Interferential coupling effect on the whispering-gallery mode lasing in a double-layered microcylinder

Enhanced mode selection through a strong interferential coupling effect was observed in a double-layered cylindrical microcavity laser. The coupling was induced by partial reflection and recombination with refracted light on the internal circular boundary of the fused silica capillary tube, filled with a dye-doped liquid having lower reflective index than that of fused silica. The observed interference period agreed well with the prediction by a ray-optic model.