  We report parity-time (PT) symmetry breaking in electrically injected,
coherently coupled, vertical cavity surface emitting laser arrays. We predict
beam steering, mode evolution and mode hopping as a consequence of the
non-Hermiticity of the array analyzed by temporal coupled mode theory with both
asymmetric gain distribution and local frequency detuning. We present
experimental confirmation of the predicted mode evolution, mode hopping and PT
symmetry breaking with quantitative agreement with the theory.
