Environmentally robust phase detection for holographic data storage

Abstract

A high transfer rate and robust phase detection for holographic data storage is newly proposed. The phase detection is used to solve problems of non-uniform beam intensity deviation and spatial phase variation in the readout beam and local oscillator beam. The phase signal of the proposed phase detection is defined as differential phase signal between two readout pages. In addition, differential phase signals detected by four cameras at different pages of holograms are used to derive the phase by canceling the constant terms in the phase reconstruction. Experimental and simulated results showed that the proposed phase detection was less susceptible to intensity deviation and spatial phase variation. We verified that the proposed phase detection was more effective when the ratio of the local oscillator beam intensity to the readout beam intensity (intensity ratio) was high. We roughly estimated that four value phase encoding could be achieved by the proposed phase detection when the intensity ratio was 70.