Active and passive hybrid mode-locking of a Nd:YVO4laser with a single partially poled KTP crystal

We report on a Nd:YVO(4) laser mode-locked with a hybrid active and passive modulator consisting of a single partially poled KTP crystal. The periodically poled part provides negative cascaded Kerr-lensing, which together with intracavity soft and hard apertures gives passive modulation. Active phase modulation comes from the electro-optic effect by applying a voltage over the unpoled part of the crystal. The active modulation provides pulse lengths of about 95 ps, which initiate pulse shortening and self-sustained passive mode-locking by the cascaded Kerr effect. The repetition rate of the laser was 94 MHz and the output power was 350 mW, with a bandwidth of 0.235 nm and pulse lengths down to 6.9 ps.