A clamp holds together at least two superposed, flexible polymeric films while they are optically sealed or cut by at least a laser beam. The clamp is comprised of two jaws wherein at least one of the jaws can be moved to allow a closing and an opening of the clamp. One of the jaws is a contact jaw to bring the films into contact. The other jaw is an optical jaw having an optical window to let at least one laser beam pass through it and wherein the window is wide enough to allow to optically seal or cut the whole width of the films if required. A support mechanism interconnects the jaws and allows a controlled opening and closing of the clamp.