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We review briefly some of the basic principles involved in quasi-phase matched multilayer semiconductor films for second-harmonic generation in waveguided, reflection and intra-cavity geometries. New applications in optical ranging for length, temperature, deformation sensors, real time optical reflectometry and vertical cavity second-harmonic generation for displays are presented. The enhancement of quasi-phase matched second-harmonic generation in vertical cavity Fabry-Perot structures is also investigated. When the optimal quasi-phase matching conditions are satisfied in the Fabry-Perot core, the second-harmonic conversion efficiency of a 4 μm thick cavity is enhanced by 1.75 × 106 relative to a homogeneous GaAs slab. This geometry is most suitable for intracavity harmonic generation in vertical cavity surface emitting lasers.

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We demonstrate a novel optical phase detector that uses sum-frequency mixing in a nonlinear waveguide. By monitoring the near-field pattern of the sum-frequency light radiated from the waveguide surface, the relative phase of two input light beams can be measured. By using an Al(x)Ga(1-x)As waveguide optimized for sum-frequency generation with lambda = 1.06 microm input light, we demonstrate a simple phase detector capable of resolving phase shifts of less than 0.2 rad. This phase detector is also used in an interferometer configuration as a gigahertz-resolution frequency monitor.