Optical particle-sizing method that provides optical isolation of the sampling volume.

We have constructed and tested a novel particle sizer that employs particle counting (the time-domain approach) rather than the ensemble-diffraction approach that currently dominates the market in atmospheric-dust particle sizers. The method does not depend on mechanical devices to restrict particles within the sampling volume but instead allows for optical isolation of the sampling volume. This technique is useful for atmospheric-dust measurements for which nonobtrusive measurement is often desirable.

Volterra series modeling of spatial light modulators.

We present a multiple-input, single-output, weakly nonlinear model of spatial light modulators by use of a second-order Volterra series and describe an experimental method to measure the nonlinear transfer functions by means of sinusoidal perturbation and synchronous detection with a lock-in amplifier. We also present an application of this method to a liquid-crystal light valve.

M-type thick holograms in bacteriorhodopsin films with a high-divergence reference beam.

The capacity to use differing read and write wavelengths for reconstructing volume holograms recorded in a shift-multiplexing geometry is analyzed and realized for M-type volume holograms recorded on bacteriorhodopsin films. The intensity distribution in the reconstructed wave is calculated as a function of the parameters of the recording and readout beams. Optimal recording and retrieving geometries, as well as a precise method for tuning the readout setup, are suggested.

Programmable spatial filtering with bacteriorhodopsin.

We describe a programmable spatial-filtering system using bacteriorhodopsin (BR) film as a programmable, optically addressed spatial light modulator illuminated by a single wavelength of light. We use a computer-controlled mirror scanning system to write time-varying filter functions to the BR film and present proof-of-principle experimental results that demonstrate several elementary filtering operations.

Wave-theory analysis of acousto-optic Bragg diffraction image formation.

We analyze anastigmatic Bragg diffraction imaging by use of an efficient numerical method that makes use of a plane-wave spectrum formalism applicable to weak acousto-optic diffraction involving threedimensional light and sound fields. Results from this wave-theory analysis are compared with previous results derived on the basis of ray theory, and are shown to be in good agreement, thus corroborating the validity of both techniques.

Improved space-marching algorithm for strong acousto-optic interaction of arbitrary fields.

We present a modification of the beam-propagation algorithm that avoids computer-intensive processing of the sound carrier and instead deals with the slowly varying complex sound profile only. Our three test cases of Gaussian beams with different waists, strongly interacting with a two-dimensional sound column, show excellent agreement with the analytical treatment and with physical experiments performed in our laboratory.

Acoustooptic analysis of high frequency wideband sound field schlieren imaging.

Schlieren imaging of acoustic waves has been used routinely for at least half a century. The nature of the image has conventionally been analyzed by various ray tracing techniques or wavefront corrugation calculations. These are restricted to low sound frequencies or thin sound fields.

Three-dimensional ray theory of astigmatic Bragg diffraction image formation with anastigmatic illumination.

We analyze and demonstrate Bragg diffraction imaging with convenient anastigmatic (e.g., spherical) illumination and find that this technique results in separately located horizontal and vertical images of the sound field with different magnification and resolution.