Mitsunobu Miyagi

Silver hollow optical fibers with acrylic silicone resin coating as buffer layer for sturdy structure

For sturdy silver hollow optical fibers, acrylic silicone resin is newly used as a buffer layer between an inner silver layer and a silica capillary. This acrylic silicone resin film prevents the glass surface from chemical and mechanical micro damages during silver plating process, which deteriorate mechanical strength of the hollow fibers. In addition, it keeps high adhesion of the silver layer with the glass surface. We discuss improvement of mechanical strength of the hollow glass fibers without deterioration of optical properties.

Fabrication of a rugged polymer-coated silver hollow fiber with a vitreous film for the infrared

A rugged hollow fiber is fabricated by liquid-phase coating techniques. A silica glass capillary is used as the substrate and a vitreous film is firstly coated on the inner surface of the capillary to protect the glass tube from moisture. This protective coating keeps the thin-wall glass tube away from damage due to the following silver plating process. On the protective coating, a silver film is deposited by the conventional mirror plating technique. Subsequently, a polymer film is coated on the silver film to reduce transmission loss by employing interference effect of the polymer film. Fabrication processes and transmission properties of the rugged polymer-coated silver hollow fiber were discussed. The loss for the 700-μm-bore size, 1-m-length hollow fiber was 2 dB under straight configuration, and 3.5 dB under the configuration of a 270 degree bending with a 15-mm bending radius at the wavelength of 2.94 μm.

Dy:PbGa2S4 laser radiation and its delivery by hollow waveguide

The mid-infrared radiation generated by bulk Dy:PbGa2S4 laser working at room temperature was characterized and for its delivery the special type of COP/Ag hollow waveguide was used. The optical pumping of Dy:PbGa2S4 laser was performed by flashlamp pumped Er:YLF laser at 1.73 μm wavelength. The compact 60 mm long Dy:PbGa2S4 laser oscillator worked in free-running mode with the repetition rate 1.5 Hz. The output energy was 5.1 mJ in 80 μs long pulse at 4.3 μm wavelength. The spatial beam structure was close to the Gaussian shape. The goal of the presented study was the preliminary investigation of the mid-infrared Dy:PbGa2S4 radiation delivery possibility by the cyclic olefin polymer and silver coated hollow glass waveguide. The length of the waveguide was 103 cm and the inner diameter was 700 μm. The thickness of the polymer inner layer was calculated for the optimal 4 μm radiation transmission. Mid-infrared laser radiation was coupled into the waveguide by the CaF2 lens with the focal length 55 mm. The characterization of delivered 4.3 μm radiation was provided. It was observed that the spatial structure is changing essentially, which follows from the transmission principle of the hollow waveguide. As conclude the delivery system for 4.3 μm mid-infrared Dy:PbGa2S4 laser radiation was investigated for the first time.

Uniform polymer-film formation in 100-μm-bore hollow fiber for Er:YAG laser transmission

Flexible 100-μm-bore hollow fibers were developed for Er:YAG laser delivery. The hollow fiber was inner coated with silver and dielectric layer to enhance the reflection rate at an objective wavelength band. A dielectric layer is formed by using the liquid-phase coating technique. Micro tube pump with an inner diameter of 300-μm is newly used to flow polymer solution through the ultra-thin silver hollow fiber with a constant speed. Fabrication process and transmission properties of the ultra thin polymer-coated silver hollow fiber were discussed. The loss for the 100-μm-bore size, 10-cm-length polymer-coated silver hollow fiber was 1.7 dB at the wavelength of 2.94 μm.

Contact versus non-contact ablation of the artificial enamel caries by Er:YAG and CTH:YAG laser radiation

The aim of study is to compare the ablation effect of contact and non-contact interaction of Er:YAG and CTH:YAG laser radiation with artificial enamel caries lesion. The artificial caries was prepared in intact teeth to simulate demineralized surface and the laser radiation was applied. Contact and non-contact ablation was compared. Two laser systems Er:YAG 2.94 μm and CTH:YAG 2.1 μm were used. The enamel artificial caries were gently removed by laser radiation and flow Sonic fill composite resin was inserted. Scanning electron microscope was use to evaluate the enamel surface.

Er:YAG and CTH:YAG laser radiation: Contact versus non-contact enamel ablation and sonic-activated bulk composite placement

Laser radiation can be used for effective caries removal and cavity preparation without significant thermal effects, collateral damage of tooth structure, or patient discomfort. The aim of this study was to compare the quality of tissue after contact or non-contact Er:YAG and CTH:YAG laser radiation ablation. The second goal was to increase the sealing ability of hard dental tissues using sonic-activated bulk filling material with change in viscosity during processing. The artificial caries was prepared in intact teeth to simulate a demineralized surface and then the Er:YAG or CTH:YAG laser radiation was applied. The enamel artificial caries was gently removed by the laser radiation and sonic-activated composite fillings were inserted. A stereomicroscope and then a scanning electron microscope were used to evaluate the enamel surface. Er:YAG contact mode ablation in enamel was quick and precise; the cavity was smooth with a keyhole shaped prism and rod relief arrangement without a smear layer. The sonic-activated filling material was consistently regularly distributed; no cracks or microleakage in the enamel were observed. CTH:YAG irradiation was able to clean but not ablate the enamel surface; in contact and also in non-contact mode there was evidence of melting and fusing of the enamel.

Optimal design for hollow fiber inner-coated by dielectric layers with surface roughness

We report the optimal design for hollow fiber inner-coated with metallic and multi-dielectric layers by using ray-optics theory. Transmission characteristics of the multilayer hollow fiber are more dependent on the film surface roughness in infrared region. Comparisons of fibers with smooth and rough films are made and discussed in detail. The optimal design for film thickness, inner radius, the number of layers and refractive indices is presented. The calculation results are important for structure design, material selection and further fabrication of metallic multilayer hollow fiber when considering imperfections in film coating techniques.