Naoto Sugimoto

Preparation of Magneto-Optic Single-Mode Buried Channel Waveguides of Lanthanum- and Gallium-Substituted Yttrium Iron Garnet

Magneto-optic single-mode buried channel waveguides are prepared using lanthanum- and gallium-substituted yttrium iron garnet [(La, Ga):YIG] liquid-phase-epitaxial film. The film growth conditions, film properties and the core ridge fabrication method are described. The refractive index of the film is controlled with the film growth temperature. The core ridge size is well controlled using ion beam etching. The obtained waveguides provide low loss coupling with a silica-based waveguide, which is a platform waveguide for a hybrid optical integrated circuit. Magneto-optic mode conversion is observed in a weak applied magnetic field, and the conversion efficiency R max and isolation ratio are evaluated. The relationship between R max and the stress-induced birefringence is discussed.

Stress-Induced Perpendicular Magnetic Anisotropy in PtMnSb Thin Films

Stress-induced perpendicular magnetic anisotropy is studied for PtMnSb thin films deposited on various substrates having different expansion coefficients. The magnetostriction constant λ of PtMnSb thin film is -30 × 10-6. The films perpendicular magnetic anisotropy constant Ku increases as tensile thermal stress in the film plane increases.

Influence of Growth Temperature on the Magnetic and Optical Properties of Liquid-Phase-Epitaxial(LPE)-Grown Lanthanum- and Gallium-Substituted Yttrium Iron Garnet((La, Ga):YIG) Films and Their Application to Waveguides

We measure the growth temperature dependence of the magnetic and optical properties of lanthanum- and gallium-substituted yttrium iron garnet films deposited on gadolinium gallium garnet substrates by the liquid-phase-epitaxial-growth method for use as integrated optical waveguides. The magnetization of the film can be saturated in the film plane by a weak external-magnetic field (<45 Oe). The refractive index is controlled in a range of 2.192 to 2.204 by the growth temperature, which ranges from 893 to 835°C. Rib waveguides with low propagation loss (2.3 dB/cm at 1.55 µm wavelength evaluated by measuring the contrast in Fabry-Perot cavity resonance signals) are also fabricated.

Formation of Ridges on Gd3Ga5O12 by Ion-Beam Etching and Subsequent Phosphoric Acid Treatment Utilizing Tri-Layered Etching Mask

This paper investigates the shapes of straight ridges about 4 µm high, that are formed on [1 1 1], [1 0 0] and [1 1 0] oriented Gd3Ga5O12 (GGG) single crystal substrates by utilizing a Ta/organic layer/Si3N4 tri-layered etching mask. Following argon ion-beam etching, the substrates are soaked in phosphoric acid solution. After soaking, the ridges on a [1 1 1] substrate have perpendicular side walls because the Si3N4 film effectively protects the top surface of the ridge from acid. The stable dissolution form of a [0 0 1] direction ridge on a [1 0 0] substrate tends to have a {1 1 0} face which is inclined at 45° from the perpendicular. The side walls of a [0 0 1] direction ridge on a [1 1 0] substrate tends to be perpendicular after dissolution.

Ar ion-beam etching of gadolinium-gallium garnet

An argon ion-beam etching technique is used to process a Gd3Ga5O12 substrate. A double-layered mask consisting of a Ta film and a photoresist shows good tolerance for the Ar-ion beam during etching. An etching depth sufficient for preparing waveguides is obtained.

Preparation of an epitaxially grown neodymium-doped yttrium aluminum garnet channel waveguide for a

where +c, = +z +, and a, b are the real and imaginary parts of AI and c, d are the real and imaginary parts of A, / , respectively. For simplicity, the small quadratic terms of subharmonics are neglected and constant modulation is assumed in Eq. (7). Figure 1 shows measured K / 2 subharmonic intensity against the detuning frequency varying extemal field from 7 kV/cm to 3 kV/cm. Detailed explanation for experimental conditions, except for the pump intensities which is 11.4 mW/ ._

Ridge Structures Formed on Nd3Ga5O12 and Sm3Ga5O12 Single Crystal Substrates.

Straight ridge patterns are formed in the [ 2] and [10] directions on (111) Nd3Ga5O12 (NGG) and Sm3Ga5O12 (SGG) single crystal substrates, and in the [001] and [10] directions on a (110) NGG substrate by argon ion-beam etching and subsequent soaking in a hot phosphoric acid solution. The ridge shapes are observed with a scanning electron microscope (SEM). The crystal faces, which appear on the ridge side walls, are examined. The anisotropic etching in the phosphoric acid solution strongly depends on the ridge direction as well as on the substrate orientation. The indices are similar to those observed for Gd3Ga5O12 (GGG).

Ion Incident Angle Dependence of Ridge Shapes Formed on [111] Oriented Gd3Ga5O12 by Ion Beam Etching

A ridge pattern is formed on a [111] oriented Gd3Ga5O12 (GGG) substrate using an argon ion-beam etching at various ion incident angles between 90° and 45°. The relation between the ridge shapes and the ion incident angles is studied. The applicability of a phosphoric acid treatment after the ion-beam etching to smooth the ridge side wall is also examined. The ridge shape strongly depends on the ion incident angle. The phosphoric acid treatment causes a noticeable change of ridge shape dependent on the GGG crystal structure.

Ytterbium- and neodymium-doped yttrium aluminum garnet channel waveguide laser operating at 1.03 /sp

gains are more likely to have a multimoded lasing spectrum? This multimode operation is in contrast to later gain coupled DFB lasers, with a longitudinal periodic modulation of gain (or loss), which have a single longitudinal mode lasing spectrum? Generally, however, in real structures, semiconductor lasers as well as dielectric (solid state) lasers, mixed cases occur and the coupling coefficient is a complex q~an t i ty .~ In a preceding paper’ a systematic study of the modulation bandwidth in planar and fiber dielectric DFB lasers has been presented with pure modulation of the index coefficient (resulting in pure real coupling coefficient). We extend approach’ to analyze the 3 dB modulation bandwidth for the complex coupled dielectric planar DFB lasers. The 3 dB modulation bandwidth can be expressed by the frequency R and the damping rate A of the relaxation oscillation in the following way:‘

The formation of ridges in various directions on (111), (100) and (110) Gd3Ga5O12 substrates

Abstract Straight ridge patterns, about 4 μm high, are formed in various directions on (111), (100) and (110) Gd3Ga5O12 single crystal substrates by argon ion-beam etching. This is followed by soaking in phosphoric acid solution in order to optimize the garnet waveguide formation process. The substrate orientation and the ridge direction both have considerable influence on the anisotropic etching of the ion-beam etched ridges in the phosphoric acid solution. The ridges parallel to the [211] direction on (111) substrate are symmetrical; however, their faces are slightly different from those reported for Y3Fe5O12 or Y3Al5O12. The ridges on the (100) and (110) substrates have smooth side walls dependent on the symmetrical garnet crystal structure. Both the intermediate and the final dissolved ridge shapes are similar to the results that have been reported for a garnet single crystal sphere.