A normal incident infrared detector has been fabricated using electron intersubband transition in a InGaAs/GaAs quantum well structure. With the light polarized in the plane of the layers (normal incident) a nominally forbidden absorption peak was observed. Such an absorption is most likely a result of spin-flip intersubband transitions induced by the spin-orbit coupling. In addition, for the light polarized in the plane of incidence, the usual intersubband absorption due to envelope function transition is observed. The responsivity of 0.2 A/W was obtained for the normal incident infrared on the detector. This work demonstrates the fabrication of high sensitivity quantum well infrared detectors operating in the normal incident mode without fabricating grating structures on the device for focal plane applications.

A suspension of short graphite fibers was shown to provide an effective medium for nonlinear microwave interactions. Using a 18-GHz pump beam with up to 20 W continuous power, changes in the 94-GHz refractive index were measured by interferometry. The induced birefringence and anisotropic absorption indicate an alignment of the fibers with the electric field of the pump beam. The resulting nonlinear refractive index coefficient of n2=2.6×10−4 cm2/W is of sufficient magnitude to demonstrate microwave bistability.

Microwave phase conjugation was observed in a liquid suspension of elongated microparticles via degenerate four-wave mixing in a collinear waveguide geometry. Longitudinal phase corrections of a double-passed phase shifter were demonstrated by interferometry. Nondegenerate four-wave mixing was demonstrated with a FWHM bandwidth of 70 MHz. The 10% scattering from the induced grating indicates that high conversion efficiency and gain can be achieved with higher pump power.

We report an easy-to-implement wafer-level electroluminescence characterization technique for InGaN/GaN light-emitting diodes (LED's) epi-wafers by means of multiple electrical probes. By first damaging the p-n junctions of the LED epilayer at localized spots, diode-like current versus voltage characteristics and emission spectra can be obtained at injection currents as high as 100 mA. This allows a relative but reliable comparison of device-related parameters such as differential quantum efficiency, leakage current, and series resistance among LED epi-wafers.

A nonperturbative method for describing the response of an orientational Kerr medium to arbitrarily strong electromagnetic fields is presented. The method is used to analyze recent phase-shift measurements for the static birefringence and new measurements for the time response of a suspension medium as functions of millimeter-wave intensity. Excellent agreement between theory and experiment provides the effective parameters in terms of which the nonlinear optical properties of the medium are assessed for applications to the millimeter-wave regime.