Integrated Optical Dipole Trap for Cold Neutral Atoms with an Optical Waveguide Coupler

NASA Astrophysics Data System (ADS)

Lee, J.; Park, D. H.; Mittal, S.; Meng, Y.; Dagenais, M.; Rolston, S. L.

2013-05-01

Using an optical waveguide, an integrated optical dipole trap uses two-color (red and blue-detuned) traveling evanescent wave fields for trapping cold neutral atoms. To achieve longitudinal confinement, we propose using an integrated optical waveguide coupler, which provides a potential gradient along the beam propagation direction sufficient to confine atoms. This integrated optical dipole trap can support an atomic ensemble with a large optical depth due to its small mode area. Its quasi-TE0 waveguide mode has an advantage over the HE11 mode of a nanofiber, with little inhomogeneous Zeeman broadening at the trapping region. The longitudinal confinement eliminates the need for a 1D optical lattice, reducing collisional blockaded atomic loading, potentially producing larger ensembles. The waveguide trap allows for scalability and integrability with nano-fabrication technology. We analyze the potential performance of such integrated atom traps and present current research progress towards a fiber-coupled silicon nitride optical waveguide integrable with atom chips. Work is supported by the ARO Atomtronics MURI. Work is supported by the ARO Atomtronics MURI.

First Measurement of the Atomic Electric Dipole Moment of (225)Ra.

PubMed

Parker, R H; Dietrich, M R; Kalita, M R; Lemke, N D; Bailey, K G; Bishof, M; Greene, J P; Holt, R J; Korsch, W; Lu, Z-T; Mueller, P; O'Connor, T P; Singh, J T

2015-06-12

The radioactive radium-225 ((225)Ra) atom is a favorable case to search for a permanent electric dipole moment. Because of its strong nuclear octupole deformation and large atomic mass, (225)Ra is particularly sensitive to interactions in the nuclear medium that violate both time-reversal symmetry and parity. We have developed a cold-atom technique to study the spin precession of (225)Ra atoms held in an optical dipole trap, and demonstrated the principle of this method by completing the first measurement of its atomic electric dipole moment, reaching an upper limit of |d((225)Ra)|<5.0×10(-22)  e cm (95% confidence).

Note: Toward multiple addressable optical trapping

PubMed Central

Faustov, Alexei R.; Webb, Michael R.; Walt, David R.

2010-01-01

We describe a setup for addressable optical trapping in which a laser source is focused on a digital micromirror device and generates an optical trap in a microfluidic cell. In this paper, we report a proof-of-principle single beam∕single micromirror∕single three-dimensional trap arrangement that should serve as the basis for a multiple-trap instrument. PMID:20192526

Dynamic analysis of trapping and escaping in dual beam optical trap

NASA Astrophysics Data System (ADS)

Li, Wenqiang; Hu, Huizhu; Su, Heming; Li, Zhenggang; Shen, Yu

2016-10-01

In this paper, we simulate the dynamic movement of a dielectric sphere in optical trap. This dynamic analysis can be used to calibrate optical forces, increase trapping efficiency and measure viscous coefficient of surrounding medium. Since an accurate dynamic analysis is based on a detailed force calculation, we calculate all forces a sphere receives. We get the forces of dual-beam gradient radiation pressure on a micron-sized dielectric sphere in the ray optics regime and utilize Einstein-Ornstein-Uhlenbeck to deal with its Brownian motion forces. Hydrodynamic viscous force also exists when the sphere moves in liquid. Forces from buoyance and gravity are also taken into consideration. Then we simulate trajectory of a sphere when it is subject to all these forces in a dual optical trap. From our dynamic analysis, the sphere can be trapped at an equilibrium point in static water, although it permanently fluctuates around the equilibrium point due to thermal effects. We go a step further to analyze the effects of misalignment of two optical traps. Trapping and escaping phenomena of the sphere in flowing water are also simulated. In flowing water, the sphere is dragged away from the equilibrium point. This dragging distance increases with the decrease of optical power, which results in escaping of the sphere with optical power below a threshold. In both trapping and escaping process we calculate the forces and position of the sphere. Finally, we analyze a trapping region in dual optical tweezers.

TweezPal - Optical tweezers analysis and calibration software

NASA Astrophysics Data System (ADS)

Osterman, Natan

2010-11-01

Optical tweezers, a powerful tool for optical trapping, micromanipulation and force transduction, have in recent years become a standard technique commonly used in many research laboratories and university courses. Knowledge about the optical force acting on a trapped object can be gained only after a calibration procedure which has to be performed (by an expert) for each type of trapped objects. In this paper we present TweezPal, a user-friendly, standalone Windows software tool for optical tweezers analysis and calibration. Using TweezPal, the procedure can be performed in a matter of minutes even by non-expert users. The calibration is based on the Brownian motion of a particle trapped in a stationary optical trap, which is being monitored using video or photodiode detection. The particle trajectory is imported into the software which instantly calculates position histogram, trapping potential, stiffness and anisotropy. Program summaryProgram title: TweezPal Catalogue identifier: AEGR_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEGR_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 44 891 No. of bytes in distributed program, including test data, etc.: 792 653 Distribution format: tar.gz Programming language: Borland Delphi Computer: Any PC running Microsoft Windows Operating system: Windows 95, 98, 2000, XP, Vista, 7 RAM: 12 Mbytes Classification: 3, 4.14, 18, 23 Nature of problem: Quick, robust and user-friendly calibration and analysis of optical tweezers. The optical trap is calibrated from the trajectory of a trapped particle undergoing Brownian motion in a stationary optical trap (input data) using two methods. Solution method: Elimination of the experimental drift in position data. Direct calculation of the trap stiffness from the positional variance. Calculation of 1D optical trapping potential from the positional distribution of data points. Trap stiffness calculation by fitting a parabola to the trapping potential. Presentation of X-Y positional density for close inspection of the 2D trapping potential. Calculation of the trap anisotropy. Running time: Seconds

Combined acoustic and optical trapping

PubMed Central

Thalhammer, G.; Steiger, R.; Meinschad, M.; Hill, M.; Bernet, S.; Ritsch-Marte, M.

2011-01-01

Combining several methods for contact free micro-manipulation of small particles such as cells or micro-organisms provides the advantages of each method in a single setup. Optical tweezers, which employ focused laser beams, offer very precise and selective handling of single particles. On the other hand, acoustic trapping with wavelengths of about 1 mm allows the simultaneous trapping of many, comparatively large particles. With conventional approaches it is difficult to fully employ the strengths of each method due to the different experimental requirements. Here we present the combined optical and acoustic trapping of motile micro-organisms in a microfluidic environment, utilizing optical macro-tweezers, which offer a large field of view and working distance of several millimeters and therefore match the typical range of acoustic trapping. We characterize the acoustic trapping forces with the help of optically trapped particles and present several applications of the combined optical and acoustic trapping, such as manipulation of large (75 μm) particles and active particle sorting. PMID:22025990

Optical trapping of nanoparticles by ultrashort laser pulses.

PubMed

Usman, Anwar; Chiang, Wei-Yi; Masuhara, Hiroshi

2013-01-01

Optical trapping with continuous-wave lasers has been a fascinating field in the optical manipulation. It has become a powerful tool for manipulating micrometer-sized objects, and has been widely applied in physics, chemistry, biology, material, and colloidal science. Replacing the continuous-wave- with pulsed-mode laser in optical trapping has already revealed some novel phenomena, including the stable trap, modifiable trapping positions, and controllable directional optical ejections of particles in nanometer scales. Due to two distinctive features; impulsive peak powers and relaxation time between consecutive pulses, the optical trapping with the laser pulses has been demonstrated to have some advantages over conventional continuous-wave lasers, particularly when the particles are within Rayleigh approximation. This would open unprecedented opportunities in both fundamental science and application. This Review summarizes recent advances in the optical trapping with laser pulses and discusses the electromagnetic formulations and physical interpretations of the new phenomena. Its aim is rather to show how beautiful and promising this field will be, and to encourage the in-depth study of this field.

Optical trapping of core-shell magnetic microparticles by cylindrical vector beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhong, Min-Cheng; Gong, Lei; Li, Di

2014-11-03

Optical trapping of core-shell magnetic microparticles is experimentally demonstrated by using cylindrical vector beams. Second, we investigate the optical trapping efficiencies. The results show that radially and azimuthally polarized beams exhibit higher axial trapping efficiencies than the Gaussian beam. Finally, a trapped particle is manipulated to kill a cancer cell. The results make possible utilizing magnetic particles for optical manipulation, which is an important advantage for magnetic particles as labeling agent in targeted medicine and biological analysis.

Optical trapping performance of dielectric-metallic patchy particles

PubMed Central

Lawson, Joseph L.; Jenness, Nathan J.; Clark, Robert L.

2015-01-01

We demonstrate a series of simulation experiments examining the optical trapping behavior of composite micro-particles consisting of a small metallic patch on a spherical dielectric bead. A full parameter space of patch shapes, based on current state of the art manufacturing techniques, and optical properties of the metallic film stack is examined. Stable trapping locations and optical trap stiffness of these particles are determined based on the particle design and potential particle design optimizations are discussed. A final test is performed examining the ability to incorporate these composite particles with standard optical trap metrology technologies. PMID:26832054

The construction and characterization of optical traps for manipulating microscopic particles

NASA Astrophysics Data System (ADS)

Thompson, Tiffany; Behringer, Ernest

2011-04-01

Optical traps use tightly focused laser light to manipulate microscopic particles and have applications in nanofabrication, characterizing DNA, and in vitro fertilization [1]. We will describe the design, construction, and characterization of an optical trap that is capable of trapping and imaging 3 μm polystyrene spheres using a 12 mW HeNe laser. The design was based on previous work [2,3] describing how to build affordable optical traps. We will discuss trapping forces and their calibration. [4pt] [1] D.G. Grier, "A Revolution in Optical Manipulation," Nature 424, 810-816 (2003). [0pt] [2] S.P. Smith et al., "Inexpensive optical tweezers for undergraduate laboratories," Am. J. Phys. 67 (1), 26-35 (1999).[0pt] [3] J. Bechhoefer et al., "Faster, cheaper, safer optical tweezers for the undergraduate laboratory," Am. J. Phys. 70 (4), 393-400 (2001).

Proton-induced radioactivity in NaI (Tl) scintillation detectors

NASA Technical Reports Server (NTRS)

Fishman, G. J.

1977-01-01

Radioactivity induced by protons in sodium iodide scintillation crystals were calculated and directly measured. These data are useful in determining trapped radiation and cosmic-ray induced, background-counting rates in spaceborne detectors.

Characterization of photoactivated singlet oxygen damage in single-molecule optical trap experiments.

PubMed

Landry, Markita P; McCall, Patrick M; Qi, Zhi; Chemla, Yann R

2009-10-21

Optical traps or "tweezers" use high-power, near-infrared laser beams to manipulate and apply forces to biological systems, ranging from individual molecules to cells. Although previous studies have established that optical tweezers induce photodamage in live cells, the effects of trap irradiation have yet to be examined in vitro, at the single-molecule level. In this study, we investigate trap-induced damage in a simple system consisting of DNA molecules tethered between optically trapped polystyrene microspheres. We show that exposure to the trapping light affects the lifetime of the tethers, the efficiency with which they can be formed, and their structure. Moreover, we establish that these irreversible effects are caused by oxidative damage from singlet oxygen. This reactive state of molecular oxygen is generated locally by the optical traps in the presence of a sensitizer, which we identify as the trapped polystyrene microspheres. Trap-induced oxidative damage can be reduced greatly by working under anaerobic conditions, using additives that quench singlet oxygen, or trapping microspheres lacking the sensitizers necessary for singlet state photoexcitation. Our findings are relevant to a broad range of trap-based single-molecule experiments-the most common biological application of optical tweezers-and may guide the development of more robust experimental protocols.

Characterization of Photoactivated Singlet Oxygen Damage in Single-Molecule Optical Trap Experiments

PubMed Central

Landry, Markita P.; McCall, Patrick M.; Qi, Zhi; Chemla, Yann R.

2009-01-01

Abstract Optical traps or “tweezers” use high-power, near-infrared laser beams to manipulate and apply forces to biological systems, ranging from individual molecules to cells. Although previous studies have established that optical tweezers induce photodamage in live cells, the effects of trap irradiation have yet to be examined in vitro, at the single-molecule level. In this study, we investigate trap-induced damage in a simple system consisting of DNA molecules tethered between optically trapped polystyrene microspheres. We show that exposure to the trapping light affects the lifetime of the tethers, the efficiency with which they can be formed, and their structure. Moreover, we establish that these irreversible effects are caused by oxidative damage from singlet oxygen. This reactive state of molecular oxygen is generated locally by the optical traps in the presence of a sensitizer, which we identify as the trapped polystyrene microspheres. Trap-induced oxidative damage can be reduced greatly by working under anaerobic conditions, using additives that quench singlet oxygen, or trapping microspheres lacking the sensitizers necessary for singlet state photoexcitation. Our findings are relevant to a broad range of trap-based single-molecule experiments—the most common biological application of optical tweezers—and may guide the development of more robust experimental protocols. PMID:19843445

Resource Letter: LBOT-1: Laser-based optical tweezers

PubMed Central

Lang, Matthew J.; Block, Steven M.

2006-01-01

This Resource Letter provides a guide to the literature on optical tweezers, also known as laser-based, gradient-force optical traps. Journal articles and books are cited for the following main topics: general papers on optical tweezers, trapping instrument design, optical detection methods, optical trapping theory, mechanical measurements, single molecule studies, and sections on biological motors, cellular measurements and additional applications of optical tweezers. PMID:16971965

Resource Letter: LBOT-1: Laser-based optical tweezers.

PubMed

Lang, Matthew J; Block, Steven M

2003-03-01

This Resource Letter provides a guide to the literature on optical tweezers, also known as laser-based, gradient-force optical traps. Journal articles and books are cited for the following main topics: general papers on optical tweezers, trapping instrument design, optical detection methods, optical trapping theory, mechanical measurements, single molecule studies, and sections on biological motors, cellular measurements and additional applications of optical tweezers.

Ultralow power trapping and fluorescence detection of single particles on an optofluidic chip.

PubMed

Kühn, S; Phillips, B S; Lunt, E J; Hawkins, A R; Schmidt, H

2010-01-21

The development of on-chip methods to manipulate particles is receiving rapidly increasing attention. All-optical traps offer numerous advantages, but are plagued by large required power levels on the order of hundreds of milliwatts and the inability to act exclusively on individual particles. Here, we demonstrate a fully integrated electro-optical trap for single particles with optical excitation power levels that are five orders of magnitude lower than in conventional optical force traps. The trap is based on spatio-temporal light modulation that is implemented using networks of antiresonant reflecting optical waveguides. We demonstrate the combination of on-chip trapping and fluorescence detection of single microorganisms by studying the photobleaching dynamics of stained DNA in E. coli bacteria. The favorable size scaling facilitates the trapping of single nanoparticles on integrated optofluidic chips.

