Laser diode arrays with apertured phase conjugate feedback

A study is made of the use of phase conjugate mirrors (PCMs) and filters which may destroy the phase conjugation quality, evoke coupling of the laser array modes (supermodes), and give new filter-dependent cavity modes. An analysis is made of this coupling and the degree of feedback as a function of the spatial filtering. In general, an increase of the spatial filtering deteriorates the phase conjugation quality, increases the coupling, and decreases the light intensity of the feedback. The applications for mode selection capabilities are given. In particular, the authors give a detailed example for a simple filter (a slit) which favors the basic (first) mode, although the highest mode is the preferred lasing mode without the filter. This is a very common situation in most of the commercially available laser diode arrays. The authors' analysis is based on the Fresnel diffraction regime, which can be applied in a cascaded form, and allows a separate calculation for each link of the light propagation.<
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