Frequency Stabilisation of Transverse Zeeman He-Ne Laser by Means of Model Predictive Control

A model predictive control (MPC) technique is proposed for the frequency stabilization of transverse Zeeman He-Ne laser. The beat frequency locking method is applied as the criterion of frequency stabilization. When heated by the voltage output of the feedback electronic circuit, the copper wire twisted around the laser tube is applied to maintain the length of the laser cavity and stabilize the frequency of the laser. Four steps for MPC design, i.e., model setup, output prediction, selection of reference path, and calculation of control quality, have been introduced. By this means, a single-chip microprocessor (80C196) generates a pulse width modulation wave that is transferred into a heating signal. The calibration result shows that the frequency stability of our proposed transverse Zeeman laser reaches 5.5× 10-11 by means of the MPC method.