Aromatic polyureas for second-order nonlinear optics

Abstract

Nonlinear optical materials possessing large second-order optical nonlinearities at short wavelengths are highly desirable for laser frequency conversion to fabricate high-power laser sources.1-4 Organic polymers are important materials because they offer the advantages of thin film processability, ease of structural modification and fabrication. Therefore organic polymers having nonlinear optical (NLO) chromophores either in the main chain or as pendant groups have attracted a great deal of attention. An efficiency/transparency trade-off is the most important factor for practical applications in the field of nonlinear optics. Organic NLO polymers having persistent large second-order optical nonlinearity coupled with desired optical transparency at the fundamental as well as at the second-harmonic wavelengths can be utilized in many applications. Bearing in mind the efficiency/transparency trade-off, we have designed and synthesized a wide variety of polyureas exhibiting large second-order optical nonlinearity and good optical transparency.5,6 This paper describes the second-order optical nonlinearities of novel aromatic polyureas having pendant NLO chromophores. The relationships between molecular structures and optical as well as nonlinear optical properties of polyureas are discussed.