Light confining microresonators based on evanescent wave propagation and whispering gallery (WG) modes have received much attention in the past decades, due to their conceptual similarity with their standing wave counterparts, improvements in fabrication technology, and their versatility in realizing various functions in telecommunications, sensing, measurement, and instrumentation. In this chapter...
This chapter discusses an ab initio frequency domain model of circular microresonators, built on the physical notions that commonly enter the description of the resonator functioning in terms of interaction between fields in the circular cavity with the modes supported by the straight bus waveguides. Quantitative evaluation of this abstract model requires propagation constants associated with the...
Densely integrated photonic devices require high-index contrast waveguides supporting small bending radii with negligible loss. However, when optical waveguides are tightly curved, polarization rotation (PR) effects can arise. In this chapter, PR in bent waveguides is theoretically and numerically investigated and its dependence on the main waveguide parameters is derived. It is shown that the efficiency...
The shape of the filter response can be controlled by a combination of ring resonators, such as series coupling, parallel coupling, and cascade topology. In particular series coupling is effective to realize box-like spectrum responses, which are required for wavelength filtering in WDM systems for photonic networks. In this chapter, the transfer function of series-coupled ring resonators is derived...
This chapter reviews the development of high-order photonic filters based on coupled microring resonators for optical spectral engineering applications. Advanced microring filter architectures capable of realizing general infinite impulse response optical transfer functions with finite transmission zeros are presented. Techniques for the analysis and exact synthesis of these devices to achieve a prescribed...
An overview of microring resonator architectures, fabricated using both fiber and integrated technologies, whose function is to reflect nearly the entire incident signal within a specified band of frequencies, is presented. The signal components that lie outside this band, called the stopband, are either transmitted through the device to exit through another port, or dissipated. The stopband reflectivity...
In the first part of this chapter, a theoretical overview is presented on the different approaches to the use of dynamic tuning for coherent optical pulse stopping and storage in coupled resonator systems, which are amenable to fabrication in on-chip devices such as photonic crystals. The use of such dynamic tuning overcomes the delay-bandwidth constraint of slow-light structures. The second part...
In this chapter, directly coupled ring resonator filters are considered. The state of the art achieved in glass and silicon technology is analyzed in detail, the discussion leading to the ring-size issue and to technological aspects. Advantages and disadvantages are pointed out. Key aspects related to structural disorder are then considered and developed. The impact of fabrication tolerances on the...
In this chapter, methods for actively controlling the resonant wavelength of photonic microresonators in order to manipulate the propagation of light are introduced. The presented tuning mechanisms are based on the free-carrier dispersion effect and the thermo-optic effect. The free carriers and the thermal power required for the tuning can be generated either electrically or optically, enabling different...
Applications of single and coupled microresonators in various photonic switching schemes are considered. It is shown that both single and coupled resonators enhance the performance of the switches based on nonlinear optical or electro-optical effect, but the enhancement occurs at the expense of reduced bandwidth. The critical bit rates at which the enhancement is still possible are derived for single...
Optical microcavities have successfully detected a wide range of analytes and analyte properties in a variety of conditions. There are several important parameters of an optical cavity which govern its operation and determine its applicability in a given sensing scenario. An overview of these conditions and a discussion of the primary microcavity geometries used in biological and chemical detection...
The manufacture of tapers from optical fibers provides the possibility to get long, uniform, and robust micrometer- or nanometer-size wires. Optical microfibers are fabricated by adiabatically stretching conventional optical fibers and thus preserve the original optical fiber dimensions at their input/output pigtails, allowing ready splicing to standard fibers. Since microfibers have a size comparable...
We present the characteristics and applications of photonic crystal ring resonators (PCRR). Photonic crystal confinement can achieve very high cavity quality factor ring resonators. Diffraction-limited ultra-compact PCRRs are feasible due to the absence of size-dependent losses. The flexible modal properties can offer flexible design and integration schemes for either forward or backward propagating...
Over the past few years, much work has been devoted to the study of microcavities in photonic crystals (PCs). High-quality factor (Q) PC microcavities exhibit attractive properties since they can confine light in wavelength-scale dimensions, making them potentially useful not only for photonic integration but also in quantum optics. Most of the high-Q PC microcavities are realized in slabs (PCSs),...
Circular resonators are promising candidates for a wide range of applications, ranging from optical communication systems through basic research involving highly confined fields and strong photon–atom interactions to biochemical and rotation sensing. The main characteristics of circular resonators are the Q factor, the free spectral range (FSR), and the modal volume, where the last two are primarily...
This chapter reviews the fundamental optical properties and applications of photonic moleculesPhotonic molecules (PMs) – photonic structures formed by electromagnetic coupling of two or more optical microcavities (photonic atoms). Controllable interaction between light and matter in photonic atoms can be further modified and enhanced by the manipulation of their mutual coupling. Mechanical and optical...
Dielectric microspheres, with sizes on the order of several wavelengths, support high-quality whispering gallery (WG) modes and provide nonresonant focusing of light into tiny spots termed nanoscale photonic jets. In this chapter, we review properties of more complicated multiple-cavity systems that are formed by microspheres assembled in chip-scale structures. The resonant optical properties of such...
Micro-electro-mechanical systems (MEMS) is a key enabling technology to realize scalable and reconfigurable optical components. Since Peterson (1982) demonstrated the first MEMS scanning mirror, many free-space optical MEMS including digital micromirror devices (DMD), micromirror switches, and optical scanners have been accomplished. In guided-wave optics, MEMS have demonstrated the ability for controlling...
Photonic microresonators exhibit a great potential for various advanced functions for communication and signal processing applications. In this chapter, we briefly review recent advances in achieving space-, power-, and spectrally efficient chip-scale optical devices and subsystems using microresonators. With an emphasis on signal integrity and system performance, we describe microresonator-based...