Robert M. Montgomery

A novel technique for double sideband suppressed carrier modulation of optical fields

We present a simple and efficient technique to produce double sideband suppressed carrier (DSBSC) modulation for coherent analog optical communications. When operating a Mach-Zehnder electro-optic modulator at the appropriate bias point the carrier exits one of the output ports while the information carrying sidebands exit the other output port. The absence of a strong carrier component in the DSBSC output allows the use of an optical amplifier immediately following the modulator where the light signals are still relatively strong hence preserving the high S/N. In our experiments using heterodyne detection at 1319 nm, we show a -28-dB carrier suppression using a commercial M-Z modulator.<<ETX>>

Acousto-optic/photorefractive processor for adaptive antenna arrays

A simple, robust architecture is proposed for adaptive antenna array processing using an acousto-optic Bragg cell array and a photorefractive material in a time integrating correlator configuration. A Bragg cell array is used for computing correlation coefficients and for forming the tapped delay line filter. The resulting processor is very compact since it can be implemented as a monolithic structure by using the same material for the acousto-optic interaction and the photorefractive implementation of adaptive tap weights. Equations are derived for expected dynamic range, and time response.

Active compensation for transient thermal effects in acousto-optic devices

Verfahren zur Kompensation thermischer transienter Effekte in einem akustooptischen Medium in einem akustooptischen Gerat mit mindestens einem Signaleinkoppel-Wandler, der mit der Oberflache des akustooptischen Mediums gekoppelt und zum Empfangen elektrischer Signale zur Modulation mindestens einer in das akustooptische Medium eingekoppelten Schallwelle ausgefuhrt ist, wobei – mindestens ein elektrothermisches Element mit dem akustooptischen Medium nahe dem mindestens einen Signaleinkoppel-Wandler gekoppelt wird, und – als Reaktion auf die Beaufschlagung des akustooptischen Mediums mit Schallenergie durch mindestens einen Signaleinkoppel-Wandler mittels eines Komparators, an dessen Ausgang elektrische Signale als Funktion (i) eines vorgeschriebenen Pegels, der die elektrische Energie reprasentiert, mit der das elektrothermische Element zu beaufschlagen ist, und (ii) der elektrischen Energie, mit der das akustooptische Medium von dem mindestens einen Signaleinkoppel-Wandler beaufschlagt wird, erzeugt werden, und – die elektrischen Signale zur Ansteuerung des mindestens einen elektrothermischen Elements eingesetzt werden, wodurch dieses mit elektrischer Energie beaufschlagt und die...

Thermal analysis of high drive transducer elements

The increasing demand for high‐power, low‐cost, compact transducer packages for underwater acoustic applications is leading to concerns of overheating in the active driving piezoelectric ceramic (lead zirconate titanate) elements and the associated passive materials (epoxies and polyurethanes). Pushing a design to its thermal limits can lead to reduced acoustic performance and reliability. There is not much guidance to be found in the literature that provides an analytical approach to cope with thermal issues of piezoelectric ceramics in the design phase. An analytic modeling effort is presented that addresses the thermal issues for compact high drive 31‐mode free‐flooded ring underwater sonar transducers. In this particular case, the thermal issues proved to be the limiting design concerns over the field and stress‐limited cases. However, with modeling (analytical and finite element) and bench testing of components, the proper choice of materials and configuration parameters were determined and the perfo...

Guest Editorial Acousto-Optics

Acousto-optic component technology and instrumentation continue to mature, and interest in practical applications has accelerated during the past year. Following our symposium in San Diego in August 1976 and publication of the Proceedings (SPI E Volume 90), it was decided to review recent progress and to report in a special issue of Optical Engineering the current state-of-the-art. Thus, this edition of the journal features a series of nine articles dealing with the theory and reduction-to-practice aspects of acoustic imaging and holography, bulk wave and surface wave devices, and other systems such as optical correlators and integrated optical radio frequency spectrum analyzers.