Hollow silica capillaries are examined as optical waveguides evaluating the antiresonant reflecting optical waveguide (ARROW) effect by sequentially reducing the wall thickness through etching and measuring the optical transmission. It is found that the periodicity of the transmission bands is proportional to the wall thickness and that the propagation loss is of the order of a few dB/m.
Gold nanoparticles have been used since antiquity for the production of red-colored glasses. More recently, it was determined that this color is caused by plasmon resonance, which additionally increases the material's nonlinear optical response, allowing for the improvement of numerous optical devices. Interest in silica fibers containing gold nanoparticles has increased recently, aiming at the integration of nonlinear devices with conventional optical fibers. However, fabrication is challenging due to the high temperatures required for silica processing and fibers with gold nanoparticles were solely demonstrated using sol-gel techniques. We show a new fabrication technique based on standard preform/fiber fabrication methods, where nanoparticles are nucleated by heat in a furnace or by laser exposure with unprecedented control over particle size, concentration, and distribution. Plasmon absorption peaks exceeding 800 dB m(-1) at 514-536 nm wavelengths were observed, indicating higher achievable nanoparticle concentrations than previously reported. The measured resonant nonlinear refractive index, (6.75 ± 0.55) × 10(-15) m(2) W(-1), represents an improvement of >50×.
The temperature characteristics of the birefringence of side-hole fibers filled with liquids or metal are investigated, aiming at providing a basis for on/off temperature sensing. Short pieces of fiber are filled and the change in birefringence is registered using measurements in reflective mode of the transmitted power through a linear polarizer at 1550 nm. The rapid change in the birefringence behavior of the fiber at the temperature of the phase transition of the filler substance is shown, and from the measurement data the phase transition temperatures can be determined as well as an estimation of the birefringence change with temperature. The experimental results are supported by numerical simulations.
The transient grating technique was used to study the optical properties of hydrogenated amorphous silicon films. A carrier lifetime τe=3.3 μs, a diffusion coefficient D=4.4×10−2 cm2/s, and effective third order nonlinear susceptibility χ(3)=(5.1±1.0)×10−7 esu were measured for λpump=532 nm. The electronic and thermal contributions of the grating were estimated by diffracting a continuous wave HeNe laser beam. For intensities 1.4–4.1 mW/cm2, ∼68% of the response at 633 nm is of electronic origin. A slowly rising diffraction component was also observed.
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