Radioactivities induced in some LDEF samples

NASA Technical Reports Server (NTRS)

Reedy, Robert C.; Moss, Calvin E.; Bobias, S. George; Masarik, Jozef

1993-01-01

Radioactivities induced in several Long Duration Exposure Facilities (LDEF) samples were measured by low-level counting at Los Alamos and elsewhere. These radionuclides have activities similar to those observed in meteorites and lunar samples. Some trends were observed in these measurements in terms of profiles in trunnion layers and as a function of radionuclide half-life. Several existing computer codes were used to model the production by the protons trapped in the Earth's radiation belts and by the galactic cosmic rays of some of these radionuclides, Mn-54 and Co-57 in steel, Sc-46 in titanium, and Na-22 in alloys of titanium and aluminum. Production rates were also calculated for radionuclides possibly implanted in LDEF, Be-7, Be-10, and C-14. Enhanced concentrations of induced isotopes in the surfaces of trunnion sections relative to their concentrations in the center are caused by the lower-energy protons in the trapped radiation. Secondary neutrons made by high-energy trapped protons and by galactic cosmic rays produce much of the observed radioactivities, especially deep in an object. Comparisons of the observed to calculated activities of several radionuclides with different half-lives indicate that the flux of trapped protons at LDEF decreased significantly at the end of the mission.

Comparative study of methods to calibrate the stiffness of a single-beam gradient-force optical tweezers over various laser trapping powers

PubMed Central

Sarshar, Mohammad; Wong, Winson T.; Anvari, Bahman

2014-01-01

Abstract. Optical tweezers have become an important instrument in force measurements associated with various physical, biological, and biophysical phenomena. Quantitative use of optical tweezers relies on accurate calibration of the stiffness of the optical trap. Using the same optical tweezers platform operating at 1064 nm and beads with two different diameters, we present a comparative study of viscous drag force, equipartition theorem, Boltzmann statistics, and power spectral density (PSD) as methods in calibrating the stiffness of a single beam gradient force optical trap at trapping laser powers in the range of 0.05 to 1.38 W at the focal plane. The equipartition theorem and Boltzmann statistic methods demonstrate a linear stiffness with trapping laser powers up to 355 mW, when used in conjunction with video position sensing means. The PSD of a trapped particle’s Brownian motion or measurements of the particle displacement against known viscous drag forces can be reliably used for stiffness calibration of an optical trap over a greater range of trapping laser powers. Viscous drag stiffness calibration method produces results relevant to applications where trapped particle undergoes large displacements, and at a given position sensing resolution, can be used for stiffness calibration at higher trapping laser powers than the PSD method. PMID:25375348

Extending the applicability of an open-ring trap to perform experiments with a single laser-cooled ion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cornejo, J. M.; Colombano, M.; Doménech, J.

A special ion trap was initially built up to perform β-ν correlation experiments with radioactive ions. The trap geometry is also well suited to perform experiments with laser-cooled ions, serving for the development of a new type of Penning trap, in the framework of the project TRAPSENSOR at the University of Granada. The goal of this project is to use a single {sup 40}Ca{sup +} ion as detector for single-ion mass spectrometry. Within this project and without any modification to the initial electrode configuration, it was possible to perform Doppler cooling on {sup 40}Ca{sup +} ions, starting from large cloudsmore » and reaching single ion sensitivity. This new feature of the trap might be important also for other experiments with ions produced at radioactive ion beam facilities. In this publication, the trap and the laser system will be described, together with their performance with respect to laser cooling applied to large ion clouds down to a single ion.« less

On-chip photonic tweezers for photonics, microfluidics, and biology

NASA Astrophysics Data System (ADS)

Pin, Christophe; Renaut, Claude; Tardif, Manon; Jager, Jean-Baptiste; Delamadeleine, Eric; Picard, Emmanuel; Peyrade, David; Hadji, Emmanuel; de Fornel, Frédérique; Cluzel, Benoît

2017-04-01

Near-field optical forces arise from evanescent electromagnetic fields and can be advantageously used for on-chip optical trapping. In this work, we investigate how evanescent fields at the surface of photonic cavities can efficiently trap micro-objects such as polystyrene particles and bacteria. We study first the influence of trapped particle's size on the trapping potential and introduce an original optofluidic near-field optical microscopy technique. Then we analyze the rotational motion of trapped clusters of microparticles and investigate their possible use as microfluidic micro-tools such as integrated micro-flow vane. Eventually, we demonstrate efficient on-chip optical trapping of various kinds of bacteria.

Single and dual fiber nano-tip optical tweezers: trapping and analysis.

PubMed

Decombe, Jean-Baptiste; Huant, Serge; Fick, Jochen

2013-12-16

An original optical tweezers using one or two chemically etched fiber nano-tips is developed. We demonstrate optical trapping of 1 micrometer polystyrene spheres at optical powers down to 2 mW. Harmonic trap potentials were found in the case of dual fiber tweezers by analyzing the trapped particle position fluctuations. The trap stiffness was deduced using three different models. Consistent values of up to 1 fN/nm were found. The stiffness linearly decreases with decreasing light intensity and increasing fiber tip-to-tip distance.

Effect of pulse temporal shape on optical trapping and impulse transfer using ultrashort pulsed lasers.

PubMed

Shane, Janelle C; Mazilu, Michael; Lee, Woei Ming; Dholakia, Kishan

2010-03-29

We investigate the effects of pulse duration on optical trapping with high repetition rate ultrashort pulsed lasers, through Lorentz-Mie theory, numerical simulation, and experiment. Optical trapping experiments use a 12 femtosecond duration infrared pulsed laser, with the trapping microscope's temporal dispersive effects measured and corrected using the Multiphoton Intrapulse Interference Phase Scan method. We apply pulse shaping to reproducibly stretch pulse duration by 1.5 orders of magnitude and find no material-independent effects of pulse temporal profile on optical trapping of 780nm silica particles, in agreement with our theory and simulation. Using pulse shaping, we control two-photon fluorescence in trapped fluorescent particles, opening the door to other coherent control applications with trapped particles.

A 6He production facility and an electrostatic trap for measurement of the beta-neutrino correlation

NASA Astrophysics Data System (ADS)

Mukul, I.; Hass, M.; Heber, O.; Hirsh, T. Y.; Mishnayot, Y.; Rappaport, M. L.; Ron, G.; Shachar, Y.; Vaintraub, S.

2018-08-01

A novel experiment has been commissioned at the Weizmann Institute of Science for the study of weak interactions via a high-precision measurement of the beta-neutrinoangular correlation in the radioactive decay of short-lived 6He. The facility consists of a 14 MeV d + t neutron generator to produce atomic 6He, followed by ionization and bunching in an electron beam ion source, and injection into an electrostatic ion beam trap. This ion trap has been designed for efficient detection of the decay products from trapped light ions. The storage time in the trap for different stable ions was found to be in the range of 0.6 to 1.2 s at the chamber pressure of ∼7 × 10-10 mbar. We present the initial test results of the facility, and also demonstrate an important upgrade of an existing method (Stora et al., 2012) for production of light radioactive atoms, viz. 6He, for the precision measurement. The production rate of 6He atoms in the present setup has been estimated to be ∼ 1 . 45 × 10-4 atoms per neutron, and the system efficiency was found to be 4.0 ± 0.6%. An improvement to this setup is also presented for the enhanced production and diffusion of radioactive atoms for future use.

Many-body Study of Core-valence Partitioning and Correlation in Systems with Large-Z Element

NASA Astrophysics Data System (ADS)

Zehtabi-Oskuie, Ana

This thesis presents optical trapping of various single nanoparticles, and the method for integrating the optical trap system into a microfluidic channel to examine the trapping stiffness and to study binding at the single molecule level. Optical trapping is the capability to immobilize, move, and manipulate small objects in a gentle way. Conventional trapping methods are able to trap dielectric particles with size greater than 100 nm. Optical trapping using nanostructures has overcome this limitation so that it has been of interest to trap nanoparticles for bio-analytical studies. In particular, aperture optical trapping allows for trapping at low powers, and easy detection of the trapping events by noting abrupt jumps in the transmission intensity of the trapping beam through the aperture. Improved trapping efficiency has been achieved by changing the aperture shape from a circle; for example, to a rectangle, double nanohole (DNH), or coaxial aperture. The DNH has the advantage of a well-defined trapping region between the two cusps where the nanoholes overlap, which typically allows only single particle trapping due to steric hindrance. Trapping of 21 nm encapsulated quantum dot has been achieved which shows optical trapping can be used in technologies that seek to place a quantum dot at a specific location in a plasmonic or nanophotonic structure. The DNH has been used to trap and unfold a single protein. The high signal-to-noise ratio of 33 in monitoring single protein trapping and unfolding shows a tremendous potential for using the double nanohole as a sensor for protein binding events at a single molecule level. The DNH integrated in a microfluidic chip with flow to show that stable trapping can be achieved under reasonable flow rates of a few microL/min. With such stable trapping under flow, it is possible to envision co-trapping of proteins to study their interactions. Co-trapping is achieved for the case where we flow in a protein (bovine serum albumin -- BSA) and co-trap its antibody (anti-BSA).

Raman microspectroscopy of optically trapped micro- and nanoobjects

NASA Astrophysics Data System (ADS)

Jonáš, Alexandr; Ježek, Jan; Šerý, Mojmír; Zemánek, Pavel

2008-12-01

We describe and characterize an experimental system for Raman microspectroscopy of micro- and nanoobjects optically trapped in aqueous suspensions with the use of a single-beam gradient optical trap (Raman tweezers). This system features two separate lasers providing light for the optical trapping and excitation of the Raman scattering spectra from the trapped specimen, respectively. Using independent laser beams for trapping and spectroscopy enables optimizing the parameters of both beams for their respective purposes. Moreover, it is possible to modulate the position of the trapped object relative to the Raman beam focus for maximizing the detected Raman signal and obtaining spatially resolved images of the trapped specimen. Using this experimental system, we have obtained Raman scattering spectra of individual optically confined micron and sub-micron sized polystyrene beads and baker's yeast cells. Sufficiently high signal-to-noise ratio of the spectra could be achieved using a few tens of milliwatts of the Raman beam power and detector integration times on the order of seconds.

Mass-manufacturable polymer microfluidic device for dual fiber optical trapping.

PubMed

De Coster, Diane; Ottevaere, Heidi; Vervaeke, Michael; Van Erps, Jürgen; Callewaert, Manly; Wuytens, Pieter; Simpson, Stephen H; Hanna, Simon; De Malsche, Wim; Thienpont, Hugo

2015-11-30

We present a microfluidic chip in Polymethyl methacrylate (PMMA) for optical trapping of particles in an 80µm wide microchannel using two counterpropagating single-mode beams. The trapping fibers are separated from the sample fluid by 70µm thick polymer walls. We calculate the optical forces that act on particles flowing in the microchannel using wave optics in combination with non-sequential ray-tracing and further mathematical processing. Our results are compared with a theoretical model and the Mie theory. We use a novel fabrication process that consists of a premilling step and ultraprecision diamond tooling for the manufacturing of the molds and double-sided hot embossing for replication, resulting in a robust microfluidic chip for optical trapping. In a proof-of-concept demonstration, we show the trapping capabilities of the hot embossed chip by trapping spherical beads with a diameter of 6µm, 8µm and 10µm and use the power spectrum analysis of the trapped particle displacements to characterize the trap strength.

Nanophotonic Trapping for Precise Manipulation of Biomolecular Arrays

PubMed Central

Soltani, Mohammad; Lin, Jun; Forties, Robert A.; Inman, James T.; Saraf, Summer N.; Fulbright, Robert M.; Lipson, Michal; Wang, Michelle D.

2014-01-01

Optical trapping is a powerful manipulation and measurement technique widely employed in the biological and materials sciences1–8. Miniaturizing optical trap instruments onto optofluidic platforms holds promise for high throughput lab-on-chip applications9–16. However, a persistent challenge with existing optofluidic devices has been controlled and precise manipulation of trapped particles. Here we report a new class of on-chip optical trapping devices. Using photonic interference functionalities, an array of stable, three-dimensional on-chip optical traps is formed at the antinodes of a standing-wave evanescent field on a nanophotonic waveguide. By employing the thermo-optic effect via integrated electric microheaters, the traps can be repositioned at high speed (~ 30 kHz) with nanometer precision. We demonstrate sorting and manipulation of individual DNA molecules. In conjunction with laminar flows and fluorescence, we also show precise control of the chemical environment of a sample with simultaneous monitoring. Such a controllable trapping device has the potential for high-throughput precision measurements on chip. PMID:24776649

Nanophotonic trapping for precise manipulation of biomolecular arrays.

PubMed

Soltani, Mohammad; Lin, Jun; Forties, Robert A; Inman, James T; Saraf, Summer N; Fulbright, Robert M; Lipson, Michal; Wang, Michelle D

2014-06-01

Optical trapping is a powerful manipulation and measurement technique widely used in the biological and materials sciences. Miniaturizing optical trap instruments onto optofluidic platforms holds promise for high-throughput lab-on-a-chip applications. However, a persistent challenge with existing optofluidic devices has been achieving controlled and precise manipulation of trapped particles. Here, we report a new class of on-chip optical trapping devices. Using photonic interference functionalities, an array of stable, three-dimensional on-chip optical traps is formed at the antinodes of a standing-wave evanescent field on a nanophotonic waveguide. By employing the thermo-optic effect via integrated electric microheaters, the traps can be repositioned at high speed (∼30 kHz) with nanometre precision. We demonstrate sorting and manipulation of individual DNA molecules. In conjunction with laminar flows and fluorescence, we also show precise control of the chemical environment of a sample with simultaneous monitoring. Such a controllable trapping device has the potential to achieve high-throughput precision measurements on chip.

Optical trapping apparatus, methods and applications using photonic crystal resonators

DOEpatents

Erickson, David; Chen, Yih-Fan

2015-06-16

A plurality of photonic crystal resonator optical trapping apparatuses and a plurality optical trapping methods using the plurality of photonic crystal resonator optical trapping apparatuses include located and formed over a substrate a photonic waveguide that is coupled (i.e., either separately coupled or integrally coupled) with a photonic crystal resonator. In a particular embodiment, the photonic waveguide and the photonic crystal resonator comprise a monocrystalline silicon (or other) photonic material absent any chemical functionalization. In another particular embodiment, the photonic waveguide and the photonic crystal resonator comprise a silicon nitride material which when actuating the photonic crystal resonator optical trapping apparatus with a 1064 nanometer resonant photonic radiation wavelength (or other resonant photonic radiation wavelength in a range from about 700 to about 1200 nanometers) provides no appreciable heating of an aqueous sample fluid that is analyzed by the photonic crystal resonator optical trapping apparatus.

Confocal Raman microscopy for monitoring chemical reactions on single optically trapped, solid-phase support particles.

PubMed

Houlne, Michael P; Sjostrom, Christopher M; Uibel, Rory H; Kleimeyer, James A; Harris, Joel M

2002-09-01

Optical trapping of small structures is a powerful tool for the manipulation and investigation of colloidal and particulate materials. The tight focus excitation requirements of optical trapping are well suited to confocal Raman microscopy. In this work, an inverted confocal Raman microscope is developed for studies of chemical reactions on single, optically trapped particles and applied to reactions used in solid-phase peptide synthesis. Optical trapping and levitation allow a particle to be moved away from the coverslip and into solution, avoiding fluorescence interference from the coverslip. More importantly, diffusion of reagents into the particle is not inhibited by a surface, so that reaction conditions mimic those of particles dispersed in solution. Optical trapping and levitation also maintain optical alignment, since the particle is centered laterally along the optical axis and within the focal plane of the objective, where both optical forces and light collection are maximized. Hour-long observations of chemical reactions on individual, trapped silica particles are reported. Using two-dimensional least-squares analysis methods, the Raman spectra collected during the course of a reaction can be resolved into component contributions. The resolved spectra of the time-varying species can be observed, as they bind to or cleave from the particle surface.

