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Parametric oscillation conditions for periodically timevariant system and stability failure of periodic motion of nonlinear dynamic system are derived within the monofrequency approximation. Graphical illustration and physically based explanation for oscillation conditions are given. Conditions for two-frequency combined oscillation of s u m and difference resonance phenomenon and high frequency synchronization are obtained. A problem of nonlinear system robust control avoiding one-frequency parametric resonances is set up.

We have developed a method to fabricate GaN planar nanowires and cavities by combination of Focused Ion Beam (FIB) patterning of the substrate followed by Metal Organic Vapor Phase Epitaxy (MOVPE). The method includes depositing a silicon nitride mask on a sapphire substrate, etching of the trenches in the mask by FIB with a diameter of 40 nm with subsequent MOVPE growth of GaN within trenches. It was observed that the growth rate of GaN is substantially increased due to enhanced bulk diffusion of the growth precursor therefore the model for analysis of the growth rate was developed. The GaN strips fabricated by this method demonstrate effective luminescence properties. The structures demonstrate enhancement of spontaneous emission via formation of Fabry-Perot modes.