In this paper we review the holographic optical element technology applied to compact disc (CD), digital versatile disc (DVD) and mini disc (MD) pickups. Using this technology, the number of optical components and the size and weight of a CD pickup are successfully reduced and its reliability is improved, because many functions of the optical components are integrated into a hologram-laser-photodiode unit. For DVD application, the focus detection for a dual-layer disk and the differential phase detection (DPD) method are realized by the hologram technology. Our unique two-segment DPD method shows more stable characteristics than the conventional DPD method. An integrated MD hologram pickup is also developed with an optical waveguide device that functions in magneto optical (MO) signal detection.

Although several analysis methods for tapered waveguides have been proposed, they dealt with the problem of a light wave traveling parallel to the tapered direction of the waveguide. Light waves that propagate at a slant in the tapered direction are discussed as mode-coupling problems, including radiation modes that are made discrete by the hypothetical boundary method. We propose a method of determining the three-dimensional wave vectors of the discrete radiation modes in the slant propagation; the slant-propagation characteristics, such as the transmission efficiency of the tapered waveguide, are analyzed.

The purpose of this paper is to clear the practicality of an optical waveguide device for magneto optical disk head. This device is made on the Si substrate with photo-diodes for magneto optical signals detection. An incident. light beam to this device is convert.ed into TE and TM modes by its optical coupler, and these mode are separated corresponding to their polarization by its thin fUm bi-prism. The optical coupler consists of a prism and a resin layer with an edge portion. The edge portion, precisely defined by a photolithography process, produces stable coupling efficiency. This coupler structure also reduces sensitivity of the incident angle and coupling dependence on the polarization direction. In addition, a taper region is made around the thin film bi-prism to obtain high transmission efficiency. These waveguide technologies realize an integrated unit for a Mini-Disc head. As the evaluation results of a pickup, the CNR of 3T signal (resonance bandwidth: 10kHz) is 45dB.

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We developed a new optical detection method for defects in multilayered optical devices. An optical detection is achieved by sensing the scattering twinkle points of guided light in a multilayered optical device and by analyzing the scattering properties of the twinkle points. We found a difference in scattering property between defective points and nondefective points, and developed a check system for the scattering direction from a scattering twinkle point. By this optical defect detection method, we realize a decrease in defect detection error.