Gold nanoparticles: enhanced optical trapping and sensitivity coupled with significant heating.

PubMed

Seol, Yeonee; Carpenter, Amanda E; Perkins, Thomas T

2006-08-15

Gold nanoparticles appear to be superior handles in optical trapping assays. We demonstrate that relatively large gold particles (R(b)=50 nm) indeed yield a sixfold enhancement in trapping efficiency and detection sensitivity as compared to similar-sized polystyrene particles. However, optical absorption by gold at the most common trapping wavelength (1064 nm) induces dramatic heating (266 degrees C/W). We determined this heating by comparing trap stiffness from three different methods in conjunction with detailed modeling. Due to this heating, gold nanoparticles are not useful for temperature-sensitive optical-trapping experiments, but may serve as local molecular heaters. Also, such particles, with their increased detection sensitivity, make excellent probes for certain zero-force biophysical assays.

Method and apparatus for removing iodine from a nuclear reactor coolant

DOEpatents

Cooper, Martin H.

1980-01-01

A method and apparatus for removing iodine-131 and iodine-125 from a liquid sodium reactor coolant. Non-radioactive iodine is dissolved in hot liquid sodium to increase the total iodine concentration. Subsequent precipitation of the iodine in a cold trap removes both the radioactive iodine isotopes as well as the non-radioactive iodine.

Nano-optical conveyor belt, part I: Theory.

PubMed

Hansen, Paul; Zheng, Yuxin; Ryan, Jason; Hesselink, Lambertus

2014-06-11

We propose a method for peristaltic transport of nanoparticles using the optical force field over a nanostructured surface. Nanostructures may be designed to produce strong near-field hot spots when illuminated. The hot spots function as optical traps, separately addressable by their resonant wavelengths and polarizations. By activating closely packed traps sequentially, nanoparticles may be handed off between adjacent traps in a peristaltic fashion. A linear repeating structure of three separately addressable traps forms a "nano-optical conveyor belt"; a unit cell with four separately addressable traps permits controlled peristaltic transport in the plane. Using specifically designed activation sequences allows particle sorting.

Characterizing conical refraction optical tweezers.

PubMed

McDonald, C; McDougall, C; Rafailov, E; McGloin, D

2014-12-01

Conical refraction occurs when a beam of light travels through an appropriately cut biaxial crystal. By focusing the conically refracted beam through a high numerical aperture microscope objective, conical refraction optical tweezers can be created, allowing for particle manipulation in both Raman spots, and in the Lloyd/Poggendorff rings. We present a thorough quantification of the trapping properties of such a beam, focusing on the trap stiffness, and how this varies with trap power and trapped particle location. We show that the lower Raman spot can be thought of as a single-beam optical gradient force trap, while radiation pressure dominates in the upper Raman spot, leading to optical levitation rather than trapping. Particles in the Lloyd/Poggendorff rings experience a lower trap stiffness than particles in the lower Raman spot, but benefit from rotational control.

Characterizing conical refraction optical tweezers

NASA Astrophysics Data System (ADS)

McDonald, C.; McDougall, C.; Rafailov, E.; McGloin, D.

2014-12-01

Conical refraction occurs when a beam of light travels through an appropriately cut biaxial crystal. By focussing the conically refracted beam through a high numerical aperture microscope objective, conical refraction optical tweezers can be created, allowing for particle manipulation in both Raman spots and in the Lloyd/Poggendorff rings. We present a thorough quantification of the trapping properties of such a beam, focussing on the trap stiffness and how this varies with trap power and trapped particle location. We show that the lower Raman spot can be thought of as a single-beam optical gradient force trap, while radiation pressure dominates in the upper Raman spot, leading to optical levitation rather than trapping. Particles in the Lloyd/Poggendorff rings experience a lower trap stiffness than particles in the lower Raman spot but benefit from rotational control.

First Measurement of the Atomic Electric Dipole Moment of Ra 225

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parker, R. H.; Dietrich, M. R.; Kalita, M. R.

The radioactive radium-225 (Ra-225) atom is a favorable case to search for a permanent electric dipole moment. Because of its strong nuclear octupole deformation and large atomic mass, Ra-225 is particularly sensitive to interactions in the nuclear medium that violate both time-reversal symmetry and parity. We have developed a cold-atom technique to study the spin precession of Ra-225 atoms held in an optical dipole trap, and demonstrated the principle of this method by completing the first measurement of its atomic electric dipole moment, reaching an upper limit of vertical bar d(Ra-225)vertical bar < 5.0 x 10(-22) e cm (95% confidence).

High Optical Access Trap 2.0.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maunz, Peter Lukas Wilhelm

2016-01-26

The High Optical Access (HOA) trap was designed in collaboration with the Modular Universal Scalable Ion-trap Quantum Computer (MUSIQC) team, funded along with Sandia National Laboratories through IARPA's Multi Qubit Coherent Operations (MQCO) program. The design of version 1 of the HOA trap was completed in September 2012 and initial devices were completed and packaged in February 2013. The second version of the High Optical Access Trap (HOA-2) was completed in September 2014 and is available at IARPA's disposal.

Effects of coating on the optical trapping efficiency of microspheres via geometrical optics approximation.

PubMed

Park, Bum Jun; Furst, Eric M

2014-09-23

We present the optical trapping forces that are generated when a single laser beam strongly focuses on a coated dielectric microsphere. On the basis of geometrical optics approximation (GOA), in which a particle intercepts all of the rays that make up a single laser beam, we calculate the trapping forces with varying coating thickness and refractive index values. To increase the optical trapping efficiency, the refractive index (n(b)) of the coating is selected such that n(a) < n(b) < n(c), where na and nc are the refractive indices of the medium and the core material, respectively. The thickness of the coating also increases trapping efficiency. Importantly, we find that trapping forces for the coated particles are predominantly determined by two rays: the incident ray and the first refracted ray to the medium.

Production and characterization of a dual species magneto-optical trap of cesium and ytterbium.

PubMed

Kemp, S L; Butler, K L; Freytag, R; Hopkins, S A; Hinds, E A; Tarbutt, M R; Cornish, S L

2016-02-01

We describe an apparatus designed to trap and cool a Yb and Cs mixture. The apparatus consists of a dual species effusive oven source, dual species Zeeman slower, magneto-optical traps in a single ultra-high vacuum science chamber, and the associated laser systems. The dual species Zeeman slower is used to load sequentially the two species into their respective traps. Its design is flexible and may be adapted for other experiments with different mixtures of atomic species. The apparatus provides excellent optical access and can apply large magnetic bias fields to the trapped atoms. The apparatus regularly produces 10(8) Cs atoms at 13.3 μK in an optical molasses, and 10(9) (174)Y b atoms cooled to 22 μK in a narrowband magneto-optical trap.

Laser cooling and imaging of individual radioactive +90Sr ions

NASA Astrophysics Data System (ADS)

Jung, Kyunghun; Iwata, Yoshihiro; Miyabe, Masabumi; Yamamoto, Kazuhiro; Yonezu, Tomohisa; Wakaida, Ikuo; Hasegawa, Shuichi

2017-10-01

We have developed an apparatus integrating resonance-ionization, ion-trap, and laser-cooling techniques for an ultratrace radioactive isotope 90Sr analysis. Trapped +90Sr isotope ions were laser cooled, and their 4 d 3/2 2D →5 p 1/2 2P transition isotope shift was experimentally measured to be -281 (17 ) MHz by comparing individual spectra of +88Sr and +90Sr ions. Crystallization of +90Sr was carried out using the resonance frequency value confirmed in our experiment, and then +90Sr individual ions were successfully observed.

Non-Evaporative Cooling Using Spin-Exchange Collision in an Optical Trap

DTIC Science & Technology

2009-02-03

transit time of the atoms across the optical trap should damp the atoms’ motion significantly. These processes are described in detail in Ref. [ 18]. The...potentials. Finally, since the optical trap was very shallow compared to a MOT, any light-assisted collision that resulted in almost any net acceleration...EXCHANGE COLLISION IN AN OPTICAL TRAP 5a. CONTRACT NUMBER FA9550-06-1-0190 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S

Submillikelvin Dipolar Molecules in a Radio-Frequency Magneto-Optical Trap.

PubMed

Norrgard, E B; McCarron, D J; Steinecker, M H; Tarbutt, M R; DeMille, D

2016-02-12

We demonstrate a scheme for magneto-optically trapping strontium monofluoride (SrF) molecules at temperatures one order of magnitude lower and phase space densities 3 orders of magnitude higher than obtained previously with laser-cooled molecules. In our trap, optical dark states are destabilized by rapidly and synchronously reversing the trapping laser polarizations and the applied magnetic field gradient. The number of molecules and trap lifetime are also significantly improved from previous work by loading the trap with high laser power and then reducing the power for long-term trapping. With this procedure, temperatures as low as 400  μK are achieved.

Stability of aerosol droplets in Bessel beam optical traps under constant and pulsed external forces

NASA Astrophysics Data System (ADS)

David, Grégory; Esat, Kıvanç; Hartweg, Sebastian; Cremer, Johannes; Chasovskikh, Egor; Signorell, Ruth

2015-04-01

We report on the dynamics of aerosol droplets in optical traps under the influence of additional constant and pulsed external forces. Experimental results are compared with simulations of the three-dimensional droplet dynamics for two types of optical traps, the counter-propagating Bessel beam (CPBB) trap and the quadruple Bessel beam (QBB) trap. Under the influence of a constant gas flow (constant external force), the QBB trap is found to be more stable compared with the CPBB trap. By contrast, under pulsed laser excitation with laser pulse durations of nanoseconds (pulsed external force), the type of trap is of minor importance for the droplet stability. It typically needs pulsed laser forces that are several orders of magnitude higher than the optical forces to induce escape of the droplet from the trap. If the droplet strongly absorbs the pulsed laser light, these escape forces can be strongly reduced. The lower stability of absorbing droplets is a result of secondary thermal processes that cause droplet escape.

Stability of aerosol droplets in Bessel beam optical traps under constant and pulsed external forces.

PubMed

David, Grégory; Esat, Kıvanç; Hartweg, Sebastian; Cremer, Johannes; Chasovskikh, Egor; Signorell, Ruth

2015-04-21

We report on the dynamics of aerosol droplets in optical traps under the influence of additional constant and pulsed external forces. Experimental results are compared with simulations of the three-dimensional droplet dynamics for two types of optical traps, the counter-propagating Bessel beam (CPBB) trap and the quadruple Bessel beam (QBB) trap. Under the influence of a constant gas flow (constant external force), the QBB trap is found to be more stable compared with the CPBB trap. By contrast, under pulsed laser excitation with laser pulse durations of nanoseconds (pulsed external force), the type of trap is of minor importance for the droplet stability. It typically needs pulsed laser forces that are several orders of magnitude higher than the optical forces to induce escape of the droplet from the trap. If the droplet strongly absorbs the pulsed laser light, these escape forces can be strongly reduced. The lower stability of absorbing droplets is a result of secondary thermal processes that cause droplet escape.

Compact setup for the production of {sup 87}Rb |F = 2, m{sub F} = + 2〉 Bose-Einstein condensates in a hybrid trap

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nolli, Raffaele; Venturelli, Michela; Marmugi, Luca, E-mail: l.marmugi@ucl.ac.uk

We present a compact experimental apparatus for Bose-Einstein condensation of {sup 87}Rb in the |F  =  2, m{sub F} = + 2〉 state. A pre-cooled atomic beam of {sup 87}Rb is obtained by using an unbalanced magneto-optical trap, allowing controlled transfer of trapped atoms from the first vacuum chamber to the science chamber. Here, atoms are transferred to a hybrid trap, as produced by overlapping a magnetic quadrupole trap with a far-detuned optical trap with crossed beam configuration, where forced radiofrequency evaporation is realized. The final evaporation leading to Bose-Einstein condensation is then performed by exponentially lowering the optical trapmore » depth. Control and stabilization systems of the optical trap beams are discussed in detail. The setup reliably produces a pure condensate in the |F = 2, m{sub F} = + 2〉 state in 50 s, which includes 33 s loading of the science magneto-optical trap and 17 s forced evaporation.« less

All-optical atom trap as a target for MOTRIMS-like collision experiments

NASA Astrophysics Data System (ADS)

Sharma, S.; Acharya, B. P.; De Silva, A. H. N. C.; Parris, N. W.; Ramsey, B. J.; Romans, K. L.; Dorn, A.; de Jesus, V. L. B.; Fischer, D.

2018-04-01

Momentum-resolved scattering experiments with laser-cooled atomic targets have been performed since almost two decades with magneto-optical trap recoil ion momentum spectroscopy (MOTRIMS) setups. Compared to experiments with gas-jet targets, MOTRIMS features significantly lower target temperatures allowing for an excellent recoil ion momentum resolution. However, the coincident and momentum-resolved detection of electrons was long rendered impossible due to incompatible magnetic field requirements. Here we report on an experimental approach which is based on an all-optical 6Li atom trap that—in contrast to magneto-optical traps—does not require magnetic field gradients in the trapping region. Atom temperatures of about 2 mK and number densities up to 109 cm-3 make this trap ideally suited for momentum-resolved electron-ion coincidence experiments. The overall configuration of the trap is very similar to conventional magneto-optical traps. It mainly requires small modifications of laser beam geometries and polarization which makes it easily implementable in other existing MOTRIMS experiments.

Non-contact fiber-optical trapping of motile bacteria: dynamics observation and energy estimation

PubMed Central

Xin, Hongbao; Liu, Qingyuan; Li, Baojun

2014-01-01

The dynamics and energy conversion of bacteria are strongly associated with bacterial activities, such as survival, spreading of bacterial diseases and their pathogenesis. Although different discoveries have been reported on trapped bacteria (i.e. immobilized bacteria), the investigation on the dynamics and energy conversion of motile bacteria in the process of trapping is highly desirable. Here, we report a non-contact optical trapping of motile bacteria using a modified tapered optical fiber. Using Escherichia coli as an example, both single and multiple motile bacteria have been trapped and manipulated in a non-contact manner. Bacterial dynamics has been observed and bacterial energy has been estimated in the trapping process. This non-contact optical trapping provides a new opportunity for better understanding the bacterial dynamics and energy conversion at the single cell level. PMID:25300713

Quantum Error Correction with a Globally-Coupled Array of Neutral Atom Qubits

DTIC Science & Technology

2013-02-01

magneto - optical trap ) located at the center of the science cell. Fluorescence...Bottle beam trap GBA Gaussian beam array EMCCD electron multiplying charge coupled device microsec. microsecond MOT Magneto - optical trap QEC quantum error correction qubit quantum bit ...developed and implemented an array of neutral atom qubits in optical traps for studies of quantum error correction. At the end of the three year

Intracavity optical trapping with Ytterbium doped fiber ring laser

NASA Astrophysics Data System (ADS)

Sayed, Rania; Kalantarifard, Fatemeh; Elahi, Parviz; Ilday, F. Omer; Volpe, Giovanni; Maragò, Onofrio M.

2013-09-01

We propose a novel approach for trapping micron-sized particles and living cells based on optical feedback. This approach can be implemented at low numerical aperture (NA=0.5, 20X) and long working distance. In this configuration, an optical tweezers is constructed inside a ring cavity fiber laser and the optical feedback in the ring cavity is controlled by the light scattered from a trapped particle. In particular, once the particle is trapped, the laser operation, optical feedback and intracavity power are affected by the particle motion. We demonstrate that using this configuration is possible to stably hold micron-sized particles and single living cells in the focal spot of the laser beam. The calibration of the optical forces is achieved by tracking the Brownian motion of a trapped particle or cell and analysing its position distribution.

