Disclosed is a method of reducing speckles appearing in a laser beam. The shot holes are equidistantly spaced from the central axis of the device and are circumferentially angularly inclined. The inventive oscillator provides a Fabry-Perot cavity between the feed and the plate. Magnetic reassembly components can be provided for facilitating release of tube components in fabrication. By bending the feeding passage, the recording sheet is prevented from waving, so deviation in feeding speed is decreased even when the load to the recording sheet is changed. The conducting layer and the cooler are electrically connected together.