Zhihai Liu, Lu Liu, Zongda Zhu, Yu Zhang, Yong Wei, Xiaonan Zhang, Enming Zhao, Yaxun Zhang, Jun Yang, and Libo Yuan
We propose and demonstrate a whispering gallery mode (WGM) resonance-based temperature sensor, where the microresonator is made of a DCM (2-[2-[4-(dimethylamino)phenyl] ethenyl]-6-methyl-4H-pyran-4-ylidene)-doped oil droplet (a liquid material) immersed in the water solution. The oil droplet is trapped, controlled, and located by a dual-fiber optical tweezers, which prevents the deformation of the liquid droplet. We excite the fluorescence and lasing in the oil droplet and measure the shifts of the resonance wavelength at different temperatures. The results show that the resonance wavelength redshifts when the temperature increases. The testing sensitivity is 0.377 nm/°C in the temperature range 25°C–45°C. The results of the photobleaching testing of the dye indicate that measured errors can be reduced by reducing the measured time. As far as we know, this is the first time a WGM temperature sensor with a liquid state microcavity has been proposed. Compared with the solid microresonator, the utilization of the liquid microresonator improves the thermal sensitivity and provides the possibility of sensing in liquid samples or integrating into the chemical analyzers and microfluidic systems.