Andrew Davis

A 1 cm/spl times/1 cm In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiode array

We report a 1 cm/spl times/1 cm array of 100 In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiodes (APD). The average breakdown voltage was 28.7 V with a standard deviation of less than 0.5 V. The distribution of breakdown voltage across the area followed a radial pattern consistent with a slight epitaxial growth nonuniformity. The mean dark current at a gain of 10, or 6.1 A/W, was 10.3 nA, and none of the 100 APDs had a dark current of more than 25 nA. The bandwidth at a gain of 10 was 6.2 GHz, and the maximum gain-bandwidth product was 140 GHz. This technology is ideally suited for next-generation three-dimensional imaging applications.

All optically driven MEMS deformable device via a photodetector array

In this paper we demonstrate the first optical actuation of a single-pixel, deformable-mirror MEMS device through a direct cascade with a photodetector. Photovoltaic, p-i-n, and avalanche photodetectors were successfully utilized. Mirror deformations were monitored by interferometry. Deformation is quasilinear at low light intensities, and saturates at higher intensities. Actuation at picowatt light intensities has been accomplished by cascading with an avalanche photodetector. We also describe the fabrication of an integrated device consisting of an all optically addressed deformable-mirror MEMS suspended over a p-i-n photodetector. Initial demonstration of optical actuation of the deformable mirror using the newly integrated device is also presented.

Partitioning of initial energy release in a tunnel environment

After the detonation of an explosive charge in the closed end of a tunnel, product gases and metal fuels can continue to react with one another as well as combust with the available air while expanding down the tunnel. It is that total reaction that drives the blast wave at long distances from the charge. The initial energy release was calculated from pressure wave time of arrival at distances of 5 to 30 tunnel diameters away for several explosives in a 127-mm diameter tunnel using point blast theory. For similarly sized explosives, the anaerobic energy was measured using a detonation calorimeter. Comparisons were made for four explosives: one nearly ideal, two with aluminum, and one with aluminum and an oxidizer. The measured tunnel and calorimeter energies were equal, within error, for the near-ideal explosive. The other three explosives had tunnel and calorimeter energies higher than that which can be accounted for from the detonable ingredients alone, especially in the tunnel. The differences between ...

Optically Actuated MEMS Deformable Mirror Device

We propose a new design, fabrication procedures and the operating theory for a very low-power optically actuated deformable mirror device. The deformable mirror consists of an array of AlGaAs PIN photo detectors bonded onto a transparent substrate, a thin film resistor, and a suspended membrane

Multi-layer far-infrared component technology

Multi-layer thin-film optics based on alternating sub-wavelength layers of silicon and air provide high index contrast to create improved components with just a few layers. Applications include ultra-high reflectivity mirrors, band-pass and band-blocking filters, anti-reflection coatings, and compact high-resolution Fabry-Perot spectrometers with broad freespectral- range. Such components may be integrated directly into airborne/satellite and man-portable sensing instrumentation. We demonstrate a process to produce ultrathin silicon optical elements with an integral raised spacer rim to provide the requisite air gap when these elements are combined directly into a Bragg stack. Laboratory measurements confirm theoretical design specifications. Individual elements may be stacked and bonded to form Bragg mirrors and other thin-film optics.

Chemical and electrical analysis of CdS interlayers on InP and related materials

Cadmium sulfide (CdS) layers were deposited from aqueous solutions of thiourea, cadmium sulfate, and ammonia on (100) InP, InGaAs, and InAlAs. X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and atomic force microscopy (AFM) were used to investigate the structural and chemical nature of the deposited CdS layer and the CdS/semiconductor interface. XPS showed that the deposition process effectively removes existing native oxides on InP and InAlAs before CdS growth occurs. Capacitance-voltage measurements of metal-insulator- semiconductor (MIS) capacitors were used to investigate the interface- state density of samples with and without CdS films between InP and a deposited insulator. CdS interlayers were found to reduce both the hysteresis and the interface-state density of the MIS capacitors. Applications of CdS interlayers for various photonic devices will be discussed.