A Novel Gravito-Optical Surface Trap for Neutral Atoms

NASA Astrophysics Data System (ADS)

Xie, Chun-Xia; Wang, Zhengling; Yin, Jian-Ping

2006-04-01

We propose a novel gravito-optical surface trap (GOST) for neutral atoms based on one-dimensional intensity gradient cooling. The surface optical trap is composed of a blue-detuned reduced semi-Gaussian laser beam (SGB), a far-blue-detuned dark hollow beam and the gravity field. The SGB is produced by the diffraction of a collimated Gaussian laser beam passing through the straight edge of a semi-infinite opaque plate and then is reduced by an imaging lens. We calculate the intensity distribution of the reduced SGB, and study the dynamic process of the SGB intensity-gradient induced Sisyphus cooling for 87Rb atoms by using Monte Carlo simulations. Our study shows that the proposed GOST can be used not only to trap cold atoms loaded from a standard magneto-optical trap, but also to cool the trapped atoms to an equilibrium temperature of 3.47 μK from ~120 μK, even to realize an all-optical two-dimensional Bose-Einstein condensation by using optical-potential evaporative cooling.

Mode division multiplexing technology for single-fiber optical trapping axial-position adjustment.

PubMed

Liu, Zhihai; Wang, Lei; Liang, Peibo; Zhang, Yu; Yang, Jun; Yuan, Libo

2013-07-15

We demonstrate trapped yeast cell axial-position adjustment without moving the optical fiber in a single-fiber optical trapping system. The dynamic axial-position adjustment is realized by controlling the power ratio of the fundamental mode beam (LP01) and the low-order mode beam (LP11) generated in a normal single-core fiber. In order to separate the trapping positions produced by the two mode beams, we fabricate a special fiber tapered tip with a selective two-step method. A yeast cell of 6 μm diameter is moved along the optical axis direction for a distance of ~3 μm. To the best of our knowledge, this is the first demonstration of the trapping position adjustment without moving the fiber for single-fiber optical tweezers. The excitation and utilization of multimode beams in a single fiber constitutes a new development for single-fiber optical trapping and makes possible more practical applications in biomedical research fields.

Dynamics of trapped atoms around an optical nanofiber probed through polarimetry.

PubMed

Solano, Pablo; Fatemi, Fredrik K; Orozco, Luis A; Rolston, S L

2017-06-15

The evanescent field outside an optical nanofiber (ONF) can create optical traps for neutral atoms. We present a non-destructive method to characterize such trapping potentials. An off-resonance linearly polarized probe beam that propagates through the ONF experiences a slow axis of polarization produced by trapped atoms on opposite sides along the ONF. The transverse atomic motion is imprinted onto the probe polarization through the changing atomic index of refraction. By applying a transient impulse, we measure a time-dependent polarization rotation of the probe beam that provides both a rapid and non-destructive measurement of the optical trapping frequencies.

The temporal evolution process from fluorescence bleaching to clean Raman spectra of single solid particles optically trapped in air

NASA Astrophysics Data System (ADS)

Gong, Zhiyong; Pan, Yong-Le; Videen, Gorden; Wang, Chuji

2017-12-01

We observe the entire temporal evolution process of fluorescence and Raman spectra of single solid particles optically trapped in air. The spectra initially contain strong fluorescence with weak Raman peaks, then the fluorescence was bleached within seconds, and finally only the clean Raman peaks remain. We construct an optical trap using two counter-propagating hollow beams, which is able to stably trap both absorbing and non-absorbing particles in air, for observing such temporal processes. This technique offers a new method to study dynamic changes in the fluorescence and Raman spectra from a single optically trapped particle in air.

Torque Induced on Lipid Microtubules with Optical Tweezers

NASA Astrophysics Data System (ADS)

wichean, T. Na; Charrunchon, S.; Pattanaporkratana, A.; Limtrakul, J.; Chattham, N.

2017-09-01

Chiral Phospholipids are found self-assembled into cylindrical tubules of 500 nm in diameter by helical winding of bilayer stripes under cooling in ethanol and water solution. Theoretical prediction and experimental evidence reported so far confirmed the modulated tilt direction in a helical striped pattern of the tubules. This molecular orientation morphology results in optically birefringent tubules. We investigate an individual lipid microtubule under a single optical trap of 532 nm linearly polarized laser. Spontaneous rotation of a lipid tubule induced by radiation torque was observed with only one sense of rotation caused by chirality of a lipid tubule. Rotation discontinued once the high refractive index axis of a lipid tubule aligned with a polarization axis of the laser. We further explored a lipid tubule under circularly polarized optical trap. It was found that a lipid tubule was continuously rotated confirming the tubule birefringent property. We modified the shape of optical trap by cylindrical lens obtaining an elliptical profile optical trap. A lipid tubule can be aligned along the elongated length of optical trap. We reported an investigation of competition between polarized light torque on a birefringent lipid tubule versus torque from intensity gradient of an elongated optical trap.

Assembling mesoscopic particles by various optical schemes

NASA Astrophysics Data System (ADS)

Fournier, Jean-Marc; Rohner, Johann; Jacquot, Pierre; Johann, Robert; Mias, Solon; Salathé, René-P.

2005-08-01

Shaping optical fields is the key issue in the control of optical forces that pilot the manipulation of mesoscopic polarizable dielectric particles. The latter can be positioned according to endless configurations. The scope of this paper is to review and discuss several unusual designs which produce what we think are among some of the most interesting arrangements. The simplest schemes result from interference between two or several coherent light beams, leading to periodic as well as pseudo-periodic arrays of optical traps. Complex assemblages of traps can be created with holographic-type set-ups; this case is widely used by the trapping community. Clusters of traps can also be configured through interferometric-type set-ups or by generating external standing waves by diffractive elements. The particularly remarkable possibilities of the Talbot effect to generate three-dimensional optical lattices and several schemes of self-organization represent further very interesting means for trapping. They will also be described and discussed. in this paper. The mechanisms involved in those trapping schemes do not require the use of high numerical aperture optics; by avoiding the need for bulky microscope objectives, they allow for more physical space around the trapping area to perform experiments. Moreover, very large regular arrays of traps can be manufactured, opening numerous possibilities for new applications.

Computer simulation on the collision-sticking dynamics of two colloidal particles in an optical trap.

PubMed

Xu, Shenghua; Sun, Zhiwei

2007-04-14

Collisions of a particle pair induced by optical tweezers have been employed to study colloidal stability. In order to deepen insights regarding the collision-sticking dynamics of a particle pair in the optical trap that were observed in experimental approaches at the particle level, the authors carry out a Brownian dynamics simulation. In the simulation, various contributing factors, including the Derjaguin-Landau-Verwey-Overbeek interaction of particles, hydrodynamic interactions, optical trapping forces on the two particles, and the Brownian motion, were all taken into account. The simulation reproduces the tendencies of the accumulated sticking probability during the trapping duration for the trapped particle pair described in our previous study and provides an explanation for why the two entangled particles in the trap experience two different statuses.

Magneto-optical trap for thulium atoms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sukachev, D.; Sokolov, A.; Chebakov, K.

2010-07-15

Thulium atoms are trapped in a magneto-optical trap using a strong transition at 410 nm with a small branching ratio. We trap up to 7x10{sup 4} atoms at a temperature of 0.8(2) mK after deceleration in a 40-cm-long Zeeman slower. Optical leaks from the cooling cycle influence the lifetime of atoms in the magneto-optical trap which varies between 0.3 and 1.5 s in our experiments. The lower limit for the leaking rate from the upper cooling level is measured to be 22(6) s{sup -1}. The repumping laser transferring the atomic population out of the F=3 hyperfine ground-state sublevel gives amore » 30% increase for the lifetime and the number of atoms in the trap.« less

A cooler Penning trap for the TITAN mass measurement facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chowdhury, U.; Kootte, B.; Good, M.

The TITAN facility at TRIUMF makes use of highly charged ions, charge-bred in an electron beam ion trap, to carry out accurate mass measurements on radioactive isotopes. We report on our progress to develop a cooler Penning trap, CPET, which aims at reducing the energy spread of the ions to ≈ 1 eV/charge prior to injection into the mass measurement trap. In off-line mode, we can now trap electron plasmas for minutes, and we observe the damping of the m = 1 diocotron plasma mode within ≈ 2 s.

Stability of aerosol droplets in Bessel beam optical traps under constant and pulsed external forces

DOE Office of Scientific and Technical Information (OSTI.GOV)

David, Grégory; Esat, Kıvanç; Hartweg, Sebastian

We report on the dynamics of aerosol droplets in optical traps under the influence of additional constant and pulsed external forces. Experimental results are compared with simulations of the three-dimensional droplet dynamics for two types of optical traps, the counter-propagating Bessel beam (CPBB) trap and the quadruple Bessel beam (QBB) trap. Under the influence of a constant gas flow (constant external force), the QBB trap is found to be more stable compared with the CPBB trap. By contrast, under pulsed laser excitation with laser pulse durations of nanoseconds (pulsed external force), the type of trap is of minor importance formore » the droplet stability. It typically needs pulsed laser forces that are several orders of magnitude higher than the optical forces to induce escape of the droplet from the trap. If the droplet strongly absorbs the pulsed laser light, these escape forces can be strongly reduced. The lower stability of absorbing droplets is a result of secondary thermal processes that cause droplet escape.« less

Optical levitation particle delivery system for a dual beam fiber optic trap.

PubMed

Gauthier, R C; Frangioudakis, A

2000-01-01

We combine a radiation-pressure-based levitation system with a dual fiber, laser trapping system to demonstrate the potential of delivering single particles into the fiber trap. The forces versus position and the trajectory of the particle subjected to the laser beams are examined with an enhanced ray optics model. A sequence of video images taken from the experimental apparatus demonstrates the principle of particle delivery, trapping, and further manipulation.

Silicon-on-insulator multimode-interference waveguide-based arrayed optical tweezers (SMART) for two-dimensional microparticle trapping and manipulation.

PubMed

Lei, Ting; Poon, Andrew W

2013-01-28

We demonstrate two-dimensional optical trapping and manipulation of 1 μm and 2.2 μm polystyrene particles in an 18 μm-thick fluidic cell at a wavelength of 1565 nm using the recently proposed Silicon-on-insulator Multimode-interference (MMI) waveguide-based ARrayed optical Tweezers (SMART) technique. The key component is a 100 μm square-core silicon waveguide with mm length. By tuning the fiber-coupling position at the MMI waveguide input facet, we demonstrate various patterns of arrayed optical tweezers that enable optical trapping and manipulation of particles. We numerically simulate the physical mechanisms involved in the arrayed trap, including the optical force, the heat transfer and the thermal-induced microfluidic flow.

Brownian motion of graphene.

PubMed

Maragó, Onofrio M; Bonaccorso, Francesco; Saija, Rosalba; Privitera, Giulia; Gucciardi, Pietro G; Iatì, Maria Antonia; Calogero, Giuseppe; Jones, Philip H; Borghese, Ferdinando; Denti, Paolo; Nicolosi, Valeria; Ferrari, Andrea C

2010-12-28

Brownian motion is a manifestation of the fluctuation-dissipation theorem of statistical mechanics. It regulates systems in physics, biology, chemistry, and finance. We use graphene as prototype material to unravel the consequences of the fluctuation-dissipation theorem in two dimensions, by studying the Brownian motion of optically trapped graphene flakes. These orient orthogonal to the light polarization, due to the optical constants anisotropy. We explain the flake dynamics in the optical trap and measure force and torque constants from the correlation functions of the tracking signals, as well as comparing experiments with a full electromagnetic theory of optical trapping. The understanding of optical trapping of two-dimensional nanostructures gained through our Brownian motion analysis paves the way to light-controlled manipulation and all-optical sorting of biological membranes and anisotropic macromolecules.

Single-ion, transportable optical atomic clocks

NASA Astrophysics Data System (ADS)

Delehaye, Marion; Lacroûte, Clément

2018-03-01

For the past 15 years, tremendous progress within the fields of laser stabilization, optical frequency combs and atom cooling and trapping have allowed the realization of optical atomic clocks with unrivaled performances. These instruments can perform frequency comparisons with fractional uncertainties well below ?, finding applications in fundamental physics tests, relativistic geodesy and time and frequency metrology. Even though most optical clocks are currently laboratory setups, several proposals for using these clocks for field measurements or within an optical clock network have been published, and most of time and frequency metrology institutes have started to develop transportable optical clocks. For the purpose of this special issue, we chose to focus on trapped-ion optical clocks. Even though their short-term fractional frequency stability is impaired by a lower signal-to-noise ratio, they offer a high potential for compactness: trapped ions demand low optical powers and simple loading schemes, and can be trapped in small vacuum chambers. We review recent advances on the clock key components, including ion trap and ultra-stable optical cavity, as well as existing projects and experiments which draw the picture of what future transportable, single-ion optical clocks may resemble.

Tune-out wavelengths and landscape-modulated polarizabilities of alkali-metal Rydberg atoms in infrared optical lattices

NASA Astrophysics Data System (ADS)

Topcu, Turker; Derevianko, Andrei

2013-11-01

Intensity-modulated optical lattice potentials can change sign for an alkali-metal Rydberg atom, and the atoms are not always attracted to intensity minima in optical lattices with wavelengths near the CO2 laser band. Here we demonstrate that such IR lattices can be tuned so that the trapping potential experienced by the Rydberg atom can be made to vanish for atoms in “targeted” Rydberg states. Such state-selective trapping of Rydberg atoms can be useful in controlled cold Rydberg collisions, cooling Rydberg states, and species-selective trapping and transport of Rydberg atoms in optical lattices. We tabulate wavelengths at which the trapping potential vanishes for the ns, np, and nd Rydberg states of Na and Rb atoms and discuss advantages of using such optical lattices for state-selective trapping of Rydberg atoms. We also develop exact analytical expressions for the lattice-induced polarizability for the mz=0 Rydberg states and derive an accurate formula predicting tune-out wavelengths at which the optical trapping potential becomes invisible to Rydberg atoms in targeted l=0 states.

Optical trapping of metal-dielectric nanoparticle clusters near photonic crystal microcavities.

PubMed

Mejia, Camilo A; Huang, Ningfeng; Povinelli, Michelle L

2012-09-01

We predict the formation of optically trapped, metal-dielectric nanoparticle clusters above photonic crystal microcavities. We determine the conditions on particle size and position for a gold particle to be trapped above the microcavity. We then show that strong field redistribution and enhancement near the trapped gold nanoparticle results in secondary trapping sites for a pair of dielectric nanoparticles.

