This PDF file contains the front matter associated with SPIE Proceedings Volume 8775, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

A novel DNA sensing platform based on a Peptide Nucleic Acid - functionalized Microstructured Optical Fibers gratings has been demonstrated. The inner surface of different MOFs has been functionalized using PNA probes, OligoNucleotides mimic that are well suited for specific DNA target sequences detection. The hybrid sensing systems were tested for optical DNA detection of targets of relevance in biomedical application, using the cystic fibrosis gene mutation, and food-analysis, using the genomic DNA from genetic modified organism soy flour. After the solutions of DNA molecules has been infiltrated inside the fibers capillaries and hybridization has occurred, oligonucleotidefunctionalized gold nanoparticles were infiltrated and used to form a sandwich-like system to achieve signal amplification. Spectral measurements of the reflected signal reveal a clear wavelength shift of the reflected modes when the infiltrated complementary DNA matches with the PNA probes placed on the inner fiber surface. Measurements have also been made using the mismatched DNA solution for the c, containing a single nucleotide polymorphism, showing no significant changes in the reflected spectrum. Several experiments have been carried out demonstrating the reproducibility of the results and the high selectivity of the sensors, showing the simplicity and the potential of this approach.

Chemical bonds of most of the molecules vibrate at a frequency corresponding to the near or mid infrared field. It is thus of a great interest to develop sensitive and portable devices for the detection of specific chemicals and biomolecules for various applications in health, the environment, national security and so on. Optical fibers define practical sensing tools. Chalcogenide glasses are known for their transparency in the infrared optical range and their ability to be drawn as fibers. They are consequently good candidates to be used in biological/chemical sensing. For that matter, in the past decade, chalcogenide glass fibers have been successfully implemented in evanescent wave spectroscopy experiments, for the detection of bio-chemical species in various fields of applications including microbiology and medicine, water pollution and CO₂ detection. Different types of fiber can be used: single index fibers or microstructured fibers. Besides, in recent years a new configuration of microstructured fibers has been developed: microstructured exposed-core fibers. This design consists of an optical fiber with a suspended micron-scale core that is partially exposed to the external environment. This configuration has been chosen to elaborate, using the molding method, a chalcogenide fiber for chemical species detection. The sensitivity of this fiber to detect molecules such as propan-2-ol and acetone has been compared with those of single index fibers. Although evanescent wave absorption is inversely proportional to the fiber diameter, the result shows that an exposed-core fiber is much more sensitive than a single index fiber having a twice smaller external diameter.

A modified Mach-Zehnder interferometer (MZI) design based on elliptical silica photonic nanowires is proposed and demonstrated numerically. The MZI is used as a highly sensitive evanescent field based refractive index sensor. By applying a full vectorial finite element method, single-mode operation, polarization maintaining and very high sensitivity are achieved by simply using 800 nm-elliptical silica nanowires. Using the highly-sensitive versatile interferometry technique, the phase shift from both arms is determined and consequently the specimen’s information can be retrieved. The proposed sensor is used to determine the refractive index (RI) of NaCl solutions with different concentrations. The sensor is capable of detecting a refractive index variation of the order of 10^-6 RI unit with a high sensitivity of 4.2 rad/μm.

We fabricate a PCF coil sensor for water-depth sensing by winding a PCF on a plastic straw. Due to the bending-induced birefringence along the PCF, we can observe clear interference pattern in the output spectrum by placing the PCF coil into a Sagnac fiber loop. As we horizontally immerse the fabricated PCF coil into water, a nonlinear relationship between the water depth and the wavelength shift can be obtained. We have also measured the interference spectrum by vertically immersing the PCF coil into water. We can observe a linear relationship between the water depth and the wavelength shift, and the measured water-depth sensitivity for vertical immersion is -1.17 nm/mm.

This paper presents results of preparation and characterization of Bragg fibers with silica and air cores designed for delivery of laser radiation at 1060 nm. The fibers consist of cores with a refractive index equal to that of air or silica which is surrounded by three pairs of Bragg layers. Each pair is composed of one layer with a high and one layer with a low refractive index and is characterized by a refractive-index contrast up to 0.03. Three structures of Bragg fibers are presented in the paper, namely the structure with a silica core of 26 μm in diameter, structure with an air core of 5 μm in diameter and that with an air core of a diameter of 72 μm.

