We used near-held scanning optical microscopy to measure the optical beam c
haracteristics of weakly-guided narrow-stripe high-power laser diodes. For
both facets of the device, we correlate changes in the near-field optical c
haracteristics with beam steering and the kink in the light output versus o
perating current curve. Our measurements demonstrate that: 1) freqeuncy-loc
king of lateral modes exists for operating currents below the kink in the L
-I curve; 2) beam steering is a result of a shift of in the beat-length pat
tern inside the laser cavity of the frequency-locked lateral modes; and 3)
the kink in the L-I curve results from a sudden increase in the beam waist
of the guided-modes.