Theoretical study of the lateral displacement of random fields at interfaces.

The lateral displacement of a totally reflected light beam from the position expected by geometrical optics has been known for some time. The effect, known as the Goos-Hänchen shift, may be understood in terms of the phase changes acquired upon reflection at the interface by the plane wave components of the angular spectrum representation of the incident field. In this work, we study the shifts that occur in the reflection of random fields from flat dielectric interfaces.

Electro-optic vortex-producing lenses using spiral-shaped ferroelectric domains.

We present electrically controlled wavefront modulators that simultaneously focus and introduce vorticity to an incident beam. These modulators are made out of spiral-shaped 180 degrees ferroelectric domains in lithium niobate; they have a virtually instantaneous response time, withstand high power and can be used throughout the transparency region of the material (0.4 - 5 microm).

Photofabrication of random achromatic optical diffusers for uniform illumination.

We propose a method of designing two-dimensional random surfaces that scatter light uniformly within a specified range of angles and produce no scattering outside that range. The method is first tested by means of computer simulations. Then a procedure for fabricating such structures on photoresist is described, and light-scattering measurements with the fabricated samples are presented.

Observation of satellite peaks and dips in the scattering of light in a double-pass geometry.

We report the experimental observation of enhanced backscattering and satellite peaks and dips in light scattered by a system that involves double passage of waves through a random-phase screen and a birefringent crystal.

Frequency and causes of infectious abortion in a dairy herd in Queretaro, Mexico.

The objective of this study was to determine the frequency of infectious bovine abortion and to identify some of its causes, specifically brucellosis, leptospirosis, bovine viral diarrhea, infectious bovine rhinotracheitis, and neosporosis. The study was carried out in a dairy herd in the state of Queretaro, Mexico, between September 2002 and March 2003. At the beginning of the study, blood samples were taken from a random 33% of the 300 lactating or pregnant cows; antibodies against Leptospira interrogans were the most commonly identified, in 91% of the 99 samples.