Low-power optical tweezers using large-diameter Gaussian and vortex beams for giant bubble trapping and rotation in...

We demonstrate a novel optical tweezers technique that enables trapping and manipulation of unusually large bubbles formed in a fluorescent dye medium using low-power laser beams. In this work, Gaussian and vortex beams with a beam diameter of a few hundred micrometers were employed at an incident power as low as a few milliWatt. Despite the low optical power, localized photothermal effects within the dye solution induced the formation of stable micron-sized to mesoscopic bubbles, whose diameters were comparable to that of the laser beam itself. The optical forces generated by the structured light field were sufficient to trap and translate these large bubbles, revealing unique bubble dynamics driven purely by light-matter interaction. Furthermore, when a linear polarizer was inserted before the microscope objective, the vortex beam exhibited a distinct dark stripe across its donut-shaped intensity profile. Rotating this polarizer resulted in a corresponding rotation of the trapped bubble, confirming the transfer of optical angular momentum modulated by polarization. This controllable rotational trapping behavior highlights a new mechanism for inducing and manipulating bubble dynamics via low-power optical fields. To the best of our knowledge, this represents the first experimental realization of optical tweezers capable of trapping and rotating bubbles of this scale using a few milliWatt power level. The proposed approach opens a pathway toward efficient, low-power optical manipulation in soft-matter and sonochemical systems, and provides new insights into light-driven bubble dynamics relevant to photothermal, microfluidic, and cavitation-assisted processes.