We propose and demonstrate an all-optical pulse generator which is based on regenerative pulsation in optical bistable systems. The novel device consists of a nonlinear interference filter, a photorefractive crystal and an optical feedback loop. In such a pulse generator, when the input beam intensity exceeds the switch-on threshold of the system, a train of square-wave pulses will be produced. The firing rate is an increasing function of the intensity of the input beam. The principle of operation and the experimental results are presented and discussed.
Cross-talk noise is a fundamental limitation to storage capacity in volume holographic memory. We present a general theoretical analysis on the cross-talk noise in angle- and wavelength-multiplexed volume holographic memory systems. Results on storage capacity and its dependence on hologram separation and required signal-to-noise ratio are obtained and discussed.
Volume holographic memory systems provide a compact method by which data can be stored with high density and rapid accessibility. In these systems, for example, wavelength, angle, and phase multiplexing approaches have been utilized for the addressing of data pages. We analyze, in general, practical limitations in such systems due to cross-talk effects, beam depleting and material heating absorption effects, and multiplexing approaches. For example, beam depletion during the writing and reading of holograms in a volume holographic memory will cause the envelope of the diffracted beams to not be rect-like as simple cross-talk theories rely on, and material heating will act to detune, smear, and redirect beams during readout. We also characterize the photon-limited information throughput rates during recall from these systems. Finally, we demonstrate advances in our sparse-wavelength angle-multiplexed volume holographic memory system, achieving the storage of 2,000 holographic pages, each with approximately 2.35 million bits each, utilizing 400 angles (over a 3 degree external tuning span) and five wavelengths (over a 56 nanometer span) in a 1.86 cubic centimeter volume of lithium niobate.
The effect of gain spatial hole burning on antiguided arrays is analyzed for the first time. Nonresonant devices, due to the nonuniformity of the in-phase-mode intensity profile, experience self-focusing and multimode operation with increasing drive level similar to the behavior of evanescent-wave-coupled devices. Resonant and near-resonant devices (i.e. resonant-optical-waveguide (ROW) arrays), due to the uniformity of the in-phase mode, display some mild defocusing with increasing drive level, while the nearest high-order mode cannot reach threshold up to drive levels in excess of 10X threshold. These results explain the fundamental single-mode stability of ROW arrays, in excellent agreement with experimental data.
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