Stability Conditions for Trapping of Low Index Contrast Particles Dual Beam Optical Trap

ORAL

Abstract

The use of radiation pressure to hold and manipulate microscopic dielectric particles is driving fundamental advancements in our understanding of the machinery that makes up living cells. The dual-beam fiber-optical trapping configuration is particularly useful due to its diverging beams, allowing larger particles to be trapped with little photodamage. Most such studies are conducted using particles in a medium where the refractive index contrast between the particle and surrounding medium is relatively large: $m \, = \, (n_{\text{particle}}/n_{\text{medium}})\, > \, 1.1$. However, the low-$m$ case is of practical interest because it often applies to cells in vivo and artificially-synthesized vesicles where the internal and external media are similar to one another. We find experimentally and theoretically that there are regimes of fiber separation, particle size and refractive index contrast where the magnitudes of the gradient forces are nearly the same as the scattering forces, leading to multiple stable trapping locations. Besides being important for understanding the unusual behavior such a system may display, it raises the possibility of using a single-fiber trap for manipulating lipid vesicles.

–

Authors

  • Alison Huff

    Univ of California - Merced

  • Chi-Yu Hu

    University of California - Berkeley, National Institute for Materials Science, Caifornia State University, Long Beach, University of Michigan, Stockholm University, California State University, Long Beach, Utrecht University, Carl von Ossietzky University of Oldenburg, Germany, Hartnell Community College, Department of Physics, Stockholm University, GRAPPA, University of Amsterdam, Paul Scherrer Institute, Switzerland, California State University, Fresno, California State University Long Beach, Cal State Univ- Long Beach, University of Nevada, Reno, University of Rogensberg, Germany, Tribhuvan University, Nepal, University of Victoria and Perimeter Institute for Theoretical Physics, Institute of Physics, Jagiellonian University, Helmholtz Institute Mainz, Johannes Gutenberg University, Physics Department of the University of Nevada, Reno, Universita del Sannio, Cal Tech, California State University, Los Angeles, Univ of California - San Diego, UC Berkeley, Lawrence Livermore National Laboratory, Department of Physics & Astronomy, University of California, Irvine 92617, Department of Chemistry and of Physics & Astronomy, University of California, Irvine 92617, SLAC National Laboratory, Humboldt State University, Physics Department, University of Nevada, Reno, Univ of California - Merced

  • Chi-Yu Hu

    University of California - Berkeley, National Institute for Materials Science, Caifornia State University, Long Beach, University of Michigan, Stockholm University, California State University, Long Beach, Utrecht University, Carl von Ossietzky University of Oldenburg, Germany, Hartnell Community College, Department of Physics, Stockholm University, GRAPPA, University of Amsterdam, Paul Scherrer Institute, Switzerland, California State University, Fresno, California State University Long Beach, Cal State Univ- Long Beach, University of Nevada, Reno, University of Rogensberg, Germany, Tribhuvan University, Nepal, University of Victoria and Perimeter Institute for Theoretical Physics, Institute of Physics, Jagiellonian University, Helmholtz Institute Mainz, Johannes Gutenberg University, Physics Department of the University of Nevada, Reno, Universita del Sannio, Cal Tech, California State University, Los Angeles, Univ of California - San Diego, UC Berkeley, Lawrence Livermore National Laboratory, Department of Physics & Astronomy, University of California, Irvine 92617, Department of Chemistry and of Physics & Astronomy, University of California, Irvine 92617, SLAC National Laboratory, Humboldt State University, Physics Department, University of Nevada, Reno, Univ of California - Merced

  • Jay Sharping

    Univ of California - Merced