Discharge Current Noise in He-Ne Laser and Its Suppression

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Abstract
Amplitude noise in He-Ne laser caused by discharge fluctuation has been studied experimentally. By using tubes with various capillary diameter, capillary length. and pressure, it was observed that a discharge current noise accompanied by a moving striation of several hundreds kHz is easily generated in tubes which have long capillaries. The effect of the moving striation on the amplitude noise in laser light was analyzed, and it was found that the laser noise is mainly contributed by the discharge current noise rather than the moving striation itself. By taking account of the condition for generation of the noise, a low noise He-Ne laser tube was constructed. The laser noise caused by the discharge current noise and the moving striation was reduced by more than 40 dB as compared with a ordinary laser.