Fabrication of a Micro Coil for Magnetooptical Data Storage

A magnetic field modulation (MFM) micro coil was developed and fabricated as part of a magnetooptical recording system. The center of the coil is transparent, allowing a beam of blue laser light to pass through and heat up locally the magnetooptical storage layer, which is then magnetized by the micro coil for data recording. The micro coil therefore not only needs to be located at a very small working distance (
$≪50 mu$
m) from the disc, it also requires the magnetic coil to be mounted between a high numerical aperture (NA) lens
$( NA≫0.8)$
and the disc. As a result, the micro coil has to be fabricated on a glass wafer being only 100
$mu$
m thick, which posed considerable technology challenges. To match these requirenments, a microcoil was developed which fulfills the system integration and operating requirements of the magnetooptical system.