Numerical analysis of lasing output in organic thin film laser with photo-induced periodic gain structure

Organic materials are becoming widely used in optical fields due to their many advantageous properties such as flexibility, ruggedness, and low cost. In particular, application of organic polymer to an optical amplifier and/or a laser oscillator has attracted much attention recently. In these circumstances, we have demonstrated a novel solid-state dye-laser by using organic thin film made of Rhodamine B (Rh-B)-doped UV-cured polymer as gain medium, in which distributed feedback operation has been achieved by inducing a periodic gain structure onto the gain medium. However, the characteristics of the lasing output of such a laser oscillator have still not been examined. In this paper we shall thus present a numerical analysis of lasing output of the solid-state dye laser with a photo-induced periodic-gain. Since in the photo-induced DFB operation an interference fringe of lightwave is used for pumping a periodic-gain stucture onto the gain medium, the output power strongly depends on the shape of the interference pattern. Using several parameters obtained in the experiments, dependences of output power on the visibility and average power of the pumping interference pattern are numerically calculated. In addition, the effects of gain saturation against the pump energy are also discussed from the viewpoint of practical applications.