Nanoheater-tuned whispering gallery mode lasing in liquid-filled hollow microcavities

An all-optical tunable whispering gallery mode (WGM) lasing from the liquid-filled hollow glass microsphere (LFHGM) is proposed and experimentally verified. The LFHGM-based microlaser is prepared by injecting ${{\rm NaNdF}_4}/{\rm dye}$NaNdF₄/dye co-doped liquid into the HGM, and WGM resonance is obtained under excitation of a 532 nm pulse laser. Since the high-efficiency absorption of the 793 nm continuous-wave laser by ${{\rm NaNdF}_4}$NaNdF₄ nanocrystals (NCs) can result in photothermal effect-induced effective refractive index change of the microcavity, a secondary 793 nm laser is irradiated into the LFHGM to excite the ${{\rm NaNdF}_4}$NaNdF₄ dispersed in the liquid core, thereby realizing a shift of resonant frequencies. The influence of the doping concentration of ${{\rm NaNdF}_4}$NaNdF₄ NCs on the tuning range and the sensitivity over the power intensity range of $0{-}1.{68}\;{{\rm W/mm}^2}$0-1.68W/mm² are investigated experimentally, obtaining maximum values of 4.95 and ${2}.{95}\;{\rm nm/}({\rm W}\;{{\rm mm}^{ - 2}})$2.95nm/(Wmm^-2). The ability to generate stable lasing in a LFHGM cavity highlights the practical application of the microscale lasers in future all-optical networks.