This PDF file contains the front matter associated with SPIE Proceedings volume 7559, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

Presented in this work is our effort to develop a simple, inexpensive high resolution fiber-optic Optical Coherence Tomography. The approach is based on common-path Fourier Domain OCT (CP-FDOCT), which can lead to applications for both microsurgical tool control and high-resolution endoscopic imaging. The system utilizes a combination of standard fiber optic components and novel signal processing techniques in order to achieve high axial resolution and to simplify the system. High axial resolution is achieved by implementing the Enhanced Lee filter to reduce speckle noise in the OCT image and Richardson-Lucy deconvolution algorithm afterwards to suppress sidelobes induced by the system's point spread function. This also improves the lateral resolution. Utilizing the simple CP-FDOCT and this algorithm, using an onion as a sample, we have obtained images that have improved resolution and signal to noise ratio by 6dB.

Integrated optical probes for detecting backscattered light in, e.g., Raman spectroscopy show desirable characteristics compared to conventional optical fiber probes, although the latter ones may have better collection efficiency in many cases. Major advantages of integrated probes include reduced size; reduced background noise due to scattering in the probe because of reduced propagation length; potential for monolithic integration with filters and spectrometers; very small collection volume, providing high spatial resolution; and polarization maintenance. We demonstrate that when scattered light needs to be collected from a thin layer close to the probe surface, integrated probes can have better collection efficiency than fiber probes do. We modeled a multimode integrated waveguide probe by adapting an analytical model that had been developed for fiber probes. The model was extended in order to account for arbitrary waveguide geometries and a low number of discrete waveguide modes compared to the quasi-continuum of modes in a typical multimode fiber. Using this model we compared the collection efficiencies of integrated and fiber probes for a thin scattering sample. We found that the integrated probe has a higher collection efficiency for scattering layer thickness and probe-to-layer distance both smaller than ~100 μm.

Silver-cladding-stainless pipe is used as the supporting tube for the infrared hollow fiber to obtain high durability and strong mechanical strength. For the dielectric inner-coating layer, cyclic olefin polymer (COP) and silver iodide (AgI) are used to lower the transmission loss. The COP layer is formed by using liquid-phase coating method as it is done before. For the AgI layer, liquid-filling technique is developed to reduce the waste liquid of iodine solution. Rigid hollow fiber with optimized COP or AgI inner film thicknesses for CO₂ laser light were fabricated and reasonable transmission losses for an output tip was demonstrated.

We describe a simple fiber optic fluorescence spectrometry system with a wide variety of biomedical applications. This low-cost, all-fiber system is portable, robust and has the capacity to acquire fluorescence spectra at rates up to 1 kHz. We demonstrate the capabilities of the system by presenting experimental measurements of action potentials in the di-4-ANEPPS stained rat heart using spectral analysis.

The aim of our work was the application of the special sealed hollow waveguide system for the urology treatment - In our experimental study we have compared the effects of Ho:YAG (wavelength 2100 nm) and Er:YAG (wavelength 2940 nm) laser radiation both on human urinary stones (or compressed plaster samples which serve as a model) fragmentation and soft ureter tissue incision in vitro. Cyclic Olefin Polymer - coated silver (COP/Ag) hollow glass waveguides with inner and outer diameters 700 and 850 μm, respectively, were used for the experiment. To prevent any liquid to diminish and stop the transmission, the waveguide termination was utilized.

A compact Raman cell based on the hollow optical fiber for highly sensitive breath analysis is reported. A polycarbonate tube-based hollow optical fiber with inner coating of silver is used for both a gas cell and a Stokes collector. An excitation laser light at 532 nm is launched into the cell filled with analytes and the Stokes light collected in the cell is detected by the multichannel Raman spectrometer. A high-reflectivity mirror was placed at the output end of the cell for the effective excitation of trace gases. The Raman spectrum of major breath molecule (oxygen, carbon dioxide, and water) is obtained without a serious decrease of the signal-to-noise ratio even if the cell is coiled into a multiple loop with a 3.8 cm radius. Because the cell examined in this report needs very small volume of only 0.4 ml or less, it has great potential for gas analyses that need fast response such as in critical care and operating rooms.

In step-index multimode-fibers, controlled excitation conditions are essential to achieve optimized transmission properties and control the output beam profile. Especially with lasers as a light-source, selective methods of mode excitation can be used easily. So far, fiber properties have been specified using meridional rays (modes), as proposed with the inverse far-field method. In addition to these meridional rays in step-index fibers, high-order skew rays can be selectively excited. Especially with excitation angles higher than the numerical aperture of the fiber, these skew rays can propagate with interesting properties. Based on these extreme test conditions, the core-cladding interface of large-core step-index fibers can be more efficiently controlled.

