  Chaotic bursts are observed in a single-mode microchip Nd:YVO$_4$ laser with
fiber feedback. The physical characteristic of the instability is a random
switching between two different dynamical states, i.e., the noise-driven
relaxation oscillation and the chaotic spiking oscillation. As the feedback
strength varied, transition which features the strong interplay between two
states exhibits and the dynamical switching is found to be non-stationary at
the transition.
