Analysis, Synthesis and Application of Lattice Two Port FIR type Birefringent Optical Circuits with Liquid Crystals

Abstract

Liquid crystals are found in a variety of equipment around us. Its most common applications are demonstrative displays in calculators, TVs or computers. However, also have other less popular applications such as temperature sensors, elements of distributed-feedback on lasers, dielectric materials with tunable permittivity, as fill component in photonic crystal fibers with tunable zero dispersion point, polarization controllers, even in optical signals filtering. In this article we study the application of this type of components to the filtering of optical signals. We present and analyzing a FIR type optical circuit with lattice structure that uses liquid crystals for filtering optical signals and the form of synthesize it, based on the techniques of discrete-time signal processing, also a novel application of it is done, illustrating it with and example. In this article first we do an introduction to electromagnetic radiation and an explanation of the techniques of optical transfer matrices. A brief explanation of light polarization is given. Subsequently the most commonly used liquid crystals types that currently exist are presented. We discuss the light behavior in a circuit with two inputs and two outputs while light go through of nematic liquid crystals cells with homogeneous alignment, as well as the necessary equations for the synthesis of optical filters with arbitrary transfer functions. Finally, we present a novel application example, in optic communications area where an equalization of the spontaneous emission of an Erbium doped fiber optical amplifier, is done.