Shin Tominaga

Three-Dimensional Recording with Electrical Beam Control

A concept of a novel optical storage system has been proposed, which has the large-capacity characteristic because of three-dimensional recording and readout, and high-reliability and low-power-consumption characteristics achieved by controlling a light beam focused in a recording medium electrically instead of mechanically. On the basis of this concept, an optics for microholographic recording was constructed, and electrical beam control elements that vary the position of focused spots in the recording medium in both in-plane and vertical directions were incorporated into the optics. Liquid crystal deflectors and liquid crystal variable-focus lenses were used as the electrical beam control elements for in-plane and vertical beam control, respectively. Plural bits were recorded and read out in both in-plane and vertical directions of the recording medium, and the concept has been experimentally demonstrated.

Proposal for Rewritable Microholographic Recording Using Polarization-Sensitive Materials

Rewritable microholographic recording using polarization-sensitive materials has been proposed. Two types of optical configuration (i.e., single-channel detection and differential detection) have been presented. Recording operation is carried out by focusing two light beams with orthogonal polarization states in the recording medium. The polarization states of the two light beams are switched with switchable waveplates according to recording signal. The polarization directions of light in which the two light beams are synthesized are recorded in the recording medium as a polarization diffraction grating. Readout operation is carried out by focusing a light beam with a certain polarization state in the recording medium. A reflected light beam from the polarization diffraction grating is detected by a photodetector. The readout signal is obtained from the intensity or the polarization state of the reflected light beam. This technology features not only rewritability but also overwritability. Readout signal simulation considering polarization has demonstrated the validity of this technology.