counterpropagating beams

counterpropagating beams

[‚kau̇n·tər‚präp·ə‚gād·iŋ ′bēmz]
(optics)
Two light beams that are propagating through a medium in precisely opposite directions.
References in periodicals archive ?
The first of these comes about when the counterpropagating beams that form the standing wave are in a plane parallel to the substrate, but are not exactly collinear (Fig.
This will happen, for example, if the mirror that reflects the counterpropagating beam is not perfectly perpendicular to the substate, or if it is not perfectly flat.