The irradiance distribution at the exit pupil of the objective lens in optical disk data storage

This dissertation examines various aspects of optical disk data storage systems from the point of view of the irradiance and phase distributions at the exit pupil of the objective lens. The research topics were chosen in order to address some of the problems facing future generations of optical disk systems. Future optical disks will have a much greater areal data density, and will undoubtedly use a shorter wavelength in order to decrease the size of the optical stylus. The research in this dissertation examines some of the problems inherent in the move to shorter wavelengths.; After a brief introduction to the irradiance distribution at the exit pupil of the objective lens (typically called the baseball pattern), we describe a novel focusing/tracking technique that uses a ring lens. We then examine the effects of substrate birefringence and tilt on the irradiance and phase distributions at the exit pupil of the objective lens. Next, we examine two distinct effects that are dependent on the incident polarization direction. The first of these is the excitation of surface plasmons at the interface between the dielectric substrate (or air, if the optical disk's storage layer is air-incident) and the metallic thin films in the disk. The second of the polarization-dependent effects concerns the differences in tracking performance with respect to the direction of the incident-light polarization. Next, we use the baseball pattern as a diagnostic tool to develop and demonstrate the concepts of a servo system for the correction of disk tilt. Finally, we address a major obstacle in the construction of future generation optical disk testers--the use of shorter wavelengths and thinner substrates. We propose a system in which a diffraction-limited spot of any wavelength in the range of 0.4 {dollar}mu{dollar}m-0.7 {dollar}mu{dollar}m can be moved by as much as {dollar}pm{dollar}100 {dollar}mu{dollar}m in both the focusing and tracking directions simply moving an aspheric singlet mounted in an off-the-shelf optical head. The system works for disks with any thickness less than 1.7 mm.