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GaAs Degradation.

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Final rept. 29 Oct 69-2 Feb 71,

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A comprehensive investigation has been concluded of the physics of GaAs laser diode failure and techniques to improve their reliability. Gradual degradation has been shown to depend partly on the structural perfection of the devices, and modifications of the close-confinement single heterojunction AlGaAs-GaAs diodes have now yielded laboratory devices with reasonably stable performance over several thousand hours at duty cycles of 0.04 operating at 300 to 400 Wcm of facet. These operating conditions are those required in a number of major applications, including gated illuminators. The present life is an order of magnitude better than previously possible with homojunction lasers. Catastrophic degradation, in which the laser facet is damaged, has been prevented by the use of antireflective SiO films andor a new laser structure, the large optical cavity laser LOC developed in the course of the present program. This new device introduces a new degree of freedom in injection laser design by permitting either high-peak-power, low-duty-cycle operation with very high efficiency, or high-average-power operation. Experimental and theoretical studies have also been made with the objective of reducing the laser beam divergence. A new model has been proposed to explain the mode propagation in heterojunction lasers which will be useful in future efforts to reduce the beam divergence which now limits the application of the very low threshold lasers. Author

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  • Electrical and Electronic Equipment
  • Lasers and Masers

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