Silicon Photonics: Fundamentals and Devices

12.1 Introduction

In the previous chapters we discussed the basic principle of waveguiding and the operation principles of a few simple passive waveguide devices like Y-switches, directional couplers, and Mach–Zehnder interferometers (MZIs). These simple devices find applications in optical communications and networking systems.

With the advent of DWDM communications systems with the number of wavelengths exceeding 100, it becomes necessary to have, in addition to active devices, passive devices like multiplexers (muxes), demultiplexers (demuxes), and some of the sophisticated versions used in switching and routing. Demuliplexers require a wavelength-selective mechanism like filtering. In the literature there are extensive reports on different principles for the realization of demux operation as well as on their practical implementation. Among them, fiber-optic and micro-optic technologies were in wider use. A comparison of these technologies with the integrated optic approach has been made by Pennings et al. 1. Due to increased complexity of the current networks, the present trend shows a bias toward integrated optic (IO) components.

The IO components belong to two classes: grating based and interference based. Both are imaging devices in the sense that an image of the field in one of the input guides is formed onto an array of output guides. The principle of operation of Bragg gratings has been studied in detail in Chapter 11. In this chapter, we focus our attention on PHASAR ...