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Most far-field optical imaging systems rely on lenses and spatially resolved detection to probe distinct locations on the object. We describe and demonstrate a high-speed wide-field approach to imaging that instead measures the complex spatial Fourier transform of the object by detecting its spatially integrated response to dynamic acousto-optically synthesized structured illumination. Tomographic filtered back-projection is applied to reconstruct the object in two or three dimensions. This technique decouples depth of field and working distance from resolution, in contrast to conventional imaging, and can be used to image biological and synthetic structures in fluoresced or scattered light employing coherent or broadband illumination. We discuss the electronically programmable transfer function of the optical system and its implications for imaging dynamic processes. We also explore wide-field fluorescence imaging in scattering media by coherence gating. Finally, we present two-dimensional high-resolution tomographic image reconstructions in both scattered and fluoresced light demonstrating a thousandfold improvement in the depth of field compared to conventional lens-based microscopy. [c] 2010 Optical Society of America OCIS codes: 110.0180, 110.6960, 110.4850, 180.6900, 180.1655, 180.2520.

Traditional lens-based photonic Fourier beam-forming systems can be used to steer multiple beams for narrowband radio-frequency (RF) phased-array antennas. For wideband RF phased-array antennas, such Fourier beam-forming systems suffer from frequency-dependent beam steering, known as beam squint. We present a novel squint-free Fourier-based photonic multibeam-forming system for wideband two-dimensional RF phased-array antennas using a lens and frequency-mapped modulation. In this new beam-forming system, we modulate the receiving wideband RF signals onto a broadband light source in a frequency-mapped manner by a traveling-wave tunable filter at each antenna element. These modulated signals are launched in a miniaturized topology of the RF antenna array, and the wavelength-scaling factor in the lens Fourier transform exactly compensates the frequency dependence of beam steering. Heterodyne detection at the Fourier plane between the focused modulated multicolor spots and the broadband laser reference beams from the same light source recovers the received RF signals. An analysis with numerical simulations and then demonstrated with preliminary experimental results of this beam-forming system is presented. OCIS codes: 320.7120, 280.4750, 280.5110, 070.1060.

A radio frequency (RF) spectrum analyzer based on spectral-hole burning (SHB) is discussed. Findings reveal that a chirped frequency-doubled fiber laser improves the spectral resolution by more than an order of magnitude.

We demonstrate a dual wavelength acousto-optic deflector (AOD) designed to deflect two wavelengths to the same angles by driving with two RF frequencies. The AOD is designed as a beam scanner to address two-photon transitions in a two-dimensional array of trapped neutral [sup.87.Rb] atoms in a quantum computer. Momentum space is used to design AODs that have the same diffraction angles for two wavelengths (780 and 480 nm) and have nonoverlapping Bragg-matched frequency response at these wavelengths, so that there will be no cross talk when proportional frequencies are applied to diffract the two wavelengths. The appropriate crystal orientation, crystal shape, transducer size, and transducer height are determined for an AOD made with a tellurium dioxide crystal (Te[O.sub.2]). The designed and fabricated AOD has more than 100 resolvable spots, widely separated band shapes for the two wavelengths within an overall octave bandwidth, spatially overlapping diffraction angles for both wavelengths (780 and 480nm), and a 4~s or less access time. Cascaded AODs in which the first device upshifts and the second downshifts allow Doppler-free scanning as required for addressing the narrow atomic resonance without detuning. We experimentally show the diffraction-limited Doppler-free scanning performance and spatial resolution of the designed AOD. OCIS codes: 230.1040, 270.5585.

The operation of an optoelectronic dynamic neural model implementation is extended to higher frequencies. A simplified model of thermal effects in vertical-cavity surface-emitting lasers correctly predicts the qualitative changes in the nonlinear mapping implementation with frequency. Experiments and simulations show the expected resonance properties of this model neuron, along with the possibility of other dynamic effects in addition to the ones observed in the original FitzHugh--Nagumo equations. Results of optical coupling between two similar pulsing artificial neurons are also presented.

An optoelectronic implementation of a modified FitzHugh--Nagumo neuron model is proposed, analyzed, and experimentally demonstrated. The setup uses linear optics and linear electronics for implementing an optical wavelength-domain nonlinearity. The system attains instability through a bifurcation mechanism present in a class of neuron models, a fact that is shown analytically. The implementation exhibits basic features of neural dynamics including threshold, production of short pulses (or spikes), and refractoriness.

We demonstrate a 20 GHz spectrum analyzer with 1 MHz resolution and >40 dB dynamic range using spectral-hole-burning (SHB) crystals, which are cryogenically cooled crystal hosts lightly doped with rare-earth ions. We modulate a rf signal onto an optical carrier using an electro-optic intensity modulator to produce a signal beam modulated with upper and lower rf sidebands. Illuminating SHB crystals with modulated beams excites only those ions resonant with corresponding modulation frequencies, leaving holes in the crystal's absorption profile that mimic the modulation power spectrum and persist for up to 10 ms. We determine the spectral hole locations by probing the crystal with a chirped laser and detecting the transmitted intensity. The transmitted intensity is a blurred-out copy of the power spectrum of the original illumination as mapped into a time-varying signal. Scaling the time series associated with the transmitted intensity by the instantaneous chirp rate yields the modulated beam's rf power spectrum. The homogeneous linewidth of the rare-earth ions, which can be < 100 kHz at cryogenic temperatures, limits the fundamental spectral resolution, while the medium's inhomogeneous linewidth, which can be >20 GHz, determines the spectral bandwidth. OCIS codes: 070.1170, 160.5690.

