Abstract
A method for increasing the coupling efficiency between ridge optical waveguides and PhCCRWs is described. This increase is achieved via W1 channel waveguide sections, formed within a two-dimensional triangular lattice photonic crystal using mode-matching. The mode-matching is achieved by low quality-factor modified cavities added to both the input and output ports of the PhCCRW. A three dimensional finite-difference time-domain method has been used to simulate light propagation through the modified PhCCRW. We have fabricated PhCCRWs working at 1.5microm in silicon-on-insulator material. Measurements and simulations show that the overall transmission is improved by a factor of two.
Highlights
A Photonic Crystal (PhC) Coupled-Resonator Waveguide (CRW) is a waveguide composed of a sequence of linked photonic crystal cavities [1,2,3,4]
To the best of our knowledge, there are no reports of techniques designed to increase the coupling efficiency between CRWs and ridge or PhC channel optical waveguides, except for the case of coupling to a single cavity [13]
We report here on structural modifications that increase the coupling efficiency between CRWs, embedded in W1 PhC channel guides, and ridge waveguides using mode-matching[14,15]
Summary
A Photonic Crystal (PhC) Coupled-Resonator Waveguide (CRW) is a waveguide composed of a sequence of linked photonic crystal cavities [1,2,3,4]. As the name implies, because this waveguide structure has strongly resonant behaviour, coupling light efficiently into and out of the CRW remains a challenge. We report here on structural modifications that increase the coupling efficiency between CRWs, embedded in W1 PhC channel guides, and ridge waveguides using mode-matching[14,15]. In a photonic crystal coupled-resonator waveguide, light typically propagates into a highly resonant waveguide from a ridge waveguide. This is accompanied by a very strong reflection, because of the large mismatch, both in modal distribution and wave impedance. The structure is based upon a triangular (hexagonally symmetric) planar photonic crystal formed by air holes in a silicon-on-insulator wafer. The depth of the holes was around 0.5μm, penetrating through the core layer and entering into the bottom cladding to a depth of approximately 50nm
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