In this paper, we propose a new advanced push–pull (APP) method as a new one-beam tracking detection method suitable for a dual-layer Blu-ray disc (BD) system. This method overcomes two issues. One of them is tracking error signal (TES) offset at the boundary between recorded tracks and unrecorded tracks, and the other is TES offset caused by the stray lights from the other layer of dual-layer discs. The new APP-TES is stable at the boundary in the dual-layer BD system, because the dividing area of a far-field pattern is optimized and the detecting areas are allocated to avoid stray lights from the other layer. Its stable characteristics are confirmed experimentally.

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The method of Kittler and Falicov for binary alloys has been extended to the case when one of the components terminates the Bethe lattice. It has been applied to hydrogenated amorphous silicon (a-Si:H) and the results compared with experimental photo-emission spectra. It is shown that complex configurations such as SiH, and SiH, are responsible for some of the experimental peaks. This theory is compared with other meanfield theories and its limitations are fully discussed.

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A polarizing holographic optical element (HOE) with compensating grooves on the surface of a LiNbO3 substrate has good polarizing beam-splitter characteristics. This polarizing HOE was applied to a recordable optical head with an integrated laser and photodetector unit. In the optical head, a correct far-field tracking method is constructed by setting the polarizing HOE and a quarter-wave plate right under the objective lens, which can be moved with the objective lens. A holographic pattern of the polarizing HOE is divided into 20 portions along a disc track direction for spot size focus error detection and far field tracking detection. Wth this optical head, conventional CD play-back and recording signals on phase change discs were performed. Then the tracking offset caused by objective lens shift was measured and determined to be markedly decreased. Signal degradation by the ±1 st light diffracted by a polarizing HOE was not observed. Good characteristics of recording and play-back for phase change discs were also obtained. This recordable optical head was found to have desirable characteristics and high productivity.