Waveguide properties of gradient periodic fiber lightguides

Propagation of lower surface waves is studied in gradient fibers with longitudinal additive inhomogeneity.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 44, No. 1, pp. 129–135, January, 1983.     

Effect of elongation deformation on power losses in polymer optical fibers

We investigate the effect of fiber elongation on power loss as rays propagate along deformed polymer optical fibers (POFs). Variations in core diameter, incident angle, stress and strain distributions, and necking of the POFs during fiber elongation are studied. The power losses in the deformed POFs are analyzed both experimentally and numerically. Theoretical analysis based on an elastic-plastic finite-element model and a planar waveguide assumption is proposed. It is found that fiber elongation significantly affects the power loss in POFs, particularly at higher values of elongation. Good agreement between the measured results and the results simulated from the proposed model is obtained. The maximum difference is less than 5%. Results indicate that the proposed theoretical analysis based on an elastic-plastic finite-element model and a planar waveguide assumption is feasible to predict the power loss variation introduced by elongated deformations. A curve-fitted equation is also proposed to estimate the power loss of POFs under different fiber elongation conditions.     

Fiber-optic lightguides in scintillator telescopes for charged particle detection

The use of flexible fiber-optic bundles as lightguides for thin scintillators in a telescope is described. The telescopes will be used in the pion induced fission experiment $\text{π}{}^{\mathrm{+}}{}^6\text{Li}\text{→ 2}{}^3\text{He}$. The fiber-optic lightguide detector was tested, under identical condi against a conventional lightguide-detector arrangement and for α-particles of 5.5 MeV. An efficiency > 99% was obtained with a relative transmission efficiency of ～ 45% compared to the conventional lightguide arrangement.     

Differential photo-calorimetry of photopolymerizable ceramic suspensions

Suspensions of alumina powders in low-viscosity acrylate monomers were produced and their curing behaviour characterized. Although these suspensions contain 50 vol % Al2O3 particles, the viscosity is between 200 and 300 mPas. These suspensions were rendered ultraviolet-curable by the addition of photoinitiators sensitive to ultraviolet radiation. Photopolymerization kinetics were characterized via differential photo-calorimetry. Photopolymerization rates and monomer conversions were unaffected by the presence of the alumina filler. Increasing the average functionality of the monomer mixture tended to increase slightly the photopolymerization rate and decrease the final conversion. Higher concentrations of photoinitiator increased both the rate of photopholymerization and the final conversion. The presence of oxygen was shown severely to restrict polymerization in these filled systems as well. © 1998 Kluwer Academic Publishers     

Application of ionic liquids in photopolymerizable holographic materials

The influence of ionic liquids in photopolymerizable holographic materials was investigated extensively. The structures of ionic liquids have important effect on the properties of the materials. Although not all tested ionic liquids can improve the properties of the materials, the ionic liquids based on imidazolium, pyridium, or phosphonium with appropriate counter anions can be used as additives to increase the sensitivity, the diffraction efficiency, and the resolution of the materials in the thin hologram. Polymerizable ionic liquids have also been used as additives. Higher sensitivity, higher diffraction efficiency and higher resolution were obtained as well. These ionic liquids can carry out the photopolymerization during exposure to UV light to recording the hologram. They may assist to form a more stable hologram.     

Investigation of the refractive index of special purpose lightguides

Translated from Izmeritel'naya Tekhnika, No. 12, pp. 19–20, December, 1989.     

Compact method for optical induction of proximal probe heating and elongation

A tapered, metal-coated, optical fiber probe will elongate when heated by light input through a fiber. The induced motion can be used for data storage or nanostructuring of a surface. The elongation produced by this alignment-free system is measured with force feedback in a near-field scanning optical microscope (NSOM). The input light intensity controls the elongation magnitude, which ranges from a few nanometers to more than 100 nm. A 0.5-mW input energy yields approximately 20 nm of probe elongation. The elongation quantified here can create artifacts in any experiment using pulsed laser light with a NSOM or an atomic force microscope.     

