Lateral mode selection of single-mode laser diode microstripe bar (1050 nm) in external cavity

Radiative characteristics of microstripe laser diode bar in an external resonator based on an aspherical lens and a flat dielectric mirror were Investigated. The bar had total emitting aperture of 185 $\mu$m, formed by 10 stripes with a width of 6 $\mu$m separated by mesa-grooves. Operation in the external resonator of the entire emitting aperture was characterized by a multimode generation regime with a peak power of 3 W/6 A. Selection of lateral modal structures and transition to a single-mode regime is possible by limiting the number of stripes involved in optical feedback. Dependences of optical mode reconfiguration were studied by introducing limiting slits into the external cavity. It was shown that limiting the emitting aperture involved in the feedback to 65 $\mu$m allows us to demonstrate high-order single-mode operation with far-field divergence for the central lobe of 1$^\circ$.