Experiments have been performed to evaluate the use of parametric laser image upconversion in proustite to convert 10.6-microm illuminated objects into visible images. The experiments evaluated the key parameters, and the results were compared to the theory. A diffuse scatterplate was illuminated with radiation from a CO(2) laser operating at 10.6 microm. The upconversion efficiency, angle of acceptance, tunability, bandwidth, and image resolution of the system were measured. The results were found to be in agreement with theory. The upconversion efficiency of the 1-cm-long mixer used was 6 x 10(-6) for a local oscillator power density of 44 W/cm(2). The half-power angle of acceptance for a 1-cm-long mixer was found to be 8 degrees . Different frequency modes of the CO(2) laser were identifiable by first tuning the laser and then following with the mixer. The tuning constant near 10.6 microm was measured to be 0.25 microm per degree of optic axis rotation. The acceptance bandwidth of the 1-cm-long proustite mixer was found to be 0.015 microm. In the imaging experiments, a diffuse reflecting, 100% contrast bar chart sequence was used to measure resolution, which, limited by transverse multimode local oscillator beam divergence, was found to be 20 mrad/cycle for a 25% depth of modulation in the upconverted signal. A source of internal parametric light was observed in the proustite mixer. Measurements of the light level, its temperature dependence, its phase matching dependence, a comparison with upconverted external blackbody radiation, and second-order parametric effects have been made. The light appears to be upconverted thermal radiation from within the proustite mixer.

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Optical communications experiments at 6328 A, comparing the fading characteristics of coherent and noncoherent optical detection, have been performed over a 1-km real atmospheric path in different weather conditions. The results show that fading is less severe for noncoherent detection and that the fading characteristic for both types vary significantly with weather conditions. In addition, the similarity of optical FM to rf FM is demonstrated. The measurements were performed using a remote laser transmitter and an optical superheterodyne receiver operating simultaneously in both a coherent and noncoherent detection mode. The receiver, tunable over a frequency range of 1 GHz at the IF difference frequency of 30 MHz, has automatic frequency control and also uses a precision angle tracking servo to maintain receiver spatial alignment with a remote transmitter. The angle and frequency tracking capability permit operation between moving transmitter and receiver terminals.