Single-Beam Holographic Tomography creates Images in Three Dimensions

In digital holography (DH), the interference between light scattered from an object and a reference wave is recorded using a CCD camera. DH has various advantages over analog holography: no film processing is needed, reconstruction is performed using numerical methods, and no further experimental setup is necessary. However, one of the disadvantages of DH is that current CCDs have a resolution of approximately 1,000 lines/mm, which is less than that of photographic film

Nonlinear Self-Organization in Photorefractive Materials

This chapter discusses self-organization and its effects in optics. One of the most exciting and potentially useful areas of current research in optics involves the understanding and exploitation of self-organization in nonlinear optical systems. This self-organization may sometimes lead to the evolution of complex spatial patterns that can be regarded as the nonlinear eigenmodes of the system. Generation of these patterns is characteristically marked by the presence of intensity thresholds. In a nonlinear system with complicated temporal dynamics, it turns out that one cannot retain purity in spatial dimensionality. It is therefore equally important to investigate the dynamics of the transverse spatial variations, which in fact give rise to very interesting patterns due to self-organization. A vast wealth of patterns can be achieved by using a nonlinear optical element with feedback that has the capability of providing field transformation, for example, by spatial filtering. These types of systems are called optical kaleidoscopes simply because of the different self-organized patterns that they can generate

Volume Holographic Recording and Readout for 90-Deg Geometry

When a prerecorded cross-beam hologram is reconstructed (so-called edge-lit readout) with a uniform plane wave and a point source, the resulting exact solutions reveal Bessel-function-type diffracted beam profiles, which are fundamentally modified under weak propagational diffraction. The case of a profiled beam readout with propagational diffraction may be analyzed using a transfer function approach based on 2-D Laplace transforms. In a second series of investigations, dynamic readout from a cross-beam volume hologram recorded with two orthogonal uniform plane waves is considered for various dependences of the refractive index modulation with intensity. Typically, refractive index profiles that are proportional to the intensity (as in the case of Kerr-type media or photorefractives with predominantly photovoltaic effect) and to the derivative of the intensity (as in diffusion-dominated photorefractives) are considered. Two-dimensional nonlinear coupled equations are developed for the two (Bragg) orders for both cases. Closed form solutions are obtained for the first case, indicating only nonlinearly induced self and cross-phase coupling. A simple experiment involving simultaneous recording and readout using photorefractive lithium niobate crystal indicates beam profile distortion, which may be expected in such 90-deg geometries

Self-Enhancement of Dynamic Gratings in Photogalvanic Crystals

We have developed a compact closed-form solution of the band transport model for high-contrast gratings in photogalvanic crystals. Our solution predicts the effect of the photoconductivity and the electric field grating enhancement due to the photogalvanic effect. We predict a pronounced dependence of the steady-state photogalvanic current on the contrast of the interference pattern and an increase of holographic storage time due to the enhancement of the photoconductivity grating contrast. In the high contrast limit and a large photogalvanic effect the refractive index grating will be shifted from the position of the intensity modulation pattern, contrary to the usually adopted model of unshifted gratings

Broadband Dynamic, Holographically Self-Recorded, and Static Hexagonal Scattering Patterns in Photorefractive KNbO3:Fe

We have observed and explained three types of hexagon pattern formation in photo refractive crystal KNb03:Fe. These are: Dynamic (laser induced) Semipermanent (holographically stored) Permanent (induced by a static domain grid) over a wide wavelength rang

Rapid Laser-assisted Nanosizing Noble Silver Nanoparticles in Plant Extracts and Physiochemical Characterization

Abstract Production of silver nanoparticles (AgNP

Remote Detection of Oil Slicks at the Ocean Surface

The 2010 Deepwater Horizon (DWH) oil slick caused by the explosion of the Macondo well was the worst man-made disaster in the history of the Gulf of Mexico, and the largest marine spill in the history of the petroleum industry. We provide an overview of our efforts to monitor the extent of these slicks using automated algorithms for the Moderate Resolution Imaging Spectroradiometer (MODIS), and the Synthetic Aperture Radar (SAR). We discuss the advantages and limitations of each of the methods in detection of oil from space, and suggest that the NIR bands may be the best option to monitor emulsified oil when using passive sensors. Additionally, we discuss current laboratory-based efforts to measure oil thickness via holographic interferometry, and propose this as an ideal technique for future remote sensing of oil.

A Unified Treatment of Radiation-Induced Photorefractive, Thermal, and Neutron Transmutation Gratings

We have reviewed different types of periodic structures (superlattices) induced by optical, infrared, and neutron irradiation. Both optical and electrical properties of these superlattices are analyzed, starting from the standard photorefractive model. New results on the thermoelectric and pyroelectric dynamic gratings are discussed in connection to the energy conversion and vibration sensing. For the neutron irradiation both real-time and static grating are analyzed, suggesting transmutation doping as a mechanism of recording

Digital Holography and 3-D Imaging

This feature issue on Digital Holography and 3-D Imaging comprises 15 papers on digital holographic techniques and applications, computer-generated holography and encryption techniques, and 3-D display. It is hoped that future work in the area leads to innovative applications of digital holography and 3-D imaging to biology and sensing, and to the development of novel nonlinear dynamic digital holographic techniques