Relationship between coherence length and output power of a multi-longitudinal-mode Ar+ laser

The relationship between the temporal coherence (i.e., the coherence length) and the output power of a multi-longitudinal-mode Ar⁺ laser operated near the threshold current is studied. The experimental measurements show that the coherence length is a hyperbola as a function of the output power. A simple model of the multimode equal-amplitude power spectrum is employed in the theoretical analysis. Good agreement between theory and experiment is obtained. It is shown that for a multi-longitudinal-mode Ar⁺ laser, the product of coherence length and the output power is almost a constant.Mailing address: Department of Physics, Suzhou University, Suzhou, Jiangsu 215006, People's Republic of China