Kohji Minami

Optical Pickup Employing a Hologram-Laser-Photodiode Unit

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.

Slant-propagation characteristics in tapered optical waveguides: analysis

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.

Optical Detection System of Defects in Multi Layered Optical Device

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.