Methods of measuring the dispersion properties of multimodal fiber lightguides

Translated from Izmeritel'naya Tekhnika, No. 11, pp. 36–39, November, 1989.     

Shrinkage control in a photopolymerizable hybrid solgel material for holographic recording

We report the correction of the shrinkage observed during UV postrecording curing in a holographic solgel material that was recently achieved by the use of various chemical formulations for the composition of the hybrid supporting matrix. We found that a chemical modification of the matrix noticeably attenuates the shrinkage (from 1.3% to 0.4% of the material's initial thickness with the inclusion of just 20% tetramethylorthosilicate), providing a material with improved stability for permanent data storage applications. The holographic properties of samples with different binders are also reported. In addition, a theoretical study has revealed the way by which to compensate for angular deviation in the Bragg condition during UV postrecording by tailoring the binder shrinkage (s), the maximum refractive-index modulation capability of the photosensitive mixture (deltan), or both.     

Optical characterization and applications of a dual-cure photopolymerizable system

The optical response of a photopolymerizable formulation consisting of a bisphenol A epoxy acrylate oligomer, a divinyl ether, and a photoinitiator system containing Rose Bengal was studied by recording holographic gratings. This blend is sensitive to blue-green light. Single- and double-exposure volume phase holograms were recorded. In addition to these examples, surface depth measurements were made by means of a holographic contour technique.     

The estimation of non-uniform elongation in low-alloy steel weld deposits

The plastic strain recorded during tensile testing of steel weld deposits has been factorized into a uniform and nonuniform component. It has been possible to express the nonuniform component in terms of the inclusion content of the weld deposits.     

Application of special functions when measuring the geometric parameters of lightguides by a diffraction method

Measurement Techniques -     

Optimization of a photopolymerizable holographic recording material based on polyvinylalcohol using angular responses

Acrylamide-based holographic recording materials have significant advantages and the composition of these materials has been optimized in terms of energetic sensitivity and diffraction efficiency. As a result, diffraction gratings with an efficiency of almost 80% for energetic exposures of 35 mJ/cm² and a spatial frequency of 1000 lines/mm in photosensitive films 65 μm thick have been obtained. In this paper we present the effects of intensity, thickness, and variation in the concentration of each component by studying the angular responses of the diffraction gratings recorded in each composition.     

Synthesis and characterization of photopolymerizable triblocks for 3D printing tissue engineering scaffolds

While previous research on polycaprolactone (PCL) and polyethylene glycol (PEG) triblock copolymers has focused on their use as hydrogels or with conventional scaffold fabrication methods, this work concentrates on producing viable photocurable resins from synthesized triblocks for use in a layer-by-layer 3D printer. After successful synthesis of PCL-PEG-PCL and PCL-PEG-PCL-diacrylate triblocks, they were combined with (hydroxyethyl)methacrylated polyethylene glycol (PEG-HEMA) and used as biomaterials in a dynamic masking 3D printing system to fabricate porous scaffolds. Diacrylation of the polymer (PCL-PEG-PCL-DA) revealed a substantial increase in mechanical strength and resulting compound resolved the re-dissolving issue significantly during the 3D printing process. Degradation tests were carried out by incubation in phosphate-buffered saline, and both biomaterials demonstrated their degradation resistance with steady pH levels and mass loss plateauing at 20% over a sixty day timeframe. Preliminary MG63 cell culture tests on the cross-linked 3D porous structures showed no significant cytotoxicity and MTT assay data verified cell proliferation on the photocured samples after three days. As a result, end-capping PCL-PEG-PCL with acrylates demonstrated advantages over PCL-PEG-PCL while keeping similar performance in degradation and biocompatibility. Overall results from this work demonstrate the suitability of the novel triblocks for use as biomaterials in tissue engineering scaffolds.