Expand this Topic clickable element to expand a topic
Skip to content
Optica Publishing Group
Journal Home About Issues in Progress Current Issue All Issues Feature Issues

Size selective trapping with optical “cogwheel” tweezers

Alexander Jesacher, Severin Fürhapter, Stefan Bernet, and Monika Ritsch-Marte

Open Access Open Access

Abstract

We experimentally investigate the size-selective trapping behavior of Laguerre-Gaussian beams (“doughnut-beams”) and “cogwheel”-shaped beams which are collinear superpositions of two doughnut beams of equal opposite helical index. Experimentally they are created by diffraction of a Gaussian laser beam at a high resolution refractive spatial light modulator (SLM). In the focus of an optical microscope such a beam looks similar to a “cogwheel”, i.e. the light intensity is periodically modulated around the circumference of a sphere with a precisely adjustable diameter. In an optical tweezers setup these modes can be used to trap particles or cells, provided their sizes exceed the ring diameter by a fixed amount. This promises a convenient method of constructing an optical tweezers system in microscopy which acts as a passive sorter for particles of differing sizes.

©2004 Optical Society of America

Full Article  |  PDF Article
More Like This
Diffractive optical tweezers in the Fresnel regime

Alexander Jesacher, Severin Fürhapter, Stefan Bernet, and Monika Ritsch-Marte
Opt. Express 12(10) 2243-2250 (2004)

Microoptomechanical pumps assembled and driven by holographic optical vortex arrays

Kosta Ladavac and David G. Grier
Opt. Express 12(6) 1144-1149 (2004)

Holographic optical tweezers for object manipulations at an air-liquid surface

Alexander Jesacher, Severin Fürhapter, Christian Maurer, Stefan Bernet, and Monika Ritsch-Marte
Opt. Express 14(13) 6342-6352 (2006)

View More...

Cited By

Optica participates in Crossref's Cited-By Linking service. Citing articles from Optica Publishing Group journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (3)
Fig. 1.
Fig. 1. Microscopic image of a slightly defocussed optical “cogwheel” of mode index l=10 (reflection at a glass coverslip) in the vicinity of two 5 µm beads for size comparison.

Download Full Size | PDF

Fig. 2.
Fig. 2. Diffractive optical tweezers with divergent beam illumination: A high resolution (1920×1200 pixels) reflective spatial light modulator (SLM) is illuminated by a laser beam which strongly diverges behind a first lens. Only laser light diffracted into the desired first order is re-collimated after diffraction at a computer designed hologram displayed at the SLM. A further set of two lenses couples this beam into the optical pathway of an inverted microscope, where it is used to trap particles in different kinds of advanced optical traps. The inset shows example holograms displayed at the SLM for producing a doughnut mode (1) or a “cogwheel” mode (2).

Download Full Size | PDF

Fig. 3.
Fig. 3. Left: Experimentally determined trap stiffness parameters for beads of various diameters, trapped in “cogwheel” modes of the same light intensity with different azimuthal mode indices. The horizontal lines are inserted as guides for the eye. Right: Maximal “cogwheel” diameters just able to trap a bead of fixed size as a function of the corresponding bead diameter. The insert demonstrates the application to living yeast cells.

Download Full Size | PDF

Select as filters
Select Topics Cancel
Top
       
© Copyright 2024 | Optica Publishing Group. All rights reserved, including rights for text and data mining and training of artificial technologies or similar technologies.
Privacy | Terms of Use