David J. Mehrl

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.

Use of angular plane-wave spectra in the analysis of three-dimensional weak acousto-optic interaction

We present a method for conveniently calculating three-dimensional weak acousto-optic scattering. In our method the conventional cumbersome volume-scattering triple-integral technique is replaced by an equivalent single-integral formalism, framed in terms of the angular plane-wave spectra of sound, incident light, and scattered light. Our technique is suitable when paraxial conditions apply and is correct to second-order terms in propagation angles. The interaction of spatially separated Gaussian optical and acoustic beams is described as an example.

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. We present a novel method, based on acoustooptic plane wave interaction theory, that not only is applicable to high frequencies but reveals some unexpected features of schlieren imaging.

Schlieren Imaging of Sound Fields

In spite of the fact that Schlieren imaging is over 120 years old, it still offers surprises when analyzed with modern concepts of acousto optics. Also, such concepts are applicable to high frequencies and thick sound fields, where conventional models fail. In this paper we present a heuristic plane wave interaction analysis to determine the exact relation between the sound field and the image. The latter is expressed as an effective sound field selected by the diffraction process through a filtering operation on the plane wave spectrum of the original sound field.

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. Results of physical experiments show good agreement with theory and demonstrate that the insertion of one relatively weak cylinder lens makes the images coincide.

DESIGN AND EVALUATION OF APODIZED PIEZOELECTRIC TRANSDUCERS

Apodization of piezoelectric transducers helps to achieve a cleaner spatial and/or temporal response. We propose apodization in one or two dimensions by segmenting the electrode structure enerizing the transducer, while applying a common voltage to the segments. This paper discusses some specific structures, analyzes the results of numerical and optical simulation, and presents initial findings of acoustooptic measurements of radiation patterns.

NOVEL ALGORITHM FOR STRONG ACOUSTO-OPTIC INTERACTION: APPLICATION TO A PHASE- PROFILED SOUND COLUMN

We present a further check of our new algorithm for strong interaction of three-dimensional, arbitrary sound and light fields. After discussion of its structure, we demonstrate its accuracy by applying it to the interaction of a plane wave of light with a two-dimensional sound column of uniform phase curvature and amplitude.

Bragg diffraction imaging with predominantly spherical lenses

The authors propose, analyze, and demonstrate a Bragg diffraction imaging system that is predominantly anastigmatic in that is relies on only one weakly correcting cylinder lens in an easily adjustable, noncritical position. It is showing that the proposed system constitutes a simple and effective means of ultrasonic imaging if aspect ratio distortion is not of primary importance.<<ETX>>