Results will be presented for the growth of CdZnTe by the low pressure Bridgman growth technique. To decrease deeplevel
trapping and improve detector performance, high purity commercial raw materials will be further zone refined to
reduce impurities. The purified materials will then be compounded into a charge for crystal growth. The crystals will be
grown in the programmable multi-zone furnace (PMZF), which was designed and built at Northrop Grumman‟s
Bethpage facility to grow CZT on Space Shuttle missions. Results of the purification and crystal growth will be
presented as well as characterization of crystal quality and detector performance.
We have grown high quality oriented nano particles of zinc selenide (ZnSe) on patterned gallium arsenide (GaAs)
substrates. We have developed and used silver and gold based templates with domains of 35 μm. We observed that
the films grew epitaxially on the non-patterned portion of GaAs wafers with 4° miscut from (001). Several samples
of thickness ranging from 5 μm to 1 mm thickness of ZnSe were grown in a vertical closed tube using the
temperature gradient as the driving force. The quality of the samples was analyzed by X-ray and morphology was
studied by SEM, FIB, and AFM and by etching the films. The rocking curve showed that the FWHM values for
different films were in the range of 300-350 arcs second. We observed that film on (001) portion of the template
grew with smooth morphology but morphology was slightly different on the templates. The grown film had strong
(111) peak also on the patterned substrate in addition to the (001) peak observed for the film on unpatterned
We have developed several binary, ternary and quaternary sulfide and selenide crystals
for nonlinear optical applications and present an overview on the crystal growth and
characterization of crystals for nonlinear optical (NLO) conversion efficiency. We have
summarized the performance of silver gallium selenide (AgGaSe<sub>2</sub>), thallium arsenic
selenide (Tl<sub>3</sub>AsSe<sub>3</sub>), and silver gallium germanium selenide (AgGaGe<sub>3</sub>Se<sub>8</sub> and
AgGaGe<sub>5</sub>Se<sub>12</sub>) crystals and have compared with gallium selenide (GaSe). All these
crystals were grown by vertical Bridgman method in quartz ampoules by using
stoichiometric compounds synthesized from constituent elements. The significant
problem of cleaving of GaSe was reduced in ternary and quaternary compounds.
Experimental results showed that binary, ternary and quaternary selenide compounds
transmit at wavelengths up to 16 μm, have reasonably high value of nonlinear
conversion merit (d<sup>2</sup>/n<sup>3</sup>, where d is the NLO coefficient and n is the refractive index) and
have the lowest absorption coefficient compared to arsenides, phosphides and other
nonlinear optical (NLO) materials.
This work showcases developments in growth and performance of nanowire (NW) based photodetectors. Specifically
the ability to transition from single NW devices to device arrays will be discussed. We have demonstrated the growth of
semiconducting nanowires (NWs) using the physical vapor transport (PVT) method. CdSe and ZnSe NWs were grown
and showed promising optical properties, including high transparency and a high ratio of band edge/deep level defect
emission in photoluminescence (PL) measurements. Metal-semiconductor-metal (MSM) structures were fabricated from
an array of ZnSe NWs, which showed an average increase of 10x in photocurrent and up to 720x for an individual
Orientation-patterned zinc selenide (OPZnSe) is a unique quasi-phase-matched nonlinear optical material for enabling frequency conversion from visible to long-wave infrared wavelengths. We have fabricated and tested OPZnSe devices over a wide spectral range. Single-crystal OPZnSe films of greater than 1 mm thickness were grown and characterized for optical loss showing an attenuation coefficient less than 0.05 cm−1 from 1 to 12 µm. We demonstrated nonlinear frequency conversion in the near infrared, mid-infrared, and long-wave infrared in these devices through a variety of nonlinear optical mixing processes.
In this paper we report the thermal and electronic characteristics of the ternary compound
TlGaSe<sub>2</sub>, grown from the melt. The phase-diagram, congruency of material and phase transition
were studied by differential thermal analysis. The material melted congruently at 812.9C and did
not show any other phases between room temperature and the melting point. Results of crystal
growth, and effect of alloying and its effect on crystal growth and properties are also discussed.
In high purity material it is easier to cleave the crystal since layers of successive rows of
tetrahedrons are turned away from each other by 90<sup>0</sup>. However, by suitable alloying, the angle
of the tetrahedrons can be changed and the tendency to cleave can be decreased. This effect will
be evaluated by comparing the microstructural properties of pure and alloyed crystals. By
measuring the optical transmission band edge we studied details absorption characteristics to
evaluate the effect of impurities on recombination characteristics. Results indicated that there
were no donor-acceptor recombinations at or above room temperature.
Effect of magnetic nanoparticles on the transparency of a transparent matrix is studied in the infrared wavelength region.
We used the iron oxide - potassium bromide system for this study. Several samples were prepared with different
concentrations of iron oxide nanoparticles. IR microscopy and transmission measurements were performed to determine
the resonance characteristics of aggregates of nanoparticles. We observed a sharp strong absorption peak at 7.22 μm.
The amplitude of the absorption peak was dependent on the nanoparticle concentration. Effect of interface diffusion on
the morphology and transmission was studied by annealing the sample at 175 C and 500C. High temperature annealing
indicated interpenetration and affected the transparency significantly.
