Steve Monacos

Delta-doped electron-multiplied CCD with absolute quantum efficiency over 50% in the near to far ultraviolet range for single photon counting applications

We have used molecular beam epitaxy (MBE) based delta-doping technology to demonstrate nearly 100% internal quantum efficiency (QE) on silicon electron-multiplied charge-coupled devices (EMCCDs) for single photon counting detection applications. We used atomic layer deposition (ALD) for antireflection (AR) coatings and achieved atomic-scale control over the interfaces and thin film materials parameters. By combining the precision control of MBE and ALD, we have demonstrated more than 50% external QE in the far and near ultraviolet in megapixel arrays. We have demonstrated that other important device performance parameters such as dark current are unchanged after these processes. In this paper, we briefly review ultraviolet detection, report on these results, and briefly discuss the techniques and processes employed.

A system and methodologies for absolute quantum efficiency measurements from the vacuum ultraviolet through the near infrared

In this paper we present our system design and methodology for making absolute quantum efficiency (QE) measurements through the vacuum ultraviolet (VUV) and verify the system with delta-doped silicon CCDs. Delta-doped detectors provide an excellent platform to validate measurements through the VUV due to their enhanced UV response. The requirements for measuring QE through the VUV are more strenuous than measurements in the near UV and necessitate, among other things, the use of a vacuum monochromator, good dewar chamber vacuum to prevent on-chip condensation, and more stringent handling requirements.

Eye-tracking architecture for biometrics and remote monitoring

Eye tracking is one of the latest technologies that has shown potential in several areas, including biometrics; human-computer interactions for people with and without disabilities; and noninvasive monitoring, detection, and even diagnosis of physiological and neurological problems in individuals. Current noninvasive eye-tracking methods achieve a 30-Hz rate with a low accuracy in gaze estimation, which is insufficient for many applications. We propose a new noninvasive optical eye-tracking system that is capable of operating at speeds as high as 6-12 kHz. A new CCD video camera and hardware architecture are used, and a novel fast algorithm leverages specific features of the input CCD camera to yield a real-time eye-tracking system. A field-programmable gate array is used to control the CCD camera and to execute the operations. Initial results show the excellent performance of our system under severe head-motion and low-contrast conditions.

Atomically precise surface engineering of silicon CCDs for enhanced UV quantum efficiency

The authors report here on a new technique, combining the atomic precision of molecular beam epitaxy and atomic layer deposition, to fabricate back illuminated silicon CCD detectors that demonstrate world record detector quantum efficiency (>50%) in the near and far ultraviolet (155–300 nm). This report describes in detail the unique surface engineering approaches used and demonstrates the robustness of detector performance that is obtained by achieving atomic level precision at key steps in the fabrication process. The characterization, materials, and devices produced in this effort will be presented along with comparison to other approaches.

A high frame rate CCD camera with region-of-interest capability

This paper presents the design and preliminary results of a custom high-speed CCD camera utilizing a Texas Instruments TC237 CCD imager chip with sub-frame window read out. The camera interfaces to a C40 digital signal processor (DSP), which is used to issue commands and read images from the camera. The camera design consists of a two-card set including the CCD imager card and the focal plane array (FPA) interface card. The CCD imager card contains the level translator and buffer circuitry for the CCD strobe lines, the TC237 CCD imager chip and a pair of analog signal processor chips, each with a 10-bit analog-to-digital converter. The analog signal processor is a TLV987 with correlated double sampling (CDS) and serial programming capability to set amplifier gain, pixel bias level and background level illumination to name a few. The second card contains a pair of field programmable gate arrays (FPGA) used to interface the CCD imager card to the C40. The goal of this camera development is to provide a high-quality, high-speed camera as part of the tracking apparatus for a free-space optical communications terminal. Preliminary data suggests frame rates of 6 kHz for 8/spl times/8 subwindows in the current testbed with 7-bit pixel resolution. Refinements in camera and testbed operation target performance goals of 17 kHz for 8/spl times/8 sub-windows with 10-bit pixel resolution.

A system to provide real-time collaborative situational awareness by web enabling a distributed sensor network

The paper presents two systems called PATS and SAP that when integrated realize Sensor Web Enablement (SWE) of spatially distributed mobile sensors. The Personal Alert and Tracking System (PATS) consists of a networked collection of custom-designed low-power wireless nodes, arranged in ad-hoc network topologies, to provide tracking for wild land firefighters. These mobile nodes form arbitrary network topologies and use a multi-hop packet routing protocol to relay sensor data to the command center. The multi-hop capability enables robust communication in a variety of environments by routing around natural and man-made terrain features. Situational Awareness and Prediction (SAP) works with the PATS sensor network to convert sensor data to information and to provide real-time collaborative situational awareness. The goal is to deliver a resource utilizing intelligent reasoning coupled with rule-based actionable intelligence using diverse knowledge fusion and modal trend forecasting. The SAP makes this data available to information sharing middleware using OGC standards. The paper describes the architecture of both the PATS and SAP systems and how these two systems interoperate with each other. The SAP system works in concert with the Unified Incident Command and Decision Support (UICDS) information sharing middleware to provide data fusion from multiple sources. UICDS can then publish the sensor data using the OGCs Web Mapping Service, Web Feature Service, and Sensor Observation Service standards. The system described in the paper is able to integrate a spatially distributed sensor system, operating without the benefit of the Web infrastructure, with a remote monitoring and control system that is equipped to take advantage of SWE.

Enabling High Performance Instruments for Astronomy and Space Exploration and ALD

Benefits of ALD for NASA instruments and applications: a) Ultrathin, highly conformal, and uniform films over arbitrarily large surface area. b). High quality films (density, roughness, conductivity, etc.) . Angstrom level control of stoichiometry, interfaces, and surface properties: 1) Multilayer nanolaminates/nanocomposites. 2) Low temperature surface engineering. Flight applications enabled by ALD: a) Anti-reflective coatings/Mirrors/Filters/Optics for UV/Vis/NIR Detectors. b) Superconducting Films for Submillimeter Astronomy.

High-rate optical communications links for virtual presence in space

As man continues the exploration of space, either from platforms in Earth-orbit or from missions to the bodies of our solar system, there will be an on-going need to keep the public engaged in the process so that the general populace can share in the excitement of discovery and the inquisitive (professional or student) can participate in the data mining. To do this will require the development of high-data-rate communications links for data return and dissemination. However, the cost constraints on future missions will require that these high-rate links be smaller and lighter-weight than even the lower-capacity systems that have been used in the past. NASA has been developing free-space optical communications technology for just such missions. This paper will discuss the technology developments and system demonstrations that have been accomplished to date, and will describe preparations for the space demonstrations that will validate the performance of this new technology.