Effect of refractive index change on the interference modulation of Q values in a layered cylindrical microlaser

We observed the effect of refractive index change on the interference modul ation of Q-values in a liquid-silica capillary tube. The lasing peaks of wh ispering-gallery (WG) modes were modulated periodically due to the interfer ence effect. As the pump fluence increased, the WG peaks showed a blueshift due to the decrease of the refractive index of liquid and the constructive interference peak jumped to the neighboring red WG peak. The interference period measured from the spectral behavior agreed with the formula predicte d by the ray-optics model within the experimental error.