Phase locking of a semiconductor diode array in an external cavity

Theoretical investigations are reported of the characteristics of high-power lasers with the active medium in the form of a semiconductor diode array. The selectivity of a Talbot cavity, of a cavity with an aspherical output mirror, and of a semiconfocal cavity is studied as a function of the array parameters. Estimates are obtained of the sensitivity of the laser radiation characteristics to fluctuations of the array parameters. It is shown that the dependence of the selectivity of an aspherical cavity on these parameters is nearly the same as that of a Talbot cavity, but the fundamental mode propagates without radiation losses between the diodes and beyond the array edges. A semiconfocal cavity is more selective than a Talbot or aspherical cavity. When the number of diodes in a linear array exceeds 20, the losses of the second mode in a semiconfocal cavity grow to more than 80%. The efficiency of a laser with a semiconfocal cavity, calculated ignoring the diode efficiency, can reach 80%-90%.