Mode competition and cavity tuning characteristics of a new integrated orthogonal polarized He-Ne laser with Y-shaped cavity

Abstract

Aiming at the new integrated orthogonal polarized He-Ne laser with Y-Shaped Cavity, an experimental system for testing cavity tuning characteristic (including the light intensity tuning and frequency difference tuning) is built. By tuning the voltage of the piezoelectric ceramics on the two sub-cavities of S and P, the cavity length of the two sub-cavities is changed to obtain different split frequency differences. In the case of different split frequency differences, the voltage of the piezoelectric ceramic PZT1 on the public cavity mirror is tuned to obtain the light intensity tuning curve of the laser and the corresponding beat frequency variation curve. By tuning the public cavity or S sub-cavity, the double S longitudinal modes are stabilized at both edges of the gain curve, and then the P sub-cavity is continuously tuned to obtain a frequency difference tuning curve. The mechanism of mode competition in the laser is analyzed by using the Lamb semi-classical gas laser theory within the third-order perturbation approximation. The analysis shows that the split frequency difference is the main factor affecting the mode competition. The split frequency difference affects the linear gain and self-saturation effect, mutual saturation effect and the loss of each longitudinal mode. These four factors, which obey the self-consistent equation of light intensity, combine to influence the intensity and competition result of mode competition, thus affecting the change of light intensity. On the basis of the analysis, the longitudinal mode distribution and competition process in each working stage of the laser are theoretically analyzed. The theoretical analysis and interpretation of the intensity tuning curve, the corresponding beat frequency variation and the frequency difference tuning curve obtained by the experiment are carried out. The influencing factors and tuning laws of the light intensity tuning curve are summarized. In the end, the experiment verifies that when the split frequency difference is in the range of 129—1302 MHz, the laser is basically in the working state which the single longitudinal mode pair (including a S longitudinal mode and the neighboring P longitudinal mode) is oscillating.