Thick Garnet Films Research Articles

Near-field diffraction by a magneto-optical grating in a ferromagnetic film

Theoretical analysis of the near-field magneto-optical (MO) diffraction of light propagating through a ferromagnetic film by a domain structure has been carried out. The results are expressed in terms of the classical theory of diffraction gratings, namely the effective perturbation of the index of refraction and generalised Bragg condition, extended to the near-field case. The near-field case is characterised by a wider variety of types of diffraction, which includes diffraction by in-plane polarisation, both anisotropic and isotropic. It has been shown, analytically and numerically, that the effective layer of a ferromagnetic film that actively contributes to the MO diffraction is severely limited by the Bragg condition, being of the order of d/4, where d is the period of the diffraction grating. Any further increase in the thickness leads only to additional optical losses due to the light absorption. This can explain the lack of resolution reported in the near-field MO experiments where relatively thick garnet films were used.

Optical Mode Conversion by Magnetostatic Surface Waves in Optical Waveguide-Type Devices Using Cerium- and Bismuth-Doped Garnet Crystalline Films

Optical devices using magnetostatic surface waves (MSSWs) have important applications in optical signal processing and optical computing. In this paper we propose the analysis and design of an optical mode conversion device that features improved switching efficiency achieved by the use of a new material with increased magneto-optic effect. The device consists of cerium- and bismuth-doped thin and thick garnet films. The design features 100% mode conversion over an interaction length of about 5 mm for an applied microwave power density in the range 1–10 mW/mm. Cerium- and bismuth-doped Yttrium Iron Garnet (YIG) films are fabricated by rf sputtering and their crystal properties are studied using X-ray microanalyzer and X-ray diffractometer.

Analysis and Design of Magnetooptic Guided Wave Devices in Cerium-Doped Garnet Thin Films

Optical devices using magnetostatic surface waves (MSSWs) have important applications in optical signal processing and optical computing. In this paper we propose the analysis and design of an optical mode conversion device that features improved properties. The device consists of cerium-doped thin and thick garnet films. The design features 100% mode conversion over an interaction length of about 5 mm for an applied microwave power density of a few mW/mm. The characteristics of optical wavelength filtering under a fixed biasing magnetic field are also investigated. The results can be used to construct an optical demultiplexer with wavelength separation as narrow as 2 nm in the wavelength band of 1.3 µm. The MSSW center frequency assumed in the calculation is f c= 3.1504 GHz.

Magneto-optical recording of sputtered garnet films using laser diode

Sputtered garnet film is so transparent in the near-infrared region that recording using a laser diode was thought to be impossible. However, we have found that it is possible if Cr is applied to a thin garnet film. We investigated the sensitivity for static recording. The optical absorption of Cr film is 60% in the 0.8 μm wavelength range, and temperature elevation ocurrs easily. Recording becomes possible through the heat transfer from the Cr to the garnet film. The sensitivity depends mainly on the thickness of the Cr and garnet films. The optical absorption of the garnet film makes little contribution to the sensitivity. Recording needs only 6mW at a pulse width of 0.15 μs for a 0.1 μm thick garnet film by applying a bias field of 150 Oe. This sensitivity is considered to be sufficient for an optical disk mediun. Furthermore, dynamic recording was carried out using a 5-inch glass disk. We obtained a rather low C/N value of 30 dB. The reason for this low C/N value is due to both the irregular bit shape and the medium noise, resulting from the poor morphology of garnet film.

Computer Simulation of Stripe Domain Stretching

Computer simulations of stripe domain stretching processes were performed for several domains together, taking into account the effects of conductors and grooves. For a 2 ?m thick garnet film supporting 5 ?m bubbles and a conductor current of 10 mA, the effects of conductor and groove fields on domains near the center is constant for about 11 or more stripe domains. Simulations showed that stripe domains may be stretched even when several exist together, and that stretching under various bias conditions is possible by appropriate choice of currents and conductor shapes.

A new Faraday rotator using a thick Gd:YIG film grown by liquid-phase epitaxy and its applications to an optical isolator and optical switch

A new Faraday rotator using a thick garnet film grown by liquid-phase epitaxy (LPE) has been proposed and film growth technology for the rotator has been investigated. The new Faraday rotator had good features of very low cost and small size, due to high productivity of the LPE-grown film and low magnetic saturation field, respectively. By using the new Faraday rotator, an optical isolator and magnetooptic switch for single-mode fiber systems have been developed. The optical isolator featured 0.8-dB insertion loss and 25-dB isolation at 1.3-μm wavelength. The magneto-optic 1 × 2 switch was independent of light polarization and featured 1.3-1.7-dB insertion loss, -25-dB crosstalk, and 30-μs switching time at 1.3-μm wavelength. Minimum switching voltage was ±5 V. Magneto-optic devices using the new Faraday rotator is practical for use in 1.2-1.7-\mu m wavelength fiber-optic systems, because of good optical properties, compactness, and low cost.