HoloTrap: Interactive hologram design for multiple dynamic optical trapping

This work presents an application that generates real-time holograms to be displayed on a holographic optical tweezers setup; a technique that allows the manipulation of particles in the range from micrometres to nanometres. The software is written in Java, and uses random binary masks to generate the holograms. It allows customization of several parameters that are dependent on the experimental setup, such as the specific characteristics of the device displaying the hologram, or the presence of aberrations. We evaluate the software's performance and conclude that real-time interaction is achieved. We give our experimental results from manipulating 5 micron-diametre microspheres using the program.Comment: 17 pages, 6 figure

Design strategies for optimizing holographic optical tweezers setups

We provide a detailed account of the construction of a system of holographic optical tweezers. While much information is available on the design, alignment and calibration of other optical trapping configurations, those based on holography are relatively poorly described. Inclusion of a spatial light modulator in the setup gives rise to particular design trade-offs and constraints, and the system benefits from specific optimization strategies, which we discuss.Comment: 16 pages, 15 figure

Control of a VanderLugt correlator using a single 8-bit frame grabber

We analyze in depth several engineering problems regarding the construction of a VanderLugt correlator. Two liquid crystal devices are used in the input and Fourier planes and the large distances involved are reduced with the help of telephoto systems. An original method to control both modulators with a single 8-bit frame grabber and a single videoprojector electronics is presented. Problems related to pixel-by-pixel addressing and the phase modulation in the panels are also discussed. All the solutions proposed in this paper have been implemented and experimental correlation results using the setup have been obtained

Artificially-induced organelles are optimal targets for optical trapping experiments in living cells

Optical trapping supplies information on the structural, kinetic or rheological properties of inner constituents of the cell. However, the application of significant forces to intracellular objects is notoriously difficult due to a combination of factors, such as the small difference between the refractive indices of the target structures and the cytoplasm. Here we discuss the possibility of artificially inducing the formation of spherical organelles in the endoplasmic reticulum, which would contain densely packed engineered proteins, to be used as optimized targets for optical trapping experiments. The high index of refraction and large size of our organelles provide a firm grip for optical trapping and thereby allow us to exert large forces easily within safe irradiation limits. This has clear advantages over alternative probes, such as subcellular organelles or internalized synthetic beads.This research was partly funded by the Spanish Ministry of Education and Science (FIS2010-16104, BFU-2009-07186 and BFU2012-33932) as well as by the regional authorities of Catalonia – ACC1Ó (VALTEC G614828324059231). C. L.-Q. acknowledges an APIF grant from the University of Barcelona and a A. F. an FI grant from the Generalitat de Catalunya (regional authorities of Catalonia).Peer reviewe

Media 1: Artificially-induced organelles are optimal targets for optical trapping experiments in living cells

Originally published in Biomedical Optics Express on 01 July 2014 (boe-5-7-1993

Multiple optical trapping and binding: new routes to self-assembly

With appropriately selected optical frequencies, pulses of radiation propagating through a system of chemically distinct and organized components can produce areas of spatially selective excitation. This paper focuses on a system in which there are two absorptive components, each one represented by surface adsorbates arrayed on a pair of juxtaposed interfaces. The adsorbates are chosen to be chemically distinct from the material of the underlying surface. On promotion of any adsorbate molecule to an electronic excited state, its local electronic environment is duly modified, and its London interaction with nearest neighbor molecules becomes accommodated to the new potential energy landscape. If the absorbed energy then transfers to a neighboring adsorbate of another species, so that the latter acquires the excitation, the local electronic environment changes and compensating motion can be expected to occur. Physically, this is achieved through a mechanism of photon absorption and emission by molecular pairs, and by the engagement of resonance transfer of energy between them. This paper presents a detailed analysis of the possibility of optically effecting such modifications to the London force between neutral adsorbates, based on quantum electrodynamics (QED). Thus, a precise link is established between the transfer of excitation and ensuing mechanical effects