The document reports a novel method of measuring dissociation constant (k_D) of antibody-antigen interaction using evanescent wave based combination tapered fiber-optic biosensor (CTFOB) dip-probes. The method was demonstrated by measuring the dissociation constant of human Interleukin-6 (IL-6) and anti-IL-6 interaction. Sandwich immunoassay was used to generate fluorescence signal proportional to antigen-antibody conjugate pairs. A portable CCD based spectrometer setup was used to record spectral profile of the fluorescence signal. The measured value of dissociation constant k_D for IL-6 and capture anti-IL-6 (clone MQ2-13A5) antibodies at room temperature is588 ±19 pM .

The high resolution manometry of the upper gastrointestinal tract is moving from research into clinical practice [1], [2]. Hence, there is a need for easy to use and patient friendly diagnosis devices for high resolution esophagus manometry. Besides established methods like perfusion manometry and solid state sensor manometry the use of optical fiber sensor catheters based on fiber Bragg gratings (FBGs) is gaining interest among physicians and medical equipment manufacturers [3], [4]. This paper presents design, prototyping and characterization of a fiber Bragg grating pressure sensor catheter. It uses a two layer polymer coating for the transformation of radial forces into axial strain of the optical fiber. The sensitivity with respect to pressure is in the range of 1 mmHg, the spatial resolution is provided by 32 sensors with a pitch of 10 mm. The coating technique is scalable to smaller diameters down to 0.5 mm and the flexibility is homogeneous over the whole length and can be adjusted by the choice of the coating materials.

The label-free technique of optofluidic intracavity spectroscopy (OFIS) uses the optical transmission spectrum of a cell in a microfluidic optical resonator to distinguish cancerous and non-cancerous cells. Based on their distinctive characteristic transmission spectra, canine hemangiosarcoma (HSA) cancer cells and normal peripheral blood mononuclear cells (PBMCs) have been differentiated using the OFIS technique with high statistical significance (p<10^{- 6}). 95% sensitivity and 98% specificity were achieved simultaneously. A cell lens model explains trends in the transverse mode pattern in the transmission spectra of HSA cells and allows extraction of cell focal length.

A Label-free optical waveguide immunosensor is investigated both theoretically and experimentally. The local evanescent array coupled (LEAC) biosensor is based on a local evanescent field shift mechanism, which differs from those of other evanescent waveguide sensors. Antigens specifically bound by immobilized antibodies on the waveguide surface increase the refractive index of the upper cladding of the waveguide, and hence shift the evanescent field distribution up. This local detection mechanism grants the LEAC sensor multi-analyte ability in a single optical path. Compared to traditional biosensors, including surface plasmon resonance and ring resonance biosensors, the nonresonant and temperature/wavelength insensitive properties of the LEAC biosensor relax its requirement on the optical source. It requires no accessory off-chip instruments such as spectrometers, making it a chip-scale biosensing platform. The on-chip detection is accomplished by integrating buried polysilicon detector arrays into silicon nitride waveguide in a commercial complementary metal oxide semiconductor (CMOS) process. Protein antigens and IgG producing biologically relevant antibody-antigen interactions were used to test the clinical utility of the LEAC biosensor platform. Advanced analysis beam propagation method (BPM) simulations and chips with different geometric parameters were used to study the relationship between the sensitivity and structure of LEAC biosensor.

Some substantial functions of collimating lens in two-lens confocal microscope configuration were studied using raytracing software and experiments. Also, basic advantages of using a high-numerical-aperture optical fiber for a confocal microscope configuration were investigated. It provides higher confocality without reducing the coupling efficiency between light signal and fiber. We performed comparative experiments using two optical fibers with different numerical apertures and the results from axial confocal response tests agreed with the theoretical prediction.

The possibility of spectroscopic gas sensing using infrared hollow fiber as the absorption cell was demonstrated. By optimizing the coating dielectric material and fiber structure parameters, hollow fiber obtains low-loss property at the absorption wavelength band of various gases. Using low-loss infrared hollow fiber as the gas absorption cell has the potential advantages of miniaturization, high sensitivity, small gas sample volume, and thus rapid response. Several kinds of dielectric-coated silver hollow fibers were fabricated and tested for corrosive gas sensing. The durability of the fibers, with inner coating film of silver and silver iodide (AgI), cyclic olefin polymer (COP), SiO₂, polycarbonate (PC), as well as Ag tube were discussed experimentally. We used NH₃, HCl, and ammonia, hydrochloric acid as the corrosive gas or liquid. By flowing the corrosive material through the hollow fiber, durability of the fiber on these corrosives were measured. Experimental results showed that AgI/Ag and COP/Ag hollow fiber have high durability.

