Demonstration of readout-signal quality improvement by homodyne detection

We experimentally demonstrated improvement in optical disc readout signal quality by homodyne detection. We introduced an optical phase servo system as an alternative to the phase-diversity detection scheme for stabilization of the interference signal in homodyne detection, which resulted in further enhancement of readout signal quality. Experimental results indicate that at least a 16-layer recordable disc can be reliably read out with a jitter of less than 8% at a 1-mW read power by homodyne detection. The estimated amplification of signal amplitude was 13 times. From these results, we believe that the homodyne detection technique is essential for fully utilizing the huge capacity of multilayer optical discs and is also applicable to other optical memory technologies such as microhologram, near field recording, and super resolution.