Noise, Oscillations, And Fluctuation Sources - THORLABS HNL100R User Manual

Red HeNe Laser Systems

6.2.1. Noise, Oscillations, and Fluctuation Sources

There are many sources of noise, oscillations and fluctuations of the output of a HeNe laser. One of the most
common is from longitudinal modes drifting into and out of the gain curve. The frequency of these fluctuations
vary from less than a Hz to as high as several kHz, depending on the stability of the environment.
Other, more constant sources of fluctuations are from the following (with corresponding frequencies):

Line Noise from AC High-Voltage Power Supplies (50/60 Hz, 100/120 Hz, etc.)

Switching Noise from DC High-Voltage Power Supplies (40 kHz)

Plasma Oscillation (Tens of MHz)

Transverse Mode Beat Notes (Hundreds of MHz)

Axial Mode Beats (at FSR, Hundreds of MHz)
Rev C, March 29, 2017
Chapter 6: Troubleshooting
Page 15