Required coupling strength for phase locking of a diode laser array in an external semiconfocal resonator

Summary form only. Depending on the magnitude of individual eigenfrequency deviations between the single emitters of the diode laser array, the coupling strength has to be increased to achieve phase locking. Strong optical coupling leading to in-phase emission of the diode laser array requires an external resonator design which minimizes diffraction losses and simultaneously leads to strong selection of the lowest-order array mode. By examining the eigenvalue problem in Fresnel approximation for a diode laser array in a generalized external resonator, it is shown that a semiconfocal resonator with the resonator length L/sub ext/=d/sup 2///spl lambda/, where d is the diode laser pitch, results in strong in-phase coupling.