Evanescent Wave Optical Manipulation

When a laser beam undergoing total internal reflection generates an evanescent wave at the surface, particles placed over the laser spot can also be manipulated indirectly. Counter-propagating beams result in the formation of optically bound matter. We can observe many interesting effects in these systems due to the light-matter interactions involved. Firstly, interference between the two light fields can create fringes which provide regular structure to trapped particles. We can also observe the effects of photon scattering between neighbouring particles, which adds a repulsive force. Interesting non-linear effects can be observed in which particles act as a microscopic Newtons cradle.

 

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