Attraction of microbubble at a fiber end face by the solute Marangoni force and its application as a tunable interferometer based on optical control

In this Letter, we show the attraction of a microbubble at a fiber end face by the solute Marangoni force. The microbubble is formed by partial filling of an ethanol-water mixture in the microcavity that is spliced to the end face of a single-mode fiber. Due to different surface tension of ethanol and water, the uneven temperature gradient induced by a laser causes the non-uniform distribution of ethanol-water molecules on the bubble surface. As a result, the solute Marangoni force that is much larger than the buoyancy is generated and it presses the microbubble against the fiber end face. The microbubble forms a high-quality Fabry-Perot (FP) interferometer, and the interferometric phase can be adjusted by changing the solute Marangoni force that is influenced by the laser power. This Letter gives a new method to achieve a tunable interferometer based on optical control.