Using a tunable optical parametric oscillator, phase‐matched second‐harmonic generation was realized in high‐quality Ti‐diffused LiNbO3optical waveguides near the 1.08‐&mgr; fundamental wavelength. At 45 W peak power in 17‐mm‐long waveguides an efficiency for TM0→TE1conversion up to 25% was achieved. This value is three orders of magnitude larger than previously published results.