HELICON WAVES - PROPAGATION-INVARIANT WAVES IN A ROTATING COORDINATE SYSTEM

The concept of propagation-invariance is extended to discrete-distance propagation-invariant waves, i.e., waves whose intensity distribution s are periodic with propagation distance. A new type of wave is presen ted which has an intensity pattern which rotates at a constant rate ab out the optical axis as it propagates, but is otherwise unchanged. The se waves consist of superpositions of different higher-order Bessel wa ves. The new waves are referred to as a 'helicons' as their lines of c onstant intensity trace out helices about the optical axis. Methods to produce 'helicon' waves are described based upon established techniqu es for producing Bessel waves approximations with computer-generated h olograms. Several such helicon elements are fabricated and tested, and the experimental results are presented. Possible practical applicatio ns of such waves, which include alignment and distance/speed measureme nts are discussed briefly.