Physiological Monitoring of Optically Trapped Cells: Studying the Effects of Confinement by 1064 NM Lazer Tweezers Using Microfluorometry

NASA Astrophysics Data System (ADS)

Liu, Yagang

A novel technique that combines microfluorometric detection and optical laser trapping has been developed for in-situ assessing the physiological state of an optically trapped biological sample. This optical diagnostic technique achieves high sensitivity (>30 dB signal -to-noise ratio) and high spatial resolution (~ 1 μm) over a broad spectral range (>400 nm). The fluorescence spectra derived from exogenous fluorescent probes, including laurdan, acridine orange, propidium iodide and Snarf, are used to assess the effects of optical confinement with respect to temperature, DNA structure, cell viability, and intracellular pH, respectively. In the latter three cases, fluorescence is excited via a two-photon absorption process, using the cw laser trap itself as the fluorescence excitation source. This enables the cw near infrared laser trapping beam to be used simultaneously as an optical diagnostic probe as well as an optical micromanipulator. Using microfluorometry, a temperature increase of less than several degrees centigrade was measured for test samples, including liposomes, Chinese hamster ovary (CHO) cells and human sperm cells that were held stationary by 1064 nm optical tweezers having a power density of ~10^7 W/cm^2. Additional physiological monitoring experiments indicated that there is no observable denaturation of DNA, or change of intracellular pH under typical continuous wave laser trapping conditions (P <= 400 mW). Under some circumstances, however, it was possible to achieve a decrease in cell viability with cw trapping, as monitored by a live/dead vital stain. In comparison, significant DNA denaturation and cellular physiological changes (e.g. cell death) were observed when a Q-switched pulsed laser at a threshold of ~30mu J/pulse was used as trapping source. These results generally support the conclusion that cw laser trapping at 1064 nm wavelength is a safe, non-invasive process and should prove to be of great value for understanding the mechanisms of laser microirradiation effects on living cells held stationary in a near-infrared trapping beam.

Nanonewton optical force trap employing anti-reflection coated, high-refractive-index titania microspheres

NASA Astrophysics Data System (ADS)

Jannasch, Anita; Demirörs, Ahmet F.; van Oostrum, Peter D. J.; van Blaaderen, Alfons; Schäffer, Erik

2012-07-01

Optical tweezers are exquisite position and force transducers and are widely used for high-resolution measurements in fields as varied as physics, biology and materials science. Typically, small dielectric particles are trapped in a tightly focused laser and are often used as handles for sensitive force measurements. Improvement to the technique has largely focused on improving the instrument and shaping the light beam, and there has been little work exploring the benefit of customizing the trapped object. Here, we describe how anti-reflection coated, high-refractive-index core-shell particles composed of titania enable single-beam optical trapping with an optical force greater than a nanonewton. The increased force range broadens the scope of feasible optical trapping experiments and will pave the way towards more efficient light-powered miniature machines, tools and applications.

Deep cooling of optically trapped atoms implemented by magnetic levitation without transverse confinement.

PubMed

Li, Chen; Zhou, Tianwei; Zhai, Yueyang; Xiang, Jinggang; Luan, Tian; Huang, Qi; Yang, Shifeng; Xiong, Wei; Chen, Xuzong

2017-05-01

We report a setup for the deep cooling of atoms in an optical trap. The deep cooling is implemented by eliminating the influence of gravity using specially constructed magnetic coils. Compared to the conventional method of generating a magnetic levitating force, the lower trap frequency achieved in our setup provides a lower limit of temperature and more freedoms to Bose gases with a simpler solution. A final temperature as low as ∼6nK is achieved in the optical trap, and the atomic density is decreased by nearly two orders of magnitude during the second stage of evaporative cooling. This deep cooling of optically trapped atoms holds promise for many applications, such as atomic interferometers, atomic gyroscopes, and magnetometers, as well as many basic scientific research directions, such as quantum simulations and atom optics.

Deep cooling of optically trapped atoms implemented by magnetic levitation without transverse confinement

NASA Astrophysics Data System (ADS)

Li, Chen; Zhou, Tianwei; Zhai, Yueyang; Xiang, Jinggang; Luan, Tian; Huang, Qi; Yang, Shifeng; Xiong, Wei; Chen, Xuzong

2017-05-01

We report a setup for the deep cooling of atoms in an optical trap. The deep cooling is implemented by eliminating the influence of gravity using specially constructed magnetic coils. Compared to the conventional method of generating a magnetic levitating force, the lower trap frequency achieved in our setup provides a lower limit of temperature and more freedoms to Bose gases with a simpler solution. A final temperature as low as ˜ 6 nK is achieved in the optical trap, and the atomic density is decreased by nearly two orders of magnitude during the second stage of evaporative cooling. This deep cooling of optically trapped atoms holds promise for many applications, such as atomic interferometers, atomic gyroscopes, and magnetometers, as well as many basic scientific research directions, such as quantum simulations and atom optics.

Loading an Optical Trap with Diamond Nanocrystals Containing Nitrogen-Vacancy Centers from a Surface

NASA Astrophysics Data System (ADS)

Hsu, Jen-Feng; Ji, Peng; Dutt, M. V. Gurudev; D'Urso, Brian R.

2015-03-01

We present a simple and effective method of loading particles into an optical trap. Our primary application of this method is loading photoluminescent material, such as diamond nanocrystals containing nitrogen-vacancy (NV) centers, for coupling the mechanical motion of the trapped crystal with the spin of the NV centers. Highly absorptive material at the trapping laser frequency, such as tartrazine dye, is used as media to attach nanodiamonds and burn into a cloud of air-borne particles as the material is swept near the trapping laser focus on a glass slide. Particles are then trapped with the laser used for burning or transferred to a second laser trap at a different wavelength. Evidence of successful loading diamond nanocrystals into the trap presented includes high sensitivity of the photoluminecscence (PL) to the excitation laser and the PL spectra of the optically trapped particles

Near real-time measurement of forces applied by an optical trap to a rigid cylindrical object

NASA Astrophysics Data System (ADS)

Glaser, Joseph; Hoeprich, David; Resnick, Andrew

2014-07-01

An automated data acquisition and processing system is established to measure the force applied by an optical trap to an object of unknown composition in real time. Optical traps have been in use for the past 40 years to manipulate microscopic particles, but the magnitude of applied force is often unknown and requires extensive instrument characterization. Measuring or calculating the force applied by an optical trap to nonspherical particles presents additional difficulties which are also overcome with our system. Extensive experiments and measurements using well-characterized objects were performed to verify the system performance.

Crosstalk elimination in the detection of dual-beam optical tweezers by spatial filtering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ott, Dino; Oddershede, Lene B., E-mail: oddershede@nbi.dk; Reihani, S. Nader S.

2014-05-15

In dual-beam optical tweezers, the accuracy of position and force measurements is often compromised by crosstalk between the two detected signals, this crosstalk leading to systematic and significant errors on the measured forces and distances. This is true both for dual-beam optical traps where the splitting of the two traps is done by polarization optics and for dual optical traps constructed by other methods, e.g., holographic tweezers. If the two traps are orthogonally polarized, most often crosstalk is minimized by inserting polarization optics in front of the detector; however, this method is not perfect because of the de-polarization of themore » trapping beam introduced by the required high numerical aperture optics. Here we present a simple and easy-to-implement method to efficiently eliminate crosstalk. The method is based on spatial filtering by simply inserting a pinhole at the correct position and is highly compatible with standard back focal plane photodiode based detection of position and force. Our spatial filtering method reduces crosstalk up to five times better than polarization filtering alone. The effectiveness is dependent on pinhole size and distance between the traps and is here quantified experimentally and reproduced by theoretical modeling. The method here proposed will improve the accuracy of force-distance measurements, e.g., of single molecules, performed by dual-beam optical traps and hence give much more scientific value for the experimental efforts.« less

Optical trapping and optical force positioning of two-dimensional materials.

PubMed

Donato, M G; Messina, E; Foti, A; Smart, T J; Jones, P H; Iatì, M A; Saija, R; Gucciardi, P G; Maragò, O M

2018-01-18

In recent years, considerable effort has been devoted to the synthesis and characterization of two-dimensional materials. Liquid phase exfoliation (LPE) represents a simple, large-scale method to exfoliate layered materials down to mono- and few-layer flakes. In this context, the contactless trapping, characterization, and manipulation of individual nanosheets hold perspectives for increased accuracy in flake metrology and the assembly of novel functional materials. Here, we use optical forces for high-resolution structural characterization and precise mechanical positioning of nanosheets of hexagonal boron nitride, molybdenum disulfide, and tungsten disulfide obtained by LPE. Weakly optically absorbing nanosheets of boron nitride are trapped in optical tweezers. The analysis of the thermal fluctuations allows a direct measurement of optical forces and the mean flake size in a liquid environment. Measured optical trapping constants are compared with T-matrix light scattering calculations to show a quadratic size scaling for small size, as expected for a bidimensional system. In contrast, strongly absorbing nanosheets of molybdenum disulfide and tungsten disulfide are not stably trapped due to the dominance of radiation pressure over the optical trapping force. Thus, optical forces are used to pattern a substrate by selectively depositing nanosheets in short times (minutes) and without any preparation of the surface. This study will be useful for improving ink-jet printing and for a better engineering of optoelectronic devices based on two-dimensional materials.

Measuring the charge density of a tapered optical fiber using trapped microparticles.

PubMed

Kamitani, Kazuhiko; Muranaka, Takuya; Takashima, Hideaki; Fujiwara, Masazumi; Tanaka, Utako; Takeuchi, Shigeki; Urabe, Shinji

2016-03-07

We report the measurements of charge density of tapered optical fibers using charged particles confined in a linear Paul trap at ambient pressure. A tapered optical fiber is placed across the trap axis at a right angle, and polystyrene microparticles are trapped along the trap axis. The distance between the equilibrium position of a positively charged particle and the tapered fiber is used to estimate the amount of charge per unit length of the fiber without knowing the amount of charge of the trapped particle. The charge per unit length of a tapered fiber with a diameter of 1.6 μm was measured to be 2-1+3×10 -11 C/m.

A new route to the stable capture and final immobilization of radioactive cesium.

PubMed

Yang, Jae Hwan; Han, Ahreum; Yoon, Joo Young; Park, Hwan-Seo; Cho, Yung-Zun

2017-10-05

Radioactive Cs released from damaged fuel materials in the event of nuclear accidents must be controlled to prevent the spreading of hazardous Cs into the environment. This study describes a simple and novel process to safely manage Cs gas by capturing it within ceramic filters and converting it into monolithic waste forms. The results of Cs trapping tests showed that CsAlSiO 4 was a reaction product of gas-solid reactions between Cs gas and our ceramic filters. Monolithic waste forms were readily prepared from the Cs-trapping filters by the addition of a glass frit followed by thermal treatment at 1000°C for 3h. Major findings revealed that the Cs-trapping filters could be added up to 50wt% to form durable monoliths. In 30-50wt% of waste fraction, CsAlSiO 4 was completely converted to pollucite (CsAlSi 2 O 6 ), which is a potential phase for radioactive Cs due to its excellent thermal and chemical stability. A static leaching test for 28 d confirmed the excellent chemical resistance of the pollucite structure, with a Cs leaching rate as low as 7.21×10 -5 gm -2 /d. This simple scheme of waste processing promises a new route for radioactive Cs immobilization by synthesizing pollucite-based monoliths. Copyright © 2017 Elsevier B.V. All rights reserved.

Optical Trap Kits: Issues to Be Aware of

ERIC Educational Resources Information Center

Alexeev, I.; Quentin, U.; Leitz, K. -H.; Schmidt, M.

2012-01-01

An inexpensive and robust optical trap system can be built from off-the-shelf optical and opto-mechanical components or acquired as a kit to be assembled in a laboratory. The primary advantages of such a trap, besides being significantly more affordable, are its flexibility, and ease of modification and upgrade. In this paper, we consider several…

Chemical characterization of single micro- and nano-particles by optical catapulting-optical trapping-laser-induced breakdown spectroscopy

NASA Astrophysics Data System (ADS)

Fortes, Francisco J.; Fernández-Bravo, Angel; Javier Laserna, J.

2014-10-01

Spectral identification of individual micro- and nano-sized particles by the sequential intervention of optical catapulting, optical trapping and laser-induced breakdown spectroscopy is presented. The three techniques are used for different purposes. Optical catapulting (OC) serves to put the particulate material under inspection in aerosol form. Optical trapping (OT) permits the isolation and manipulation of individual particles from the aerosol, which are subsequently analyzed by laser-induced breakdown spectroscopy (LIBS). Once catapulted, the dynamics of particle trapping depends both on the laser beam characteristics (power and intensity gradient) and on the particle properties (size, mass and shape). Particles are stably trapped in air at atmospheric pressure and can be conveniently manipulated for a precise positioning for LIBS analysis. The spectra acquired from the individually trapped particles permit a straightforward identification of the material inspected. Variability of LIBS signal for the inspection of Ni microspheres was 30% relative standard deviation. OC-OT-LIBS permits the separation of particles in a heterogeneous mixture and the subsequent analysis of the isolated particle of interest. In order to evaluate the sensitivity of the approach, the number of absolute photons emitted by a single trapped particle was calculated. The limit of detection (LOD) for Al2O3 particles was calculated to be 200 attograms aluminium.

Improved Radio-Frequency Magneto-Optical Trap of SrF Molecules.

PubMed

Steinecker, Matthew H; McCarron, Daniel J; Zhu, Yuqi; DeMille, David

2016-11-18

We report the production of ultracold, trapped strontium monofluoride (SrF) molecules with number density and phase-space density significantly higher than previously achieved. These improvements are enabled by three distinct changes to our recently-demonstrated scheme for radio-frequency magneto-optical trapping of SrF: modification of the slowing laser beam geometry, addition of an optical pumping laser, and incorporation of a compression stage to the magneto-optical trap. With these improvements, we observe a trapped sample of SrF molecules at density 2.5×10 5  cm -3 and phase-space density 6×10 -14 , each a factor of 4 greater than in previous work. Under different experimental conditions, we observe trapping of up to 10 4 molecules, a factor of 5 greater than in previous work. Finally, by reducing the intensity of the applied trapping light, we observe molecular temperatures as low as 250 μK. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhanced and selective optical trapping in a slot-graphite photonic crystal.

PubMed

Krishnan, Aravind; Huang, Ningfeng; Wu, Shao-Hua; Martínez, Luis Javier; Povinelli, Michelle L

2016-10-03

Applicability of optical trapping tools for nanomanipulation is limited by the available laser power and trap efficiency. We utilized the strong confinement of light in a slot-graphite photonic crystal to develop high-efficiency parallel trapping over a large area. The stiffness is 35 times higher than our previously demonstrated on-chip, near field traps. We demonstrate the ability to trap both dielectric and metallic particles of sub-micron size. We find that the growth kinetics of nanoparticle arrays on the slot-graphite template depends on particle size. This difference is exploited to selectively trap one type of particle out of a binary colloidal mixture, creating an efficient optical sieve. This technique has rich potential for analysis, diagnostics, and enrichment and sorting of microscopic entities.

Microrheometric upconversion-based techniques for intracellular viscosity measurements

NASA Astrophysics Data System (ADS)

Rodríguez-Sevilla, Paloma; Zhang, Yuhai; de Sousa, Nuno; Marqués, Manuel I.; Sanz-Rodríguez, Francisco; Jaque, Daniel; Liu, Xiaogang; Haro-González, Patricia

2017-08-01

Rheological parameters (viscosity, creep compliance and elasticity) play an important role in cell function and viability. For this reason different strategies have been developed for their study. In this work, two new microrheometric techniques are presented. Both methods take advantage of the analysis of the polarized emission of an upconverting particle to determine its orientation inside the optical trap. Upconverting particles are optical materials that are able to convert infrared radiation into visible light. Their usefulness has been further boosted by the recent demonstration of their three-dimensional control and tracking by single beam infrared optical traps. In this work it is demonstrated that optical torques are responsible of the stable orientation of the upconverting particle inside the trap. Moreover, numerical calculations and experimental data allowed to use the rotation dynamics of the optically trapped upconverting particle for environmental sensing. In particular, the cytoplasm viscosity could be measured by using the rotation time and thermal fluctuations of an intracellular optically trapped upconverting particle, by means of the two previously mentioned microrheometric techniques.

