Tailoring the response and temperature characteristics of multiple serial-coupled resonators in Silicon on Insulator

Silicon-on-Insulator (SOI) has emerged as promising material choice for various integrated optoelectronic devices. Two issues make SOI attractive for complex optical systems: the cost reduction due to compatibility with CMOS technology and high refractive index contrast between core and cladding, which is an important property for good confinement of light and efficient guiding and coupling in sub-micron waveguides. However, for those devices that are intended to be part of broadband optical networks, for example multiplexers and de-multiplexers, it is desirable to demonstrate a high selectivity and a tunable response. Thus, it is necessary to provide wavelength selective elements with the ability to filter input data streams producing a large Free Spectral Range (FSR), a small Full Width at Half Maximum (FWHM), and a high quality factor (Q), all conditions set by communication standards. Owing to the generic and adaptable operation, ring-resonator-types of filters in SOI are often considered as candidates to meet these demands. Herein two different designs are investigated from both experimental and modelling standpoints in order to tailor the filter transfer function. These are mutually coupled (Vernier) resonators and cascaded resonators based on small SOI photonic wires. Fabricated filters designed to provide a large FSR and a polarisation independent (PI) response are analysed and improvements proposed. Issues associated with temperature control of the transfer function have also been addressed