We introduce a new approach to coherent lidar range-Doppler sensing by utilizing random-noise illuminating waveforms and a quantum-optical, parallel sensor based on spatial-spectral holography (SSH) in a cryogenically cooled inhomogeneously broadened absorber (IBA) crystal. Interference between a reference signal and the lidar return in the spectrally selective absorption band of the IBA is used to sense the lidar returns and perform the front-end range-correlation signal processing. Modulating the reference by an array of Doppler compensating frequency shills enables multichannel Doppler filtering. This SSH sensor performs much of the postdetection signal processing, increases the lidar system sensitivity through range-correlation gain before detection, and is capable of not only Doppler processing but also parallel multibeam reception using the high-spatial resolution of the IBA crystals. This approach permits the use of ultrawideband, high-power, random-noise, cw lasers as ranging waveforms in lidar systems instead of highly stabilized, injection-seeded, and amplified pulsed or modulated laser sources as required by most conventional coherent lidar systems. The capabilities of the IBA media for many tens of gigahertz bandwidth and resolution in the 30-300 kHz regime, while using either a pseudo-noise-coded waveform or just a high-power, noisy laser with a broad linewidth (e.g., a truly random noise lidar) may enable a new generation of improved lidar sensors and processors. Preliminary experimental demonstrations of lidar ranging and simulation on range-Doppler processing are presented. OCIS codes: 070.4340, 120.0280, 200.4740, 280.3640.

We present an optoelectronic implementation of an adaptive-array processor that is capable of performing beam forming and jammer nulling in signals of wide fractional bandwidth that are detected by an array of arbitrary topology. The optical system makes use of a two-dimensional scrolling spatial light modulator to represent an array of input signals in 256 tapped delay lines, two acousto-optic modulators for modulating the feedback error signal, and a photorefractive crystal for representing the adaptive weights as holographic gratings. Gradient-descent learning is used to dynamically adapt the holographic weights to optimally form multiple beams and to null out multiple interference sources, either in the near field or in the far field. Space-integration followed by differential heterodyne detection is used for generating the system's output. The processor is analyzed to show the effects of exponential weight decay on the optimum solution and on the convergence conditions. Several experimental results are presented that validate the system's capacity for broadband beam forming and jammer nulling for linear and circular arrays. OCIS codes: 200.4560, 280.5110, 070.1060, 090.7330, 230.6120, 040.2840.

The finite impulse response neural network is described in detail. Different algorithms capable of temporal back-propagation are considered, including a novel modification to the conventional algorithm, called the delayed-feedback back-propagation algorithm. We present and analyze different optoelectronic processors making use of adaptive volume holograms and three-dimensional optical processing. Two single-layer architectures are presented: the input delay plane architecture and the output delay plane architecture. By combining them it is possible to implement both forward and backward propagation two multi-layer architectures: the first making use of the conventional temporal back-propagation the second making use of delayed-feedback back-propagation. OCIS codes: 200.4260, 200.4560.

We demonstrate a method of simultaneous holographic recording and readout in photorefractive crystals that provides high write-read beam isolation and wide angular bandwidth. The method uses orthogonally polarized read and write beams and parallel tangent diffraction geometry near the equal curvature condition to provide spatially separable, orthogonally polarized diffracted output beams with high isolation and wide Bragg-matched angular bandwidth. The available angular bandwidth of this read-write technique is analyzed, simulated, and experimentally investigated. The measured angular bandwidth internal to the crystal is approximately 18 [degrees] x 6 [degrees] for our 45 [degrees]-cut BaTi[O.sub.3] crystal, yet the entire hologram still demonstrates high Bragg selectivity. In contrast, traditional nonparallel-tangent geometries yield angular apertures of the order of 1 [degree] x 4 [degrees]. Key words: Volume holography, diffraction efficiency, information storage, wide angular aperture, photorefractive, polarization.

A new approach to incoherent-to-coherent optical conversion based on a real-time five-wave-mixing technique in photoanisotropic organic film is presented. A uniform grating is written holographically in the sample and then erased locally by an incident white-light image. Subsequent coherent diffraction of the spatially modulated grating imposes the incoherent image upon the reading laser beam, permitting subsequent coherent optical processing. A theoretical analysis of the holographic recording and erasing mechanism in these photoanisotropic materials is presented, and the saturation is shown to be responsible for the grating intermodulation that produces the incoherent-to-coherent conversion. Experimental results of white-light images converted to inverted coherent images in real time are presented, and the resolution is shown to exceed 28 line pairs/mm.

Both Schaefer-Bergmann diffraction and resonant ultrasound spectroscopy were used to measure the six independent elastic-stiffness coefficients of the trigonal, non-piezoelectric crystal a-α-BaB2O4. The two measurement sets resulted in a root-mean-square variance of 1.2%. This paper provides a detailed analysis of the two different measurement techniques and discusses the similarities and differences. [ABSTRACT FROM AUTHOR]