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Research

Our research focuses primarily on statistical physics, soft matter, optical manipulation, and stochastic phenomena. We are interested in both experimental and theoretical aspects. We have also been active in plasmonics, Raman spectroscopy, biophotonics, cylindrical vector beams, and fiber optics.

  • Optical Tweezers & Photonic Force Microscopy

    Optical Tweezers & Photonic Force Microscopy The photonic force microscope (PFM) can measure femtonewton and piconewton forces. Using a PFM we performed the first measurement of surface plasmon radiation forces. We have also extended the PFM potential to the characterization of rotational force fields, with applications, e.g., in microfluidics. The photonic force microscope (PFM) can measure femtonewton and piconewton forces. Using a PFM we performed the first measurement of surface plasmon radiation forces. We have also extended the PFM potential to the characterization of rotational force fields, with applications, e.g., in microfluidics. [ read more ]
  • Total Internal Reflection Microscopy

    Total Internal Reflection Microscopy Total internal reflection microscopy (TIRM) is a sensitive non-invasive technique to measure the interaction potentials between a colloidal particle and a wall with femtonewton resolution. Our work has largely extended the range of conditions accessible with TIRM, e.g. gold coated surfaces or large penetration depths. Total internal reflection microscopy (TIRM) is a sensitive non-invasive technique to measure the interaction potentials between a colloidal particle and a wall with femtonewton resolution. Our work has largely extended the range of conditions accessible with TIRM, e.g. gold coated surfaces or large penetration depths. [ read more ]
  • Force Measurement at the Nanoscale

    Force Measurement at the Nanoscale The ineluctable presence of thermal noise alters the measurement of forces acting on microscopic and nanoscopic objects, such as biomolecules and nanodevices. Our results demonstrate that the force-measurement process is prone to artifacts if the noise is not correctly taken into account. Our results are intimately connected to the long-standing issue of the interpretation of multiplicative noise in stochastic differential equations (Ito-Stratonovic dilemma). The ineluctable presence of thermal noise alters the measurement of forces acting on microscopic and nanoscopic objects, such as biomolecules and nanodevices. Our results demonstrate that the force-measurement process is prone to artifacts if the noise is not correctly taken into account. Our results are intimately connected to the long-standing issue of the interpretation of multiplicative noise in stochastic differential equations (Ito-Stratonovic dilemma). [ read more ]
  • Surface Plasmon Radiation Forces

    Surface Plasmon Radiation Forces We reported the first experimental observation of momentum transfer from a surface plasmon to a single dielectric sphere. We showed that the force magnitude at resonance gets strongly enhanced compared to a nonresonant illumination. We are also studying the possibilities of fractal plasmonics. We reported the first experimental observation of momentum transfer from a surface plasmon to a single dielectric sphere. We showed that the force magnitude at resonance gets strongly enhanced compared to a nonresonant illumination. We are also studying the possibilities of fractal plasmonics. [ read more ]
  • Cylindrical Vector Beams

    Cylindrical Vector Beams We proposed a method to efficiently produce light beams with radial, azimuthal, and hybrid polarization, through a few-mode fiber excited by a Laguerre–Gaussian beam. We demonstrated how to transform the output beam into a cylindrical vector beam (CVB) in free-space through various polarization transformations. Finally, we used such CVB for the optical manipulation of colloidal particles. We proposed a method to efficiently produce light beams with radial, azimuthal, and hybrid polarization, through a few-mode fiber excited by a Laguerre–Gaussian beam. We demonstrated how to transform the output beam into a cylindrical vector beam (CVB) in free-space through various polarization transformations. Finally, we used such CVB for the optical manipulation of colloidal particles. [ read more ]
  • Optical Tweezers Raman Spectroscopy

    Optical Tweezers Raman Spectroscopy The natural environment of many cells is in suspension. By using optical tweezers, we could constrain a single floating cell in order to measure its Raman spectrum. This permitted us to study the evolution of various  biochemical constituents of a single yeast cell during different phases of its cell-cycle. We also demonstrated the first Raman image of a floating cell, with movement completely controlled by holographic tweezers. The natural environment of many cells is in suspension. By using optical tweezers, we could constrain a single floating cell in order to measure its Raman spectrum. This permitted us to study the evolution of various biochemical constituents of a single yeast cell during different phases of its cell-cycle. We also demonstrated the first Raman image of a floating cell, with movement completely controlled by holographic tweezers. [ read more ]