Recent advances in optical manipulation have made it an ideal tool to create one, two, and three dimensional periodic optical potential. Such periodic potentials have found interesting technological and fundamental applications such as micro particle sorting and optical fractionation. Plasmon enhanced optical trapping techniques using metallic nanostructures can overcome the diffraction limits of far-field optical trap techniques and therefore permit trapping of nanoparticle with deep sub wavelength dimensions. Here we report the trapping of nanoparticles for a plasmon-enhanced two dimensional optical lattice integrated with microfluidic chip. We observe the trapping of nanoparticles over such an optical lattice. Such an integrated device allows the directional control of nano particles and provides a suitable platform for stochastic transport experiment such as nanoscale optical sorting.
Optical manipulation of small particles has long been challenging mainly due to reduced gradient force. Rotation of particles by light is even more difficult since that requires the particle to be absorbing or to exhibit large polarizability and optical anisotropy. Otherwise, the optical field has to carry orbital angular momentum. Recently surface-plasmonenhanced optical near field has been used to effectively trap small particles. However, rotation and spinning of isotropic dielectric particles by light has not been demonstrated, not to mention a single device capable of multiple functions. Here, we report the first demonstration of selective trapping or rotation of isotropic dielectric micro-particles using one single plasmonic device, a plasmonic Archimedes spiral. Such functionality is of great interest and may find applications in various fields, such as protein folding analysis and local mixing in microfluidic channels.
We introduce the possibility of performing two-pulse correlation measurements in order to probe the dynamics of twophoton
photoluminescence in Au nanostructures. Our preliminary results obtained from single-crystal Au nanorods are
consistent with the two-step model for the photoluminescence process.
We explore the possibility to control the polarization state of light confined into sub-diffraction volumes by means of
plasmonic optical antennas. To this aim, we describe a resonant cross antenna, constituted of two perpendicular two-wire
antennas sharing the same gap, which is able to maintain the polarization state in the plane of the antenna. We also
discuss how, by proper tuning of the arm length in a slightly off-resonance cross antenna, it is possible to effectively
realize a nanoscale quarter-waveplate antenna. We present experimental results for the preparation of individual cross
antennas by means of focused ion beam milling starting from single-crystalline Au microflakes, and finally show
preliminary characterization results based on two-photon photoluminescence confocal imaging with linearly-polarized