Volume holographic recording using spatial spread-spectrum multiplexing

A new recording method called spatial spread-spectrum (SSS) multiplexing, which is particularly suitable for holographic disc recording, is proposed. Multiplexing holograms by phase modulation and demodulation onto the signal beams themselves (not onto reference beams) provides a new degree of freedom in the design of holographic storage systems, thereby making it possible to improve storage density by combining with other multiplexing methods. In our newly proposed recording geometry with spatial filtering, uncorrelated noise coming from undesired pages can be efficiently deflected away from a detector. Calculations show that the theoretically achievable multiplicity of the SSS recording system with spatial filtering is improved up to 70 when the numerical aperture (NA) of the signal beam is 0.1.