Photorefractive detection of tissue optical and mechanical properties by ultrasound modulated optical tomography.

Ultrasound-modulated optical tomography is a developing hybrid imaging modality that combines high optical contrast and good ultrasonic resolution for imaging soft biological tissue. We developed a photorefractive-crystal-based, time-resolved detection scheme with the use of a millisecond long ultrasound burst to image both the optical and the mechanical properties of biological tissues, with improved detection efficiency of ultrasound-tagged photons.

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.

Implementation of optical associative memory by a computer-generated hologram with a novel thresholding scheme.

An associative memory based on a model by Rizvi and Zubairy [Appl. Opt. 33, 3642 (1994)] is experimentally demonstrated.

Opposite Goos-Hänchen shifts for transverse-electric and transverse-magnetic beams at the interface associated with single-negative materials.

Goos-Hänchen shifts are investigated when total reflection occurs at the interfaces associated with single-negative materials (SNMs). A general rule for judging the direction of the Goos-Hänchen lateral shift concerning lossless media is obtained: Whether the lateral shift is positive or negative depends on the sign of micro1micro2 for TE-polarized incident beams and epsilon1epsilon2 for TM-polarized incident beams. It was theoretically demonstrated that, at the interface associated with SNMs, TE- and TM-polarized incident beams experience opposite Goos-Hänchen lateral shifts.

Goos-Hänchen shifts at the interfaces between left- and right-handed media.

The Goos-Hänchen shift caused by total internal reflection at the interface between two media is analyzed. For two media of the same handedness the Goos-Hänchen phase shift opposes the phase variation associated with propagation through the incident medium. The Goos-Hänchen lateral shift is in the same direction as the horizontal component of the incident energy flux.

Convective-diffusion-based fluorescence correlation spectroscopy for detection of a trace amount of E. coli in water.

Fluorescence correlation spectroscopy (FCS) is adapted for a new procedure to detect trace amounts of Escherichia coli in water. The present concept is based on convective diffusion rather than Brownian diffusion and employs confocal microscopy as in traditional FCS. With this system it is possible to detect concentrations as small as 1.