Preforms of the Bragg fibers in the form of a rod or tube have been prepared by the MCVD method using germanium dioxide, phosphorous pentoxide and fluorine as silica dopants. The fibers have been drawn from the preforms under controlled temperatures in order to obtain fibers with air or solid cores. Results of characterization of prepared fibers with optical microscopy and by measuring their refractive-index profiles, losses and angular distributions of the output optical power are presented. The characterization of fibers for delivery radiation of a Nd:YAG laser with nanosecond pulses at 1060 nm, namely the transmission, attenuation coefficient, spatial profiles of transmitted beams, and bending losses are also presented. Fiber damage thresholds in a range 25-30 GW/cm² have been determined.

In this contribution we demonstrate the effect of the nanostructured optical fiber core matrix, doped with erbium and Al₂O₃, on the resulting optical properties. Several optical fibers with nanostructured cores were drawn from preforms prepared by different techniques, i.e., by conventional doping from solution of erbium and aluminium chlorides, by deposition of the dispersed alumina nanoparticles with either Er³⁺ ions or Er₂O₃. Reference bulk samples were prepared by the solid-state approach and thermally treated by similar way as optical fibers. Prepared optical fibers and bulk samples were investigated by the absorption spectroscopy. Reference samples were analyzed by the X-ray diffraction for the determination of the crystalline properties of formed nanostructures. It was found that nanocrystals inside the optical fiber core matrix improves the homogeneity and decreases the basic optical attenuation. Nanostructured alumina inside the fiber core matrix enhances the absorption properties of Er³⁺ ions.

Rare earth (RE) doped optical fibers have shown tremendous progress for producing high power fiber lasers for industrial, medical and strategic applications. However, fabrication of large core, high Yb-doped fiber is still a challenge through conventional process due to poor repeatability and limitation regarding core size. This paper presents successful fabrication of Yb-doped fibers through vapor phase doping technique. Preform fabrication was carried out using a specially constructed MCVD system containing High Temperature Vapor Delivery Unit with sublimators for Al and Yb precursors. The novelty of the present work lies in deposition of Al₂O₃ and Yb₂O₃ in vapor phase simultaneously with silica during formation of sintered core layer which result in uniform dopants distribution in the preform. The fibers exhibited lasing efficiency of 76% with low ‘photodarkening effect’.

The current status of UV-damage in several different UV fibers due to defects in their synthetic high-OH silica core and cladding will be described. Further, steps to improve UV resistance and adequate measurement techniques based on a deuterium lamp setup are included. For the first time, the main parameters and their influences on UV induced losses are discussed in detail with an emphasis towards future standardization purposes. Applications based on two new UV light sources, a laser driven xenon plasma broad band source and a high pulse-power 355 nm Nd:YAG laser, are introduced. UV photo-darkening and -bleaching in UV fibers caused by this extremely powerful light source is demonstrated. Finally, first results on transmission of UV light in optical fibers at cryogenic temperatures are shown.

We numerically investigated the possibility of generating high-quality ultra-short optical pulses with broad frequencycombs spectra in a system consisting of three optical fibres. In this system, the first fibre is a conventional single-mode fibre, the second one is erbium-doped, and the last one is a low-dispersion fibre. The system is pumped with a modulated sine-wave generated by two equally intense lasers with the wavelengths λ₁and λ₂ such that their central wavelength is at λ_c = (λ₁ + λ₂)/2 = 1531 nm. The modelling was performed using the generalised nonlinear Schrödinger equation which includes the Kerr and Raman effects, as well as the higher-order dispersion and gain. We took a close look at the pulse evolution in the first two stages and studied the pulse behaviour depending on the group-velocity dispersion and the nonlinear parameter of first fibre, as well as the initial laser frequency separation. For these parameters, the optimum lengths of fibre 1 and 2 were found that provide low-noise pulses. To characterise the pulse energy content, we introduced a figure of merit that was dependent on the group-velocity dispersion, the nonlinearity of fibre 1, and the laser separation.

We have characterized ytterbium–doped fiber laser and described in detail the effect of pump wavelength on self–induced laser line sweeping (SLLS). SLLS is a transient laser regime manifested by a relatively slow laser line shifting and usually observed in the near of pump laser threshold. The fiber laser under consideration is cladding–pumped by a temperature stabilized multimode laser diode (LD) at about 976 nm. The output wavelength of the diode is tunable by changing the diode temperature and current through the diode. The cavity of the laser is formed by perpendicularly cleaved fiber ends. Using this laser layout we made detailed study of sweeping dependences on pump wavelength by adjustment of the LD current and LD case temperature. The laser manifested laser line sweeping within the range of 5–7 nm on a wide span of pump laser diode power and temperature: 15–45°C LD temperature scale and pump range reaching to more than twice the amount of excess over threshold. We performed the measurement of the laser line sweeping span, period and rate as the dependence of pump wavelength.

