Modulation of Discharge Current in a He-Ne Laser

In order to study the characteristic of modulation noise and the mechanism of oscillation in a gas discharge laser， the current has been modulated in square wave. In the present experiment， the discharge current of a 6328A He-Ne laser is periodically under square wave modulation of 10 percent. The frequency dependence of discharge current and laser emission is also observed. The resonance phenomena appear near 30 kHz and the critical frequency appears near 100 kHz. The response time of laser emission is found to be 30 μsec. As modulation frequency is increased，pulse waveform of laser light does not form a square wave. It is found that the component of high frequency noise，or quantum noise of 300 MHz，is superposed on modulation waveform of laser ligh