Optomechanical forces and electrostriction in laser optical materials

With optical tweezer methods now firmly established and the nature of optical forces on individual particles well understood, one of the separate but related issues that has only recently come to the fore concerns the effects of intense optical radiation on inter-particle forces. It has already been established that such forces, which are not dependent on optical field gradients, can effect a weak binding between particles leading in some cases to optical clustering and in others to pattern formation. In this presentation it is shown by quantum electrodynamical analysis that a variety of other optomechanical effects can be produced in materials or systems subjected to the throughput of intense, non-resonant laser radiation. In particular, an optical electrostriction phenomenon is identified and shown to be widely operative in laser optical materials. Although a classical electrodynamical interpretation (in terms of interactions between induced dipoles) comfortably predicts the sign of the resulting mechanical force, it is shown that such a picture has significant limitations in addressing this fundamentally photonic phenomenon. The key parameters that determine the size and character of optical electrostriction are delineated and its significance is quantitatively assessed. The experimental challenges involved in characterizing such phenomena are also given a detailed appraisal.