Brief Review on Integrated Planar Waveguide-Based Optical Sensor

Abstract

Planar optical waveguides are the input devices to build an integrated optical sensor. This chapter provides review made in the recent advancement of integrated optical sensor that involves guided light with substantial developments made at a very rapid pace. The basic concept and equations of electromagnetic (EM) wave theory requisite for lightwave propagation in optical waveguides are presented. The light confinement and formation of modes in the waveguide are qualitatively explained, considering a slab waveguide. Maxwell’s equations, boundary conditions, are described as they form the basis for the following chapters. Theoretical consideration and supportive calculation to understand the basic properties of optical waveguide is presented for a step-index waveguide. Further, the derivation of dispersion equations is explained in detail in order to understand the dispersion characteristics of optical waveguide. Rigorous three-dimensional analysis usually requires numerical calculations, and therefore, this chapter presents several methods such as finite element method, finite difference time domain, and beam propagation method necessary for mode analysis of optical waveguide. The detection of glucose level in blood is a highly researched area in the quest for a sensor that can give accurate measurements, in short time, with minimum invasiveness. Although several optical techniques are being explored for glucose detection including infrared spectroscopy however, there are limitations to these techniques and involve complications. A short review is done on available medical and engineering concepts and attempt is made to discuss how far these can be applied to optical waveguide-based sensor with fine accuracy and high sensitivity.