Satoshi Ishizuka

Mixed rare‐earth iron garnet (TbY)IG for magnetic field sensors

Temperature dependence of sensitivity constants, corresponding to Verdet constant, of dodecahedrally substituted (TbxY1−x)IG crystals grown by a conventional flux method and liquid‐phase epitaxy method are studied. By measuring the variation of the sensitivity constant with temperature, it was found that crystals with X=0.19 show a minimum value of ±1% between 300 and 400 K. The temperature dependence of sensitivity constants on Tb concentration was explained by a simple theoretical calculation.

Small optical magnetic-field sensor that uses rare-earth iron garnet films based on the Faraday effect

Highly accurate optical magnetic-field probe sensors that use iron garnet films have been developed. New probe-type sensors were designed with a confocal optical system. A new garnet composition, Bi(0.98)Gd(0.92)La(0.03)Y(1.07)Fe(4.72)Ga(0.28)O(12), was found that shows high temperature stability for a sensitivity of less than 2.0% from -20 to +80 degrees C. The linearity error of the sensor output was within 1.0% for alternating magnetic fields from 0.3 to 42 mT. An optical current transformer that uses the proposed sensor has an ac linearity of 1.0% for input current up to nearly 300 A. The sensor realized high performance in actual use.

Optical Fiber Current Sensors Using Garnet Crystal for Power Distribution Fields

We introduce applied examples (already put to practical use) of power distribution fields of optical fiber current sensors using iron garnet crystal that have high sensitivity, high linearity and stable temperature characteristics. We also describe two types of new optical fiber current sensors developed recently aimed at cost reduction and high performance.

Temperature-stabilized optical isolator for collimated light using (BiLuGd) 3 Fe 5 O 12 /(BiGd) 3 (FeGa) 5 O 12 composite film

We have fabricated optical isolators whose temperature dependence of the isolation ratio has a stability of <0.2 dB using (BiLuGd)(3)Fe(5)O(12)/(BiGd)(3)(FeGa)(5)0(12) composite film. It has been confirmed that the temperature-dependent forward loss of the isolators originates from the thermal fluctuation of the absorption peak in the films. We have also evaluated the degradation of the isolation ratio for collimated light depending on the incident angle of the collimated light, the incident position with respect to the optic axis, and the wavelength range needed for practical use.

Integration of a Faraday rotator and a mode selector for a magnetic field sensor

We have demonstrated an integrated magnetic field sensor consisting of a Faraday rotator and a mode selector for the first time. The sensor is a loaded waveguide which has a waveguide layer made of a garnet with magneto‐optical effect for Faraday rotation and a metal clad layer for mode selection. The magnetic field can be measured by detecting the change of optical output power from the waveguide. An output power change of ±5% has been observed as the magnetic field is changed from zero to ±60 Oe.

Three-dimensional (BiY) 3 Fe 5 O 12 waveguide with a load layer made of SiO 2

We have developed a loaded (BiY)(3)Fe(5)O(12) waveguide for integrated magnetooptic devices. The load layer made of SiO(2) was fabricated with a reactive ion etching using CHF(3) gas. The waveguiding loss was measured by the streak method and by the cutback method. The measured values were <7 cm(-1), and the waveguiding loss caused by the lateral confinement was deduced to <1 cm(-1).

Real-time measurement of wavelength selectivity of reflection holograms.

The wavelength selectivities of reflection holograms are measured in real time during exposure by using a system that can measure a spectrum at intervals of tens of milliseconds.

Thick Film Crystal Growth of the Highly Bi-Substituted Garnet for Optical Isolator

The molar ratio of (Lu<inf>2</inf>O<inf>3</inf>/Lu<inf>2</inf>O<inf>3</inf> + Gd<inf>2</inf>O<inf>3</inf>) and R<inf>1</inf> parameter of the LPE melt for (BiLuGd)<inf>3</inf>Fe<inf>5</inf>O<inf>12</inf> growth were varied to determine the region of pit-free thick film growth. The borderline between the presence and absence of pits is in the neighborhood of Gd<inf>2</inf>O<inf>3</inf>/Lu<inf>2</inf>O<inf>3</inf> = 1 in the melt. The magneto-optical properties of the 250 ¿m thick film were studied. 2408°/cm of the Faraday rotation (¿ = 1.153 ¿m) and 37.4 dB of extinction ratio were obtained. This result confirms that it is suitable for compact isolators.

1.3 μLD Module with Optical Isolator Using YIG Crystals by the Floating Zone Method

This paper reports on fabrication of an LD (laser diode) module with an optical isolator using YIG crystals in which the optical parts are fixed by soldering and YAG laser welding. The LD to single-mode fiber coupling efficiency was less than -4.6 dB, and the isolator insertion loss was 0.1 dB. Output variation in the 0 to 50°C temperature range was as low as 0.4 dB and after heat treatment, coupling loss variation was less than 0.25 dB, a very stable value. This seems to be due to the fact that the optical fiber and the lens were fixed by the metal fixing methods. Laser output noise induced by the reflected laser beam from the far end of the single-mode fiber is reduced by the optical isolator. Using YIG made by the FZ method and fabricating the module using the metal fixing methods realizes high isolation ratio and high reliability.

Optical Magnetic Field Sensors Using Mixed Rare-Earth Iron Garnet Crystals

Optical magnetic field (current) sensors have recently reached practical application. This paper reports on evaluations of LPE garnet (TbY) IG crystals for magnetic field sensors, and on their optical characteristics. 100 ¿m thick films were produced on {111} GGG substrate, but pits appeared even when using a Pbo/B2O3 melt with a low 6.0 molar ratio. We studied the sensitivity and linearity of the Faraday rotation of these LPE films.