Optimizing phase to enhance optical trap stiffness.

PubMed

Taylor, Michael A

2017-04-03

Phase optimization offers promising capabilities in optical tweezers, allowing huge increases in the applied forces, trap stiff-ness, or measurement sensitivity. One key obstacle to potential applications is the lack of an efficient algorithm to compute an optimized phase profile, with enhanced trapping experiments relying on slow programs that would take up to a week to converge. Here we introduce an algorithm that reduces the wait from days to minutes. We characterize the achievable in-crease in trap stiffness and its dependence on particle size, refractive index, and optical polarization. We further show that phase-only control can achieve almost all of the enhancement possible with full wavefront shaping; for instance phase control allows 62 times higher trap stiffness for 10 μm silica spheres in water, while amplitude control and non-trivial polarization further increase this by 1.26 and 1.01 respectively. This algorithm will facilitate future applications in optical trapping, and more generally in wavefront optimization.

Light trapping structures in wing scales of butterfly Trogonoptera brookiana.

PubMed

Han, Zhiwu; Niu, Shichao; Shang, Chunhui; Liu, Zhenning; Ren, Luquan

2012-04-28

The fine optical structures in wing scales of Trogonoptera brookiana, a tropical butterfly exhibiting efficient light trapping effect, were carefully examined and the reflectivity was measured using reflectance spectrometry. The optimized 3D configuration of the coupling structure was determined using SEM and TEM data, and the light trapping mechanism of butterfly scales was studied. It is found that the front and back sides of butterfly wings possess different light trapping structures, but both can significantly increase the optical path and thus result in almost total absorption of all incident light. An optical model was created to check the properties of this light trapping structure. The simulated reflectance spectra are in concordance with the experimental ones. The results reliably confirm that these structures induce efficient light trapping effect. This functional "biomimetic structure" would have a potential value in wide engineering and optical applications. This journal is © The Royal Society of Chemistry 2012

Raman Spectroscopy of Optically Trapped Single Biological Micro-Particles

PubMed Central

Redding, Brandon; Schwab, Mark J.; Pan, Yong-le

2015-01-01

The combination of optical trapping with Raman spectroscopy provides a powerful method for the study, characterization, and identification of biological micro-particles. In essence, optical trapping helps to overcome the limitation imposed by the relative inefficiency of the Raman scattering process. This allows Raman spectroscopy to be applied to individual biological particles in air and in liquid, providing the potential for particle identification with high specificity, longitudinal studies of changes in particle composition, and characterization of the heterogeneity of individual particles in a population. In this review, we introduce the techniques used to integrate Raman spectroscopy with optical trapping in order to study individual biological particles in liquid and air. We then provide an overview of some of the most promising applications of this technique, highlighting the unique types of measurements enabled by the combination of Raman spectroscopy with optical trapping. Finally, we present a brief discussion of future research directions in the field. PMID:26247952

Molecular dynamics in an optical trap of glutamate receptors labeled with quantum-dots on living neurons

NASA Astrophysics Data System (ADS)

Kishimoto, Tatsunori; Maezawa, Yasuyo; Kudoh, Suguru N.; Taguchi, Takahisa; Hosokawa, Chie

2017-04-01

Molecular dynamics of glutamate receptor, which is major neurotransmitter receptor at excitatory synapse located on neuron, is essential for synaptic plasticity in the complex neuronal networks. Here we studied molecular dynamics in an optical trap of AMPA-type glutamate receptor (AMPAR) labeled with quantum-dot (QD) on living neuronal cells with fluorescence imaging and fluorescence correlation spectroscopy (FCS). When a 1064-nm laser beam for optical trapping was focused on QD-AMPARs located on neuronal cells, the fluorescence intensity of QD-AMPARs gradually increased at the focal spot. Using single-particle tracking of QD-AMPARs on neurons, the average diffusion coefficient decreased in an optical trap. Moreover, the decay time obtained from FCS analysis increased with the laser power and the initial assembling state of AMPARs depended on culturing day, suggesting that the motion of QD-AMPAR was constrained in an optical trap.

High-resolution dual-trap optical tweezers with differential detection: alignment of instrument components.

PubMed

Bustamante, Carlos; Chemla, Yann R; Moffitt, Jeffrey R

2009-10-01

Optical traps or "optical tweezers" have become an indispensable tool in understanding fundamental biological processes. Using our design, a dual-trap optical tweezers with differential detection, we can detect length changes to a DNA molecule tethering the trapped beads of 1 bp. By forming two traps from the same laser and maximizing the common optical paths of the two trapping beams, we decouple the instrument from many sources of environmental and instrumental noise that typically limit spatial resolution. The performance of a high-resolution instrument--the formation of strong traps, the minimization of background signals from trap movements, or the mitigation of the axial coupling, for example--can be greatly improved through careful alignment. This procedure, which is described in this article, starts from the laser and advances through the instrument, component by component. Alignment is complicated by the fact that the trapping light is in the near infrared (NIR) spectrum. Standard infrared viewing cards are commonly used to locate the beam, but unfortunately, bleach quickly. As an alternative, we use an IR-viewing charge-coupled device (CCD) camera equipped with a C-mount telephoto lens and display its image on a monitor. By visualizing the scattered light on a pair of irises of identical height separated by >12 in., the beam direction can be set very accurately along a fixed axis.

Optical Trapping of Ion Coulomb Crystals

NASA Astrophysics Data System (ADS)

Schmidt, Julian; Lambrecht, Alexander; Weckesser, Pascal; Debatin, Markus; Karpa, Leon; Schaetz, Tobias

2018-04-01

The electronic and motional degrees of freedom of trapped ions can be controlled and coherently coupled on the level of individual quanta. Assembling complex quantum systems ion by ion while keeping this unique level of control remains a challenging task. For many applications, linear chains of ions in conventional traps are ideally suited to address this problem. However, driven motion due to the magnetic or radio-frequency electric trapping fields sometimes limits the performance in one dimension and severely affects the extension to higher-dimensional systems. Here, we report on the trapping of multiple barium ions in a single-beam optical dipole trap without radio-frequency or additional magnetic fields. We study the persistence of order in ensembles of up to six ions within the optical trap, measure their temperature, and conclude that the ions form a linear chain, commonly called a one-dimensional Coulomb crystal. As a proof-of-concept demonstration, we access the collective motion and perform spectrometry of the normal modes in the optical trap. Our system provides a platform that is free of driven motion and combines advantages of optical trapping, such as state-dependent confinement and nanoscale potentials, with the desirable properties of crystals of trapped ions, such as long-range interactions featuring collective motion. Starting with small numbers of ions, it has been proposed that these properties would allow the experimental study of many-body physics and the onset of structural quantum phase transitions between one- and two-dimensional crystals.

A simple optical tweezers for trapping polystyrene particles

NASA Astrophysics Data System (ADS)

Shiddiq, Minarni; Nasir, Zulfa; Yogasari, Dwiyana

2013-09-01

Optical tweezers is an optical trap. For decades, it has become an optical tool that can trap and manipulate any particle from the very small size like DNA to the big one like bacteria. The trapping force comes from the radiation pressure of laser light which is focused to a group of particles. Optical tweezers has been used in many research areas such as atomic physics, medical physics, biophysics, and chemistry. Here, a simple optical tweezers has been constructed using a modified Leybold laboratory optical microscope. The ocular lens of the microscope has been removed for laser light and digital camera accesses. A laser light from a Coherent diode laser with wavelength λ = 830 nm and power 50 mW is sent through an immersion oil objective lens with magnification 100 × and NA 1.25 to a cell made from microscope slides containing polystyrene particles. Polystyrene particles with size 3 μm and 10 μm are used. A CMOS Thorlabs camera type DCC1545M with USB Interface and Thorlabs camera lens 35 mm are connected to a desktop and used to monitor the trapping and measure the stiffness of the trap. The camera is accompanied by camera software which makes able for the user to capture and save images. The images are analyzed using ImageJ and Scion macro. The polystyrene particles have been trapped successfully. The stiffness of the trap depends on the size of the particles and the power of the laser. The stiffness increases linearly with power and decreases as the particle size larger.

An efficient method for the creation of tunable optical line traps via control of gradient and scattering forces.

PubMed

Tietjen, Gregory T; Kong, Yupeng; Parthasarathy, Raghuveer

2008-07-07

Interparticle interaction energies and other useful physical characteristics can be extracted from the statistical properties of the motion of particles confined by an optical line trap. In practice, however, the potential energy landscape, U(x), imposed by the line provides an extra, and in general unknown, influence on particle dynamics. We describe a new class of line traps in which both the optical gradient and scattering forces acting on a trapped particle are designed to be linear functions of the line coordinate and in which their magnitude can be counterbalanced to yield a flat U(x). These traps are formed using approximate solutions to general relations concerning non-conservative optical forces that have been the subject of recent investigations [Y. Roichman, B. Sun, Y. Roichman, J. Amato-Grill, and D. G. Grier, Phys. Rev. Lett. 100, 013602-4 (2008).]. We implement the lines using holographic optical trapping and measure the forces acting on silica microspheres, demonstrating the tunability of the confining potential energy landscape. Furthermore, we show that our approach efficiently directs available laser power to the trap, in contrast to other methods.

Optical trapping of nanoshells

NASA Astrophysics Data System (ADS)

Hester, Brooke C.; Crawford, Alice; Kishore, Rani B.; Helmerson, Kristian; Halas, Naomi J.; Levin, Carly

2007-09-01

We investigate near-resonant trapping of Rayleigh particles in optical tweezers. Although optical forces due to a near-resonant laser beam have been extensively studied for atoms, the situation for larger particles is that the laser wavelength is far from any absorption resonance. Theory predicts, however, that the trapping force exerted on a Rayleigh particle is enhanced, and may be three to fifty times larger for frequencies near resonance than for frequencies far off resonance. The ability to selectively trap only particles with a given absorption peak may have many practical applications. In order to investigate near-resonant trapping we are using nanoshells, particles with a dielectric core and metallic coating that can exhibit plasmon resonances. The resonances of the nanoshells can be tuned by adjusting the ratio of the radius of the dielectric core, r I, to the overall radius, r II, which includes the thickness of the metallic coating. Our nanoshells, fabricated at Rice University, consist of a silica core with a gold coating. Using back focal plane detection, we measure the trap stiffness of a single focus optical trap (optical tweezers), from a diode laser at 853 nm for nanoshells with several different r I/r II ratios.

Optical trapping and propulsion of red blood cells on waveguide surfaces.

PubMed

Ahluwalia, Balpreet Singh; McCourt, Peter; Huser, Thomas; Hellesø, Olav Gaute

2010-09-27

We have studied optical trapping and propulsion of red blood cells in the evanescent field of optical waveguides. Cell propulsion is found to be highly dependent on the biological medium and serum proteins the cells are submerged in. Waveguides made of tantalum pentoxide are shown to be efficient for cell propulsion. An optical propulsion velocity of up to 
6 µm/s on a waveguide with a width of ~6 µm is reported. Stable optical trapping and propulsion of cells during transverse flow is also reported.

Optical Manipulation along Optical Axis with Polarization Sensitive Meta-lens.

PubMed

Markovich, Hen; Shishkin, Ivan; Hendler, Netta; Ginzburg, Pavel

2018-06-27

The ability to manipulate small objects with focused laser beams opens a broad spectrum of opportunities in fundamental and applied studies, where a precise control over mechanical path and stability is required. While conventional optical tweezers are based on bulky diffractive optical elements, developing compact integrable within a fluid cell trapping devices is highly demanded. Here, plasmonic polarization sensitive metasurface-based lens, embedded within a fluid, is demonstrated to provide several stable trapping centers along the optical axis. The position of a particle is controlled with the polarization of the incident light, interacting with plasmonic nanoscale patch antennas, organized within overlapping Fresnel zones of the lens. While standard diffractive optical elements face challenges to trap objects in lateral direction outside the depth of focus, bi-focal Fresnel meta-lens demonstrates the capability to manipulate a bead along 4 micrometers line. Additional fluorescent module, incorporated within the optical trapping setup, was implemented and enabled accurate mapping of optical potential via a particle tracking algorithm. Auxiliary micro- and nano- structures, integrated within fluidic devices, provide numerous opportunities to achieve flexible optomechanical manipulation, including, transport, trapping and sorting, which are highly demanded in lab-on-a-chip applications and many others.

Trapping and assembling of particles and live cells on large-scale random gold nano-island substrates

PubMed Central

Kang, Zhiwen; Chen, Jiajie; Wu, Shu-Yuen; Chen, Kun; Kong, Siu-Kai; Yong, Ken-Tye; Ho, Ho-Pui

2015-01-01

We experimentally demonstrated the use of random plasmonic nano-islands for optical trapping and assembling of particles and live cells into highly organized pattern with low power density. The observed trapping effect is attributed to the net contribution due to near-field optical trapping force and long-range thermophoretic force, which overcomes the axial convective drag force, while the lateral convection pushes the target objects into the trapping zone. Our work provides a simple platform for on-chip optical manipulation of nano- and micro-sized objects, and may find applications in physical and life sciences. PMID:25928045

Precision Tests of the Electroweak Interaction using Trapped Atoms and Ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Melconian, Daniel George

The objective of the proposed research is to study fundamental aspects of the electroweak interaction via precision measurements in beta decay to test our current understanding of fundamental particles and forces as contained in the so-called "Standard Model" of particle physics. By comparing elegant experiments to rigorous theoretical predictions, we will either confirm the Standard Model to a higher degree and rule out models which seek to extend it, or find evidence of new physics and help guide theorists in developing the New Standard Model. The use of ion and neutral atom traps at radioactive ion beam facilities has openedmore » up a new vista in precision low-energy nuclear physics experiments. Traps provide an ideal source of decaying atoms: they can be extremely cold (~1 mK); they are compact (~1 mm^3); and perhaps most importantly, the daughter particles escape with negligible distortions to their momenta in a scattering-free, open environment. The project is taking advantage of these technologies and applying them to precision beta-decay studies at radioactive beam facilities. The program consists of two complementary efforts: 1) Ion traps are an extremely versatile tool for purifying, cooling and bunching low-energy beams of short-lived nuclei. A large-bore (210~mm) superconducting 7-Tesla solenoid is at the heart of a Penning trap system for which there is a dedicated beamline at T-REX, the upgraded radioactive beam facility at the Cyclotron Institute, Texas A&M University. In addition to providing a general-purpose decay station, the flagship program for this system is measuring the ft-values and beta-neutrino correlation parameters from isospin T=2 superallowed beta-delayed proton decays, complimenting and expanding the already strong program in fundamental interactions at the Institute. 2) A magneto-optical trap is being used at the TRIUMF Neutral Atom Trap facility to observe the (un)polarized angular distribution parameters of isotopes of potassium. We are able to highly polarize laser-cooled atoms and observe their decay with unprecedented precision. The correlation of the daughter beta particle with the initial nuclear spin as well as other correlations are sensitive to physics beyond the Standard Model. Both of these cutting-edge and exciting research efforts will test our understanding of the fundamental symmetries underlying our current theory of electroweak interactions. Complementary to high-energy collider experiments, these low-energy nuclear physics "table-top" experiments will search for new particles and interactions which are not already described by the Standard Model of particle physics. The value of this research is recognized to be cross-disciplinary, exciting and potentially revolutionary in our understanding of nature's fundamental interactions. Accordingly, it has been endorsed by the recent (2007) Nuclear Science Advisory Committee's Long Range Plan as part of their recommendation for a "New Standard Model Initiative." In addition to the near-term benefits of scholarly publications and visibility through description of this work at international conferences, an important benefit of this research program is the training of new, young and enthusiastic nuclear physicists. Participants in this demanding and rewarding field develop a very strong background in physics with experience in a range of its subfields since we use atomic techniques and apply them to a nuclear physics experiment which in the end tests the theories of high-energy physics.« less

Salts of the iodine oxyacids in the impregnation of adsorbent charcoal for trapping radioactive methyliodide

DOEpatents

Deitz, Victor R.; Blachly, Charles H.

