Nanosecond image processing using stimulated photon echoes

Graphene plasmonically induced analogue of tunable electromagnetically induced transparency without structurally or spatially asymmetry

Electromagnetically induced transparency (EIT) arises from the coherent coupling and interference between a superradiant (bright) mode in one resonator and a subradiant (dark) mode in an adjacent resonator. Generally, the two adjacent resonators are structurally or spatially asymmetric. Here, by numerical simulation, we demonstrate that tunable EIT can be induced by graphene ribbon pairs without structurally or spatially asymmetry. The mechanism originates from the fact that the resonate frequencies of the bright mode and the dark mode supported by the symmetrical graphene ribbon pairs can be respectively tuned by electrical doping levels, and when they are tuned to be equal the graphene plasmon coupling and interference occurs. The EIT in symmetrical nanostructure which avoids deliberately breaking the element symmetry in shape as well as in size facilitates the design and fabrication of the structure. In addition, the work regarding to EIT in the structurally symmetric could provide a fresh contribution to a more comprehensive physical understanding of Fano resonance.

Coherent interaction effects in pulses propagating through a doped nonlinear dispersive medium

Using a numerical approach we report on the cloning dynamics of simultaneous self-induced transparency (SIT) and nonlinear Schrödinger (NLS) solitons in a doped nonlinear dispersive medium. This technique involves a three-level atomic system interacting resonantly with two optical fields within a Lambda scheme. As a result, a pulse in the signal frequency is transformed into a replica of the pulse in the pump frequency. The atomic population evolution shows that the basic mechanism behind the cloning process is the coherent population trapping effect. Furthermore, it is shown that the signal clone presents characteristics of both the SIT soliton and NLS soliton.

Enhanced nondegenerate four-wave mixing owing to electromagnetically induced transparency in a spectral hole-burning crystal

We have demonstrated electromagnetically induced transparency (EIT) in an inhomogeneously broadened spectral hole-burning system of Pr(3+)-doped Y(2)SiO(5) at 6 K. We have also shown enhancement of four-wave mixing under conditions of reduced absorption. This demonstration opens the possibilities of pursuing EIT applications such as high-resolution optical image processing and optical data storage in solids.

Direct pattern recognition of a motion picture by hole-burning holography of Eu(3+):Y(2)SiO(5)

We propose and demonstrate a novel technique for direct pattern recognition of motion pictures based on frequency- and spatial-domain holography using a cryogenic Eu(3+):Y(2)SiO(5) crystal. The fast hole-burning speed of the crystal allows a moving image to be continuously recorded in it by a frequency-scanned laser. Using Fourier transform holography permitted direct pattern recognition of a 25-s movie stored in the crystal to be realized. The correlation spot continuously followed the moving object with the same time resolution (10 ms) as the reproduced movie.

Impulse-equivalent time-domain optical memory

We propose a novel approach to time-domain storage of serial optical data. In this approach, two identical impulse-equivalent sequences are used as write and read pulses to store and later retrieve optical information. These pulse sequences are both amplitude and phase modulated in such a way that their autocorrelations resemble, as closely as theoretically possible, the autocorrelation of a single large brief pulse to ensure faithful data retrieval. Such impulse-equivalent sequences are known to exist for all lengths, permitting the storage of large-bandwidth data. The advantages of this approach include modest laser power requirement, high signal fidelity, and encrypted recording.

Experimental demonstration of swept-carrier time-domain optical memory

Swept-carrier time-domain optical memory [Opt. Lett. 17, 535 (1992)] has been proposed as a means of storing optical data streams in inhomogeneously broadened spectral recording materials. The process provides for full utilization of the material storage bandwidth regardless of the data rate and permits storage of data sequences with durations exceeding the material dephasing time. We report what we believe is the first experimental demonstration of this storage process. Our experiments, implemented with frequency-swept diode lasers and Tm(3+):YAG storage material, demonstrate single-event storage of 98-bit data streams whose duration is an order of magnitude longer than the material dephasing time.

Time-domain holographic image storage

We describe a practical approach to image storage in a coherent time-domain optical memory that can be readily implemented with existing technologies. In this approach, two-dimensional images are stored spectroholographically in narrow ( less, similar 1-MHz) frequency channels of a time-domain storage material by use of a low-power laser, with one image per channel. Advantages of this approach include fast single-frame recording time, variable playback speeds, and random frame access. Experimental results demonstrating the use of this approach for high-speed, long-term image storage in Eu(3+):Y(2)SiO(5) are presented.

Electric-field-modulated photon echoes in Pr(3+):YAlO(3)

We measured the Stark coefficient for the (3)H(4)(1) ? (1)D(2)(1) transition of Pr(3+):YAlO(3), using the technique of Stark-modulated photon echoes. This gave a value of 58 kHz/(V cm(-1)) for the vector difference between ground-and excited-state electric dipole moments. The resolution with which Stark shifts could be measured in these experiments was ~500 Hz, which is more than an order of magnitude less than the homogeneous linewidth.

Time-domain optical data storage by use of Raman coherent population trapping

We experimentally demonstrate time-domain storage and retrieval of amplitude- and phase-encoded optical data, using Raman coherent population trapping, despite the loss of information about absolute optical phases that occurs as a result of the dissipative nature of the process. In this Raman optical storage process homogeneous decay of the optical coherence does not prevent interference between time-separated fields, thus relaxing the requirement for long-lived optical coherences.

Time-domain optical memory for image storage and high-speed image processing

We present an experimental study on the use of the time-domain optical memory for image storage and high-speed image processing. We focus on examining the fidelity of the recalled images and their spatial resolution as well as various image-processing operations offered by the memory. The recalled images were found to be of good quality because of their phase-conjugate nature. This unique feature further motivated us to examine the feasibility of fiber optics being used for image transmission, an issue important to the development of such a memory device. Two primary processing operations, two-image convolution and correlation, were demonstrated, and implications of the results for high-speed pattern recognition and optical interconnections are discussed.

Spatial mixed binary multiplication by photon echoes

We demonstrate mixed binary multiplication of two or three numbers represented as spatial bit patterns by using a backward stimulated photon echo in a low-temperature solid activated by rare-earth ions. The photon-echo output image is the convolution-correlation of input images in a holographic arrangement, which can be interpreted as multiplication in a mixed binary format. The computation is extremely fast (~ 50 ns) and may be combined with temporal data processing for a versatile vector and matrix processor.

High-speed pattern recognition by using stimulated echoes

We present experimental results demonstrating the use of stimulated echoes for high-speed pattern recognition. One data image and two reference images (spatially encoded laser pulses) were stored and processed in a Pr(3+):LaF(3) crystal by focusing the pulses sequentially into the storage material. The processed information was later retrieved by a read pulse, generating two temporally separated echo images that are the spatial correlations between the data and reference images. Identification of the data image was accomplished by finding the echo image that showed the highest spatial correlation with the data image. The present processing speed is 30 ns per correlation operation.