Abstract

Nonlinear optical devices may change completely the character of optical signal processing and computing systems by making logic decisions and switching beam directions. This may better utilize the ability of optics to make high-speed massively parallel transformations by preprocessing the results and reducing the amount of data fed back to an electronic system. Such nonlinear devices can be classified as nonlinear waveguides and nonlinear etalons (interference filter and Fabry-Perot). Both use thin films. Both require an intensity-dependent phase change, δϕ= (2π/λ)δ(nL), of 0.1π to π, where δ (nL) is the change in optical path length. This makes the large nonlinearities of semiconductors highly attractive (δn of 10⁻⁴ to 1 cm²/kW for band-edge nonlinearities due to excitonic, band-filling, thermal, bound-exciton, etc. effects). Waveguide devices, which can use smaller nonlinearities because a high intensity is maintained over millimeter lengths, are especially applicable to optical communications and other serial processing situations. Micron-thick etalons are a natural for parallel processing of multiple beams and for imaging whole arrays of data at once. The success of thin-film nonlinear optical devices hinges not only on large nonlinear refraction but also on low background absorption and on uniformity sufficient for low-scatter guides and arrays of high-finesse etalons. Thin-film technology offers a variety of growth techniques and the opportunity for engineering desirable properties.

© 1985 Optical Society of America