Laser Stabilization Through Optical Turbulence

Laser jitter presents a significant issue in the fields of laser communication and sensing. There are two main categories of positional noise in regards to the instantaneous centroid of a laser propagating over long distances: jitter resulting from optical turbulence and jitter resulting from mechanical vibrations. Optical turbulence was generated using Clemson University’s Variable Turbulence Generator (VTG). The VTG is capable of creating a desired level of optical turbulence that is comparable to atmospheric conditions with fried parameters greater than 0.3 cm. A gaussian laser was transmitted through the VTG and a system of Fast Steering Mirrors and Position Sensing Detectors were used to attenuate random fluctuations in the beam’s centroid. PID and LMS control systems were found to have a significant impact on the standard deviations of the radial distance from the beam’s long term centroid. Frequency analysis of the positional error and system identification of the set-up is also discussed