Kaoru Matsuda

Bi-substituted rare-earth iron garnet composite film with temperature independent Faraday rotation for optical isolators

(BiLuGd)IG/(BiGd)(FeGa)G composite films of which the temperature derivatives of Faraday rotation angle at 45 degree ( \equiv\beta ) are nearly zero, were grown by a two-step liquid phase epitaxial (LPE) method. The relative intensity noise (RIN) of the 1.3 μm laser diode (LD) with an optical isolator using the β=0.00 deg/°C garnet composite film were measured in comparison with an isolator using the garnet crystal with β of 0.05 deg/ °C. The relation between the RIN and the feedback light power and the relation between the RIN and β value were clarified. It was found that the increase of the RIN by periodic noise caused by feedback light to the LD from the fiber-far-end was observed when the feedback light power increases more than -62dB. In the practical temperature range of -20\sim+60\deg C garnet composite films with β=0.00 deg/°C are required in order to prevent the periodic noise.

Single longitudinal mode operation of long, integrated passive cavity InGaAsP lasers

We propose a new 1.3‐μm wavelength InGaAsP laser—the integrated passive cavity (IPC) laser—and demonstrate its device performances compared with conventional lasers fabricated under similar procedures. The long IPC laser (3.55‐mm‐long passive cavity), as well as the short IPC laser, exhibited single frequency oscillation even just above the threshold, and the maximum ratio of longitudinal main to submode exceeded 30 dB. They also showed favorable effects in the oscillation frequency stabilization.

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.

Magnetless Faraday rotator of (BiY)3Fe5O12 waveguide with stripe magnetic domains

We propose and demonstrate a magnetless Faraday rotator of a (BiY)3Fe5O12 waveguide with stripe magnetic domains. It has a potential application to compact optical isolators. The specific Faraday rotation angle of −150 deg/cm and the extinction ratio of 13 dB are obtained without a magnet.

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).

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.