Integrated optical ring resonators: Modelling and technologies

In the last decade, a strong research effort has been spent to investigate both theoretically and experimentally integrated optical ring resonators (RRs), and a number of applications have been envisaged for these components. In fact, reconfigurable optical add-drop multiplexers, modulators, switches and optical sensors employing integrated RRs as fundamental building blocks have been proposed on a range of materials, i.e. glass, silica, III-V semiconductors, silicon, silicon oxynitride, polymers, and lithium niobate. Accurate numerical methods for integrated optical resonator modelling have been also developed. Transfer-matrix and bidirectional approaches, Z-transform-based method, time-dependent model, two-dimensional (2D) and three-dimensional (3D) finite-difference time-domain (FDTD) algorithms, have been used for theoretical investigation and design of both single and coupled integrated optical resonators. In this chapter we describe the operating principle of optical RRs review materials and technologies utilized to fabricate these components. Most popular modelling techniques reported in literature for RRs design are discussed. Some RRs applications, i. e. optical modulation, signals processing, optical estimation of angular rate, acceleration, electric field and concentration of chemical species, are illustrated.