Light turn-on transient of a whispering gallery mode resonance spectrum in different gas atmospheres.

We examine the resonance spectrum change after turning on the light to feed the fiber taper evanescently coupled to a silica whispering gallery mode (WGM) resonator surrounded by different gases at different pressures. The resonance shifted to a longer wavelength, indicating a temperature rise, before reaching a steady state. The increment was proportional to the power of the light and approximately reciprocally proportional to the thermal conductivity of the surrounding gas, whereas the rate of the shift was approximately proportional to the thermal conductivity.