Substantial progress in power scaling of diode-pumped monolithic Nd:YAG ring lasers is reported. By using a new crystal geometry with a negative curved front facet the thermally induced lens inside the active medium is partially compensated. Applying this design single-frequency operation at 1064 nm is observed at output powers of more than 1.8 W cw. Coherent superposition of the radiation from two miniature ring lasers is achieved by injection locking of these systems. Amplitude and frequency stability of the miniature ring lasers will be discussed for the free-running and the injection-locked laser systems.