1. Introduction

Nonlinear optics has become a vibrant field of research since the optical second-harmonic generation (SHG) was first observed in the early 1960s [1]. A better understanding was achieved on the origin of nonlinear optical (NLO) phenomena and the structure-property relationships of NLO chromophores in the late 1970s when various tools were developed to accurately measure and calculate hyperpolarizabilities [2]. Organic NLO materials, which can be modulated and processed readily, are of much contemporary interest because of their potential applications in modulation of optical signals, medicine, spectroscopic and

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

electrochemical sensing, microfabrication and imaging, laser technology, data storage, and telecommunication [3]. Recent studies were focused on the synthesis of the organic molecules with special geometry and certain electronic molecular parameters to possess nonlinear optical (NLO) properties [3–24]. The demand of substances with NLO properties for numerous industrial applications has resulted in many articles reporting the manufacture of various novel molecules, with highly active chromophores and superior optical activity. However, it remains the issue of processing these materials, as long as the specific optical properties have to be preserved, together with new requirements added, such as chemical stability, mechanical strength, etc. The main materials used as host for the embedding of chromophores and fabrication methods are discussed. The influence of parameters (such as chemical structure of the host material, synthesis conditions, and external stimuli) on the optical and electrical properties of the final product is also evidenced.
