QC laser active regions with multiple transitions from strongly coupled upper laser states to lower laser states were
designed to achieve broad gain spectra as well as high performance. Two broad gain QC laser designs in the 7-9 μm
wavelength region were demonstrated based on the continuum-to-bound design. The first embodiment of one design at
~8 μm enables external cavity tuning over 190 cm-1 (7.5 - 8.8 μm) in pulsed mode operation at 0°C. We also
demonstrated a QC laser structure based on a continuum-to-continuum active region in the 4-5 μm wavelength region
with a gain spectrum of ~ 430 cm-1. External cavity tuning over 340 cm-1 (4.4 - 5.2 μm) was achieved with this design in
pulsed mode operation at 15°C. In spite of the broad gain spectrum, a low threshold current density (1.6 kA/cm2), large
slope efficiency (4.5 W/A), good temperature performance (T0=160 K), high peak power (up to 5 W) and high wall plug
efficiency (WPE, up to 20%) were achieved for ridge lasers with as cleaved facets, in pulsed mode operation at 295 K,
demonstrating that it is possible to make a wide gain spectrum compatible with high power and efficiency performance.
The ν1+ν3 combination band of uranium hexafluoride (UF6) is targeted to perform analytical enrichment measurements
using laser absorption spectroscopy. A high performance widely tunable EC-QCL sources emitting radiation at 7.74 μm
(1291 cm-1) is employed as an UF6-LAS optical source to measure the unresolved rotational-vibrational spectral
structure of several tens of wavenumbers (cm-1). A preliminary spectroscopic measurement based on a direct laser
absorption spectroscopy of methane (CH4) as an appropriate UF6 analyte simulant, was demonstrated.
The Tunable Acoustic Gradient Index of Refraction (TAG) lens is shown to be an alternative method of generating Bessel beam for optical manipulation. The TAG lens exhibits a combination of tunability, optical throughput, and fast switching speed, overcoming many limitations linked with conventional Bessel beam techniques. A refractive fluid is contained within a circular piezoelectric that is driven with an AC signal to establish a periodic index of refraction in the liquid. Simple changes in amplitude or frequency of the driving signal allows for the rapid modification to the transmitted pattern. The switching speed is characterized by the time to reach a steady state pattern, which is shown to depend primarily on the viscosity of the filling liquid. Times between 300 and 2000 μs are obtained corresponding to fluids with viscosity of 640 cs and 0.65 cs respectively.
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