In order to enhance the efficiency of a blue‐green laser through spectrum conversion of the pumping light, a converter dye BBQ was mixed in the laser dye solutions. The laser was pumped with a plasma radiation source. The increase of laser output over the maximum obtainable from the pure dye operation was better than 80% for the dye mixture of LD490+BBQ or coumarin 503+BBQ. The estimated enhancement calculated by a simple spectrum conversion model agrees well with the experimental results. The enhancement is mainly effected by irradiance in the UV from the pumping source, the fairly good match of the fluorescence band of converter dye with the absorption band of the laser dye, and the lack of the overlap of the fluorescence band of the laser dyes with the triplet–triplet absorption band of the converter dye used.