High power He–Ne laser with flat discharge tube

Abstract

A high-power He–Ne laser with a flat discharge tube has been realized. Its output power can be enhanced by increasing the transverse size of the discharge tube. This high-power flat He–Ne laser tube of 1.4 m discharge length can achieve above 180 mW of output power at a wavelength of 0.6328 µm. Its optimum discharge parameters and the gain characteristics are investigated experimentally. The experiments indicate that the optimum current increases with decreasing total gas pressure. But the increase in the optimum current is almost independent of the gas mixture ratio. The increase in the gain coefficient at the axis of the discharge tube with discharge current is not obvious. The boost in laser output power is mainly caused by the expansion of the lasing gain region. To achieve the higher output power, four of the laser tubes mentioned above are placed into one laser box. The laser beams are coupled into a quartz optic fibre and the output power from the end of the optic fibre can reach above 480 mW. This high-power He–Ne laser has been used in a clinical application, photodynamic therapy (PDT) of cancer, and its effective rate is above 90% in 183 clinical cases. The structure, characteristics and applications of this high-power flat He–Ne laser are introduced and discussed in this paper.

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

“…Moreover, a high-power He-Ne laser with a flat discharge tube has been realized and used for clinical photodynamic therapy ͑PDT͒ of cancer. [3][4][5][6] The output patterns of the reported high-power flat He-Ne laser include the rich higher-order transverse mode, so that it has an evener luminous intensity distribution and suits in uniform irradiation, such as in the use for PDT and laser physical therapy, etc. However, its multi-transverse mode laser output will fail in the other application, demanding the single-transverse mode output, due to its worse spatial coherence.…”

Two Versions of He-Ne Laser 3.39 μm with Radio Frequency Excitation

“…The volume and μ power can be increased by making the cross section elliptical or rectangular. A He-Ne laser tube with a cross section of 20×4.5 mm and a discharge length of 1.7 m can give an output power above 200 mW [2,4].…”