Dispersion properties of a 37 cm long photonic crystal fibre were studied using spectral interferometry. The interferograms were evaluated by the conventional and the windowed Fourier-transform method, as well as other commonly used ones, such as the cosine function fit, the stationary phase point and the minima-maxima methods. It is shown that from the five techniques the conventional Fourier-transform method provided the dispersion coefficients with the highest accuracy, and both Fourier-transform techniques could detect phase jumps in the vicinity of the absorption valleys seen in the transmission spectrum of the fibre. We present a novel simple evaluation procedure based on Fouriertransform for a quick retrieval of the spatial and temporal pulse shape after the fibre. The time delay between the higher and the fundamental transversal modes was also measured by the Fourier-transform method.

We examine through simulation and experiments the operation of multi-mode-optical fiber that reimages a periodic input optical pattern. Besides the observation of a partial Talbot self-imaging effect we also find a recurrence effect due to the core/cladding boundary of the optical fiber. We use the beam propagation method to simulate diffraction and refraction of light in the optical fiber device. The details of the device are described and its optical properties using a close-packed hexagonally-shaped array of apertures placed at regular positions on a triangular lattice are examined. Our simulations identify the optimal length of the Multi-mode fiber to get high fidelity self-image. Experiments are performed to validate the simulation results.

A versatile method for integrating liquid waveguides into PDMS microfluidic flow-cytometer chips is presented. By using a one-step direct replication, PDMS chips are produced with both liquid and waveguide channels. Filling the waveguide channels with high refractive index media, a simple waveguide is created using the PDMS of the chip itself as cladding. Optical fibers are used to couple laser light and fluorescence into, and out of the chip. Experimental results and ray-tracing simulations show that the light intensity at distances above 5 mm from the source is more than four times higher when using gelatin or DMSO as compared to channels containing only air.

Indium-Tin-Oxide (ITO) is one of the most widely used transparent semiconductors due to its electrical conductivity and optical transparency. Thin layers of ITO are prepared in industrial scale by a range of physical deposition techniques such as magnetron sputtering, dip-coating method etc. The ITO thin films with tailored thickness from 220 nm to 550 nm were prepared by dip-coating method on planar substrates. The resistivity of prepared films was tailored from 2.5 Ω•m to 0.02 Ω•m by the annealing temperature. The deposition technology was adapted to the fiber optic substrates. ITO layers were successfully deposed on the decladded polymer coated silica fibers (PCS) and inside the capillary fibers. The resistivity of prepared optical fiber was below 0.15 MΩ•m^-1. Prepared films appeared values of the refractive index around 1.458. The strong dependence of the resistivity of prepared ITO films on the humidity was found. The reason could be found in the relatively high porosity of prepared ITO film which supports the adsorption of the water to the grain boundaries of ITO nanocrystals.

Today there is an increasing surge in Surface Plasmon based research and recent studies have shown that a wide range of plasmon-based optical elements and techniques have led to the development of a variety of active switches, passive waveguides, biosensors, lithography masks, to name just a few. The Terahertz (THz) frequency region of the electromagnetic spectrum is located between the traditional microwave spectrum and the optical frequencies, and offers a significant scientific and technological potential in many fields, such as in sensing, in imaging and in spectroscopy. Waveguiding in this intermediate spectral region is a major challenge. Amongst the various THz waveguides suggested, the metal-clad waveguides supporting surface plasmon modes waves and specifically hollow core structures, coated with insulating material are showing the greatest promise as low-loss waveguides for their use in active components and as well as passive waveguides. The H-field finite element method (FEM) based full-vector formulation is used to study the vectorial modal field properties and the complex propagation characteristics of Surface Plasmon modes of a hollow-core dielectric coated rectangular waveguide structure. Additionally, the finite difference time domain (FDTD) method is used to estimate the dispersion parameters and the propagation loss of the rectangular waveguide.

We investigate the self-similar mode of laser pulse propagation in the medium with both nonlinear absorption (twophoton or multi-photon) and cubic nonlinear response (both self-focusing and de-focusing). This mode of laser pulse propagation takes place along certain distance. We showed that the self-similar shape of pulse is like optical soliton, propagating in a medium with cubic nonlinearity. However, the duration of this pulse is less in comparison with the soliton duration for Kerr medium under the corresponding conditions. We used as analytical approach for considered problem as well as computer simulation.

