Collinear non-interferometric phase retrieval for holographic data storage.

A collinear non-interferometric phase retrieval method for holographic data storage is proposed. The code rate of the collinear system can be increased by 2 times due to transferring the 50% embedded data from a signal beam to a reference beam. Because the reference beam should be always known both in the recording process and reading process, there is no extra material cost for saving the embedded data. Therefore, the storage density of collinear system is increased by about 2 times compared with previous off-axis non-interferometric phase retrieval systems. Besides, we can enhance the algorithm constraint to shorten iteration numbers by increasing the amplitude weight of the reference beam. In the experiment, we shortened the iteration number and the BER by about 3 times. We also find that the reference number can be reduced by using the collinear way and increasing the amplitude weight of reference. This law allows us to give more code positions to signal so that the data amount in one data page can be increased.