We report an efficient dual signal wave intracavity optical parametric oscillator (IOPO) inside a diode-end-pumped acousto-optically Q-switched Nd : YVO 4 laser. The nonlinear crystal in the IOPO is periodically poled MgO -doped lithium niobate ( PPMgLN ) with a phase-reversed grating. In the experiment, dual signal waves at 1475.1 nm and 1489.8 nm are achieved at a crystal temperature of 40°C. At an incident diode pump power of 6.1 W and a Q-switch repetition rate of 19 kHz, an average dual signal output power of 0.66 W is achieved, leading to a conversion efficiency of 10.8%. During half an hour, the instability of the dual signal waves is less than 1.5% (rms).