Jacob Dror

Characterization of hollow fibers for the transmission of infrared radiation.

Plastic hollow fibers were made from plastic tubes covered on the internal wall with a metal layer (a-type) or a metal layer and dielectric layer on top of it (b-type). The CO(2) laser energy transmission through the hollow fiber was measured as a function of the radius of curvature and the coupling lens (focal length at a constant fiber length). The yield of the transmission decreased in subtle curvatures (radius of curvature up to 100 cm) and remained almost constant as the curvature became sharper (down to radius of curvature of 13 cm). For the a-type fibers, the characteristics of attenuation depended on the focal length of the coupling lenses. The energy distribution at the output was measured and mapped. The experimental results showed that the maximum of the energy distribution is asymetrically positioned relative to the center and closer to the internal wall at a smaller bending radius. This was predicted in our previous theoretical calculation. The value of transmitted power attenuation was up to 1.4 dB/m. Maximum power at the output was 30 W, for a fiber of 50-cm length and a cross-sectional diameter of 1.9 mm. These types of hollow fiber have already been used in surgical experiments on dogs.

Plastic hollow fibers as a selective infrared radiation transmitting medium

Plastic hollow waveguides (used as fibers) for infrared (IR) transmission were made from plastic tubes covered, on the internal wall, with a metal layer (Ag) and growing a dielectric thin (AgI) overlayer by direct iodination on it. The existence of several absorption lines at given wavelengths in the middle infrared (mid‐IR) region is predicted theoretically and measured experimentally. From the wavelengths of absorption lines the thickness of the AgI film has been computed. The average thickness of the AgI in the hollow waveguide increased with the iodination time and with the concentration of the iodine solution. The crystal size of the AgI was increased with the increase of the AgI thickness. By controlling the iodination process it was possible to make waveguides which can be employed as filters for various wavelengths of the transmitted mid‐IR radiation.

Flexible waveguides for Er-YAG laser radiation delivery

Flexible plastic waveguides (FPW) were devised for the delivery of Er-YAG laser radiation. The FPW characteristics were studied under various conditions. In vitro studies were carried out to explore the drilling procedure on extracted teeth and the FPW-tissue mutual effects. The results which were obtained proved that the FPW as a delivery device might be a substitute hand applicator for the pneumatic turbine for drilling in teeth.<<ETX>>

Chalcogenide glasses Ge–Sn–Se, Ge–Se–Te, and Ge–Sn–Se–Te for infrared optical fibers

Chalcogenide glasses of the systems Ge–Sn–Se, Ge–Se–Te, and Ge–Sn–Se–Te have been prepared. Several compositions were found suitable for drawing fibers for CO 2 laser radiation (λ = 10.6 μ m) transmission. The glasses were characterized by x-ray diffraction, DSC (Differential Scanning Calorimetry), SEM with EDX analysis, FTIR spectrometry, density, and microhardness measurements. The glass transition temperature and microhardness of Ge–Se–Sn and Ge–Sn–Se–Te glasses decreased with increasing Sn content, for most of the samples. The region of high IR transparency of Ge–Se–Sn, Ge–Se–Te, and Ge–Sn–Se–Te glasses was slightly expanded (1–2 μ m) toward longer wavelengths, compared to Ge–Se glasses, mainly for the glasses containing 70 at.% Se. The intensity of the impurity absorption peak of Ge–O (at λ ∼ 12.8 μ m), which usually appears in Ge–Se glasses, was reduced or absent in Ge–Sn–Se–Te glasses. The best fibers were produced with the glass composition Ge– 0.8 Sn 0.2 Se 3.5 Te 0.5 . An attenuation of 20 dB/m at 10.6 μ m, and a transmitted maximum power density of 2.4 ⊠ 10 6 W/m 2 were measured. The mechanical and optical characteristics of these glasses have been related to the glasses structure. Corresponding to the reduced masses of the bonds formed in the Ge–Sn–Se–Te system (in the amorphous region), it is expected that the multiphonon edge is slightly shifted. As a consequence, as was measured, the transparency region has been expanded by less than 2 μ m toward longer wavelengths.

Ray model for transmission of metallic-dielectric hollow bent cylindrical waveguides.

The problem of transmitting CO(2) laser radiation through metallic or metallic with inner dielectric coating (metallic-dielectric) bent hollow cylindrical waveguides is investigated using a ray model. Computer calculations of transmission as a function of the geometrical dimensions of the waveguide are performed. The coupling of laser radiation at the entrance of the waveguide is also taken into account. The theoretical calculated transmission is compared with previously published experimental data and good agreement is obtained for a large range of curvatures. The devised ray model contributes to a better understanding of the role of the dielectric layer in the metallic-dielectric waveguide, increasing the transmission of the radiation. The calculation of the transmission as a function of the radius of the cross section of the waveguide shows that, for a best metallic-dielectric waveguide, an optimal cross-sectional diameter appears where the transmitted energy is maximum. The method presented will be of value as a tool in the design of hollow cylindrical waveguides.

Characterization of chemically formed silver iodide layers for hollow infrared guides

Abstract The process of iodination of a thin layer of Ag deposited by electrodes on the internal well of a tube was investigated. The AgI layer was formed employing several methods, which give a mixture of β and γ AgI phases. The substrate of the silver layer (teflon or glass) has no influence on the β and γ distribution. The fastest achieved is a γ form which is converted during the forming process partially into β isomer. The γ isomer is the most suitable form for IR light guiding.

Ray model for transmission of infrared radiation through multibent cylindrical waveguides

An improved ray model for simulating the transmission of laser radiation through a metallic or metallic-dielectric multibent hollow cylindrical waveguide has been developed. It calculates the power transmission and the power density at any point along the curved waveguide, as a function of geometrical dimensions of the waveguide, coupling lens at the entrance, polarization (random, vertical, or perpendicular), and the 3-D trajectory of the waveguide. The theoretical calculations are compared with the experimental results.

Use of metallic and dielectric films for hollow fibers

Abstract The problem of transmission of CO2 laser radiation through hollow fibers and waveguides was studied theoretically and confirmed experimentally. The transmission of the laser radiation through metal and metal-dielectric tubes was measured and compared with the theoretical data based on a ray model solution. This makes possible the investigation of the transmission of the CO2 radiation through waveguides when the internal wall is covered with a metal or a metal- dielectric film. It was shown theoretically and proved experimentally that the transmission of the CO2 radiation is possible even through bent waveguides.

Improved Metallic Tube Infrared Waveguides With Inside Dielectric Coating

Hollow fibers were made of plastic materials with both metallic and dielectric inside coating. Previous theoretical investigation had shown that by the use of optimal metallic and dielectric layers, low attenuation could be achieved, even for bent fibers. Experimentally, the attenuation of 2 dB/m was measured for a 3 mm diameter flexible plastic waveguide.

Use Of Metallic And Dielectric Films For Hollow Fibers

The problem of transmission of CO2 laser radiation through hollow fibers and waveguides was studied theoretically and confirmed experimentally. The transmission of the laser radiation through metal and metal-dielectric tubes was measured and compared with the theoretical data based on a ray model solution. This makes possible the investigation of the transmission of the CO2 radiation through waveguides when the internal wall is covered with a metal or a metal-dielectric film. It was shown theoretically and proved experimentally that the transmission of the CO2 radiation is possible even through bent waveguides.