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High-Average-Power Room-Temperature Large Optical Cavity (LOC) Lasers.

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Final rept. 28 Jun 71-27 Jun 72,

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This report concerns the results of a one-year research program aimed at the study and development of laser structures suitable for high-power, high-duty cycle operation at room temperature. Of the laser structures which can be used, the large optical cavityLOC laser is the most suitable one. This program included studies of improved techniques for preparing the required multilayer epitaxial structures of GaAs and AlGaAs by liquid phase epitaxy, the effect of major structural parameters on the threshold current density and differential quantum efficiency, the nature and origin of the transverse modes in the laser, and the limitation in the internal quantum efficiency. Among the major accomplishments of this program are 1 The emission of 4 W from a single diode was obtained for the first time at a duty cycle of 1 with a drive current as low as 11 A 2 An improved growth method was developed which allows a greatly improved degree of control of the thin epitaxial layers needed for efficient laser fabrication 3 Design criteria were developed for preventing the dominance of the internally circulating modes which result in low externally observed laser efficiency because the radiation is effectively trapped inside the laser structure and 4 A complete theoretical treatment checked by experiment was made of the transverse mode selection process in LOC lasers which determines the far-field radiation pattern. From these results it is possible to predict the order of the propagating mode and the shape of the radiation pattern once the basic laser parameters are known. Author

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  • Lasers and Masers

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