Phase-modulated optical data storage

A system for reading a sector of voxels embedded in a transparent substrate, the system comprising:

• a refractive-index-sensitive microscope;
• and
• a controller configured to
• capture an image of the sector of voxels embedded in the transparent substrate using the refractive-index-sensitive microscope, the sector of voxels comprising a 2-dimensional group of voxels, the 2-dimensional group of voxels comprising a first phase voxel having a first strength and a second phase voxel having a second strength that is different from the first strength, and
• recover a first data symbol encoded by the first strength of the first phase voxel and a second data symbol encoded by the second strength of the second phase voxel based on brightnesses of pixels in the image, the second data symbol being different than the first data symbol.