Revealing light momentum in dielectric media through standing-wave radiation pressure

Air-water interface deformation has been used as a testbed to resolve the momentum of light debate (AbrahamMinkowski) inside the dielectric medium, but to date, experiments or theory which have resolved this debate precisely are lacking. Here, we present the experimental observation of both momenta in a single setup. The model employed in interpreting our experimental results suggests that the total momentum associated with light inside a dielectric is represented by the mean value of the Abraham and Minkowski momenta, which is 1 2 (n + 1/n)h over bar omega/c. We used a clean and relatively simple pump-probe-type setup to investigate the light momentum inside the dielectric medium. Using a pump beam, we generate a standing wave, formed due to an incident and reflected pump beam in a water drop, placed on a partially metallic coated prism. A weak red probe laser beam was used to detect the nanoscale height variation of the air-water interface, where natural evaporation enabled us to measure the radiation pressure variations (spacing between the node and antinodes, lambda/2n) in the standing wave. Our results clearly depict the dependence of radiation pressure upon the phase of the incident and reflected light. We also performed numerical simulations in realistic experimental settings and found good agreement with the experimental results, and offer potential applications in microfluidics and optofluidics.