Morphology-dependent resonance induced by two-photon excitation in a micro-sphere trapped by a femtosecond pulsed laser.

We report on the measurement of morphology-dependent resonance within a laser-trapped micro-sphere excited under two-photon absorption. Both trapping and two-photon excitation are simultaneously achieved by a single femtosecond pulsed laser beam. The effect of the laser power as well as the pulse width on the transverse trapping force is first investigated. The dependence of two-photon-induced morphology-dependent resonance on the scanning velocity of a trapped particle is then experimentally determined.