Optical ROM Research Articles

Magnonic Holographic Read-Only Memory

In this work, we consider the possibility of building magnonic holographic read-only memory (MH-ROM) devices exploiting spin-wave interference for readout. MH-ROM consists of a grid of magnetic waveguides connected via cross junctions. Some of the cross junctions have a hole in the center of junctions, whereas others do not. The presence/absence of the hole is assigned to the memory states 0 and 1, respectively. We present experimental data showing spin-wave propagation modification in the Permalloy cross junction due to the presence of the hole. The results show prominent spin-wave modulation which is applicable for application in MH-ROM. Similar to the optical compact-disk ROM (CD-ROM), the internal memory states can be recognized via spin-wave interference. The advantages of using of spin waves instead of optical beams are scalability and compatibility with conventional electronic devices. The memory density scales inversely proportional to the operational wavelength. According to the estimates, the memory density of MH-ROM can be 1 Tb/cm 2 at wavelength λ = 100 nm. We discuss the physical limitations and physical constrains associated with the spin-wave interference. The development of MH-ROMs opens a new horizon for building scalable holographic devices compatible with conventional electronic devices.

Realization of Synchronous Writing and Reading in Optical ROM and RAM

Realization of Synchronous Writing and Reading in Optical ROM and RAM

Polarization Effect on Signal from Optical ROM Using Solid Immersion Lens

In a high-numerical-aperture optical head using a solid immersion lens (SIL), it is anticipated that the polarization of the diffracted beam is disturbed, this affects the signals. To study this problem, a rigorous simulator based on the three-dimensional vector diffraction theory has been developed. Polarization disturbance for various NAs has been estimated and it has been clarified that the polarization is disturbed not only in the SIL head but also in the conventional high-NA head whose disk substrate is not covered with protective glass. The influence of polarization disturbance on the readout signals has been determined and discussed for the various polarizations.

Three-Dimensional Finite-Difference Time-Domain Analysis of Optical Disk Storage System

A rigorous three-dimensional optical electromagnetic finite-difference time-domain (FDTD) modeling for the accurate analysis of an optical disk storage system is detailed. In this model, not only the complex material properties of typical optical storage systems, such as the magneto-optical (MO) disk and the phase-change optical disk, but also the complex aperiodic disk structure is considered. Moreover, the model enables us to consider the high-numerical-aperture optical storage system, which is a necessity in the consideration of the near-field optical recording. Numerical investigations of the optical ROM, the phase-change optical disk and the MO disk are presented as examples to demonstrate the utility of the model.

Three-dimensional optical disks using metallic island films: a proposal

New multifrequency three-dimensional optical ROM disks using metallic island films have been proposed and the basic operation has been confirmed experimentally. Very compact optical disks with large storage density are expected to be realised by using the films.

90 mm rewritable optical disk drive

A half-height-size 90 mm optical disk drive (ODD), including an embedded optical disk controller, was developed. Several advanced features, such as high-speed seek, compatibility for optical ROM, lower power dissipation, and SCSI-2 host computer interface, were implemented. Principal features of the 90 mm ODD, as well as several technical problems that were considered and solved during its development, are discussed. >