A rapid and cost-effective combination tapered fiber-optic biosensor (CTFOB) dip-probe was used for quantitative estimation of interleukin (IL)-6 in serum/plasma samples. Sandwich immunoassay was used as the detection technique. Probes could successfully detect presence of IL-6 in two serum samples, non-neoplastic autoimmune patient (lupus) sample and lymphoma patient sample. The estimated amount of IL-6 in lupus patient sample was 4.8 ± 0.9 pM and in lymphoma patient sample was 2 ± 1 pM. It is demonstrated that the developed CTFOB dip-probe is capable of quantitative estimation of proteins in serum/plasma samples with high specificity.

The potential of thin film thickness variation measurement method, reflectometric interference spectroscopy (RIfS), for a compact label-free biosensor is investigated. A model to estimate thickness variation is built based on RIfS. A set-up of the sensor having dual Light Emitting Diodes (LEDs) and one photo detector are introduced. To verify the model, sample chips with different thicknesses of silica film layers ranging from 2 to 20nm are used in the experiment. The estimated values are compared with their reference values which are measured by an Atomic Force Microscopy (AFM). Since the chosen LEDs' wavelength is not an ideal one, the comparison shows that the model underestimates the thickness variation. By using dual LEDs and a photo detector with the reliable model, the handheld device for transparent thin film measurement will become practical.

Hard Plastic Clad Silica (HPCS) optical fibers with pure silica cores have been developed which are robust and have NA(Numerical Aperture)>0.50. Improved clad only HPCS fibers have been produced for both new 'standard' and 'high' NA versions. Based on new cladding formulations, the 'standard' NA fiber has an NA of 0.41, while the new ultrahigh NA fiber has an NA of 0.54. Mechanical strength and preliminary fatigue data are presented along with spectral characterization data. For the first time significant results were obtained for clad only high NA fibers, The fibers are useful for diagnostic and surgical applications. Short to medium length time to failure results, indicate that the static fatigue parameters of the new high numerical aperture (NA) optical fibers are at least as good as those for former standard NA (0.37) HPCS fibers, which is an advance from previous results on the older formulation high NA fibers.

Noninvasive near infrared (NIR) spectroscopic measurement of muscle oxygenation requires the penetration of light through overlying skin and fat layers. We have previously demonstrated a dual-light source design and orthogonalization algorithm that corrects for inference from skin absorption and fat scattering. To achieve accurate muscle oxygen saturation (SmO₂) measurement, one must select the appropriate source-detector distance (SD) to completely penetrate the fat layer. Methods: Six healthy subjects were supine for 15min to normalize tissue oxygenation across the body. NIR spectra were collected from the calf, shoulder, lower and upper thigh muscles with long SD distances of 30mm, 35mm, 40mm and 45mm. Spectral preprocessing with the short SD (3mm) spectrum preceded SmO₂ calculation with a Taylor series expansion method. Three-way ANOVA was used to compare SmO₂ values over varying fat thickness, subjects and SD distances. Results: Overlying fat layers varied in thickness from 4.9mm to 19.6mm across all subjects. SmO₂ measured at the four locations were comparable for each subject (p=0.133), regardless of fat thickness and SD distance. SmO₂ (mean±std dev) measured at calf, shoulder, low and high thigh were 62±3%, 59±8%, 61±2%, 61±4% respectively for SD distance of 30mm. In these subjects no significant influence of SD was observed (p=0.948). Conclusions: The results indicate that for our sensor design a 30mm SD is sufficient to penetrate through a 19mm fat layer and that orthogonalization with short SD effectively removed spectral interference from fat to result in a reproducible determination of SmO₂.

This document reports a novel method of measuring association rate constant (k_a) for antibody-antigen interaction using evanescent wave-based combination tapered fiber-optic biosensor (CTFOB) dip-probes. The method was demonstrated by measuring association rate constant for bovine serum albumin (BSA) and anti-BSA antibody interaction. "Direct method" was used for detection; goat anti-BSA "capture" antibodies were immobilized on the probe surfaces while the antigen (BSA) was directly labeled with Alexa 488 dye. The probes were subsequently submerged in 3nM Labeled BSA in egg albumin (1 mg/ml). The fluorescence signal recorded was proportional to BSA anti-BSA conjugates and continuous signal was acquired suing a fiber optic spectrometer (Ocean Optics, Inc.). A 476 nm diode laser was use as an excitation source. Association constant was estimated from a plot of signal as a function of time. Measured association rate constant ka for the binding of BSA with anti-BSA at room temperature is (8.33 ± 0.01) x 10⁴ M^-1s^-1.

