49 research outputs found
Shift-multiplexed holographic memory using the two-lambda method
We present theoretical and experimental results on the application of the two-lambda method for prolonged readout of holographic memories to shift multiplexing implemented with a spherical-wave reference beam
Macroscopic Invisibility Cloak for Visible Light
Invisibility cloaks, a subject that usually occurs in science fiction and
myths, have attracted wide interest recently because of their possible
realization. The biggest challenge to true invisibility is known to be the
cloaking of a macroscopic object in the broad range of wavelengths visible to
the human eye. Here we experimentally solve this problem by incorporating the
principle of transformation optics into a conventional optical lens fabrication
with low-cost materials and simple manufacturing techniques. A transparent
cloak made of two pieces of calcite is created. This cloak is able to conceal a
macroscopic object with a maximum height of 2 mm, larger than 3500
free-space-wavelength, inside a transparent liquid environment. Its working
bandwidth encompassing red, green and blue light is also demonstrated
Volume holographic hyperspectral imaging
A volume hologram has two degenerate Bragg-phase-matching dimensions and provides the capability of volume holographic imaging. We demonstrate two volume holographic imaging architectures and investigate their imaging resolution, aberration, and sensitivity. The first architecture uses the hologram directly as an objective imaging element where strong aberration is observed and confirmed by simulation. The second architecture uses an imaging lens and a transmission geometry hologram to achieve linear two-dimensional optical sectioning and imaging of a four-dimensional (spatial plus spectral dimensions) object hyperspace. Multiplexed holograms can achieve simultaneously three-dimensional imaging of an object without a scanning mechanism. © 2004 Optical Society of America
Shift multiplexing with spherical reference waves
Shift multiplexing is a holographic storage method particularly suitable for the implementation of holographic disks. We characterize the performance of shift-multiplexed memories by using a spherical wave as the reference beam. We derive the shift, selectivity, the cross talk, the exposure schedule, and the storage density of the method. We give experimental results to verify the theoretical predictions. (C) 1996 Optical Society of Americ
Real-time spectral imaging in three spatial dimensions
We report what is to our knowledge the first volume-holographic optical imaging instrument with the capability to return three-dimensional spatial as well as spectral information about semitranslucent microscopic objects in a single measurement. The four-dimensional volume-holographic microscope is characterized theoretically and experimentally by use of fluorescent microspheres as objects. (C) 2002 Optical Society of America
Compact, integrated dynamic holographic memory with refreshed holograms
An innovative architecture for compact, integrated volume holographic memories is described. It is based on phase-conjugate readout and on a modulator-detector-memory array implemented in a silicon integrated circuit. The lensless memory module sustains dynamic read-write holograms by periodic refreshing. The integrated circuit is described and experimentally characterized. Holograms were stored in a prototype storage module that uses a 30 degrees-cut BaTiO3 crystal and the 90 degrees recording geometry. As many as three angularly multiplexed holograms were periodically refreshed and subjected to >40% decay from exposure to the reference beam over 50 to 100 cycles. Experimental data are presented. (C) 1997 Optical Society of America
Imaging using volume holograms
We present an overview of imaging systems that incorporate a volume hologram as one of the optical field processing elements in the system. We refer to these systems as volume holographic imaging (VHI) systems. The volume hologram is recorded just once, and the recording parameters depend on the functional requirements of the imaging system. The recording step offers great flexibility in designing application-specific imaging systems. We discuss how a VHI system can be configured for diverse imaging applications ranging from surface profilometry to real-time hyperspectral microscopy, and summarize recent developments in this field. © 2004 Society of Photo-Optical Instrumentation Engineers
Design of thin-film photonic metamaterial L\"uneburg lens using analytical approach
We design an all-dielectric L\"uneburg lens as an adiabatic space-variant
lattice explicitly accounting for finite film thickness. We describe an
all-analytical approach to compensate for the finite height of subwavelength
dielectric structures in the pass-band regime. This method calculates the
effective refractive index of the infinite-height lattice from effective medium
theory, then embeds a medium of the same effective index into a slab waveguide
of finite height and uses the waveguide dispersion diagram to calculate a new
effective index. The results are compared with the conventional numerical
treatment - a direct band diagram calculation, using a modified
three-dimensional lattice with the superstrate and substrate included in the
cell geometry. We show that the analytical results are in good agreement with
the numerical ones, and the performance of the thin-film L\"uneburg lens is
quite different than the estimates obtained assuming infinite height.Comment: 11 pages, 8 figures, uses opex3.st
Holographic Storage Using Shift Multiplexing
We demonstrate theoretically and experimentally a new multiplexing method for volume holographic storage using a single reference beam that is composed of multiple plane waves or is a spherical wave. We multiplex the holograms by shifting the recording material or the recording/readout head. The volume properties of the recording medium allow selective readout of holograms stored in successive overlapping locations. High storage densities can be achieved with a relatively simple implementation by use of the new method
Diffraction from deformed volume holograms: perturbation theory approach
We derive the response of a volume grating to arbitrary small deformations, using a perturbative approach. This result is of interest for two applications: (a) when a deformation is undesirable and one seeks to minimize the diffracted field's sensitivity to it and (b) when the deformation itself is the quantity of interest and the diffracted field is used as a probe into the deformed volume where the hologram was originally recorded. We show that our result is consistent with previous derivations motivated by the phenomenon of shrinkage in photopolymer holographic materials. We also present the analysis of the grating's response to deformation due to a point indenter and present experimental results consistent with theory. (c) 2005 Optical Society of America