Two electro-mechanical actuators are examined for a semi­ active Helmholtz resonator acoustic device. The device is used to reflect narrowband noise back to the source in an acoustic duct. The controller and actuator are used to tune the system on-line allowing optimum performance over a range of operating conditions. Actuator. dynamics play an important role in the controller design and the op...

We demonstrate the collapse of a continuum of transverse modes in a self-imaging ring resonator that is photorefractively pumped. The resulting localized mode has an arbitrary transverse location. The mode collapse results from placing saturable photorefractive gain and loss media in spatially conjugate resonator planes. The transverse position of the localized mode is unstable under small cavi...

A regenerative amplifier free-electron laser (RAFEL) is a highgain resonator FEL which achieves saturation in a few round-trips of the radiation in a high-loss, and hence low feedback, optical cavity. Because the radiation feedback fraction is low it is feasible that the use of low reflectivity optics in the resonator makes the RAFEL a candidate for short wavelength operation [1]. Several RAFEL...

A small 4-cavity assembly designed to operate at W-band was built using OFE copper parts machined by wire and plunge EDM proocesses. The machined pieces were then diffusion bonded together. A cutaway section of one the cavity modules is shown in figure 1. Each of the four cavities approximates a one-half guided wavelength at 90 Ghz of reduced height WR 10 waveguide coupled to full height WR10 w...

A piezoelectric voltage coupled microwave reentrant cavity has been developed. The central cavity post is bonded to a piezoelectric actuator allowing the voltage control of small post displacements over a high dynamic range. We show that such a cavity can be implemented as a voltage tunable resonator, a transducer for exciting and measuring mechanical modes of the structure, and a transducer fo...

In this letter, a passive microring-resonator-coupled semiconductor laser structure is proposed. The weakly coupled high-Q microring resonator provides a strong mode-selection filter and could considerably extend the effective cavity length of a conventional Fabry–Perot laser. The side-mode suppression ratio, the linewidth and the frequency chirp of this laser are dramatically improved comparin...

This paper presents a thorough study of the time-domain theory of metal cavity resonators. The completeness of the vector modal functions of a perfectly conducting metal cavity is first proved by symmetric operator theory, and analytic solution for the field distribution inside the cavity excited by an arbitrary source is then obtained in terms of the vector modal functions. The main focus of t...

The major objective of this paper is to demonstrate higher noise reduction when an acoustic cavity is coupled to a combination of Helmholtz resonators (HRs) tuned to slightly different frequencies. An acoustic cavity, whose first two modes are close to each other, is selected for carrying out experiments. These are carried out to understand the behaviour of the coupled Helmholtz resonator-cavit...