Stabilizing single mode lasers using intracavity phase modulation

The description of a method of generating optical-frequency-sensitive signals in single mode lasers is presented in this paper. The technique involves the coupling of energy from the mode having gain to the other, non-oscillating modes. The theory which applies to this work was obtained starting from the coupled mode equations of Harris and McDuff. The experiments were performed using a multimode HeNe laser by applying phase modulation at a frequency which coupled longitudinal cavity modes greater than one doppler linewidth apart. The results were found to compare favorably with the theory.