  Fast speckle suppression is crucial for time-resolved full-field imaging with
laser illumination. Here, we introduce a method to accelerate the spatial
decoherence of laser emission, achieving speckle suppression in the nanosecond
integration time scale. The method relies on the insertion of an intracavity
phase diffuser into a degenerate cavity laser to break the frequency degeneracy
of transverse modes and broaden the lasing spectrum. The ultrafast decoherence
of laser emission results in the reduction of speckle contrast to $3\%$ in less
than 1 nanosecond.
