We demonstrate that self-induced gain gratings can provide nonlinear o
ptical feedback that results in single-frequency selection and passive
self e-switching of a conventional linear laser cavity. An experiment
al Nd:YAG laser system is described that yields a temporally-smooth 20
ns pulse at 1.064 mu m. In addition, we show that the feedback has ph
ase-conjugate properties that permit ''flower-like'' mode formation ev
en though the azimuthal symmetry of the cavity is broken.