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Schuster J.,Boston University | D'Souza A.,DRS Sensors and Targeting Systems | Bellotti E.,Boston University
Optics Express | Year: 2014

We have numerically analyzed the electromagnetic and electrical characteristics of InAsSb nBn infrared detectors employing a photon-trapping (PT) structure realized with a periodic array of pyramids intended to provide broadband operation. The three-dimensional numerical simulation model was verified by comparing the simulated dark current and quantum efficiency to experimental data. Then, the power and flexibility of the nBn PT design was used to engineer spectrally filtering PT structures. That is, detectors that have a predetermined spectral response to be more sensitive in certain spectral ranges and less sensitive in others. © 2014 Optical Society of America.


Spencer H.M.,DRS Sensors and Targeting Systems
Optics InfoBase Conference Papers | Year: 2010

Long focal length IR optics cause difficulties in achieving performance over varying temperatures due to the large Dn/Dt of IR materials. Modeling results are sensitive to the lens setup. Techniques for design optimization are presented. © 2010 Optical Society of America.


Spencer H.M.,DRS Sensors and Targeting Systems
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

Sensors operating in the 8-12 micron long wave infrared (LWIR) portion of the electromagnetic spectrum have long been used to extend the useful range of operating conditions beyond those of sensor systems operating in the visual spectral band. Infrared systems must cover widely varying fields-of-view (FOV) depending on application, at fast f/numbers compared to systems operating in the visible band. Typical FOVs for LWIR sensors run the gamut from < 1 degree to >50 degrees for large focal planes, necessitating the use of long focal lengths. When the focal length of the optics increases, the sensitivity to defocus caused by thermal effects also increases. Optical materials with useful transmission in the infrared region exhibit larger changes (> 400X) in refractive index with temperature (dN/dT) than optical glass. This in turn introduces larger changes in focus over temperature for infrared systems compared to comparable focal length visual systems. Thermal expansion and contraction of the materials also contribute to changes in system performance and the coefficient of thermal expansion (CTE) is generally larger for infrared materials than for visual band optical glasses. The thermal performance problem is exacerbated with low f-numbers systems. The ability to detect targets having a small temperature difference from ambient is proportional to the light collecting ability of the optics, especially when uncooled detectors are used. It is typical to require f-numbers in the f/1 regime for the LWIR for uncooled applications. Methods have been developed to find optical designs with reduced thermal sensitivity for these applications. © 2010 Copyright SPIE - The International Society for Optical Engineering.


Khalap V.,DRS Sensors and Targeting Systems | Hogue H.,DRS Sensors and Targeting Systems
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

DRS is the inventor and a leading developer of Blocked Impurity Band detector technology for ground, airborne and space-based observing applications and the sole developer of antimony doped silicon (Si: Sb) blocked impurity band (BIB) FPAs. Arsenic doped silicon (Si: As) and Si: Sb arrays in 1282 pixel formats were developed by DRS for use on the Spitzer Space telescope. In the subsequent years these arrays were extended in both format and capability. 10242 pixel format, low flux Si: As arrays were developed for the NASA WISE mission, and Si: As and Si: Sb arrays were developed for higher flux applications such as JPL's MegaMIR camera and Cornell's FORCAST instrument for SOFIA, in both 2562 and 10242 pixel array formats. Si: Sb arrays have advanced to offer similar responsivity, response uniformity, high operability and low dark currents long associated with Si: As BIB arrays but with high quantum efficiency that extends to 40 μm, compared to only 28 μm for Si: As. Recently, Si: Sb detector material has been further developed for low flux astronomy applications. Specifically, Si: Sb material has been grown to satisfy exceptionally low dark current requirements (such as < 0.5 e -/s/pixel at 5 K) for large format focal plane arrays for future infrared telescopes. This paper will focus on the characterization of this low flux Si: Sb detector material. © 2012 SPIE.


Klem E.,Rti International | Lewis J.,Rti International | Gregory C.,Rti International | Cunningham G.,Rti International | And 5 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2013

RTI has demonstrated a novel photodiode technology based on IR-absorbing solution-processed PbS colloidal quantum dots (CQD) that can overcome the high cost, limited spectral response, and challenges in the reduction in pixel size associated with InGaAs focal plane arrays. The most significant advantage of the CQD technology is ease of fabrication. The devices can be fabricated directly onto the ROIC substrate at low temperatures compatible with CMOS, and arrays can be fabricated at wafer scale. Further, device performance is not expected to degrade significantly with reduced pixel size. We present results for upward-looking detectors fabricated on Si substrates with sensitivity from the UV to ∼1.7 μm, compare these results to InGaAs detectors, and present measurements of the CQD detectors temperature dependent dark current. © 2013 Copyright SPIE.

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