing systems are among the most promising techniques following the recent trends towards continuously operating in-situ analytical tools. The mid-infrared spectral region considered from 2 - 20 micrometers is of particular interest, as compound-specific information based on fundamental rotational and vibrational transitions is provided. Thus, inherently selective qualitative and quantitative data can be obtained. With the development of mid-infrared transparent optical fibers, conventional spectroscopic techniques, such as Fourier transform infrared spectroscopy, can be evolved into a sensor format. The appearance of novel mid-infrared light sources, e.g. quantum cascade lasers, and the potential of microfabrication technologies, allows to significantly scale down the optical components. In combination with advanced molecular recognition schemes, such as molecularly imprinted polymers, a new generation of mid-infrared optical sensing devices can be envisaged, with applications ranging from environmental and process analysis to the biochemical/biomedical field.

A dichloromethane (DCM) gas optical fiber sensor has been fabricated building up a grating with poly(diallyldimethyl) ammonium chloride), poly(sodium-4-styrenesulfonate) and Poly S-119 using the Electrostatic Self-Assembly Monolayer Process. The mechanism of this sensor relies on the reflectance change of an optical grating deposited at the end of a standard communications multimode optical fiber. The total length of this grating is less than 1.5 micrometers and the structure is HLHLH, where H means material with higher refractive index and L means material with lower refractive index. Experiments with an Optical Spectrum Analyzer showed that with this technique it is also possible to choose the optical working wavelength and the reference wavelength of the sensor, in this case 1310 and 1645 nm respectively, around 1 dB of variation was observed at the working wavelength when the sensor was exposed to DCM gas. Neither hysteresis nor cross-sensitivity with temperature were detected. In addition, experimental results after 8 months from the fabrication of the sensors are also presented.

Lower stress, higher quality assemblies as well as quantum increases in productivity are now possible with `new generation', light curing adhesives. This new technology makes obsolete the industry-accepted assumption that low strain requires slow curing UV adhesives, epoxies and cements. Curing in only seconds and without the need for secondary thermal cure, these new light curing adhesives produce laminates which are essentially strain-free, and edge bonds with shrinkage as low as 0.2%. This paper will compare and contrast these new adhesives with existing bonding technologies in typical applications. Included are comparisons between epoxies, UV curing mercaptoesters, and the new light curing Aerobic Acrylates, as well as the incorporation of adhesives into optical component design.

A four-fiber optical trapping/detection system build on silicon, utilizing the natural alignment of anisotropically etched Si V-grooves for positioning of the optical fibers, has been demonstrated. Two, pigtailed laser diodes emitting at 830 nm are connected to cleaved, single-mode, counter- propagating fibers, which are used for trapping polystyrene beads. Orthogonal to the trapping fibers are two additional fibers: one fiber is connected to a laser diode emitting at 660 nm (excitation source) and the opposing detection fiber is connected to a spectrometer. Changes in the relative intensity of the trapping light and the excitation light are used to indicate the capture and position of a bead in the trap. The spectrometer may be interfaced with a computer allowing for complete automation for position, size and fluorescence detection of the trap with an eventual goal of integration with MEMS (Micro ElectroMechanical Systems) and lab on a chip (LOC) technology.

The authors report on the design of a system which will enable real time measurements of (therapeutic) drug concentrations in the anterior chamber of the eye. Currently the concentration of therapeutic drugs in the anterior chamber is determined by analyzing samples which have been removed from the aqueous humor of laboratory animal eyes. This sampling via paracentesis can be painful and does not provide a continuous measurement. Our system will be far less invasive, removing the need for sampling via paracentesis, and also providing a continuous measurement, enabling a more complete understanding of the kinetics of ophthalmic drugs. A key component in our novel system is a specially constructed contact lens. We report on the design, optimization and manufacture of such a contact lens system capable of directing UV/VIS light in, across and out of the anterior chamber of the eye, thereby enabling absorption spectroscopy measurements of the aqueous humor to be undertaken. Design of the one piece contact lens/mirror system was achieved using the Zemax optical design software package and the lens was fabricated from synthetic fused silica. Results from modeling of the lens and experimental measurements on light propagation across the anterior chamber of animal eyes assisted by the lens will be reported.

Recent progress in fiber laser technology has provided lasers operating at mid-infrared wavelengths, at power levels and temporal regimes previously inaccessible to bulk crystal lasers. This paper reports on the development of new continuous wave fiber lasers; a Tm-silica fiber laser operating at 1.98 micrometers , an Er,Pr:ZBLAN fiber laser at 2.78 micrometers and a Yb:Er-silica fiber laser at 1.5 micrometers , and pulsed fiber laser sources; gain-switched and Q-switched Tm- silica systems, specifically targeting applications in medicine. The first studies on the interaction of high- power, continuous wave mid-infrared fiber laser light and soft biological tissues are presented, demonstrating the ability of 2 and 3 micrometers fiber lasers to remove soft tissue cleanly, and with minimum collateral damage.

