Scanning particle trapped optical microscopy based on two-photon-induced morphology-dependent resonance in a trapped microsphere

We report on scanning particle trapped optical microscopy based on two-photon-induced morphology-dependent resonance (MDR) in a trapped microsphere. In this imaging mode, a femtosecond pulsed laser is adopted for simultaneous laser trapping and two-photon excitation. Due to the localized excitation, MDR is significantly enhanced. As a result, an image contrast enhancement of 9.3% is achieved by the spectral detection of a single on-resonance MDR mode compared with that obtained by the off-resonance MDR mode without compromise in transverse resolution.