ABSTRACT
This chapter focuses on light propagation in waveguides: special material structures that confine and direct the propagation of light with near perfect efficiency. Waveguides can be thought of as wires for light; they allow to send optical signals over long distances in fiber optics and allow the construction of larger photonic circuits and systems on integrated chips. In a photonic Integrated circuit (PIC), waveguides guide light between different components of the PIC. Once the ability to guide light on-chip is established, the next capability for photonic processing is the ability to have signals interact with one another. Interwaveguide couplers transfer optical fields coherently, which enables interferometric circuits. For a photodetector, bandwidth is a measure of how fast it responds to variations in incident optical power. Photonic devices can be separated into active and passive categories based on the various mechanisms of how materials interact with light.
