Takashi Yamagishi

Recent advances and trends in chalcogenide glass fiber technology : a review

Abstract Sulfide, selenide and telluride glass fibers were prepared for infrared optical applications. A new crucible drawing method was developed for the drawing of fibers with glass cladding. The extrinsic losses caused by some oxide impurities were suppressed by the purification of raw elements. The transmission loss and mechanical strength, i.e., bending and tensile, of each fiber were investigated before and after the heat treatment under humid conditions. The fibers obtained were used for the power delivery of CO2 laser (10.6 μm) and CO laser (5.4 μm). The antireflection coating onto fiber ends and cooling of fiber with gas or water were examined for the improvement of power transmission efficiency. A fiber cable having ZnSe lens at the output end was prepared for medical and other applications. Temperature monitoring, thermal imaging and gas sensing were also tried using the fibers.

Chalcogenide glass fiber with a core–cladding structure

GeAsSeTe, GeSeTeTl, and GeSeTe glass fibers with a core-cladding structure were prepared by one of two methods: crucible drawing or preform drawing. The diameter of the core was 340 microm and that of the cladding was 440 microm. The transmission loss spectra of the fibers were measured by the cut-back method. The crucible drawing method was preferable to reduce the loss due to structural imperfections at the interface of the core and cladding. The lowest loss of 1.7 dB/m was achieved at 10.6 microm (the wavelength of the CO(2) laser) in the fibers with a GeSeTe core and a GeAsSeTe cladding. Transmission of CO(2) laser power was examined using a 1.5-m long fiber and an output power of 2 W (2.2 kW/cm(2) in power density) was obtained.

Coherent infrared fiber image bundle

Coherent infrared (IR) image bundle was developed for the delivery of the IR thermal image. The fiber employed was the As2S3 glass core of 65 μm diam and Teflon (perfluoronated ethylene propylene) cladding of 75 μm diam, which has the transmission range in the wavelength region between 1 and 7 μm. Two kinds of bundles of 100 cm long were prepared, which consisted of 1550 fibers (NPB75‐1550) and of 8400 fibers (NPB75‐8400). The IR imaging system was constructed by coupling the bundle to an IR television camera. The performance of the system was investigated by detecting the thermal image of an operating LSI package.

Optical and thermal properties of chalcogenide Ge-As-Se-Te glasses for IR fibers

Chalcogenide Ge-As-Se-Te glasses for infrared fiber have been investigated. The extent of the glass forming region, the thermal properties and the infrared transmissions are reported. The glasses were purified by the distillation method containing Mg getter to remove oxide absorption peaks. The fibers were fabricated by the crucible method using high purified glasses and their transmission loss spectra were measured in a wavelength region 3–13 μm. The lowest transmission loss at 10.6 μm obtained is 1.5 dB/m. In the glass system, the appropriate Te content for low-loss fiber at 10.6 μm was found in the vicinity of 50 atomic %.

Gradient-index rod lens with high N.A.

new gradient-index lens with high numerical aperture has been fabricated by a new ion-exchange technique. In this treatment, a glass rod doped with a highly polarizable ion (dopant A) is immersed into KNO3 salt doped with a medium polarizability ion (dopant B). Dopant B penetrates into the rod and modifies the refractive-index profile of the lens. This new lens has 0.6 N.A. and gives a 1.18-micron spot diam in the light-focusing system. This lens gives good results also in a light source coupling system and is useful in microoptic devices.

Low‐loss chalcogenide glass fiber with core‐cladding structure

Ge‐As‐Se‐Te glass fiber having the core‐cladding structure was prepared using a rod‐in‐tube method. Fibers more than 30 m in length were drawn from a crucible with a nozzle and coated with an UV curable polymer. The diameters of the core and clad were 300 and 420 μm, respectively. The transmission loss spectra of the fibers were measured by the cut‐back method and 0.6 dB/m was attained at the wavelength of 8.5 μm.

Transmission loss of Ge-Se-Te and Ge-Se-Te-Tl glass fibers

Transmission loss spectra of Ge-Se-Te and Ge-Se-Te-Tl unclad glass fibers were measured in a wavelength region between 2 and 13μm. Raw materials were purified by the H2 reduction for Ge and Tl and by the distillation for Se and Te. The minimum loss of the Ge-Se-Te fibers was 0.6dB/m at 8.2μm(1.5dB/m at 10.6μm) where the glass composition was Ge27Sel8Te55. Although the introduction of Tl above 4mol % increased the intrinsic absorption loss, the best result of 1.0dB/m at 9.0μm(1.5dB/m at 10.6μm) was achieved for Ge25Se13Te60 Tl2 glass fiber.

Fabrication of a new gradient-index rod lens with high performance

Abstract A gradient-index rod lens was fabricated by the new ion-exchange technique, in which another dopant was added to the fused salt. It was found that this dopant remained only in the merginal region of the glass rod and modified the improper refractive index distribution in this region. The lens has high numerical aperture of 0.6 and gives good results in the light focusing system and the light source coupling system.

Refractive index measurement of the TeX glasses

Abstract Refractive index measurements have been performed as a function of wavelength and as a function of temperature for different tellurium halide based glasses (the TeX glasses). The dispersion properties have been discussed and compared with chalcogenide glasses. It has been indicated that a small modification of the glass composition can lead to an important change of the refractive index. These results are interesting for the design of fibres having a core-cladding structure. As far as the d n /d T is concerned, this thermal-optical parameter is almost the same for different glasses in the same family.

Transmission-loss spectra of chalcohalide Se−Te−I glass fibers and its delivery of CO2 laser power

Chalcohalide Se-Te-I glass fibers have been investigated. The glasses stable against crystallization were found in the region of Se20-70Te10-40I20-45 (at.%). Unclad fibers were prepared by the pressurized crucible fiber-drawing method. The lowest transmission loss of 0.9 dB/m at 10.6 µm wavelength, which is lower than that of previously reported chalcogenide glass fiber, was achieved for the Se25Te30I45 glass fiber. The maximum CO2 laser power delivered through a fiber of 400 µm in diameter and 1 m in length was only 0.8 W. Both the absorbance increments with temperature and the low glass transition temperature of this glass have imposed a limitation on its deliverable power.