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.
We carried out ghost imaging experiments using nondegenerate entangled beams with the central wavelengths at 810 nm
and 1550 nm. The pulsed pump at 532 nm had the high efficiency of parametric down conversion and enabled ghost
imaging although its average pump power was 10 mW. For the first time, we demonstrated ghost imaging with two
disparate detectors: Si avalanche photodiode on one arm and InGaAs avalanche photodiode on the other. Objects were
placed in the arm of the 1550 nm beam, whereas the imaging lens was placed in the arm of the 810 nm beam. Ghost
imaging was constructed by using the quantum correlated portion of the data due to the nature of the entangled beams.
Current theory for this configuration predicted that the image magnification by a degenerate source should be one and
half times larger than that of this nondegenerate source; the observed magnification followed closely the value predicted
by the theory.
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.
We observed the second order correlation peak for nondegenerate spontaneous parametric down conversion (SPDC) of a
pulsed pump at 532 nm into 810 nm and 1550 nm entangled beams. We used a Si avalanche photodiode (APD) to detect
the 810 nm photons, and an InGaAs APD to detect those at 1550 nm. We defined both a visibility and signal-to-noise
ratio (SNR) based on the data, which were obtained at various pump powers. In contrast to classical imaging systems,
for which SNR increases monotonically with transmitted power, the SNR for the correlation peak in our setup exhibited
a gradual decay as the pump power increased. We derived an empirical relation for the SNR, which was inversely
proportional to the square root of pump power.
Quantum imagers have been demonstrated in the laboratory by several groups. However, there are many practical
concerns that must be considered in order to make such a system as successful as classical imagers in field applications.
Consequently, we develop a model for signal-to-noise ratio (SNR) to estimate the performance of a quantum imager in
comparison with that of the classical case. We assume simple architectures for both systems with components in the two
as common to each other as possible. Comparisons between the imagers are made under conditions of solar background
for ranges up to 2 km. The performance of quantum imager is shown to be superior to that of the classical case under
conditions of narrow joint (or coincidence) detection windows and very strong pumping of the spontaneous parametric
downconverter illumination source, for which the degree of photon entanglement may be severely degraded.
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 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.