This invention relates to a device for rapid focus control of one or more lasers. The controlled beam (5), is refracted by the dynamic refraction device (1) whose refractive index is set by its response to the control beam (3). The invention can be used for rapid focus and re-focus of a laser on a target as might be useful in such industries as flat panel television manufacturing, fuel injector nozzle manufacture, laser material processing/machining, laser scanning and indirect drive inertial confinement fusion.