Performance of TAS crystal for AOTF imaging

Self Cite

Sensing from space requires the development of hyperspectral imagers operating in the two atmospheric window regions (3-5 µm and 8-12 µm) in the infrared region. At the Army Research Laboratory we are developing hyperspectral imagers operating in these two regions based on using acousto-optic tunable filters (AOTFs). Research is going on in the growth of new acousto-optic materials-mercurous halides (Hg 2 Cl 2 and Hg 2 Br 2 ) and tellurium (Te) for development of AOTF cells. We have developed a hyperspectral imager using a tellurium dioxide (TeO 2 ) AOTF with a liquid-nitrogencooled indium antimonide (InSb) 256×256 focal plane array (FPA) that covers 2-4.5 m region and another imager using a thallium arsenic selenide (TAS) AOTF with liquid-nitrogen-cooled mercury cadmium telluride (HgCdTe) 256×256 FPA to cover 7.8-9.8 m region. Each of these imagers has been integrated on a tripod-mountable platform with an appropriate optical train. Control of RF electronics, and image acquisition and storage operations are carried out under full computer-control with a user-friendly interface. We will discuss the progress in material development and present imaging results.

Section: Materials For Ir Aotfsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Acousto-optic tunable filters for infrared imaging

Gupta

2005

Self Cite

“…In this paper we present a purification, synthesis and crystal growth of Tl3AsSe3 crystals. Previous studies [4][5][6][7][8][9][10][11] have shown that low impurity content in the reactants, accurate stoichiometric control over the reaction mixture and a proper growth sequence play a vital role in improving the quality of the TAS crystals. We report the characteristics of TAS crystals to achieve high resistivity using in-house purified source materials.…”

Section: Introductionmentioning

confidence: 99%

Design and growth of novel compounds for radiation sensors: multinary chalcogenides

Singh

Nagaradona

et al. 2016

Increasing threats of radiological weapons have revitalized the researches for low cost large volume -ray and neutron ray sensors In the past few years we have designed and grown ternary and quaternary lead and thallium chalcogenides and lead selenoiodides for detectors to meet these challenges. These materials are congruent, can be tailored to enhance the parameters required for radiation sensors. In addition, this class of compounds can be grown by Bridgman method which promises for large volume productions. We have single crystals of several compounds from the melt including Tl3AsSe3, Tl3AsSe3-xSx, TlGaSe2, AgGaGe3Se8, AgxLi1-xAgGaGe3Se8 and PbTlI5-x Sex compounds. Experimental studies indicate that these have very low absorption coefficient, low defect density and can be fabricated in any shape and sizes. These crystals do not require post growth annealing and do not show any second phase precipitates when processed for electrode bonding and other fabrication steps. In this paper we report purification, growth and fabrication of large Tl3AsSe3 (TAS) crystals. We observed that TAS crystals grown by using further purification of as supplied high purity source materials followed by directionally solidified charge showed higher resistivity than previously reported values. TAS also showed constant value as the function of voltage.

“…At ARL, we have developed prototype AOTF-based hyperspectral imagers operating in the UV, the visible to near-infrared (VNIR), the SWIR, the MWIR, and the LWIR . Noncollinear AOTFs were used in these hyperspectral imagers based on using single crystals of potassium dihydrophosphate (KDP), 7-9 magnesium fluoride (MgF 2 ), 10 tellurium dioxide (TeO 2 ), [11][12][13][14][15][16][17][18][19][20][21][22] thallium arsenic selenide (Tl 3 AsSe 3 or TAS), [22][23][24] tellurium (Te) [25][26][27][28] and mercurous bromide (Hg 2 Br 2 ). [29][30][31][32][33] The most commonly used AOTF crystal is TeO 2 .…”

Section: Introductionmentioning

confidence: 99%

Materials for imaging acousto-optic tunable filters

Gupta

2014

Self Cite

Research and development of robust compact hyperspectral imagers that can acquire both spectral and spatial features from a scene of interest is of utmost importance for standoff detection of targets as well as chemical and biological agents and backgrounds. Hyperspectral imagers can acquire images with a large number of narrow spectral bands and take advantage of the characteristic spectral signatures of different materials making up the scene. At the Army Research Laboratory (ARL), we are developing hyperspectral imagers based on acousto-optic tunable filters (AOTFs) that can provide adaptive no-moving-parts imagers from the ultraviolet (UV) to the long wave infrared (LWIR) to acquire a two-dimensional spectral image and build up a two-dimensional image cube as a function of time instead of using traditional grating or prism based approach that requires relative motion between sensor and scene. Here, we will review the development of different imaging AOTFs operating from the UV to the LWIR based on a variety of birefringent materials and include the spectral imaging carried out with these filters including both with single and double piezoelectric transducers. We will also include the theoretical background needed to carry out the filter design and discuss development of mercurous halide crystals that can be used to develop AOTFs operating over a wide spectral region from the visible to the LWIR.