Yasutake Ohishi

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The aim of this paper is to present an overview of the recent achievements of our group in the fabrication and optical characterizations of As(2)S(3) microstructured optical fibers (MOFs). Firstly, we study the synthesis of high purity arsenic sulfide glasses. Then we describe the use of a versatile process using mechanical drilling for the preparation of(More)
We fabricated a series of glasses with the composition 94.7-␹GeO 2-5Al 2 O 3-0.3Bi 2 O 3-␹PbO ͑␹ =0–24 mol. %͒. Characteristic absorption bands of bismuth centered at 500, 700, 800, and 1000 nm were observed. Adding PbO was found to decrease the strength of bismuth absorption. The addition of 3%–4% PbO resulted in a 50% increase in lifetime, a 20-fold(More)
Tellurite glass microstructure fibers with a 1 microm hexagonal core were fabricated successfully by accurately controlling the temperature field in the fiber-drawing process. The diameter ratio of holey region to core (DRHC) for the fiber can be adjusted freely in the range of 1-20 by pumping a positive pressure into the holes when drawing fiber, which(More)
We demonstrate the supercontinuum (SC) generation in a suspended-core As(2)S(3) chalcogenide microstructured optical fiber (MOF). The variation of SC is investigated by changing the fiber length, pump peak power and pump wavelength. In the case of long fibers (20 and 40 cm), the SC ranges are discontinuous and stop at the wavelengths shorter than 3500 nm,(More)
We report emission from a bismuth doped chalcogenide glass which is flattened, has a full width at half maximum (FWHM) of 600 nm, peaks at 1300 nm and covers the entire telecommunications window. At cryogenic temperatures the FWHM reaches 850 nm. The quantum efficiency and lifetime were as high as 32% and 175 mus, respectively. We also report two new(More)
We report what we believe to be the first demonstration of supercontinuum generation spanning over three octaves from UV (at least approximately 350 nm) to 3.85 microm in a 2.5-cm-long fluoride fiber pumped by a 1450 nm femtosecond laser. The spectral broadening in the fluoride fiber is caused primarily by self-phase modulation. Its performance is also(More)
We demonstrate third-harmonic generation (THG) in an elliptical-core ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fluoride fiber, for the first time to our best knowledge. Linearly polarized THG around 523 nm is obtained when pumped by a pulse laser at 1560 nm. The extinction ratios of average power and peak power are ~6.7 and ~6.8 dB, respectively, in a 10 m long(More)
We have fabricated a highly nonlinear complex microstructure tellurite fiber with a 1.8 micron core surrounded by four rings of holes. The cane for the fiber was prepared by combining the methods of cast rod in tube and stacking. In the process of fiber-drawing a positive pressure was pumped into the holes of cane to overcome the collapse of holes and(More)
We report the realization of a solar-pumped fiber laser (SPFL) using a double-clad (a center core/ an inner clad working also as optical waveguide/ an outer clad) Nd-doped fluoride optical fiber as a laser medium. With a compact off-axis parabolic mirror of 5 cm in aperture diameter, the natural sunlight is concentrated by a factor 10⁴, and introduced(More)
A highly nonlinear composite fiber, which has a 1.5 microm chalcogenide glass core surrounded by a tellurite glass microstructure cladding, has been fabricated by the method of stack and draw. A tellurite glass capillary containing a As(2)S(3) rod was sealed with negative pressure inside. Then this capillary and other empty capillaries were stacked into a(More)