Yoshinori Hibino

Polarization-insensitive arrayed-waveguide wavelength multiplexer with birefringence compensating film

An integrated-optic polarization-insensitive wavelength multiplexer that is based on an arrayed-waveguide grating is described. Polarization dependence due to thermal stress was eliminated by depositing an a-Si birefringence compensation film on the arrayed-waveguide. The multiplexing operation of 16 wavelength channels with a 0.8 nm spacing was confirmed to be independent of the polarization state.<<ETX>>

Photosensitivity in Ge-doped silica optical waveguides and fibers with 193-nm light from an ArF excimer laser.

Photosensitivity in optical fibers and waveguides has been associated with the bleaching of an absorption band located near 5.0 eV (or 242 nm). We present new results for Bragg grating formation and UV bleaching experiments carried out using 193-nm light from an ArF excimer laser instead of the usual laser sources operating near 242 or 248 nm.

Integrated-optic ring resonators with two stacked layers of silica waveguide on Si

A ring resonator with a radius of 1.5 mm is demonstrated using a stack structure consisting of two layers of GeO/sub 2/-doped silica waveguide with different refractive index differences ( Delta ). One is a high- Delta waveguide layer with a Delta of 2% for a small-radius ring and the other is a waveguide layer with a Delta of 0.75% for good fiber coupling. The waveguides and a flattened middle-cladding layer are stacked on a Si substrate. The ring resonator exhibited a wide free spectral range (FSR) of 21.6+or-0.1 GHz and a high finesse of 110+or-10.<<ETX>>

Neodymium-doped silica optical waveguide laser on silicon substrate

A waveguide laser with a Nd-doped silica core fabricated on a Si substrate using flame hydrolysis deposition and reactive ion etching techniques is described The Nd ion concentration was about 2000 p.p.m. and the optical loss at 1.05 mu m was 0.85 dB/cm. CW lasing at a wavelength of 1.0515 mu m with a threshold of about 150 mW was achieved successfully with pumping at 0.80 mu m.<<ETX>>

PHOTOSENSITIVITY IN PHOSPHORUS-DOPED SILICA GLASS AND OPTICAL WAVEGUIDES

Irradiation of hydrogen loaded or flame brushed phosphorus doped, germanium free silica glass with a 193‐nm ArF excimer laser changes the optical absorption at ultraviolet wavelengths by 40–140 dB/mm and the refractive index by more than 2×10−4. Bragg gratings with 90%–95% reflectivity are photoinduced in channel optical waveguides made from this glass. The thermal stability of the photosensitivity is measured by annealing up to 700 °C.

Low-loss planar lightwave circuit OADM with high isolation and no polarization dependence

A passive optical add-drop multiplexer with 1 dB of insertion loss and 36 dB of isolation is fabricated by writing Bragg gratings in a waveguide Mach-Zehnder interferometer using ArF excimer laser light. The spectral properties and bit-error-rate performance of the device are fully characterized using polarized light.

Wavelength division multiplexer with photoinduced Bragg gratings fabricated in a planar-lightwave-circuit-type asymmetric Mach-Zehnder interferometer on Si

A planar-lightwave-circuit (PLC)-type wavelength division multiplexer with photoinduced Bragg gratings is successfully fabricated on Si. The Bragg gratings are formed in the arms of an asymmetric four-port Mach-Zehnder interferometer (MZI). We demonstrate that signals with three wavelengths can be demultiplexed to three output ports. Heaters are used to compensate for the phase error in the MZI and to switch the output ports. An insertion loss at a Bragg wavelength of 1534.78 nm can be changed from 1.5 to about 19 dB by controlling the heater, indicating that photoinduced Bragg gratings are useful for expanding PLC functions.

Raman study on silica optical fibers subjected to high tensile stress

For silica (pure and synthetic) optical fibers, on which tensile stresses from 0 to 4 GPa were imposed, Raman studies were carried out. It has become evident by deconvoluting the silica Raman peaks that the main peak intensity at 440 cm−1 decreases with increasing stress while the peaks at 490, 604, and 800 cm−1 remain practically unchanged. The fact that the 490 cm−1 defect line was not affected by the stress applied to fibers is contrary to the conclusion by G. E. Walrafen, P. N. Krishnan, and S. W. Freiman [J. Appl. Phys. 52, 2832 (1981)]. The results obtained in the present study are rather extensively discussed from a microscopic view of silica glass networks.

400-channel 25-GHz spacing arrayed-waveguide grating covering a full range of C- and L-bands

We realized a 400-channel 25-GHz spacing arrayed-waveguide (AWG) on a 6-inch Si wafer using 1.5%-/spl Delta/ silica-based waveguides. This AWG covers the full C- and L-bands and exhibits an on-chip loss of 3.8-6.4 dB.

Residual stress effects on refractive indices in undoped silica‐core single‐mode fibers

It is reported for the first time that refractive indices are reduced remarkably by residual stress in undoped silica‐core/fluorine‐doped silica‐clad single‐mode fibers. The very high residual stress concentrated at the small diameter core is induced by drawing tension because of the difference in viscosity between the core and cladding. The decrease in refractive indices results from photoelastic effects due to residual stress in the core.