The goal of this paper is to investigate selected fluoride optical materials and to present a photonic crystal fiber designed for specific applications in dispersion compensation by using those materials. The idea how to restrict chromatic dispersion is to increase the index contrast by using calcium fluoride or barium fluoride in the first ring of holes, which lower the effective index. In general, fluoride materials compared to standard silica glass in many aspects offer better mechanical and optical properties. The use of fluorides allows achieving broadband dispersion suppression impossible to achieve in standard fibers with similar geometry. The presented result comprises a numerical model of a photonic crystal fiber in a submicron lattice, specific for its negative dispersion coefficient achieved for broad spectrum of telecommunication wavelengths, i.e. 1300 – 1700 nm. The core consists of pure silica surrounded by three doped regions and three air-holes. Holes doped with fluoride materials enhance negative dispersion coefficient to -438 ps.nm^-1.km^-1. The diameter of doped regions is about 1 micrometer. Simulations were done by using the full-vector FDFD method. The wavelength evolution of refractive index of materials was introduced by using the Sellmeier approximation. The major advantage of the designed fibers is their material composition, low attenuation and broadband utilization.

Recently, the thermo-optic effect, which causes refractive index change in active optical fibers, emerged as one of the most limiting factor to power scaling of fiber lasers. The thermally-induced refractive index gradient in the fiber cross-section jeopardizes the extreme guiding properties required to obtain single-mode propagation in ultra Large Mode Area (LMA) fibers, eventually causing the rise of mode instabilities. In this paper the resilience to thermal effects of different rod-type Double Cladding Photonic Crystal Fiber designs, namely the 19-cell core, the distributed modal filtering and the large-pitch PCFs, have been compared through numerical simulations. The single-mode properties of each fiber have been obtained for different heating conditions. The causes of the different behavior have been investigated, providing a detailed overview of the influence of thermo-optical effects on the guiding properties of LMA PCFs, as well as some guidelines for the design of LMA PCFs for high-power applications.

We report on the use of a fiber Bragg grating (FBG) based sensor written in a photonic crystal fiber (PCF) to monitor the cure cycle of composite materials. The PCF under study has been specifically designed to feature a high phase modal birefringence sensitivity to transverse strain and a very low sensitivity to temperature. We exploit these particular properties to measure strain inside a composite material in the out-of-plane direction. The embedded FBG sensor has been calibrated for transverse and axial strain as well as for temperature changes. These FBGs have then been used as embedded sensors during the manufacturing of a composite material in order to monitor how strain develops inside the composite during the cure cycle. We show that our sensors allow gaining insight in the composite cure cycle in a way that would be very difficult to achieve with any other sensor technology.

We present the numerical design of a turn-around-point long-period grating in a photonic crystal fiber (TAP PCFLPG) for high-sensitivity, high-resolution refractometry of gases. High refractive-index sensitivity is achieved by operating LPGs in the vicinity of the dispersion turning point of the optimized PCF. Despite the resonant wavelength of the optimized PCF-LPG is highly sensitive to the refractive index of analytes, its large shifts could be monitored with a reduced resolution because the resonance dip in the TAP LPG transmission spectrum is broad. To provide also high refractive-index resolution, twin TAP-LPGs have been proposed to be used as 3 dB broadband mode converters in the interferometric scheme. The first LPG couples a portion of the light in the core mode to a forward propagating cladding mode and the second LPG couples the light back to the core mode. The resulting interference fringes within the envelope of LPG attenuation dip provide a means for higher resolution sensing. Instead of monitoring the wavelength shift as a result of a refractive index change, the transmission spectrum can also be analyzed in terms of the shift in phase suffered by the fringe pattern. This is a more accurate way of interpreting the interferometric sensor measurements, since the phase shift is a direct result of an analyte-induced change in optical path length.

Thermoluminescence (TL) flat optical fibers (FF) have been proposed as radiation sensor in medical dosimetry for both diagnostic and radiotherapy applications. A flat optical fiber with nominal dimensions of (3.226 × 3.417 × 0.980) mm³ contains pure silica SiO₂ was selected for this research. The FF was annealed at 400°C for 1 h before irradiated. Kinetic parameters and dosimetric glow curve of TL response were studied in FF with respect to electron irradiation of 6 MeV, 15 MeV and 21 MeV using linear accelerator (LINAC) in the dose range of 2.0-10.0 Gy. The TL response was read using a TLD reader Harshaw Model 3500. The Time-Temperature-Profile (TTP) of the reader used includes; initial preheat temperature of 80°C, maximum readout temperature is 400°C and the heating rate of 30°Cs^-1. The proposed FF shows excellent linear radiation response behavior within the clinical relevant dose range for all of these energies, good reproducibility, independence of radiation energy, independence of dose rate and exhibits a very low thermal fading. From these results, the proposed FF can be used as radiation dosimeter and favorably compares with the widely used of LiF:MgTi dosimeter in medical radiotherapy application.

