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.
InGaAs/InAlAs avalanche photodiode with undepleted absorber
We report an avalanche photodiode with an undepleted p-type InGaAs absorption region and a thin InAlAs multiplication layer. The motivation for utilizing an undepleted absorption layer, which is similar to that in the unitraveling carrier photodiode, is to reduce the dark current. A dark current below 1 nA at a gain of 10 and a gain–bandwidth product of 160 GHz are demonstrated.
Statistical properties of the impulse response function of double-carrier multiplication avalanche photodiodes including the effect of dead space
The statistical properties of the impulse response function of double-carrier multiplication avalanche photodiodes (APDs) are determined, including the effect of dead space, i.e., the minimum distance that a newly generated carrier must travel in order to acquire sufficient energy to become capable of causing an impact ionization. Recurrence equations are derived for the first and second moments and the probability distribution function of a set of random variables that are related, in a deterministic way, to the random impulse response function of the APD. The equations are solved numerically to produce the mean impulse response, the standard deviation, and the signal-to-noise ratio (SNR), all as functions of time. >