Bianisotropics'97 For The Layperson

Why do peas get cooked in a microwave oven, but the cup containing them does not? Why does transparent window glass look greenish sideways? How can a laser scanner at the supermarket checkout counter distinguish between black and white bars? The answers to all of these questions lie in the electromagnetic response properties of materials.

Light, microwaves, infrared waves, etc., are different forms of electromagnetic radiation. When a piece of bulk material encounters electromagnetic radiation, its molecules momentarily absorb energy from the radiation. Some of the absorbed energy is quickly re-emitted as electromagnetic radiation, but a part is converted into heat, sound, motion, and so on.

The response of a piece of bulk material thus depends on its molecules. The molecules of the simplest materials can be thought of either as randomly oriented tiny rods or as tiny little balls, separated from one another so much that they hardly interact. The molecules of a complex material have a more complex shape. They may also be close together to form crystals.

The delegates at Bianisotropics '97 are interested in the electromagnetic response properties of a huge class of complex materials called bianisotropic materials. They are also interested in the response properties of artificial complex materials which are composites of several different bianisotropic materials. A wide variety of novel response properties become achievable with the use of composites.

Many bianisotropic materials have a property called chirality. Imagine Alice is standing in front of a mirror, holding a piece of a chiral material in her hands. The Alice-image in the mirror holds a piece of chiral material-image in her hands. Just as the right and the left hands of Alice and the Alice-image are reversed, so too can certain properties of the material and the material-image. Sugar is chiral, so are many drugs and pesticides. All new drugs are nowadays required by the US Food and Drug Administration to be chirally pure for maximum effectiveness and to avoid catastrophic side-effects.

A wide class of bianisotropic materials has a property called nonreciprocity. Suppose light from a pinhole falls on a nonreciprocal material and you observe the light transmitted through the material. Suppose next that your position and the position of the pinhole are interchanged. If you find that the transmitted light has also changed, the material is nonreciprocal. Non- reciprocal materials have direction-dependent response properties, but not all materials with direction-dependent response properties are nonreciprocal.

Thus, bianisotropic materials have many different response properties which are only now being studied owing to their complexity. Many different types of engineering applications have become possible in electrical engineering, optics and microwaves. A recent development are sculptured thin films with nanoengineered response properties. New composite materials with nonlinear optical applications, such as in displays, are emerging.

The complexity of bianisotropic materials necessitates that research on them be interdisciplinary. Hence, the delegates at Bianisotropics '97 are drawn from mathematics, engineering and science departments from various universities as well as from government research laboratories and from industry.

(last updated 31-05-97)