Effects associated with bubble formation in optical trapping

Abstract

Heating of absorbing particles in a liquid medium by an optical trapping beam may lead to bubble formation. Powerful currents, which we identify as due to Marangoni convection, can be observed in the vicinity. At the micron size scale such surface tension effects can be very powerful, whereas normal thermal convection is negligible. Similar effects cause bubbles to be attracted to regions of higher temperature, providing a very powerful means of trapping bubbles, which are repelled by optical forces in a Gaussian beam. Measurements of the temperature required for bubble formation show that it occurs above the boiling point of the surrounding liquid, in reasonable agreement with nucleation theories.