We demonstrate the capability of 100-GB density recording by electron beam mastering and readout by a near-field optical pickup with an effective NA of 2.05 and a blue LD of 405-nm wavelength. A silicon (Si) disk of 100-GB density is fabricated by an optimized Si etching process condition to form suitable pit pattern shapes for the near-field readout.
We improved the electron beam recorder with a differential pumping head for higher density discs and mass production. The beam diameters were improved by exchanging the aperture size of the objective lens and beam stability were also improved by adding a sound proof case. As for the performance of the improved electron beam recorder, we showed that a 104Gb/in2 (150GB capacity/layer) density disc with EFM plus modulation codes can be fabricated. We also improved the pit shape uniformity and a margin of the process by introducing the appropriate write strategy that is simulated by the Monte Carlo simulation to the recording pulses.
KEYWORDS: Silicon, Electron beams, Eye, Etching, Near field, Near field optics, Signal processing, Reactive ion etching, Modulation, Atomic force microscopy
We have demonstrated the capability of 100GB density recording by the electron beam mastering and readout by a near-field optical pick-up with an effective NA of 2.05 and a blue LD of 405 nm wavelength. The Si disc of 100GB density was fabricated by the optimized Si etching process condition to form suitable pit pattern shape for the near-field readout.
We have achieved high density near field readout of a 100 GB capacity (69.5 Gbit/in2) disc by using a solid immersion lens with numerical aperture of 2.05. In order to realize the solid immersion lens wtih numerical aperture of 2.05, the solid immersion lens was made from Bi4Ge3O12 mono-crystal. The refractive index of Bi4Ge3O12 is 2.23 at the wavelegnth of 405 nm. A conventional optical pick-up actuator with the solid immersion lens was used for the near field optical disc system. We confirmed that the near field readout system is promising method of realizing a high density optical disc system.
We studied the performance of the center-aperture-detection type of magnetically induced super-resolution disk using a blue laser diode and an objective lens with a numerical aperture of 0.6. We confirmed the practicability of 11 Gbit/in2 recording density by the evaluation of the system margins. The recording density we confirmed is equivalent to 15 GB user capacity on a 120-mm-sized disk. We can expect higher recording density by the reduction of the crosstalk.
We have investigated high density magneto-optical recording on a center aperture detection (CAD) type of magnetically induced super resolution (MSR) disk using a GaN blue laser diode. The substrate treatment by an ultraviolet rays irradiation, the optimum thermal structure, and the stabilization of copy process by tripled layer recording films were applied to improve the CAD-MSR media for a blue laser. The carrier to noise ratio of 0.227 micrometers mark length was 43 dB and the jitter without cross-talk from adjacent tracks was 10.3% at the areal density of 10.8 Gbit/in2. We confirmed that a blue laser is the most promising method in order to realize the higher areal density for CAD-MSR disk.
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