High-frequency, resonant acousto-optic modulators fabricated in a MEMS foundry platform

We report the design and characterization of high frequency, resonant acousto-optic modulators (AOM) in a MEMS foundry process. The doubly-resonant cavity design, with short ($L{\sim}10.5\, {\mu}m$) acoustic and optical cavity lengths, allows us to measure acousto-optic modulation at GHz frequencies with high modulation efficiency. In contrast to traditional AOMs, these devices rely on the perturbation induced by the displacement of cavity boundaries, which can be significantly enhanced in a suspended geometry. This platform can serve as the building block for fast 2D spatial light modulators (SLM), low-cost integrated free space optical links and optically enhanced low-noise RF receivers.Comment: References and Figure 8 update

Subharmonic Generation by Resonant Three‐Wave Interaction of Deep‐Water Capillary Waves

Subharmonic generation has been observed during the propagation of deep‐water capillary waves. The observations are shown to be in agreement with the theory of degenerate resonant noncollinear three‐wave interaction in a nonlinear, dispersive medium

High-radix division and square-root with speculation

The speed of high-radix digit-recurrence dividers and square-root units is mainly determined by the complexity of the result-digit selection. We present a scheme in which a simpler function speculates the result digit, and, when this speculation is incorrect, a rollback or a partial advance is performed. This results in operations with a shorter cycle time and a variable number of cycles. The scheme can be used in separate division and square-root units, or in a combined one. Several designs were realized and compared in terms of execution time and area. The fastest unit considered is a radix-512 divider with a partial advance of six bits.Peer ReviewedPostprint (published version

Analytical Modeling and Multiphysics Simulation of Acousto-Electromagnetic Interaction

A model for interaction between acoustic and elec- tromagnetic waves based on photoelasticity is presented. A radar equation based on physical, geometric and system parameters is shown, as well as a condition for maximizing interaction (equivalent to the Bragg condition in acousto-optics). The photoelastic model is used to implement a multiphysics simulation of the problem. The Bragg condition is shown to hold for the simulated case. Additionally, simulations are used to show how a contrast in material properties in a small inclusion affects the interaction

Resonant acousto-optics in the terahertz range: TO-phonon polaritons driven by an ultrasonic wave

The resonant acousto-optic effect is studied both analytically and numerically in the terahertz range where the transverse-optical (TO) phonons play the role of a mediator which strongly couples the ultrasound and light fields. A propagating acoustic wave interacts with the TO phonons via anharmonic channels and opens band gaps in the TO-phonon polariton energy dispersion that results in pronounced Bragg scattering and reflection of the incoming light. The separation in frequency of different Bragg replicas, which is at the heart of acousto-optics, allows us to study the resonant acousto-optic effect in the most simple and efficient geometry of collinear propagation of electromagnetic and ultrasonic waves. The acoustically induced energy gaps, Bragg reflection spectra, and the spatial distribution of the electric field and polarization are calculated for CuCl parameters, in a wide range of frequencies and intensities of the pumping acoustic wave. Our results show drastic changes in terahertz spectra of semiconductor crystals that opens the way for efficient and accessible manipulation of their infrared properties, by tuning the parameters of the acoustic wave.Comment: 20 pages, 14 figure

Full-field mapping of ultrasonic field by light-source-synchronized projection

A simple method for imaging ultrasonic fields in clear media is introduced. A modulated laser source is used to project the ultrasonic field onto a CCD camera. By use of the source-synchronized lock-in detection scheme, 2D images of the amplitude and phase distributions can be determined simultaneously. This technique is experimentally demonstrated with a 1-MHz and a 3.5-MHz ultrasonic transducer operated in continuous-wave mode. This method is very straightforward to implement and can be combined with the traditional tomographic reconstruction technique to obtain the 3D distribution of an ultrasonic field

Using GIS Technology for Iowa Pesticide Distribution and Transport Modeling

The patterns of pesticide occurrence in surface and ground waters are linked to agricultural practices and the product\u27s susceptibility to leaching and runoff. Pesticide use information has historically been catalogued in relation to points of sale from agrichemical dealerships. In an effort to provide a wide audience with an understanding of these occurrences and patterns, an atlas was developed during 2006 that provided a web-based front end to the data. The atlas links pesticide calculations of pounds of active ingredients sold with geographic information and water monitoring data using Geographic Information System (GIS) software

Self‐Refraction of Nonlinear Capillary‐Gravity Waves

Self‐refraction effects have been observed during the propagation of deep‐water capillary‐gravity waves. The observations are shown to be in qualitative agreement with the theory of self‐focusing and defocusing in a cubically nonlinear medium in the presence of diffraction

Kring Nijmegen en de kleine bedrijven.

Enquete-onderzoek naar de problemen en perspectieven van de kleinere agrarische gezinsbedrijven in de kring Nijmegen van de Noordbrabantse Christelijke Boerenbon