Implementation of single-beam multiplexing encoding with a dually modulated spatial light modulator

Abstract

We propose a novel method for signal storage and encryption, called single-beam multiplexing encoding. The single beam is composed of an inside signal beam and an outside reference beam. The signal beam is amplitude modulated, and the reference beam is phase modulated. The dual modulation is implemented by a spatial light modulator (SLM). Multiplexing holography with different reference beams from different directions, called directional multiplexing, is analyzed in detail. With an SLM based on a twisted nematic liquid crystal display, we demonstrate a single-beam directional multiplexing method using a holographic encoding technique, and the retrieved signals are presented. This encoding system is more stable, miniaturized, and flexible. It should be of great interest for applications in signal encryption as well as for high-capacity data storage.

Coaxial holographic encoding based on pure phase modulation

“…A coaxial holographic layout will reduce the sensitivity as the vibration between the reference beam and the object beam is avoided. It has been demonstrated in some research works [11][12][13] with dually modulated SLMs. However, the holograms are recorded a little distance away from the FT plane, as the dc component intensity is relatively high.…”

“…The advantage of FTH is that only a minimum bandwidth of spatial frequency is needed for reconstruction, and since the Fourier spectrum of every spot in the image plane spreads in the whole FT plane, it will be easier to reconstruct the image with high signal-to-noise ratio. However, most of the FT holograms are carried out near the FT plane instead of on the exact FT plane, due to the high intensity of the dc component generated by the amplitude modulated images [11][12][13].…”

Single-beam data encoding using a holographic angular multiplexing technique

“…We report here a novel configuration for angular multiplexing holographic data encoding, in which the reference beam and the signal beam are bundled in a single beam. The setup of this singlebeam angular multiplexed holographic encoding is similar to the directional multiplexing technique [18], but the reference beam is changed differently.…”

“…Single-beam holography has been widely reported recently, with a spatial light modulator (SLM) to simultaneously display the signal and the reference beams [16][17][18][19][20]. However, little has been reported on the angular multiplexing technique in a singlebeam holographic system.…”

“…A reference beam modulated with a blazed grating pattern will be diffracted and irradiated onto the hologram plate. Rather than changing the direction of the reference grating lines [18], we vary the period of the grating, by which the incident angle of the reference beam will be changed and, thus, angular multiplexing recording can be achieved. Compared with a traditional angular multiplexing holographic recording system, the single-beam configuration is more compact, easier to adjust, and less sensitive to the vibration of the environment.…”