Development of a pyramidal write-read head array for high-density optical storage by optical near field

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(1) Numerical analyzes were carried out to generate a high-intensity and small-spot optical near field by using a mode interference effect. As a result, a wedge-type head was found to be superior to a pyramidal-type. Based on it, a wedge-type head was fabricated by anisotropic etching of silicon. The head of 200 nm-width and 100 micron-length was fabricated.(2) Beam deflection technique was proposed for tracking experiment. The optical near field from the head was deflected by a compact electro-optical modulator to get the deflection efficiency of 2 nm/V. It met the requirement for the tracking servo-control.(3) Using a solid immersion lens was proposed for more increase in the optical near field intensity on the head. This lens was fabricated by photo-lithography and reactive etching to realize the 1micron-height and 15 micron-diameter. Increase in the optical near field intensity was confirmed.(4) By assembling the components obtained above, head array and pads were fabricated. Write-read experiments were carried out by using a spin-stand for disk rotation. As a result, it was found that careful selection of the phase change direction of the storage media, and readout by reflection-mode were promising to realize the 1 Tb/in^2 storage density and 40 dB CNR for readout.