Thermal-aware synthesis of integrated photonic ring resonators

Photonic ring-resonators are key components of many on-chip optical-interconnect wavelength division multiplexing (WDM) network architectures. Thermal interactions between on-chip heat-sources and ring resonators pose significant operational and integration challenges, as these devices are extremely sensitive to temperature-induced changes in refractive index. Contemporary literature proposes active compensation for such refractive index variations (e.g. carrier-injection based tuning and/or WDM channel remapping); however, these are costly in terms of power and area. This paper presents a thermal-aware synthesis approach for ring-resonator compensation. We show how ring-resonators are analyzed in the presence of external thermal gradients, and employ a perturbation analysis to derive an equivalent, trimming-enabled, ring-resonator design. Our methodology produces a design-template that can be used to compensate for thermal variations through modifications to the waveguide´s geometric structure. This approach complements active compensation techniques, and the synthesis is compatible with contemporary lithographic methods. Using this approach, we perform design space exploration with respect to variations to the waveguide structure and their effect on the range and precision of thermal compensation.