A loss-spectrum measuring-system for hollow waveguides was established based on the Fourier Transform infrared Spectrometer (FTIR). In order to obtain better repeatability, we designed and fabricated two couplers for the system. One is a silver-coated hollow tube with the same inner diameter as the measured hollow waveguide. The other is a silver-coated tapered coupler whose inner diameter of the output end is the same as the measured hollow waveguide. Characteristics of the measuring system were discussed theoretically and experimentally when using the two couplers. Several kinds of hollow waveguides were measured and the properties of the loss spectra were discussed. The measured loss property showed that loss property depends on the output divergence angle of the coupler. Tapered coupler has a much larger output divergence than that of the hollow tube. Both of the couplers attains stable coupling with the hollow waveguides. Loss spectra were successfully measured for hollow waveguides with the length ranging from several centimeters to 3 meters.

Fiber-coupled organic plastic scintillators enable on-line dose rate monitoring in conjunction with pulsed radiation sources like linear medical accelerators (linacs). The accelerator, however, generates a significant amount of stray ionizing radiation. This radiation excites the long optical fiber (15-20 m), connecting the scintillator, typically with a diameter of 1 mm and 5 mm in length, with the optical detector circuit, causing parasitic luminescence in the optical fiber. In this paper we propose a method for circumventing this problem. The method is based on the use of an organic scintillator, 2-Naphthoic acid, doped in an optical polymer. The organic scintillator possesses a long luminescent lifetime (room temperature phosphorescence). The scintillator is molded onto the distal end of a polymer optical fiber. The luminescent signal from the scintillator is detected by a PMT in photon-counting mode. The long lifetime of the scintillator signal facilitates a temporal gating of the dose rate signal with respect to the parasitic luminescence from the optical fiber. We will present data obtained using a solid water phantom irradiated with 6 MV Xrays from a medical linac at the Copenhagen University Hospital. Also issues pertaining to the selection of proper matrix as well as phosphorescent dye will be presented in this paper.

A multi-channel fiber optic photoluminescence system was developed for real time, in situ and continuous quantitative monitoring of chemical parameters in analytes, with the advantages of ease of use and low cost in manufacturing. The system sequentially excites 8 optodes and measures the resulting photoluminescence with a single photomultiplier. The oxygen sensitive phosphorescent dye or pH sensitive fluorescent dye in the optodes transduces the activity of an enzyme genetically engineered to detect a specific chemical species such as a chlorinated ethene. System operation is described and the relative signal is compared to measurements made with single channel system based on a commercial spectrometer.

We have tested various methods to suppress the modal noise in multi-mode fiber (MMF) output from an ultrabroadband supercontinuum light which is generated in a nonlinear photonic-crystal fiber (PCF) pumped with a 1.06-μmwavelength, sub-nanosecond-pulse-width, 8-kHz-rep-rate Nd:YAG laser source. Significant amount of modal noise including spectral fluctuations was observed when the output from the photonic crystal single-mode fiber (SMF) was directly coupled into MMF. Standard mode-exciting and -mixing techniques such as mode scrambling and fiber stretching showed minimal effect on noise suppression. We observed significant suppression of modal noise by expanding the output beam from the PCF and tightly focus back into MMF using multiple lenses. The resulting spectra of the different MMFs are compared with the output from different SMFs coupled to the supercontinuum source, which are necessary to cover the broadband range of the supercontinuum source over more than two octaves, from 450 nm up to 2100 nm wavelength.

We are reporting detection of IL-8 in a mixed protein solution, using combination tapered fiber-optic biosensor (CTFOB) dip-probe. Sandwich immunoassay was used as the detection technique. The specificity of the sensor was established by using two types of negative control probes. It is demonstrated that with the help of these CTFOB dipprobe we could successfully detect IL-8 with high specificity in protein mixture. The lowest detected concentration of IL-8 was 150 pM.

Homogeneous polymeric thin layers have been used as functionalising agents on silica microresonators in view of immunosensing applications. We have characterised the microspheres functionalised with poly-L-lactic acid and Eudragit® L100, as an alternative to the commonly used silanes. It is shown that after polymeric functionalization the quality factor of the silica microspheres remains around 10⁷, and that the Q factor is still about 3x10⁵ after chemical activation and covalent binding of immunogammaglobulin. This functionalising process of the microresonator constitutes a promising step towards the achievement of a highly sensitive immunosensor.

There is an increasing demand for UV single-mode fibers with long-term stability. Due to the small diameter, the coupling efficiency is extremely low, if broadband light-sources or LEDs with near field diameter in the order of approx. 500 μm are used. Therefore, UV lasers are the real candidates for these fibers. Although the power is in the order of several milliwatts, the intensity in the small fiber core is significantly high. Therefore, UV damage has to be taken into account, even in the wavelength region above 300 nm. After the introduction of adjusted measurement systems for these fibers, the properties of some low-mode and single-mode fibers will be shown and discussed.