Compensation of the Thermal Effect in a Mounted Microbubble Resonator

To mitigate the temperature dependence of the resonance frequency in microcavities, athermal photonic devices have been developed by incorporating materials with an opposite thermo-optical coefficient (TOC). Here, we conduct an experimental demonstration of the athermal effect in a microbubble resonator, employing an aluminum (Al) holder for its mounting. By converting the thermal expansion of the holder into controlled geometry adjustments in the microbubble resonator, we achieve athermal optical modes at a specific temperature. The athermal compensation is accomplished by counterbalancing the pulling force resulting from the thermal expansion of the Al holder against the thermal characteristics of the material, specifically SiO2. Especially, the optical modes located around the equator are particularly susceptible to the influence of the pulling force exerted by the Al holder. This temperature-insensitive feature of the resonance establishes a new avenue towards athermal microresonator through this special structure.