Photorefractive delay line for the visualization and processing of time-dependent signals

Time-bandwidth problem in room temperature slow light

For many applications of slow or stopped light, the delay-time-bandwidth product is a fundamental issue. So far, however, slow-light demonstrations do not show a large delay-time-bandwidth product, especially in room temperature solids. Here we demonstrate that the use of artificial inhomogeneous broadening has the potential to solve this problem. A proof-of-principle experiment is done using slow light produced by two-beam coupling in a photorefractive crystal Ce:BaTiO3 where Bragg selection is used to provide the artificial inhomogeneity. Examples of how to generalize this concept for use with other room temperature slow-light solids are also given.

Self-organized learning of purely temporal information in a photorefractive optical resonator

A photorefractive resonator containing an optical delay line is shown to learn temporal information through a self-organization process. We present experiments in which a resonator mode selectively learns the mostfrequently presented signals at the input. We also demonstrate the self-organized association of two different analog signals with two different resonator modes.

Photorefractive mixing of amplitude-modulated signals

We analyze the circumstances under which a real-time hologram written with amplitude-modulated beams behaves as a linear mixer. We calculate nonlinear correction terms that can be used to analyze the linearity of a variety of photorefractive time-integrative devices.

Acoustic signal recognition with a photorefractive time-delay neural network

We present a photorefractive processor for audio-acoustic signal recognition based on the time-delay neural network model of Hopfield and Tank [in Neural Models of Plasticity, J. H. Byrne, ed. (Academic, New York, 1989), p. 363-377]. We demonstrate the recognition of three words by programming the interconnection weights of the time-delay network.