Application of a phase-SLM and low-pass Fourier filtering to generate spatial patterns simultaneously modulated in phase and amplitude

摘要

Holographic data storage systems convert several bits of information into data pages, and record them in the form of holograms. The data to be stored is usually displayed as a binary pattern by an amplitude modulation spatial light modulator (SLM). For practical reasons, the Fourier transform of the SLM pattern is recorded in the hologram in most cases. In order to avoid the unfavourable effects of high intensity peaks, characteristic to such Fourier transforms, the SLM pattern should also be modulated in phase. Several methods are common to solve this problem, e.g. random phase masks aligned pixel-by-pixel to the amplitude SLM. More sophisticated approaches use SLMs in ternary modulation mode. These latter work either in a limited wavelength range, or do not produce sufficient phase modulation.