Abstract: Cigarette tipping paper is perforated by a laser 31 emitting a beam which is directed onto the tipping paper via an acousto-optical beam deflector 33 and a beam splitter 34 producing two parallel perforation tracks 24 along the tipping paper. Each track may include a number of rows of perforations, the laser beam being deflected for that purpose by the acousto-optical device. The porosity of the tipping paper and/or the dilution of the completed cigarettes can be controlled in various ways, particularly by the use of an acousto-optical device; the latter may be used to vary the perforation pattern, the laser beam being directed onto a heat sink 52 when it is not required to perforate the tipping paper. Control of the perforation pattern, as well as allowing different patterns to be applied, is used to control the dilution factor of the finished cigarettes.

Abstract: The power supply includes an oscillator (20) which generates a radio-frequency signal amplified by an amplifier (21). The amplified signal is applied to a laser (22) to initiate and maintain a discharge in the laser gaseous active medium. Power control means (24) are provided operable after initiation of the discharge to adjust the power applied to the laser to the value required to operate the laser at maximum efficiency. Automatic gain control means (25) may be provided, responding to the output from a power meter (23).

Abstract: A transversely-excited waveguide laser made up from the two blocks of electrically-insulating material. One block (1) has three parallel slots (3, 4 and 5) formed in one face, while the other block (2) forms a cover which may be secured to the first block to close the slots. The two outermost slots (4 and 5) each contain a layer (7) of electrically-conductive material to which an electrical conductor (8) is attached to form an electrode, while the dimensions of the center slot (3) are such as to enable it to form a laser cavity which will support waveguide laser action.