Spatially tunable noncritical phase matching of second-harmonic generation in a doped LiNbO3 crystal

We present, theoretically and experimentally, phase-matched noncritical off-axis second-harmonic generation which is easily tuned using a spatial light modulator. The phase-matching condition depends on both the spatial properties of the fundamental beam and the thermal properties of the medium. We show that a thermally induced phase mismatch can be compensated by choosing the pump beam spatial properties resulting in phase-matched noncollinear second-harmonic generation.