Tunable coupling-induced resonance splitting in a self-coupled silicon ring cavity with robust spectral characteristics

Abstract

We propose and demonstrate a self-coupled micro ring resonator for resonance splitting by mutual mode coupling of cavity mode and counter-propagating mode in Silicon-on-Insulator platform The resonator is constructed with a self-coupling region that can excite counter-propagating mode. We experimentally study the effect of selfcoupling on the resonance splitting, resonance extinction, and quality-factor evolution and stability. Based on the coupling, we achieve 72% of FSR splitting for a cavity with FSR 2.1 nm with ¡ 5% variation in the cavity quality factor. The self-coupled resonance splitting shows highly robust spectral characteristic that can be exploited for sensing and optical signal processing.Advances in Silicon photonics (SiP) has provided tremendous impetus to achieve the next generation high-speed short and long reach communication. It provides the advantages of optical transparency and large-bandwidth along with CMOS compatibility to deliver compact energy-efficient circuits [1]. Moreover, improvements in the fabrication technology has enabled low-loss waveguides and highly-uniform device response that was once considered a challenge in adapting SiP for practical applications [2].Micro-Ring Resonators (MRRs) are one of the fundamental building blocks of SiP integrated circuits. Si MRRs have found applications in areas such as sensors [3], modulators [4] and filters [5]. A simple MRR consist of a ring waveguide evanescent-coupled to one or two straight waveguides. Typically, MRRs have only forward propagating cavity modes at resonant wavelengths. However, in practice, any non-ideality in the resonator can result in the generation of counter-propagating modes in the cavity. The two primary sources of such non-idealities are sidewall roughness in the waveguides and non-unidirectional coupling between the bus and the ring waveguide. The sidewall roughness act as scattering points that redistributes the energy into counter-propagating mode, while coupling region between a ring and the straight waveguide can excite contra-directional modes because of reflections caused due to mode mismatch between the straight bus waveguide and the cavity mode [6,7]. Such counterpropagating modes result in resonance splitting and are referred to as Autler-Townes splitting

All-Optical Wavelength Multicasting in Quadruple Resonance-Split Coupled Silicon Microring Cavity

“…We have earlier shown that splitting the resonances is a potential solution where a cavity resonance could be selectively splitted into closely spaced reconences [17]. Such splitting of resonances have already been demonstrated and utilized in areas like photonic links [18].…”

“…It is an assembly of a conventional MRR externally loaded with a Self−Coupled MRR (SCMRR). A detailed discussion on the design and working principle of the SCMRR is presented in ref [17]. A typical MRR has mode propagating in either clockwise or anti-clockwise direction and resonates at wavelengths that phase match with the cavity.…”