Mode conversion in optical second harmonic generation: theory and experiment

Kingston and McWhorter's theory of mode conversion in second harmonic generation with a thin crystal [1] has been extended to include all positions of the crystal relative to the focus of the fundamental beam. Phase differences between the harmonic modes are predicted which depend upon the crystal position. Experiments to test these predictions have been performed with a 1.15 μm helium-neon laser and non-critical phase-matching in lithium niobate. Results are presented for a number of fundamental modes