(SiC)<sub>x</sub> (AlN)<sub>1-x</sub> Solid-solution films were deposited on on-axis Si-face 4H-SiC (0001) substrates by the physical vapor
transport (PVT) method. Attempts were made to dope this film with
Nd<sup>+3</sup> for high power laser applications. SiC or its
alloys will have better properties compared to oxides because of extremely high thermal conductivity and damage
threshold. The doped film was characterized for its quality by X-ray, Photoluminescence (PL) and scanning electron
microscope (SEM). X-ray rocking curves showed that crystals with FWHM of less than 200 arc seconds could be grown.
The results were compared with previous results published on rare earth doped SiC material. Effect of annealing at high
temperature on PL characteristics is also reported.
We have developed and fabricated a Tl<sub>3</sub>AsSe<sub>3</sub> (TAS) crystal based acousto-optic tunable filter
(AOTF) for operation between the 8 to 12.0 μm wavelength regions. We have demonstrated
peak efficiency greater than 60% with a 10.6 μm source and 2 watts of RF input power. This
high efficiency should enable high resolution and large throuput for AOTF based imaging and
Orientation-patterned zinc selenide (OPZnSe) is a unique quasi-phase-matched nonlinear optical material for enabling
frequency conversion from visible to long-wave infrared wavelengths. We have fabricated and tested OPZnSe devices
over a wide spectral range. Single crystal OPZnSe films of greater than 1 mm thickness were grown and characterized
for optical loss showing an attenuation coefficient less than 0.05 cm<sup>-1</sup> from 1 to 12 μm. We demonstrated nonlinear
frequency conversion in the near infrared, mid-infrared, and long-wave infrared in these devices through a variety of
nonlinear mixing processes.
We have experimentally demonstrated and report on the results of crystal growth, fabrication, design, development, and performance for the long-wavelength infrared (LWIR) hyperspectral imager based on an acousto-optic tunable filter (AOTF) utilizing an efficient crystal, thallium arsenic selenide (Ti3AsSe3 TAS). Results on the growth of 40-mm-diameter, 15-cm-long crystal boules, to fabricate 4.0-cm-long AOTF devices, and on the system design and performance are presented. To achieve an 8-cm−1-resolution AOTF, we developed a design utilizing growth at 10.6 deg off from the c axis of the crystal and achieved >37% efficiency. A system concept was developed with high efficiency, resolution, and throughput utilizing this TAS AOTF. The test setup consisted of an LWIR camera (microbolometer), the AOTF, and a blackbody radiative source (hot filament), and represents the first time AOTF imaging has been achieved with a microbolometer camera. The filament was placed 25 cm in front of the AOTF, and the camera was aligned to the first-order diffracted beam of the AOTF. The AOTF was tuned to 10.6-µm wavelength by applying a 13.9-MHz rf signal to the transducer. Preliminary experimental results obtained for SF6 gas utilizing this system are reported.
Device-quality single crystals of mercurous bromide were grown by the physical vapor transport method. Crystals transmitted light wavelengths up to 30 µm and did not show any absorption bands. Detailed x-ray Laue and x-ray diffraction studies were used to characterize and orient the crystals. Optical evaluation was performed by fabricating slabs of crystals. A design was developed to fabricate acousto-optic tunable filters with 10-deg off-axis orientation operating in the mid- and long-wavelength regions. An acousto-optic tunable filter (AOTF) was fabricated using a crystal with a 16-mm optical aperture for the 10-deg design. A theoretical tuning curve for a mercurous bromide crystal-based AOTF using this design was also computed for the first time. Experimentally measured data on frequency matching agreed well with the theoretical predictions, and the transducer thickness was suitable for filtering 7.58 µm with the fabricated AOTF.
Northrop Grumman has designed, developed and demonstrated acousto-optic tunable filter (AOTF) based hyperspectral imager to cover visible to long wavelength infrared (LWIR) spectral region. We have experimentally demonstrated and report the results of crystal growth, fabrication, design, development and performance for the long wavelength infrared (LWIR) acousto-optic tunable filter (AOTF)-based hyperspectral imager based on an efficient crystal thallium arsenic selenide. The results on the growth of 40 mm diameter and 15 cm long crystals, 4.0 cm long AOTF fabrication, and system design and performance are presented. A system concept was developed with high efficiency, resolution, and throughput utilizing this TAS AOTF. The test setup consisted of an LWIR camera (microbolometer), the AOTF, and SF<sub>6</sub>. The object was placed ~20" in front of the AOTF. The camera was aligned to the first order diffracted beam of the AOTF. The AOTF was tuned to 10.6 um wavelength by applying a 13.9 MHz RF signal on the transducer. The results on the growth of crystals, AOTF fabrication, and systems design and performance are presented.
We have synthesized large batches of GaSe reacted mixtures and grown centimeter size indium doped single crystals by the vertical Bridgman technique. Second harmonic measurements were made for high rep rates and data showed a "d" value of 51 pm/V for the GaSe crystals. SHG values were also theoretically calculated and appear to be in good agreement with the experimental data. These values were smaller compared to solid solution GaSe crystals, which showed a "d" value higher than 72 pm/V.
Mercurous bromide crystals with very good optical transparency were grown by the physical vapor transport method. A design was developed to fabricate 10-degree orientation acousto-optic tunable filters operating in the mid and long wavelength regions. An acousto-optic tunable filter (AOTF) was fabricated using a crystal with a 13-15 mm diameter. A theoretical tuning curve for a mercurous bromide crystal based AOTF using this design was also computed for the first time.