Diffractive-optic polarization-sensing element for magneto-optic storage heads

A cascaded planarized holographic optical sensor consisting of a combination of a leaky beam splitter and a polarization beam splitter is evaluated for possible use in magneto-optic data storage pickup heads. The performance requirements for each element are specified, and two cascaded grating designs are considered. In one design we reconstruct the gratings with the grating vector in the plane of incidence, using a half-wave plate. In the second design we reconstruct the gratings with the grating vector of the polarization beam splitter out of the plane of incidence without using a half-wave plate. The two systems are fabricated with gratings formed in dichromated gelatin emulsions, and they can detect 0.5° rotations in the polarization state of an incident beam by use of a differential detection system.