Experimental and theoretical investigations on localized states in waveguide arrays

In the last decade there was an increasing interest in the investigation and application of so called metamaterials, such as photonic crystals or photonic crystal fibers, where optical properties can be tailored by means of geometry data. Waveguide arrays are another typical example of metamaterials, where the evolution of electromagnetic fields can be controlled by the effective index of the individual guides and the coupling strength between two adjacent guides. In this paper, the formation of localized states at defects in waveguide arrays is investigated both, theoretically and experimentally. Depending on the relation of the effective waveguide index and the coupling strength different guiding scenarios at an array defect can be observed, which have no analogon in conventional integrated optics. The experimental investigations are realized in polymer waveguides fabricated by UV-lithography. Typical field distributions in the waveguide array are visualized by means of the detection of the fluorescence light above the sample. Using coupled mode theory the experimental results are simulated providing an analytical description.