We report an inexpensive diode-pumped Nd:YVO4 laser mode-locked with combined effects of nonlinear mirror (NLM) and cascade second-order optical nonlinearities (CSON) in a KTP crystal. Detailed analysis, which takes into account the transverse effect of cavity modes, shows that the CSON effect dominates the mode locking process. The resulting self-defocusing lens couples with an aperture appearing in the gain medium and then produces a cavity loss modulation. The mode locking self starts at a pump power of 2.2 W with a 35% transmission output coupler and generates pulses with a duration of 14 ps and an averaged power of 350 mW. The laser was shown to be useful for probing polar structures of nonlinear optical materials with second harmonic microscopy.