Study on single-transverse mode output of high-power flat He-Ne laser

The multimode output power of He-Ne lasers with a flat discharge tube can be enhanced by increasing the transverse size of the discharge tube. By using an N-type fold optical resonator, the high-power flat He-Ne laser tube can give the output in the lower-order mode. Inserting a limiting-mode circular-hole diaphragm into the N-type fold optical resonator, the lower-order modes are suppressed gradually with the reduction in its aperture. The high-power flat He-Ne laser tube of 1.4 m discharge length can achieve above 80 mW of the single-transverse mode output power using an N-type fold optical resonator with a limiting-mode circular-hole diaphragm of 4 mm aperture. Its output characteristics and laser mode patterns are investigated experimentally. The experimental method is introduced and its results are discussed briefly in this paper.