Optical levitation of a droplet under a linear increase in gravitational acceleration

The optical levitation of a liquid droplet in the gas phase was investigated under a time-dependent change in the gravitational acceleration in an airplane following a specific flight profile. Through multiple trials under a linear increase in effective gravitational acceleration, we performed an experiment on the optical trapping of a droplet from 0.3g0 to 0.9g0, where g0 = 9.8 m/s2. During this change in the effective gravitational acceleration, the trapping position of a droplet with a radius of 14 μm was found to be lowered by ca. 100 μm. The essential feature of the change in the trapping position was reproduced by a theoretical calculation under the framework of ray optics. To the best of our knowledge, this study is the first to report on optical levitation under a time-dependent gravitational change.