Simple method to determine the gain and saturation irradiance of a laser

A new method is proposed to determine the gain parameter and the saturation irradiance of a partially homogeneously broadened gaseous laser medium in a unidirectional ring cavity. The proposed method is applied to a He-Xe 3.5-microm line, and the gain parameter and the saturation irradiance are then determined to be 0.0665 cm(-1) and 4.69 microW/mm(2), respectively. The method developed here is expected to be more accurate than conventional methods such as that using more than one laser and that with frequency detuning because less ambiguity is involved in the experiments and the theoretical treatment.