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A polarized photoresponse to mm-wave radiation over the frequency range of 40 to 108 GHz is demonstrated in a grating-gated high electron mobility transistor (HEMT) formed by an InGaAs/InP heterostructure. The photoresponse is observed within the plasmon resonance absorption band of the HEMT, whose gate consists of a 9 μm period grating that couples incident radiation to plasmons in the 2D electron gas. Gate-bias changes the channel carrier concentration, causing a corresponding change in photoresponse in agreement with theoretical expectations for the shift in the plasmon resonance band. The noise equivalent power is estimated to be 235 pW/Hz1/2. [ABSTRACT FROM AUTHOR]

Allowing xenon or nitrogen gas to condense onto a photonic crystal slab nanocavity maintained at 10–20 K results in shifts of the nanocavity mode wavelength by as much as 5 nm (≅4 meV). This occurs in spite of the fact that the mode defect is achieved by omitting three holes to form the spacer. This technique should be useful in changing the detuning between a single quantum dot transition and the nanocavity mode for cavity quantum electrodynamics experiments, such as mapping out a strong coupling anticrossing curve. Compared with temperature scanning, it has a much larger scan range and avoids phonon broadening. [ABSTRACT FROM AUTHOR]

A system is described for ultrasonic viewing of objects by flooding them with coherent CW ultrasound, focusing the scattered or reflected energy through a single sonic lens, and projecting this onto a rotating sonic mirror, which sweeps a sonic image across a linear transducer placed at the appropriate focal distance. The transducer is a single narrow crystal bearing on its rear face a vertical row of 64 small, closely-spaced electrodes, which are sampled in sequence for the piezoelectric voltage they are detecting. Conventional electronic circuitry is described for converting the electrode voltages into a video signal by way of diode switching. Horizontal spot motion on an oscilloscope is controlled by voltage derived from the scanning mirror position and vertical spot position relates to the particular electrode being sampled. A sonic mirror sweeping the image across the crystal in 15 sec and an electrode sampling rate of 20 000 samplings/sec is able to give 4000 picture elements or a picture of 64 lines where the horizontal and vertical resolutions are about equal. Mechanical and circuit diagrams of the system are shown and static video signals of two simple image conditions are illustrated. Critical comparisons are made between this and other systems for ultrasonic viewing, possible advantages and disadvantages of this system are mentioned, and practical and theoretical design problems are discussed. [ABSTRACT FROM AUTHOR]

We have used in the past, as an ultrasonic image conversion system, a capacity probe tracing mechanically over the dry face of a crystal set in a tank wall. An image took several minutes to scan. The present system comprises 64 electrodes fixed in a line 3 in. long across a crystal. Diode switching brings in the electrodes consecutively. A scan of the line takes 1/300 sec. Experiments with a rotating sonic mirror indicate that a sonic image can be moved across the line of probes in 15 sec. The system then gives a video signal allowing the construction of a converted sonic picture comprising 4000 picture elements 5 times each second. Noise levels depend mainly on the switching diodes and since band widths can be quite restricted, are expected to be in the tens of microvolts. Illustrations of the video signal obtained from a parallel beam of 3 Mc/sec continuous wave ultrasound focused onto the array and from an image of two slots 116 in. wide and spaced 18 in. will be shown. [ABSTRACT FROM AUTHOR]