A thin single crystal of 2‐methyl‐4‐nitroaniline for second harmonic generation experiment is prepared by vapor phase growth. The crystal is used as a high‐index top layer on a tapered slab‐type waveguide. A Nd:yttrium aluminum garnet laser (1.064 &mgr;m) is guided as a fundamental wave. The phase match condition between the fundamental wave (the TE first wave) and the second harmonic wave (the TE second wave) is realized by coincidence of both propagation constants with translational adjustment of the thickness of the waveguide.