HOME    »    PROGRAMS/ACTIVITIES    »    Annual Thematic Program
IMA Workshop 9
Nonlinear Optical Materials
March 4-8, 1996

Organizers: Jerry Moloney and John Sipe .

The study of nonlinear optics from a fundamental point of view is concerned with how materials react to the external stimulus of an incident light field and thereby modify a characteristic property of the latter. The basic interaction between light and matter is intrinsically quantum mechanical by nature involving induced dipoles reradiating their fields back into the incident optical wave. Loosely speaking, optical interactions with bulk materials can be classified into two types: resonant and nonresonant. Resonant interactions involve either a coherent and incoherent transfer of energy between the optical wave and a material oscillation whereas nonresonant interactions involve no energy exchange but instead modify the propagation constant of the electromagnetic wave. The latter are called induced refractive index changes. In any event, the strength of the nonlinear interaction and the effective interaction length play a crucial role in determining whether a material may prove useful or not for a particular application. The great technological success of optical fibers as soliton transmission systems, for example, hinges on very large interaction lengths available in modern single-mode low-loss fibers which compensates for the very weak nonlinear refractive interaction of the glass. Many nonlinear optical applications require very short interaction lengths (microns) for ultrafast integrated optical processing of information. In addition to the processing stage, reliable sources of stable ultrashort optical pulses are needed. Lasers, through nonlinear resonant interactions and some form of external modulation, provide such pulsed sources. Suitable materials for laser operation include semiconductors, solid state and Erbium doped fibers.

In many instances, the intrinsic nonlinear optical interactions coefficients are too small to be useful and one has to resort to novel schemes for enhancement of the effective interaction. Low dimensional structures grown by Molecular Beam Epithaxy (MBE), MOCVD and various precision materials growth techniques, impose geometric enhancements of the effective linear and nonlinear interaction coefficients. Examples abound in current nonlinear optica applications involving both laser sources (semiconductor Quantum-Well, quantum wire, dot structures and Erbium doped fiber lasers) and optical processing elements (thin-film organic planar waveguides, nonlinear Bragg grating structures, photonic bandgap materials). All of these low-dimensional materials benefit from a localization phenomenon of some sort (either quantum mechanical or optical) in order to greatly enhance the effective nonlinear interaction coefficient.

Despite significant advances in materials growth technology, the potential impact of nonlinear optics in modern technology is yet to be felt, primarily due to a lack of suitable materials with large enough interaction coefficients. Typically a large nonlinear optical interaction coefficient implies a slow response time, ruling out multi-Gigahertz processing operations. In fact most functioning nonlinear optics-based switches require some form of electrical assistance in order to offset such weak interactions.

This workshop will serve to highlight the current state of affairs with regard to materials for nonlinear optics applications. An ongoing theme of the period of concentration in nonlinear optics will be whether there exist scaling laws which would allow one to a priori design nonlinear optical materials which compromise between large interaction strengths and fast response times.
structure of deposited films, and mechanical, electrical and magnetic properties of films.

The workshop will bring together experts doing experimental work, materials and mathematical modeling.


Back to Mathematical Methods in Materials Science Page

Go