Search results for "Optical tweezers"
showing 10 items of 26 documents
Assembly of microparticles by optical trapping with a photonic crystal nanocavity
2012
International audience; In this work, we report the auto-assembly experiments of micrometer sized particles by optical trapping in the evanescent field of a photonic crystal nanocavity. The nanocavity is inserted inside an optofluidic cell designed to enable the real time control of the nanoresonator transmittance as well as the real time visualization of the particles motion in the vicinity of the nanocavity. It is demonstrated that the optical trap above the cavity enables the assembly of multiple particles in respect of different stable conformations.
Synthesis and Photodynamics of Fluorescent Blue BODIPY-Porphyrin Tweezers Linked by Triazole Rings
2012
Novel zinc porphyrin tweezers in which two zinc porphyrins were connected with π-conjugated boron dipyrromethenes (BDP meso-Por(2) and BDP β-Por(2)) through triazole rings were synthesized to investigate the photoinduced energy transfer and electron transfer. The UV-vis spectrum of BDP β-Por(2) which has less bulky substituents than BDP meso-Por(2) exhibits splitting of the Soret band as a result of the interaction between porphyrins of BDP β-Por(2) in the excited state. Such interaction between porphyrins of both BDP β-Por(2) and BDP meso-Por(2) is dominant at room temperature, while the coordination of the nitrogen atoms of the triazole rings to the zinc ions of the porphyrins occurs at l…
Diffusion of colloids in one-dimensional light channels
2004
Single-file diffusion (SFD), prevalent in many chemical and biological processes, refers to the one-dimensional motion of interacting particles in pores which are so narrow that the mutual passage of particles is excluded. Since the sequence of particles in such a situation remains unaffected over time t, this leads to strong deviations from normal diffusion, e.g. an increase of the particle mean-square-displacement as the square root of t. We present experimental results of the diffusive behaviour of colloidal particles in one-dimensional channels with varying particle density. The channels are realized by means of a scanning optical tweezers. Based on a new analytical approach (Kollmann 2…
Nanofiber-based optical trapping of cold neutral atoms
2012
We present experimental techniques and results related to the optimization and characterization of our nanofiber-based atom trap [Vetsch et al., Phys. Rev. Lett. 104, 203603 (2010)]. The atoms are confined in an optical lattice which is created using a two-color evanescent field surrounding the optical nanofiber. For this purpose, the polarization state of the trapping light fields has to be properly adjusted. We demonstrate that this can be accomplished by analyzing the light scattered by the nanofiber. Furthermore, we show that loading the nanofiber trap from a magneto-optical trap leads to sub-Doppler temperatures of the trapped atomic ensemble and yields a sub-Poissonian distribution of…
Fractal zone plates with variable lacunarity.
2009
Fractal zone plates (FZPs), i.e., zone plates with fractal structure, have been recently introduced in optics. These zone plates are distinguished by the fractal focusing structure they provide along the optical axis. In this paper we study the effects on this axial response of an important descriptor of fractals: the lacunarity. It is shown that this parameter drastically affects the profile of the irradiance response along the optical axis. In spite of this fact, the axial behavior always has the self-similarity characteristics of the FZP itself.
Devil’s vortex-lenses
2009
In this paper we present a new kind of vortex lenses in which the radial phase distribution is characterized by the "devil's staircase" function. The focusing properties of these fractal DOEs coined Devil's vortex-lenses are analytically studied and the influence of the topological charge is investigated. It is shown that under monochromatic illumination a vortex devil's lens give rise a focal volume containing a delimited chain of vortices that are axially distributed according to the self-similarity of the lens.
Dynamic force sensing of filamin revealed in single-molecule experiments
2012
Mechanical forces are important signals for cell response and development, but detailed molecular mechanisms of force sensing are largely unexplored. The cytoskeletal protein filamin is a key connecting element between the cytoskeleton and transmembrane complexes such as integrins or the von Willebrand receptor glycoprotein Ib. Here, we show using single-molecule mechanical measurements that the recently reported Ig domain pair 20–21 of human filamin A acts as an autoinhibited force-activatable mechanosensor. We developed a mechanical single-molecule competition assay that allows online observation of binding events of target peptides in solution to the strained domain pair. We find that fi…
Volumetric multiple optical traps produced by Devil's lenses
2010
We propose the use of a new diffractive optical element coined Devil's Vortex-Lens (DVL) to produce optical tweezers. In its more general form it results as the combination of a Devil’s lens and a helical vortex phase mask. It is shown that under monochromatic illumination a DVL generates a focal volume with several concatenated doughnut modes that are axially distributed according to the self-similarity of the lens. The orbital angular momentum associated to each link in the chain is investigated.
Germanium microparticles as optically induced oscillators in optical tweezers
2019
Oscillatory dynamics is a key tool in optical tweezers applications. It is usually implemented by mechanical interventions that cannot be optically controlled. In this work we show that Germanium semiconductor beads behave as optically induced oscillators when subjected to a highly focused laser beam. Such unusual motion is due to the competition between the usual optical forces [1-3] and the radiometric force related to thermal effects, which pushes the beads from the focal region [4]. We characterize the behavior of the Germanium beads in detail and propose a model accounting for the related forces, in good agreement with the experimental data. The well defined direction of oscillations c…
Integrated plasmonic nanotweezers for nanoparticle manipulation.
2016
We numerically demonstrate that short gold nanoparticle chains coupled to traditional SOI waveguides allow conceiving surface plasmon-based nanotweezers. This configuration provides for jumpless control of the trapping position of a nano-object as a function of the excitation wavelength, allowing for linear repositioning. This novel feature can be captivating for the conception of compact integrated optomechanical nanoactuators.