HgCdTe APDs and APD arrays offer unique advantages for high-performance eyesafe LADAR sensors. These include: operation at room temperature, low-excess noise, high gain, high-quantum efficiency at eyesafe wavelengths, GHz bandwidth, and high-packing density. The utility of these benefits for systems are being demonstrated for both linear and area array sensors. Raytheon has fabricated 32 element linear APD arrays utilizing liquid phase epitaxy (LPE), and packaged and integrating these arrays with low-noise amplifiers. Typical better APDs configured as 50-micron square pixels and fabricated utilizing RIE, have demonstrated high fill factors (>80%), low crosstalk (<2%), excellent uniformity, low dark currents (<10nA), and noise equivalent power (NEP) from 1 -2 nW. Two units have been delivered to NVESD, assembled with range extraction electronics, and integrated into the CELRAP laser radar system. Tests on these sensors in July and October 2000 have demonstrated excellent functionality, detection of 1-cm wires, and range imaging. Work is presently underway under DARPA's 3-D imaging Sensor Program to extend this excellent performance to area arrays. High-density arrays have been fabricated using LPE and molecular beam epitaxy (MBE). HgCdTe APD arrays have been made in 5 x 5, 10 x 10 and larger formats. Initial data shows excellent typical better APD performance with unmultiplied dark current <10 nA; and NEP <2.0 nW at a gain of 10.

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A CO(2) laser has been FM chirp modulated by a CdTe intracavity modulator. A frequency deviation-of-100 MHz in 2 micros was attained in this fashion. Following heterodyne detection the chirped pulse was compressed to 15 ns using a surface acoustic wave compression filter. This corresponded to a compression factor of 130. The suppression of unwanted sidelobes with a weighting filter was demonstrated. We have explored the use of this technique for laser radar systems and described an electrooptically FM modulated CO(2) waveguide laser with postdetection pulse compression by a surface acoustic wave compressive filter. To our knowledge this is the first report of the successful operation of this important system.

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An optical amplifier is described using an active dielectric film. Electromagnetic scattering from this type of active film has been studied in the past using infinite plane waves. The use of unbounded fields resulted in scattering coefficients that approached infinity at resonance. In this paper, the active scatterer is viewed as an optical amplifier with finite incident and scattered fields. An analytical description is presented and then supported by a numerical analysis. Finite gains are calculated. This analysis also predicts spatial filtering of the incident field, and experimental results confirm these predictions.