Masatoshi Tsuji

Three-Dimensional Two-Photon Bit-Recording With a Compact Fiber Laser

We presented a three-dimensional optical memory using a newly developed compact fiber laser. The fiber laser can produce pulse with high peak power of 5.3 kW. This allows two-photon absorption recording for next generation optical recording media possible for consumer application. We demonstrated two-photon absorption recording on a photochromic materials; diarylethene and achieved multilayer recording using the developed fiber laser.

Compact and High-Power Mode-Locked Fiber Laser for Three-Dimensional Optical Memory

We developed a compact and high-power mode-locked fiber laser for three-dimensional optical memory. Fiber lasers have the potential to be compact and stable light sources that can replace bulk solid-state lasers. To generate high-power pulses, we used stretched-pulse mode locking. The average power and pulse width of the output pulse from the fiber laser that we developed were 109 mW and 2.1 ps, respectively. The dispersion of the output pulse was compensated with an external single-mode fiber of 2.5 m length. The pulse was compressed from 2.1 ps to 93 fs by dispersion compensation. The pulse emitted from this fiber laser has an energy sufficient to generate two photon recording effectively, so the fiber laser we have developed is possible to use as a light source of three-dimensional optical memory.

Alignment-Free Fiber Confocal Microscope and All-Fiber Optical System for Multilayered Optical Memories

We propose a fiber confocal microscope as an alignment-free readout system of multilayered optical memories. The fiber confocal microscope does not require fine pinhole position alignment because the fiber core is used as the point light source and the pinhole, and both of which are always located at the conjugated point. The configuration reduces the required accuracy of pinhole position alignment. The fiber confocal microscope can also achieve a compact pickup head. Recording layers in a multilayered medium could be detected with an axial resolution of approximately 900 nm. We demonstrated eight-layer readout with the fiber confocal microscope. We also propose an all-fiber recording and readout system for multilayered memories.

Parallel Signal Readout for Roll-Type Optical Advanced Memory

We demonstrated one-dimensional parallel readout of a roll-type optical advanced memory. Using a line shape focused beam, multiple signals can be detected simultaneously. To demonstrate one-dimensional parallel readout, we fabricated groove-structured roll-type optical advanced memory. The groove-structures were imprinted by a digital versatile disc stamper. We could detect multiple signals from each groove-structured layer without crosstalk by using line-scanning confocal microscopy. We demonstrated the simultaneous detection of eleven signals.

Fiber Optics for Multilayered Optical Memory

We have developed a compact and high-power mode-locked fiber laser for multilayered optical memory. Fiber lasers have the potential to be compact and stable light sources that can replace bulk solid-state lasers. To generate high-power pulses, we used stretched-pulse mode locking. The average power and pulse width of the output pulse from the fiber laser that we developed were 109 mW and 2.1 ps, respectively. The dispersion of the output pulse was compensated with an external single-mode fiber of 2.5 m length. The pulse was compressed from 2.1 ps to 93 fs by dispersion compensation. The fiber laser we have developed is possible to use as a light source of multilayered optical memory. We also present a fiber confocal microscope as an alignment-free readout system of multilayered optical memories. The fiber confocal microscope does not require fine pinhole position alignment because the fiber core is used as the point light source and the pinhole, and both of which are always located at the conjugated point. The configuration reduces the required accuracy of pinhole position alignment. With these techniques we can present an all-fiber recording and readout system for multilayered memories.