Integrated photonics on silicon with wide bandgap GaN semiconductor

We report on GaN self-supported photonic structures consisting in freestanding waveguides coupled to photonic crystal waveguides and cavities operating in the near-infrared. GaN layers were grown on Si (111) by metal organic vapor phase epitaxy. E-beam lithography and dry etching techniques were employed to pattern the GaN layer and undercut the substrate. The combination of low-absorption in the infrared range and improved etching profiles results in cavities with quality factors as high as $5400. The compatibility with standard Si technology should enable the development of low cost photonic devices for optical communications combining wide-bandgap III-nitride semiconductors and silicon

Global Optimization of Ultrahigh-Q H0 Photonic Crystal Nanocavity in Silicon

The design of photonic crystal cavities has always presented a considerable challenge over the past two decades. In this work, a global optimization technique has been used to maximize the Q/V ratio of a simple H0 type nanocavity. The optimization is carried out by allowing for shifts of several neighbouring holes along the x-and y-axes. The objective function of the evolutionary optimization was the cavity Q-factor, while reasonable restrictions were imposed on the magnitudes of the shifts in order to limit the variations in modal volume. The fabricated devices were coupled using a side-coupled scheme involving a photonic crystal W1 waveguide and the Q-factors measured. A maximum value of 418'000 was measured along with a modal volume (computed) of 0.34(lambda/n)(3) enabling an extremely high Q/V ratio of 1.2 million, which has also resulted in the onset of nonlinear optical effects including optical bistability at mu W input powers

Near-infrared characterization of gallium nitride photonic-crystal waveguides and cavities

We report the design and optical characterization of fully suspended wire waveguides and photonic crystal (PhC) membranes fabricated on a gallium nitride layer grown on silicon substrate operating at 1.5 mu m. W1-type PhC waveguides are coupled with suspended wires and are investigated using a standard end-fire setup. The experimental and theoretical dispersion properties of the propagating modes in the wires and photonic-crystal waveguides are shown. Modified L3 cavities with quality factors of up to 2200 and heterostructure cavities with quality factors of up to 5400 are experimentally demonstrated. (C) 2012 Optical Society of Americ