Chapter 12 - Poling of Glasses and Optical Fibers

Abstract

This chapter reviews the areas related to photosensitivity and charge transport: poling of glass, fibers, and their applications. The process of electric field poling, which is a key element in breaking the symmetry of glass leading to a second-order nonlinearity, allows glass to morph into yet another magical form: possessing characteristics highly desirable in waveguides and the ability to modulate light by the application of an electric field. This field was driven by the desire to induce a large nonlinearity and to integrate this property in probably the best waveguide system available today—the optical fiber. Several glass systems are explored and their properties presented with a view of finding the right “sauce” and “recipe” for enhancing the modest, though usefully observable, effect. The physics of the problem was complex to unravel and has been an area of fervent activity. Regrettably, the large nonlinearity remains elusive: Either it can be large but short lived or small and longer lived, depending on the glass type. Transport in glass, therefore, comes under the microscope and different models have led to a better but not complete understanding of the process. However, research has led to several spin-offs, including fiber-optic modulators, tunable gratings, electric field sensors, Q-switches, polarimeters, and others.