The phenomena of high frequency-selective transmission of a plane wave by a dielectric two-dimensional (2-D) periodic waveguide, comprising a uniform dielectric layer sandwiched by two finite thickness 2-D periodic structures served as the waveguide wall is described. This structure is termed a leaky parallel-plate-like waveguide because the waveguide walls are not perfect reflection mirrors. The scattering characteristics and dispersion relation, including the phase and attenuation constants, of the 2-D periodic waveguide are thoroughly analyzed with the modal transmission-line method and Floquet theory. The extraordinary open stopbands caused by the contra-flow coupling between a leaky parallel-plate-like waveguide and the leaky waves, which are generated by 2-D periodic structures (waveguide walls), are displayed in the form of the Brillouin diagram. The phase-match condition is used to verify the resonant coupling between the incident plane wave and the leaky parallel-plate-like waveguide modes. Specifically, the transmission peak frequencies are accurately predicted.Index Terms-Frequency selective structure (FSS), leaky parallel-plate-like waveguide, resonant coupling, two-dimensional (2-D) periodic structures.

In order to increase the storage capacity and the density of near-field optical disk drives, a flying pickup-head has to allow a slider to fly at a stable height above the disk surface with the use of near-field optics. Since both the precision of the track pitch and the flying height are of a nanometre scale, it is necessary to increase the motion accuracy of the pickup-head. In this study, a piezoelectric bender is used as an actuator of the pickup-head, and two quadrant photodetectors are used to sense the pickup-head displacement and the rotating disk deformation. Based on an optical lever method that magnifies a small displacement, the flying height variation of the pickup-head above the disk is measured. Further results show that using the proposed measurement method in the real-time control of flying height is feasible.

Near-field optical disk drives represent a promising technique for optical data recording to achieve an even larger storage density and capacity than DVD-ROM and Blu-ray disk drives. To realize near-field optics, unlike conventional optical disk drives, a flying pickup head is required. In this study, the pickup head consists of a suspension arm, a slider and a bimorph piezoelectric bender between the suspension arm and the slider. The dynamic model of the pickup head is identified using measurement, but the whole dynamics including both pickup head and interface dynamics between the disk and slider is unmodeled. Adaptive inverse control of robustness is developed to track the vibratory deformation of rotating optical disks, so that the flying height of a pickup head can remain stable in the presence of modeling error. Experimental results demonstrate that using the proposed method the pickup head can not only track disk deformation but also maintain the flying height.

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