With 1064-nm, nanosecond laser pulses delivered from hollow waveguide, ablation characteristics of porcine myocardium tissue have been investigated in vitro. For the hollow waveguide a vacuum-cored scheme was introduced to suppress the laser-induced air breakdown that limited the available transmitted laser energy/power. The delivered laser pulse beam was focused with a collimation lens and a focusing lens, and it was shown that higher efficiency ablation was obtained when a focusing lens with a shorter focal length was used. Waveguide bending (bending angle 90 degree(s)C, bending radius approximately 50 cm) caused no deteriorating effect on the ablation characteristics for ablation energies up to approximately 60 mJ/pulse. It was demonstrated that deep and sharp ablated holes with aspect ratios > 8 was obtained with the hollow-waveguide-delivered laser pulses. It may be a realistic option to aim at using the present hollow waveguide system for trocar-based applications or replacing articulated mirror-based laser delivery systems. It is an important part of the future works to downsize the waveguide output unit for catheter-based applications.

We demonstrate a novel all-optical-fiber system for infrared (IR) laser radiation delivery into a precise tissue area. The operating principle of the laser delivery system is based on the use of a direct laser-to-taper coupling and an IR delivery fiber with angle-shaped tip. In our experiment, instead of a conventional lens-based laser-to-fiber coupling we use an uncoated glass hollow taper for a laser-to-fiber coupling. It is a funnel-shaped grazing-incidence-based hollow taper. The laser emission is launched directly, without any focusing elements, into the taper and next into the delivery fiber by a direct taper-to-fiber coupling. The IR fiber delivers the forward emission from a Er:YAG laser ((lambda) equals 2.94 micrometers ) to the tissue to be treated. Moreover, in order to realize a regime of evanescent wave delivery, we use a specially shaped fiber tip with an angled (porro-prism) profile. When the fiber tip is out of the tissue area, the laser emission is backreflected at the angled tip due to total-internal-reflection. However, when the fiber tip is placed on absorbing tissue, it becomes `transparent' for laser emission because of the frustrated- total-internal-reflectance and the energy then is coupled into the absorber. When sufficient energy is transferred, dermatology or other precise surgical processes can be controlled or stopped.

Due to UV-fiber improvements within the last years, silica- based fibers with small core diameters are available for usage in fiber-bundles extending the range of applications into the deep UV-region below 250 nm. The well-known cross- section converter can be modified for usage in a capillary- holder for capillary electrophoresis. Y-assemblies for DUV- applications are tested within the thin-layer chromatography, leading to an significant improvement of this `old' technique. So, the short processing time including the preparation and low cost are advantageous, in respect to other separation-techniques. In addition to the properties of the different Y-assemblies under test, the separation results of polyaromatic hydrocarbons with the proposed TLC-method will be shown.

The Single Fiber Scanning Endoscope (SFSE) is a new class of endoscopes being developed at the University of Washington's Human Interface Technology lab which uses combinations of a resonating optical fiber and a single photodetector to produce large field of view, high-resolution images from a small flexible package. Although current prototypes show the validity of the concept, the nonlinear response of the resonant optical fiber under open loop control creates image distortion or limits the frame rate. Due to low damping and nonlinear effects in the fiber, open loop control, phase lock loops, PID control, classical and modern controllers are all unable to produce accurate, reproducible, robust high frequency 2D scans. A nonlinear control scheme, feedback linearization, is capable of accurately producing a scan and is robust to most of the unavoidable manufacturing and environmental variability in the resonant scanner. Through theoretical analysis and simulations, this paper reviews the application of the following variety of open loop and closed loop controllers to the nonlinear scanner of the SFSE: open loop control, modelless closed loop control (phase lock loop and PID control), feedforward plus feedback classical and modern state space tracking control, and nonlinear feedback linearization control.

Optical PNC-diagnostics is one of the methods to diagnose biotissue in norm and pathology. In primary case backscattering and fluorescent components of detected secondary radiations are registered by means of PNC-method. These radiations are stimulated and occur when probing laser beam radiates biotissue.

In this work we present our effort to develop an infrared method to differentiate between malignant and healthy tissue in vivo. This paper will present the technical design of the laboratory set up and the results obtained in experiments carried out on melanoma tumors in the skin of male mice. Silver halide fibers were used to carry our ATR measurements on tumor sections. Further results were compared with detailed measurements carried out using an FTIR-microscope and thin tissue sections in the spectral range of 4000 - 900 cm^-1. The results indicate that IR spectroscopy would be a useful tool for biodiagnosis, in vivo and in real time. The fiberoptic method described here will easily lend itself to endoscopic applications.