Phase-matched guided optical second harmonic wave generation in oriented ZnS polycrystalline thin-film waveguides

The first experimental verification of phase-matched SHG was performed in the polycrystalline ZnS thin-film waveguide deposited on a BK-7 glass substrate. The complete phase-matching between the TE1 mode at the fundamental frequency of 1.054 μm and the TM4 mode at its second harmonic wave was realized by using a tunable optical parametric oscillator. The interaction length estimated from the tuning curve for the phase matching was about 35 μm and the output harmonic power was of the order of milliwatts at 300-W fundamental input under the phase-matched condition.