ABSTRACT
To accommodate the continuously growing amount of digital data and qualitatively new requirements demanded by industry and people in society, optics is expected to be highly integrated and to play a wider role in enhancing system performance. However, many technological diµculties remain to be in overcome in adopting optical technologies in critical information and communication systems; one problem is the poor integrability of optical hardware due to the di˜raction limit of light (Pohl and Courjon 1993, Ohtsu and Hori 1999).
