Excess noise of the misaligned off-axis confocal unstable resonators

摘要

The misalignment of the output mirror will cause serious decline of the output power of the positive branch off-axial confocal unstable resonators. In this paper, we try to explain this phenomenon by investigating the excess noise factor K for the misaligned resonator. Numerical result shows that the jump of the value of K due to the well-known mode crossing also occurs periodically against the degree of the misalignment (epsilon), the locations and the period of the jump are related the equivalent Fresnel number N-eq. In addition, it shows the value of K, the loss, and the far-field divergence angle are small even for large downward misalignment, it implies that it may be able to gain laser output under the condition.