In order to solve problems of photochromic memory, a super-low power readout method and a crosstalk reduction method for multi-wavelength recording were proposed. In the demonstration of 2-wavelength recording using photochromic diarylethenes, the crosstalk between multiplexed channels, which is caused from broad absorption bands of compounds, was effectively reduced by the method. A new high density optical memory, a super-resolution disk with a photochromic mask layer, was also introduced. The super-resolution method has enabled us to increase the recording density of conventional optical disks.