Experimental Demonstration of Optical Phase Multilevel Recording in Microhologram

Abstract

The microhologram is one of the most promising candidates for the next generation optical disc. It can achieve a huge data capacity because it is suitable for multilayer recording. However, it cannot increase the data transfer rate because of its comparable areal recording density with conventional optical discs. Moreover, the signal level in the readout process of this scheme is in general very low, which prevents its practical use. Recently, an optical phase multilevel scheme that overcomes the above drawbacks of the microhologram has been proposed. The scheme uses an optical phase as stored information, which enables data readout with an extremely high signal-to-noise ratio and multilevel modulation. In this report, recording and readout processes of the proposed scheme are demonstrated experimentally. Four-level phase modulation was successfully regenerated from weak 30 nW microholograms with errors of +7.0/-12.2°, suggesting that a further increase in the number of levels is possible.