Nonlinear Optical Materials

Abstract

Nonlinear optical materials are the building blocks of an emerging technology of photonics that uses light to acquire, process, transmit, and store information. These materials perform functions such as modulation, switching, rectification, frequency generation, limiting, and amplification, all of which are typically performed by semiconductors in electronic technology. Nonlinear optical materials and phenomena can be classified as second or third‐order, reflecting the order of electric field interactions involved. Second‐order phenomena are observed only for noncentrosymmetric materials. Such phenomena include electrooptic modulation, spatial light modulation, and second harmonic generation. Electro‐optic modulation may play a critical role in electric‐to‐optical signal transduction and in switching in local area networks. Third‐order phenomena include the dynamic Kerr effect, degenerate four‐wave mixing, third harmonic generation, saturable absorption, reverse saturable absorption, etc. The dynamic Kerr effect can be exploited for all‐optical switching and also for beam focusing, such as in mode‐locking of the Ti:sapphire laser. Reverse saturable absorption can be exploited for sensor protection. Both organic and inorganic materials have been observed to exhibit large optical nonlinearities. Material morphologies ranging from crystalline to polymeric have been considered for nonlinear optical applications; examples of materials are given.

Polymeric Electro-optic Modulators: From Chromophore Design to Integration with Semiconductor Very Large Scale Integration Electronics and Silica Fiber Optics

“…Electro-optic activity is one example of second-order nonlinear optical activity (the activity associated with the quadratic term in the power series expansion of polarization in terms of an applied electric field). [1][2][3] Another example of second-order optical nonlinearity is second harmonic generation or frequency doubling. Third-order optical nonlinearity, leading to optical rectification, phase conjugation, third harmonic generation, and the Kerr effect, is also of considerable interest but will not be discussed here.…”

“…Third-order optical nonlinearity, leading to optical rectification, phase conjugation, third harmonic generation, and the Kerr effect, is also of considerable interest but will not be discussed here. [1][2][3] Typically, and as expected for a power series expansion, third-order coefficients are sufficiently smaller than second-order effects as to make their application impossible except for situations involving very long interaction lengths of material.…”

“…For more detailed information, the reader is referred to the reviews cited in this article. [1][2][3]8,9 This article rather aims to acquaint the reader with critical concepts which have defined the progress of organic electro-optic materials evolving from laboratory curiosities to potential commercial devices and which guide the reader to anticipate future research directions and applications.…”

“…Electro-optic activity is one example of second-order nonlinear optical activity (the activity associated with the quadratic term in the power series expansion of polarization in terms of an applied electric field). − Another example of second-order optical nonlinearity is second harmonic generation or frequency doubling. Third-order optical nonlinearity, leading to optical rectification, phase conjugation, third harmonic generation, and the Kerr effect, is also of considerable interest but will not be discussed here. − Typically, and as expected for a power series expansion, third-order coefficients are sufficiently smaller than second-order effects as to make their application impossible except for situations involving very long interaction lengths of material.…”

“…It is to be emphasized that this article is not intended to be a comprehensive review of the organic electro-optic materials literature, which has now grown to many thousands of articles. For more detailed information, the reader is referred to the reviews cited in this article. − ,, This article rather aims to acquaint the reader with critical concepts which have defined the progress of organic electro-optic materials evolving from laboratory curiosities to potential commercial devices and which guide the reader to anticipate future research directions and applications.…”