Cardiac positron emission tomography (PET) provides a precise method in order to diagnose obstructive coronary artery disease (CAD), compared to single photon emission tomography (SPECT). PET is suitable for obese and patients who underwent pharmacologic stress procedures. It has the ability to evaluate multivessel coronary artery disease by recording changes in left ventricular function from rest to peak stress and quantifying myocardial perfusion (in mL/min/g of tissue). However, the radiation dose to the radiosensitive organs has become crucial issues in the Positron Emission Tomography/Computed Tomography(PET/CT) scanning procedure. The objective of this study was to estimate radiation dose to radiosensitive organs of patients who underwent PET/CT myocardial perfusion examination at Centre for Diagnostic Nuclear Imaging, Universiti Putra Malaysia in one month period using versatile optical fibres (Ge-B-doped Flat Fibre) and LiF (TLD-100 chips). All stress and rest paired myocardial perfusion PET/CT scans will be performed with the use of Rubidium-82 (⁸²Rb). The optic fibres were loaded into plastic capsules and attached to patient’s eyes, thyroid and breasts prior to the infusion of ⁸²Rb, to accommodate the ten cases for the rest and stress PET scans. The results were compared with established thermoluminescence material, TLD-100 chips. The result shows that radiation dose given by TLD-100 and Germanium-Boron-doped Flat Fiber (Ge-B-doped Flat Fiber) for these five organs were comparable to each other where the p>0.05. For CT scans,thyroid received the highest dose compared to other organs. Meanwhile, for PET scans, breasts received the highest dose.

In this contribution we present numerical study of propagation of the multimode pump radiation in the inner cladding of the developed double-clad fiber. Field evolution was simulated using full vector finite element beam propagation method. Due to reeling of the fiber on the spool, the curvature of the fiber is involved in the model. The longitudinal dependence of power distribution was then analyzed. The simulations showed that after the length of propagation of about 40 mm the field becomes homogeneously distributed in the structure. Over 90 % of pump energy is absorbed in 3 m of the rare-earth-doped fiber with core-absorption of 2000 dB/m and cladding-core diameter ratio of 18.5. This confirms suitability of the tailored cross section for effective pump absorption along the rare-earth-doped fiber.

The dependence of chromatic dispersion of tellurite microstructured optical fiber on composition and structure was investigated. The material dispersion is mainly dependent on material composition of core glass. And the waveguide dispersion of fiber mainly depends on refractive index distribution in cross-section. The radial step of refractive index produces a peak in waveguide dispersion curve whose value and position are related to both contrast of refractive index and its position. Based on this guidance, some particular dispersion profiles were designed in tellurite fibers.

A spectral interferomeric technique to measure the chromatic dispersion, the zero-dispersion wavelength and the dispersion slope of a highly nonlinear suspended-core fiber is presented. This method utilizes an experimental configuration with a supercontinuum source in combination with a dispersion balanced Mach-Zehnder interferometer. A low-resolution spectrometer is employed at the output of the setup to record spectral interferograms for the path lengths adjusted in the interferometer. The spectral interference fringes of the highest visibility are resolved in the vicinity of the stationary-phase point corresponding to the equalization wavelength. First, from a series of spectral interferograms the dependence of the equalization wavelength on the path length adjusted in the Mach-Zehnder interferometer is measured. Then, the dependence of the path length difference on the equalization wavelength is obtained, which enables to determine dispersion of the differential group index of the fiber. Next, the chromatic dispersion including the zero-dispersion wavelength is determined exploiting a least-square fitting. Finally, the dispersion slope is obtained.

A novel photonic crystal fiber for compression of optical pulses is designed and studied in this paper. The fiber comprises a silica core surrounded by nine rings of air-holes, where air-hole diameter of the innermost ring is gradually reduced along the entire fiber length. In order to obtain the required wavelength dependence of the effective refractive index, finite difference frequency domain method is employed. The calculated chromatic dispersion is flat from 1250 to 1700 nm at the fiber output, and therefore the photonic crystal fiber can be used at a desired wavelength in this range. On the contrary to other studies, chromatic dispersion in this paper is decreasing along the fiber length with the effective mode area. Therefore, during the propagation of solitary waves, the fiber nonlinear parameter increases and consequently the compression ratio is increased. Compression of solitary waves is investigated at the wavelengths of 1250, 1310, 1400, 1550, and 1700 nm. The compression ratio up to 30 for the first-order solitary wave with the length of 1550 nm can be achieved primarily by dispersion varied from 137 to 6 ps·nm^-1·km^-1 during the wave propagation.