Atomic, Molecular, and Optical Physics Seminar
Near-Field Optical Microscopy of Extended Objects
Dipartimento di Fisica, “Enrico Fermi”
Universita di Pisa, Italy
Near-field optical microscopy (NSOM) is one way to overcome the diffraction limit while preserving the advantages of optical microscopy. NSOM provides imaging of objects much smaller than the visible light wavelength and it allows the investigation of laser-matter interactions at sub-wavelength scale. In this seminar a simple overview of near-field techniques is presented, proving optical imaging and spectroscopy with resolution well beyond the half wavelength limit. NSOM is however a surface technique and optical super-resolution is demonstrated only in objects with thickness in the nano-meter scale. For extended objects, the far-field contribution due to the interaction of the propagating wave inside the object may dominate the optical signal and spoil the resolution. Recently, we have proposed to enhance the weight of the near-field components of the optical signal by modulation of the surface optical properties with an external sinusoidal field localized at the sample surface. This principle is demonstrated by exploiting surface-localized electro-optic modulation, where a significant improvement of spatial resolution has been found in optical imaging of ferroelectric domain walls.
Monday, October 16, 2006
Gant Science Complex