Energy-efficient communication links are crucial for future processors and optoelectronic microchips in order to continue growths in computing and information technologies [1]. Wavelength-division multiplexing (WDM) techniques based on silicon photonic circuits are ideal for high bandwidths data communication systems with small footprints [2,3]. Compact double ring resonators (DRRs) provide excellent properties to realize spectral filters with flat-top transmission characteristics, providing a steep roll-off with low channel crosstalk at dense frequency grids. Hence, cascaded DRRs as illustrated in Fig. 1 (a) are well-suited for integrated WDM systems on optoelectronic microchips. The high refractive index of silicon facilitates small ring perimeters and the wide free spectral range (FSR ∝1/Lr) enables multiplexing tens of data channels to a common bus waveguide. The high energy-efficiency which is enhanced by the strong thermo-optic effect (TOE) combined with the short physical lengths is another relevant advantage of the compact size. However, manufacturing variability and associated photonic component deviations remain a serious drawback [4]. Hence, most recent works use thermal heaters for the dynamic filter control as well as to counterbalance inevitable manufacturing deviations [5-7].
