Advanced receiver technology for commercial threat warning systems
Advanced threat warning technology will begin to play a more significant role for Homeland defense and National security. Of particular concern are landing and take-off patterns of slow moving commercial airliners here and abroad. Recognizing this vulnerability has triggered renewed interest in high sensitivity internal gain optical detectors and 2D arrays. Avalanche photo detectors (APD’s) are the most highly sought after low-noise, high-gain photo sensors. They are being developed for highly sensitive LADAR receiver systems in autonomous munitions and for data communications (for example) and will be the “eyes” of modern commercial threat warning systems. This paper reviews several LADAR technologies and the corresponding requirements placed on APD’s. Performance of commercial and experimental APD’s will be discussed. Recent results on large format InAlAs APD arrays fabricated by the authors will also be presented.
A high-responsivity high-bandwidth asymmetric twin-waveguide coupled InGaAs-InP-InAlAs avalanche photodiode
The authors demonstrate an integratable high-responsivity high-bandwidth long wavelength InGaAs-InP-InAlAs avalanche photodiode based on an asymmetric twin-waveguide structure. The device has an external quantum efficiency of 48 /spl plusmn/ 1.5% at /spl lambda/ = 1.55 /spl mu/m, a 3-dB bandwidth of 28.5 /spl plusmn/ 0.5 GHz with gain of up to 4, and a fiber-to-waveguide misalignment tolerance of /spl plusmn/ 1.0 /spl mu/m in the vertical and /spl plusmn/ 1.3 /spl mu/m in the horizontal directions resulting in a 1-dB sensitivity penalty.
Spin label motion in fatty acids.
Spin labels dissolved in highly purified fatty acid systems exhibit nearly identical tumbling rates in liquid and solid phases. Even though the spin labels do not have the same molecular geometry as the lipid matrix the melting point of the matrix can be inferred by measurements of the temperature dependency of molecular motion.