1977-04-05

Radioactive iodine and radioactive methyliodide can be more than 99.7 per cent removed from the air stream of a nuclear reactor by passing the air stream through a 2-inch thick filter which is made up of impregnated charcoal prepared by contacting the charcoal with a solution containing KOH, iodine or an iodide, and an oxyacid, followed by contacting with a solution containing a tertiary amine.

Method for removing cesium from a nuclear reactor coolant

DOEpatents

Colburn, Richard P.

1986-01-01

A method of and system for removing cesium from a liquid metal reactor coolant including a carbon packing trap in the primary coolant system for absorbing a major portion of the radioactive cesium from the coolant flowing therethrough at a reduced temperature. A regeneration subloop system having a secondary carbon packing trap is selectively connected to the primary system for isolating the main trap therefrom and connecting it to the regeneration system. Increasing the temperature of the sodium flowing through the primary trap diffuses a portion of the cesium

Status and outlook of CHIP-TRAP: The Central Michigan University high precision Penning trap

NASA Astrophysics Data System (ADS)

Redshaw, M.; Bryce, R. A.; Hawks, P.; Gamage, N. D.; Hunt, C.; Kandegedara, R. M. E. B.; Ratnayake, I. S.; Sharp, L.

2016-06-01

At Central Michigan University we are developing a high-precision Penning trap mass spectrometer (CHIP-TRAP) that will focus on measurements with long-lived radioactive isotopes. CHIP-TRAP will consist of a pair of hyperbolic precision-measurement Penning traps, and a cylindrical capture/filter trap in a 12 T magnetic field. Ions will be produced by external ion sources, including a laser ablation source, and transported to the capture trap at low energies enabling ions of a given m / q ratio to be selected via their time-of-flight. In the capture trap, contaminant ions will be removed with a mass-selective rf dipole excitation and the ion of interest will be transported to the measurement traps. A phase-sensitive image charge detection technique will be used for simultaneous cyclotron frequency measurements on single ions in the two precision traps, resulting in a reduction in statistical uncertainty due to magnetic field fluctuations.

Optical trapping and manipulation of neutral particles using lasers

PubMed Central

Ashkin, Arthur

1997-01-01

The techniques of optical trapping and manipulation of neutral particles by lasers provide unique means to control the dynamics of small particles. These new experimental methods have played a revolutionary role in areas of the physical and biological sciences. This paper reviews the early developments in the field leading to the demonstration of cooling and trapping of neutral atoms in atomic physics and to the first use of optical tweezers traps in biology. Some further major achievements of these rapidly developing methods also are considered. PMID:9144154

A compact multi-trap optical tweezer system based on CD-ROM technologies

NASA Astrophysics Data System (ADS)

McMenamin, T.; Lee, W. M.

2017-08-01

We implemented an integrated time sharing multiple optical trapping system through the synchronisation of high speed voice coil scanning lens and laser pulsing. The integration is achieved by using commonly available optical pickup unit (OPU) that exists inside optical drives. Scanning frequencies of up to 2 kHz were showed to achieve arbitrary distribution of optical traps within the one-dimensional scan range of the voice coil motor. The functions of the system were demonstrated by the imaging and trapping of 1 μm particles and giant unilamellar vesicles (GUVs). The new device circumvents existing bulky laser scanning systems (4f lens systems) with an integrated laser and lens steering platform that can be integrated on a variety of microscopy platforms (confocal, lightsheet, darkfield).

A model of optical trapping cold atoms using a metallic nano wire with surface plasmon effect

NASA Astrophysics Data System (ADS)

Thi Phuong Lan, Nguyen; Thi Nga, Do; Viet, Nguyen Ai

2016-06-01

In this work, we construct a new model of optical trapping cold atoms with a metallic nano wire by using surface plasmon effect generated by strong field of laser beams. Using the skin effect, we send a strong oscillated electromagnetic filed through the surface of a metallic nano wire. The local field generated by evanescent effect creates an effective attractive potential near the surface of metallic nano wires. The consideration of some possible boundary and frequency conditions might lead to non-trivial bound state solution for a cold atom. We discus also the case of the laser reflection optical trap with shell-core design, and compare our model with another recent schemes of cold atom optical traps using optical fibers and carbon nanotubes.

Deep levels in as-grown and Si-implanted In(0.2)Ga(0.8)As-GaAs strained-layer superlattice optical guiding structures

NASA Technical Reports Server (NTRS)

Dhar, S.; Das, U.; Bhattacharya, P. K.

1986-01-01

Trap levels in about 2-micron In(0.2)Ga(0.8)As(94 A)/GaAs(25 A) strained-layer superlattices, suitable for optical waveguides, have been identified and characterized by deep-level transient spectroscopy and optical deep-level transient spectroscopy measurements. Several dominant electron and hole traps with concentrations of approximately 10 to the 14th/cu cm, and thermal ionization energies Delta-E(T) varying from 0.20 to 0.75 eV have been detected. Except for a 0.20-eV electron trap, which might be present in the In(0.2)Ga(0.8)As well regions, all the other traps have characteristics similar to those identified in molecular-beam epitaxial GaAs. Of these, a 0.42-eV hole trap is believed to originate from Cu impurities, and the others are probably related to native defects. Upon Si implantation and halogen lamp annealing, new deep centers are created. These are electron traps with Delta-E(T) = 0.81 eV and hole traps with Delta-E(T) = 0.46 eV. Traps occurring at room temperature may present limitations for optical devices.

Statistical Modeling of an Optically Trapped Cilium

NASA Astrophysics Data System (ADS)

Flaherty, Justin; Resnick, Andrew

We explore, analytically and experimentally, the stochastic dynamics of a biologically significant slender microcantilever, the primary cilium, held within an optical trap. Primary cilia are cellular organelles, present on most vertebrate cells, hypothesized to function as a fluid flow sensor. The mechanical properties of a cilium remain incompletely characterized. Optical trapping is an ideal method to probe the mechanical response of a cilium due to the spatial localization and non-contact nature of the applied force. However, analysis of an optically trapped cilium is complicated both by the geometry of a cilium and boundary conditions. Here, we present experimentally measured mean-squared displacement data of trapped cilia where the trapping force is oppositely directed to the elastic restoring force of the ciliary axoneme, analytical modeling results deriving the mean-squared displacement of a trapped cilium using the Langevin approach, and apply our analytical results to the experimental data. We demonstrate that mechanical properties of the cilium can be accurately determined and efficiently extracted from the data using our model. It is hoped that improved measurements will result in deeper understanding of the biological function of cellular flow sensing by this organelle.

Fiber optical tweezers for microscale and nanoscale particle manipulation and force sensing

NASA Astrophysics Data System (ADS)

Liu, Yuxiang

2011-12-01

Optical tweezers have been an important tool in biology and physics for studying single molecules and colloidal systems. Most of current optical tweezers are built with microscope objectives, which are: i) expensive, ii) bulky and hard to integrate, iii) sensitive to environmental fluctuations, iv) limited in terms of working distances from the substrate, and v) rigid with the requirements on the substrate (transparent substrate made with glass and with a fixed thickness). These limitations of objective-based optical tweezers prevent them from being miniaturized. Fiber optical tweezers can provide a solution for cost reduction and miniaturization, and these optical tweezers can be potentially used in microfluidic systems. However, the existing fiber optical tweezers have the following limitations: i) low trapping efficiency due to weakly focused beams, ii) lack of the ability to control the positions of multiple particles simultaneously, and iii) limited functionalities. The overall objective of this dissertation work is to further the fundamental understanding of fiber optical tweezers through experimental study and modeling, and to develop novel fiber optical tweezers systems to enhance the capability and functionalities of fiber optical tweezers as microscale and nanoscale manipulators/sensors. The contributions of this dissertation work are summarized as follows. i) An enhanced understanding of the inclined dual-fiber optical tweezers (DFOTs) system has been achieved. Stable three dimensional (3D) optical trapping of a single micron-sized particle has been experimentally demonstrated. This is the first time that the trapping efficiency has been calibrated and the stiffness of the trap has been obtained in the experiments, which has been carried out by using two methods: the drag force method and power spectrum analysis. Such calibration enables the system to be used as a picoNewton-level force sensor in addition to a particle manipulator. The influence of system parameters on the trapping performance has been carefully investigated through both experimental and numerical studies. ii) Multiple traps have been created and carefully studied with the inclined DFOTs for the first time. Three traps, one 3D trap and two 2D traps, have been experimentally created at different vertical levels with adjustable separations and positions. iii) Multiple functionalities have been achieved and studied for the first time with the inclined DFOTs. Particle separation, grouping, stacking, rod alignment, rod rotation, and optical binding have been experimentally demonstrated. The multiple functionalities allow the inclined DFOTs to find applications in the study of interaction forces in colloidal systems as well as parallel particle manipulation in drug delivery systems. iv) Far-field superfocusing effect has been investigated and successfully demonstrated with a fiber-based surface plasmonic (SP) lens for the first time. A planar SP lens with a set of concentric nanoscale rings on a fiber endface has been developed. For the first time, a focus size that is comparable to the smallest achievable focus size of high NA objective lenses has been achieved with the fiber-based SP lens. The fiber-based SP lens can bridge the nanoscale particles/systems and the macroscale power sources/detectors, which has been a long standing challenge for nanophotonics. In addition to optical trapping, the fiber-based SP lens will impact many applications including high-resolution lithography, high-resolution fluorescence detection, and sub-wavelength imaging. v) Trapping ability enhanced with the fiber-based SP lens has been successfully demonstrated. With the help of the fiber-based SP lens, the trapping efficiency of fiber optical tweezers has been significantly enhanced, which is comparable with that of objective-based optical tweezers. A submicron-sized bacterium has been successfully trapped in three dimensions for the first time with optical tweezers based on single fibers.

Single-beam, dark toroidal optical traps for cold atoms

NASA Astrophysics Data System (ADS)

Fatemi, Fredrik K.; Olson, Spencer E.; Bashkansky, Mark; Dutton, Zachary; Terraciano, Matthew

2007-02-01

We demonstrate the generation of single-beam dark toroidal optical intensity distributions, which are of interest for neutral atom storage and atom interferometry. We demonstrate experimentally and numerically optical potentials that contain a ring-shaped intensity minimum, bounded in all directions by higher intensity. We use a spatial light modulator to alter the phase of an incident laser beam, and analyze the resulting optical propagation characteristics. For small toroidal traps (< 50 μm diameter), we find an optimal superposition of Laguerre-Gaussian modes that allows the formation of single-beam toroidal traps. We generate larger toroidal bottle traps by focusing hollow beams with toroidal lenses imprinted onto the spatial light modulator.

All-optical spinor Bose-Einstein condensation and the spinor dynamics-driven atom laser

NASA Astrophysics Data System (ADS)

Lundblad, Nathan Eric

Optical trapping as a viable means of exploring the physics of ultracold dilute atomic gases has revealed a new spectrum of physical phenomena. In particular, macroscopic and sudden occupation of the ground state below a critical temperature---a phenomenon known as Bose-Einstein condensation---has become an even richer system for the study of quantum mechanics, ultracold collisions, and many-body physics in general. Optical trapping liberates the spin degree of the BEC, making the order parameter vectorial ('spinor BEC'), as opposed to the scalar order of traditional magnetically trapped condensates. The work described within is divided into two main efforts. The first encompasses the all-optical creation of a Bose-Einstein condensate in rubidium vapor. An all-optical path to spinor BEC (as opposed to transfer to an optical trap from a magnetic trap condensate) was desired both for the simplicity of the experimental setup and also for the potential gains in speed of creation; evaporative cooling, the only known path to dilute-gas condensation, works only as efficiently as the rate of elastic collisions in the gas, a rate that starts out much higher in optical traps. The first all-optical BEC was formed elsewhere in 2001; the years following saw many groups worldwide seeking to create their own version. Our own all-optical spinor BEC, made with a single-beam dipole trap formed by a focused CO2 laser, is described here, with particular attention paid to trap loading, measurement of trap parameters, and the use of a novel 780 nm high-power laser system. The second part describes initial experiments performed with the nascent condensate. The spinor properties of the condensate are documented, and a measurement is made of the density-dependent rate of spin mixing in the condensate. In addition, we demonstrate a novel dual-beam atom laser formed by outcoupling oppositely polarized components of the condensate, whose populations have been coherently evolved through spin dynamics. We drive coherent spin-mixing evolution through adiabatic compression of the initially weak trap. Such dual beams, nominally number-correlated through the angular momentum-conserving collision 2m0 ⇋ m+1 + m-1 have been proposed as tools to explore entanglement and squeezing in Bose-Einstein condensates.

Simulation of a 3D MOT-Optical Molasses Hybrid for Potassium-41 Atoms

NASA Astrophysics Data System (ADS)

Peterson, W. A.; Wrubel, Jonathan

2017-04-01

We report a design and numerical model for a 3D magneto-optical trap (MOT)-optical molasses hybrid for potassium-41 atoms. In this arrangement, the usual quadrupole magnetic field is replaced by an octupole field. The octupole field has a central region of very low magnetic field where our simulations show that the atoms experience an optical molasses, resulting in sub-doppler cooling not possible in a quadrupole MOT. The simulations also show that the presence of the magneto-optical trapping force at the edge of the cooling beams provides a restoring force which cycles atoms through the molasses region. We plan to use this hybrid trap to directly load a far off-resonance optical dipole trap. Because the atoms are recycled for multiple passes through the molasses, we expect a higher phase-space density of atoms loaded into the dipole trap. Similar hybrid cooling schemes should be relevant for lithium-6 and lithium-7, which also have poorly resolved D2 hyperfine structure. Research Corporation for Science Advancement, Cottrell College Science Award.

Liquid crystal emulsion micro-droplet WGM resonators

NASA Astrophysics Data System (ADS)

Ježek, Jan; Pilát, Zdeněk.; Brzobohatý, Oto; Jonáš, Alexandr; Aas, Mehdi; Kiraz, Alper; Zemánek, Pavel

2014-12-01

We introduce tunable optofluidic microlasers based on optically stretched or thermally modified, dye-doped emulsion droplets of liquid crystals (LC) confined in a dual-beam optical trap. Droplets were created in microfluidic chips or by shaking. Optically trapped microdroplets emulsified in water and stained with fluorescent dye act as an active ultrahigh-Q optical resonant cavity hosting whispering gallery modes (WGMs). Tuning of the laser emission wavelength was achieved by a controlled deformation of the droplet shape using light-induced forces generated by dual-beam optical trap and by thermal changing of the order in the LC.

Radio Frequency Magneto-Optical Trapping of CaF with High Density.

