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Lowell, MA, United States

Lu X.,University of Massachusetts Lowell | Vaillancourt J.,Applied NanoFemto Technologies, LLC | Wen H.,University of Massachusetts Lowell
Applied Physics Letters | Year: 2010

In this letter, we report a photoluminescence (PL) study of the temperature-dependent energy gap variation in InAs/GaAs quantum dots (QD). Energy gaps E (T) of different InAs/GaAs QD samples with various numbers of QD stacking layers were measured from the ground state PL emissions at various sample temperatures. For each of the QD samples, linear dependences between [E (T) - E0] (β+T) and T (where E0 =0.42 eV and β=-550 K) is obtained in low and high temperature regions. The transition temperatures between the two temperature regions are found to be related to the numbers of QD stacking layers. A linear relation between the number of the QDs and the phonon densities at the corresponding transition temperatures is obtained. © 2010 American Institute of Physics. Source


Grant
Agency: Department of Defense | Branch: Office for Chemical and Biological Defense | Program: SBIR | Phase: Phase II | Award Amount: 749.93K | Year: 2011

Longwave infrared (LWIR, 8-12µm) focal plane arrays (FPAs) play an important role in hyperspectral chemical and biological (CB) sensing and spectral imaging. Existing thermal detectors are unable to meet the high sensitivity and fast response requirements of many hyperspectral chemical and biological sensing applications. FPAs based on photon excited electron generation process can fulfill the speed and sensitivity requirements. However, they show high noise, and thus need to be cooled down to<80 K to reduce the noise. The requirement for cryogenic cooling systems adds cost, power consumption and reliability issues, thereby making it unsuitable for standoff sensing and detections. In SBIR phase I research, we have developed a new low noise LWIR photodetector, demonstrated large photoresonsivity, high photodetectivity and its chemical sensing and imaging capability. Motivated by the Phase I feasibility and advantages demonstration, In Phase II, we will optimize the LWIR photodetector and FPA technology specifically for long distance standoff CB molecule and aerosol detection and spectral sensing and mapping. A prototype of the LWIR FPA will be developed and packaged with integrated detector dewar cryocooler assembly (IDDCA) and assess interface compatibility with Edgewood Chemical Biological Center (ECBC)'s existing CB molecule and aerosol spectral sensing system.


Grant
Agency: National Aeronautics and Space Administration | Branch: | Program: STTR | Phase: Phase I | Award Amount: 100.00K | Year: 2009

Middle-wave infrared (LWIR, 3.2-3.6 ƒÝm) photodetectors with a high specific photodetectivity (D*) are of great importance in NASA¡¦slidar and remote sensing applications. However, existing MWIR photodetectors are required to be operated at low temperature of below 77K to achieve high photodetectivity (D*). The requirement for cryogenic cooling systems adds cost, weight and reliability issues, thereby making it unsuitable for space and planetary exploration applications. The proposed STTR research aims to develop a new type of MWIR photodetector with a significantly enhanced quantum efficiency of ~ 60% and photodetectivity of > 10^10 cm Hz^1/2/W. Successfully developing the proposed innovation is expected to provide an enabling technology for compact high performance MWIR detection and imaging systems suitable for NASA¡¦s space exploration and earth remote sensing applications. In phase I, a preliminary MWIR photodetector with the high specific photodetectivity (D*) will be developed and delivered to NASA for proof-of-concept demonstration. In Phase II, an ultra-compact highly-sensitive focal plane array (FPA) prototype will be developed and hybridized with readout circuits. A preliminary high sensitivity LWIR camera will be also demonstrated and delivered to NASA in Phase II.


Grant
Agency: National Aeronautics and Space Administration | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 124.89K | Year: 2014

Hyperspectral middlewave infrared and longwave infrared (MWIR/LWIR) imaging systems capable of obtaining hundreds of narrow band (10-15 nm) spectral information of Earth's surface, the atmosphere, and land use in agriculture are of great importance in NASA's Earth remote sensing missions. Existing hyperspectral MWIR/LWIR imaging systems are bulky and heavy and thus not suitable for portable and small satellite applications. This SBIR project aims to develop an on-chip hyerspectral imaging system with integrated narrow-band (15 nm) hyperspectral filers on the pixels of the MWIR/LWIR image array. Successfully developing the proposed innovation will provide an enabling ultra-compact on-chip hyperspectral imaging technology with significantly reduced size, weight, and power consumption suitable for NASA's portable and small satellite earth remote sensing missions. In phase I, the proposed on-chip hyperspctral imaging system will be evaluated and compared with existing technologies. A preliminary MWIR/LWIR photodetector with the integrated plasmonic narrow-band filter will be fabricated and characterized. In Phase II, a prototype of the miniature on-chip mega pixel (1024x1024) MWIR/LWIR hyperspectral imaging system will be developed for laboratory demonstration.


Grant
Agency: Department of Defense | Branch: Air Force | Program: STTR | Phase: Phase I | Award Amount: 100.00K | Year: 2010

Multi-modal (including spatial, spectral and polarimetric) photodetectors and focal plane arrays (FPA) can dramatically enhance the target detection, tracking and identification capability of a battle field sensing system. Most existing multi-spectral polarimetric sensing systems employ dispersive optics (gratings or prisms), or external polarizer technologies to obtain spectral and polarimetric characteristics of targets. These systems are usually heavy, bulky, and unable to perform on-demand spectral-tuning and waveband selection. Due to the large format (e.g 1Kx1K) FPA and multiple wavebands and polarization states involved in a battle field sensing system, the lack of dynamic detection waveband tuning capability will result in a tremendous amount of unproductive and decision-irrelevant data. This SBIR proposal aims to develop a voltage-tunable multi-spectral polarimetric photodetector and FPA capable of adaptive waveband selection and polarization sensing with significantly reduced device size and enhanced reliability. In phase I, a preliminary adaptive multi-mode photodetector will be developed for proof-of-concept demonstration. In Phase II, an ultra-compact focal plane array (FPA) prototype with voltage-tunable waveband selections and simultaneous polarimetric imaging capability will be developed and hybridized with readout circuits. A preliminary adaptive multi-modal IR camera will be also demonstrated and delivered to Air Force Research Lab in Phase II. BENEFIT: The proposed innovation provides an enabling technology for ultra-compact adaptive multi-modal sensing imaging systems with on-demand waveband and polarization imaging capability. It forms a key building block for space and airborne target detection, identification and discrimination systems. Commercial markets include portable IR sensing and imaging systems for atmospheric pollution and drug monitoring, spectroscopy, and medical diagnostics. The technology developed herein is expected to significantly advance multispectral polarimetric imaging technologies and greatly accelerate the commercialization of the ultra-compact and portable multi-spectral polarization IR imaging technologies to meet the potential needs of the billion-dollar defense and commercial market.

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