Shiro Takahashi

Pr 3+ -doped fluoride fiber amplifier operating at 1.31 μm

We propose what is to our knowledge the first use of a Pr(3+)-doped fluoride fiber amplifier as a practical amplifier operating at the 1.3-microm band, based on a demonstration of signal amplification and a spectroscopic investigation. The feasibility of the fluoride fiber amplifier is confirmed.

Concentration effect on gain of Pr/sup 3+/-doped fluoride fiber for 1.3 mu m amplification

The concentration quenching mechanism in Pr/sup 3+/-doped fluoride fiber operating at the 1.3- mu m band is investigated. It is confirmed that the cooperative upconversion process causes signal gain saturation with pump power and degrades the gain characteristics of Pr/sup 3+/-doped fluoride fiber at a concentration of 1000 p.p.m. The reduction in gain coefficient due to cooperative upconversion is almost suppressed at a concentration of 500 p.p.m. A Pr/sup 3+/ concentration of 500 p.p.m. is a practical concentration for the fabrication of efficient Pr/sup 3+/-doped fluoride fiber amplifiers.<<ETX>>

15.1-dB-gain Pr/sup 3+/-doped fluoride fiber amplifier pumped by high-power laser-diode modules

A Pr/sup 3+/-doped fluoride amplifier pumped by high-power 1.017- mu m laser diode modules is demonstrated. Fiber-pigtail-type devices are used. A net gain of 15.1 dB is achieved for a 1.31- mu m signal at a pump power of 160 mW.<<ETX>>

The Amplification Properties of a Highly Er3+-Doped Phosphate Fiber

The amplification properties of a highly Er3+-doped phosphate fiber were measured. Gain was observed in the wavelength region of 1.525-1.57 µm and the wavelength at maximum gain was 1.535 µm. Since the absorbed pump threshold obtained experimentally agreed with the calculated result, no cooperative upconversion process occurred in the 1.53 wt% Er2O3 fiber.

Gain characteristics of Pr/sup 3+/-Yb/sup 3+/ codoped fluoride fiber for 1.3 mu m amplification

The authors report on the ability of the Pr/sup 3+/-Yb/sup 3+/ codoped system to move the pumping wavelength to wavelengths shorter than 1.017 mu m. It was demonstrated that, by codoping of Yb/sup 3+/ with Pr/sup 3+/-doped fluoride fiber, amplifiers can be moved to the spectral range where effective pumping can be done with InGaAs laser diodes that have strained-layer quantum-well structures that were developed as a pumping source for Er/sup 3+/-doped fiber amplifiers. The pumping wavelength range was extended down to 0.93 mu m.<<ETX>>

Athermal silica-based interferometer-type planar light-wave circuits realized by a multicore fabrication method

Athermal silica-based interferometer-type planar light-wave circuits were realized by a newly developed multicore fabrication method. In this method, inductively coupled chemical-vapor deposition and polishing technologies are adopted on a silica substrate with a trench-type waveguide pattern prepared by reactive ion etching. Two kinds of deposited core material, 10GeO2-90SiO2 (mol. %) and 8GeO2-5B2O3-87SiO2 (mol. %), which show wavelength temperature dependence of 9.7 and 8.1 pm/degree C, respectively, were used to prepare the waveguide sections in a device. By adjustment of the lengths of waveguide sections with these two different core materials, athermal characteristics of less than 0.5 pm/degree C were achieved for Mach-Zehnder interferometer filter devices at the 1.55-microm wavelength range while the temperature varied from -20 to 80 degrees C. The new method is also applicable for the preparation of many other kinds of functional devices.

Preparation of ZBLAN Fluoride Glass Particles by Chemical Vapor Deposition Process

We have successfully synthesized NaF-containing ZrF4-based fluoride glass (ZrF4-BaF2-NaF) (ZrF4-BaF2-LaF3-AlF3-NaF) particles by the chemical vapor deposition (CVD) process. In this process, Na β-diketonate (Na(ppm)) was used for the Na source. Differential scanning calorimetry (DSC) results suggested that NaF should be contained uniformly in the glass particles. The thermal properties of the glass which was prepared in this experiment were almost the same as those glass prepared by the conventional melt-casting method.