Optical Microring Resonators

Theory, Techniques, and Applications

Vien Van

• Publisher: CRC Press
• Year: 2016
• ISBN:
  9781315303499
• Edition: 1
• Topic: Physical Sciences
• Subtopic: Physics
• Index: Physics

"a detailed, cognizant account of numerous crucial aspects of optical microring resonators" – Amr S. Helmy, Professor of Electrical & Computer Engineering, University of Toronto

"an excellent choice for gaining an insight into the vast potential of microring resonators" – Jalil Ali, Professor, Laser Center ISI-SIR, University of Technology, Malaysia

"a thorough treatment… appeal[s] to a wide range of audiences" – L. Jay Guo, Professor of Electrical Engineering & Computer Science, The University of Michigan

The field of microring resonator research has seen tremendous growth over the past decade, with microring resonators now becoming a ubiquitous element in integrated photonics technology. This book fills the need for a cohesive and comprehensive treatment of the subject, given its importance and the proliferation of new research in the field. The expert author has as an introductory guide for beginners as well as a reference source for more experienced researchers. This book aims to fulfill this need by providing a concise and detailed treatment of the fundamental concepts and theories that underpin the various applications. To appeal to as wide a readership as possible, major areas of applications of microring resonators will also be covered in depth.

CHAPTER 1

Elements of an Optical Microring Resonator

An optical microring resonator is an integrated optic traveling wave resonator constructed by bending an optical waveguide to form a closed loop, typically of a circular or racetrack shape. Light propagating in the microring waveguide interferes with itself after every trip around the ring. When the roundtrip length is exactly equal to an integer multiple of the guided wavelength, constructive interference of light occurs which gives rise to sharp resonances and large intensity buildup inside the microring. The high wavelength selectivity, strong dispersion, large field enhancement, and high quality factor are important characteristics which make microring resonators extremely versatile and useful for a wide range of applications in optical communication, signal processing, sensing, nonlinear optics and, more recently, quantum optics.

Microring and microdisk resonators were first proposed by Marcatili in 1969 for realizing channel dropping filters based on planar optical waveguides (Marcatili 1969b). Similar traveling wave filters based on microwave striplines had been proposed and studied earlier by Coale (1956). However, it was not until the late 1990s that advances in the microfabrication technology for integrated photonic devices enabled optical microring resonators to be realized with high quality factors. Since then, microring and microdisk resonators have been demonstrated for a wide range of applications in various material systems such as silicon-on-insulator (SOI), III–V semiconductors, glass, and polymers.

Broadly defined, an optical resonator is a structure which confines light in all spatial directions. In a microring resonator, this is achieved in two ways: transversely by the refractive index contrast of the dielectric waveguide used to form the microring and longitudinally by the periodic boundary condition imposed by the ring or racetrack structure. The propagation characteristics of the dielectric waveguide, and especially those of the curved waveguide, thus have a major impact on the characteristics of the microring resonator. In addition, the manner by which light is coupled into and out of the resonator is also of practical importance. Typically this is achieved via evanescent field coupling between the microring waveguide and one or two external straight waveguides, called access or bus waveguides, by which light is coupled into or out of the resonator. Figure 1.1 illustrates a microring resonator coupled to two bus waveguides and its microdisk variant coupled to a single waveguide.

Figure 1.1 Schematic of (a) a microring resonator coupled to two bus (or access) waveguides and (b) a microdisk resonator coupled to one bus waveguide.

This chapter provides a brief...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Table of Contents
• Preface
• 1 Elements of an Optical Microring Resonator
• 2 Analytical Models of a Microring Resonator
• 3 Coupled Microring Optical Filters
• 4 Nonlinear Optics Applications of Microring Resonators
• 5 Active Photonic Applications of Microring Resonators
• Index