Cavity length and absorption dependent longitudinal beat in iodine photodissociation laser

As the cavity length of the iodine photodissociation laser (iodine PDL) is varied, the number of neighboring coherent modes increases and the time-dependent mode-competition effect gives rise to typical changes in the pulse shape. The ratio of the number of all coherent modes to that of all oscillating modes is found to be as high as 80 percent when the cavity length is 450 cm. The frequency width in which the neighboring modes are coherent is approximately 0.1 GHz for all cavity lengths used. The effect of a BDN absorber placed in the cavity is distinct in the shorter cavities.