Thermo-optical control of dielectric loaded plasmonic racetrack resonators

The optical properties of racetrack shaped dielectric loaded surface plasmon polariton resonators are studied experimentally for various radius, interaction lengths, and separation gaps between the resonator and the bus waveguide. Using radiation leakage microscopy, their power transmission spectra is recorded over the telecom frequency range and modeled by a notch filter made of a lossy bus waveguide coupled to a lossy resonator. For a typical separation gap around 250 nm, the optimum critical coupling condition is determined by a radius of 6 μm and an interaction length of 2.5 μm. Extinction ratios of the order of -30 dB are reported for resonators featuring quality factors that are found to be of the order of 110. The static thermo-optical control of such racetrack resonators produces a blueshift of the resonance frequency that can be as large as 4.5 nm for a temperature increase of 75 K. Extinction ratio of the order of 9 dB can be achieved between hot and cold states.