Overcoming traditional manufacturing limitations in high Q micro- ring resonators using non-linear effects in silicon

High sensitivity to fabrication errors is a main challenge in using high-Q resonators. Here we show that by carefully choosing the optical tuning using an evolutionary algorithm, a drastically distorted transmission function can be restored. High Q ring resonators have been shown to enable novel functionalities on chip[1,2], however the main challenge in using high Q resonators is their high sensitivity to fabrication errors. These errors affect the dimensions of all the parameters of the resonator such as its radius, its quality factor Q and its resonance wavelength. As a results complex transmission functions, that are obtained by coupling such resonators are then drastically distorted. Here we show that solely by choosing carefully the degree of tuning of the resonators, i.e., its resonance wavelength, a drastically distorted transmission function (due to variations in all of its geometrical parameters) can be recovered. The resonance wavelength of ring resonators can be tuned in silicon using all-optical modulation of the effective index induced due to two photon absorption, as recently demonstrated in ref. 5 and 6. Here the degree of tuning of each ring’s resonances is determined by applying an optimization algorithm to the system. Fig. 1. Device structure. The structure analyzed is shown in Fig. 1. Each stage of the device is a double-ring resonator. It consists of a pair of silicon ring resonators coupled to a pair of parallel silicon strip waveguides. The double-ring resonator has a sharp transmission line (EIT-like mode) resulting from a mode due to the interference between the two ring resonators [3]. By tuning the resonance wavelength of each resonator in the pair, one can control the effective-Q of this mode providing a high degree of freedom to tailor the spectrum. The structure of each stage of the device is defined by the parameters listed in Table I. The range of each parameter corresponds to the one that is typically achieved experimentally in such structures [4]: Variable Restricted Range κ 0.0 – 1.0 α 0.0 – 0.005 Φ0 0 2π Φ1 0 2π Φ2 0 2π R 3000 – 10000 nm Table I. Range of parameters describing each doubled ring resonator. The parameters controlled externally by alloptical effects are φ1 and φ2 shown in bold a186_1.pdf WE22.pdf © 2007 OSA/NLO 2007