PubMed

Anderegg, Loïc; Augenbraun, Benjamin L; Chae, Eunmi; Hemmerling, Boerge; Hutzler, Nicholas R; Ravi, Aakash; Collopy, Alejandra; Ye, Jun; Ketterle, Wolfgang; Doyle, John M

2017-09-08

We demonstrate significantly improved magneto-optical trapping of molecules using a very slow cryogenic beam source and either rf modulated or dc magnetic fields. The rf magneto-optical trap (MOT) confines 1.0(3)×10^{5} CaF molecules at a density of 7(3)×10^{6}  cm^{-3}, which is an order of magnitude greater than previous molecular MOTs. Near Doppler-limited temperatures of 340(20)  μK are attained. The achieved density enables future work to directly load optical tweezers and create optical arrays for quantum simulation.

Fabrication and application of a non-contact double-tapered optical fiber tweezers.

PubMed

Liu, Z L; Liu, Y X; Tang, Y; Zhang, N; Wu, F P; Zhang, B

2017-09-18

A double-tapered optical fiber tweezers (DOFTs) was fabricated by a chemical etching called interfacial layer etching. In this method, the second taper angle (STA) of DOFTs can be controlled easily by the interfacial layer etching time. Application of the DOFTs to the optical trapping of the yeast cells was presented. Effects of the STA on the axile trapping efficiency and the trapping position were investigated experimentally and theoretically. The experimental results are good agreement with the theoretical ones. The results demonstrated that the non-contact capture can be realized for the large STA (e.g. 90 deg) and there was an optimal axile trapping efficiency as the STA increasing. In order to obtain a more accurate measurement result of the trapping force, a correction factor to Stokes drag coefficient was introduced. This work provided a way of designing and fabricating an optical fiber tweezers (OFTs) with a high trapping efficient or a non-contact capture.

Environmental analysis of Lower Pueblo/Lower Los Alamos Canyon, Los Alamos, New Mexico

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ferenbaugh, R.W.; Buhl, T.E.; Stoker, A.K.

1994-12-01

The radiological survey of the former radioactive waste treatment plant site (TA-45), Acid Canyon, Pueblo Canyon, and Los Alamos Canyon found residual contamination at the site itself and in the channel and banks of Acid, Pueblo, and lower Los Alamos Canyons all the way to the Rio Grande. The largest reservoir of residual radioactivity is in lower Pueblo Canyon, which is on DOE property. However, residual radioactivity does not exceed proposed cleanup criteria in either lower Pueblo or lower Los Alamos Canyons. The three alternatives proposed are (1) to take no action, (2) to construct a sediment trap in lowermore » Pueblo Canyon to prevent further transport of residual radioactivity onto San Ildefonso Indian Pueblo land, and (3) to clean the residual radioactivity from the canyon system. Alternative 2, to cleanup the canyon system, is rejected as a viable alternative. Thousands of truckloads of sediment would have to be removed and disposed of, and this effort is unwarranted by the low levels of contamination present. Residual radioactivity levels, under either present conditions or projected future conditions, will not result in significant radiation doses to persons exposed. Modeling efforts show that future transport activity will not result in any residual radioactivity concentrations higher than those already existing. Thus, although construction of a sediment trap in lower Pueblo Canyon is a viable alternative, this effort also is unwarranted, and the no-action alternative is the preferred alternative.« less

Convection currents enhancement of the spring constant in optical tweezers

NASA Astrophysics Data System (ADS)

Zenteno-Hernández, J. A.; Gómez-Vieyra, A.; Torres-Hurtado, S. A.; Ramirez-San-Juan, J. C.; Ramos-García, R.

2016-09-01

In this work we demonstrate the increasing of the trap stiffness (spring constant) constant of an optical trap of particles suspended in water by laser-induced convection currents. These currents are the result of thermal gradients created by a light absorption in a thin layer of hydrogenated amorphous silicon (a:Si-H) deposited at the bottom of cell. Since convection currents (and therefore drag forces) are symmetric around the beam focus particles trapped by the beam are further contained. Around the focus the drag force is directed upwards and partially compensated by radiation pressure depending on the laser power increasing the stiffness of the optical trapping increases significatively so a particle trapped could dragged (by moving the translation stage leaving the beam fixed) at velocities as high as 90μm/s without escaping the trap, whereas with no a:Si-H film, the particle escapes from the trap at lower velocities (30μm/s).

Optically assisted trapping with high-permittivity dielectric rings: Towards optical aerosol filtration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alaee, Rasoul; Kadic, Muamer; Rockstuhl, Carsten

Controlling the transport, trapping, and filtering of nanoparticles is important for many applications. By virtue of their weak response to gravity and their thermal motion, various physical mechanisms can be exploited for such operations on nanoparticles. However, the manipulation based on optical forces is potentially most appealing since it constitutes a highly deterministic approach. Plasmonic nanostructures have been suggested for this purpose, but they possess the disadvantages of locally generating heat and trapping the nanoparticles directly on the surface. Here, we propose the use of dielectric rings made of high permittivity materials for trapping nanoparticles. Thanks to their ability tomore » strongly localize the field in space, nanoparticles can be trapped without contact. We use a semianalytical method to study the ability of these rings to trap nanoparticles. Lastly, the results are supported by full-wave simulations and application of the trapping concept to nanoparticle filtration is suggested.« less

Optically assisted trapping with high-permittivity dielectric rings: Towards optical aerosol filtration

DOE PAGES

Alaee, Rasoul; Kadic, Muamer; Rockstuhl, Carsten; ...

2016-10-04

Controlling the transport, trapping, and filtering of nanoparticles is important for many applications. By virtue of their weak response to gravity and their thermal motion, various physical mechanisms can be exploited for such operations on nanoparticles. However, the manipulation based on optical forces is potentially most appealing since it constitutes a highly deterministic approach. Plasmonic nanostructures have been suggested for this purpose, but they possess the disadvantages of locally generating heat and trapping the nanoparticles directly on the surface. Here, we propose the use of dielectric rings made of high permittivity materials for trapping nanoparticles. Thanks to their ability tomore » strongly localize the field in space, nanoparticles can be trapped without contact. We use a semianalytical method to study the ability of these rings to trap nanoparticles. Lastly, the results are supported by full-wave simulations and application of the trapping concept to nanoparticle filtration is suggested.« less

Ferroelectric nanotraps for polar molecules

NASA Astrophysics Data System (ADS)

Dutta, Omjyoti; Giedke, G.

2018-02-01

We propose and analyze an electrostatic-optical nanoscale trap for cold diatomic polar molecules. The main ingredient of our proposal is a square array of ferroelectric nanorods with alternating polarization. We show that, in contrast to electrostatic traps using the linear Stark effect, a quadratic Stark potential supports long-lived trapped states. The molecules are kept at a fixed height from the nanorods by a standing-wave optical dipole trap. For the molecules and materials considered, we find nanotraps with trap frequency up to 1 MHz, ground-state width ˜20 nm with lattice periodicity of ˜200 nm . Analyzing the loss mechanisms due to nonadiabaticity, surface-induced radiative transitions, and laser-induced transitions, we show the existence of trapped states with lifetime ˜1 s , competitive with current traps created via optical mechanisms. As an application we extend our discussion to a one-dimensional (1D) array of nanotraps to simulate a long-range spin Hamiltonian in our structure.

Nanohole optical tweezers in heterogeneous mixture analysis

NASA Astrophysics Data System (ADS)

Hacohen, Noa; Ip, Candice J. X.; Laxminarayana, Gurunatha K.; DeWolf, Timothy S.; Gordon, Reuven

2017-08-01

Nanohole optical trapping is a tool that has been shown to analyze proteins at the single molecule level using pure samples. The next step is to detect and study single molecules with dirty samples. We demonstrate that using our double nanohole optical tweezing configuration, single particles in an egg white solution can be classified when trapped. Different sized molecules provide different signal variations in their trapped state, allowing the proteins to be statistically characterized. Root mean squared variation and trap stiffness are methods used on trapped signals to distinguish between the different proteins. This method to isolate and determine single molecules in heterogeneous samples provides huge potential to become a reliable tool for use within biomedical and scientific communities.

Development and test of a cryogenic trap system dedicated to confinement of radioactive volatile isotopes in SPIRAL2 post-accelerator

NASA Astrophysics Data System (ADS)

Souli, M.; Dolégiéviez, P.; Fadil, M.; Gallardo, P.; Levallois, R.; Munoz, H.; Ozille, M.; Rouillé, G.; Galet, F.

2011-12-01

A cryogenic trap system called Cryotrap has been studied and developed in the framework of nuclear safety studies for SPIRAL2 accelerator. The main objective of Cryotrap is to confine and reduce strongly the migration of radioactive volatile isotopes in beam lines. These radioactive gases are produced after interaction between a deuteron beam and a fissile target. Mainly, Cryotrap is composed by a vacuum vessel and two copper thermal screens maintained separately at two temperatures T1=80 K and T2=20 K. A Cryocooler with two stages at previous temperatures is used to remove static heat losses of the cryostat and ensure an efficient cooling of the system. Due to strong radiological constraints that surround Cryotrap, the coupling system between Cryocooler and thermal screens is based on aluminum thermo-mechanical contraction. The main objective of this original design is to limit direct human maintenance interventions and provide maximum automated operations. A preliminary prototype of Cryotrap has been developed and tested at GANIL laboratory to validate its design, and determine its thermal performance and trapping efficiency. In this paper, we will first introduce briefly SPIRAL2 project and discuss the main role of Cryotrap in nuclear safety of the accelerator. Then, we will describe the proposed conceptual design of Cryotrap and its main characteristics. After that, we will focus on test experiment and analyze experimental data. Finally, we will present preliminary results of gas trapping efficiency tests.

Advances in laser and tissue interactions: laser microbeams and optical trapping (Invited Paper)

NASA Astrophysics Data System (ADS)

Serafetinides, Alexander A.; Makropoulou, Mersini; Papadopoulos, Dimitris; Papagiakoumou, Eirini; Pietreanu, D.

2005-04-01

The increasing use of lasers in biomedical research and clinical praxis leads to the development and application of new, non-invasive, therapeutic, surgical and diagnostic techniques. In laser surgery, the theory of ablation dictates that pulsed mid-infrared laser beams exhibit strong absorption by soft and hard tissues, restricting residual thermal damage to a minimum zone. Therefore, the development of high quality 3 μm lasers is considered to be an alternative for precise laser ablation of tissue. Among them are the high quality oscillator-two stages amplifier lasers developed, which will be described in this article. The beam quality delivered by these lasers to the biological tissue is of great importance in cutting and ablating operations. As the precision of the ablation is increased, the cutting laser interventions could well move to the microsurgery field. Recently, the combination of a laser scalpel with an optical trapping device, under microscopy control, is becoming increasingly important. Optical manipulation of microscopic particles by focused laser beams, is now widely used as a powerful tool for 'non-contact' micromanipulation of cells and organelles. Several laser sources are employed for trapping and varying laser powers are used in a broad range of applications of optical tweezers. For most of the lasers used, the focal spot of the trapping beam is of the order of a micron. As the trapped objects can vary in size from hundreds of nanometres to hundreds of microns, the technique has recently invaded in to the nanocosomos of genes and molecules. However, the use of optical trapping for quantitative research into biophysical processes requires accurate calculation of the optical forces and torques acting within the trap. The research and development efforts towards a mid-IR microbeam laser system, the design and realization efforts towards a visible laser trapping system and the first results obtained using a relatively new calibration method to calculate the forces experienced in the optical trap are discussed in detail in the following.

Optical stretching of giant unilamellar vesicles with an integrated dual-beam optical trap.

PubMed

Solmaz, Mehmet E; Biswas, Roshni; Sankhagowit, Shalene; Thompson, James R; Mejia, Camilo A; Malmstadt, Noah; Povinelli, Michelle L

2012-10-01

We have integrated a dual-beam optical trap into a microfluidic platform and used it to study membrane mechanics in giant unilamellar vesicles (GUVs). We demonstrate the trapping and stretching of GUVs and characterize the membrane response to a step stress. We then measure area strain as a function of applied stress to extract the bending modulus of the lipid bilayer in the low-tension regime.

Plasmonic optical nanotweezers

NASA Astrophysics Data System (ADS)

Kotb, Rehab; El Maklizi, Mahmoud; Ismail, Yehea; Swillam, Mohamed A.

2017-02-01

Plasmonic grating structures can be used in many applications such as nanolithography and optical trapping. In this paper, we used plasmonic grating as optical tweezers to trap and manipulate dielectric nano-particles. Different plasmonic grating structures with single, double, and triple slits have been investigated and analyzed. The three configurations are optimized and compared to find the best candidate to trap and manipulate nanoparticles. The three optimized structures results in capability to super focusing and beaming the light effectively beyond the diffraction limit. A high transverse gradient optical force is obtained using the triple slit configuration that managed to significantly enhance the field and its gradient. Therefore, it has been chosen as an efficient optical tweezers. This structure managed to trap sub10nm particles efficiently. The resultant 50KT potential well traps the nano particles stably. The proposed structure is used also to manipulate the nano-particles by simply changing the angle of the incident light. We managed to control the movement of nano particle over an area of (5μm x 5μm) precisely. The proposed structure has the advantage of trapping and manipulating the particles outside the structure (not inside the structure such as the most proposed optical tweezers). As a result, it can be used in many applications such as drug delivery and biomedical analysis.

Characterizing physical properties and heterogeneous chemistry of single particles in air using optical trapping-Raman spectroscopy

NASA Astrophysics Data System (ADS)

Gong, Z.; Wang, C.; Pan, Y. L.; Videen, G.

2017-12-01

Heterogeneous reactions of solid particles in a gaseous environment are of increasing interest; however, most of the heterogeneous chemistry studies of airborne solids were conducted on particle ensembles. A close examination on the heterogeneous chemistry between single particles and gaseous-environment species is the key to elucidate the fundamental mechanisms of hydroscopic growth, cloud nuclei condensation, secondary aerosol formation, etc., and reduce the uncertainty of models in radiative forcing, climate change, and atmospheric chemistry. We demonstrate an optical trapping-Raman spectroscopy (OT-RS) system to study the heterogeneous chemistry of the solid particles in air at single-particle level. Compared to other single-particle techniques, optical trapping offers a non-invasive, flexible, and stable method to isolate single solid particle from substrates. Benefited from two counter-propagating hollow beams, the optical trapping configuration is adaptive to trap a variety of particles with different materials from inorganic substitution (carbon nanotubes, silica, etc.) to organic, dye-doped polymers and bioaerosols (spores, pollen, etc.), with different optical properties from transparent to strongly absorbing, with different sizes from sub-micrometers to tens of microns, or with distinct morphologies from loosely packed nanotubes to microspheres and irregular pollen grains. The particles in the optical trap may stay unchanged, surface degraded, or optically fragmented according to different laser intensity, and their physical and chemical properties are characterized by the Raman spectra and imaging system simultaneously. The Raman spectra is able to distinguish the chemical compositions of different particles, while the synchronized imaging system can resolve their physical properties (sizes, shapes, morphologies, etc.). The temporal behavior of the trapped particles also can be monitored by the OT-RS system at an indefinite time with a resolution from 10 ms to 5 min, which can be further applied to monitor the dynamics of heterogeneous reactions. The OT-RS system provides a flexible method to characterize and monitor the physical properties and heterogeneous chemistry of optically trapped solid particles in gaseous environment at single-particle level.

State-dependent fluorescence of neutral atoms in optical potentials

NASA Astrophysics Data System (ADS)

Martinez-Dorantes, M.; Alt, W.; Gallego, J.; Ghosh, S.; Ratschbacher, L.; Meschede, D.

2018-02-01

Recently we have demonstrated scalable, nondestructive, and high-fidelity detection of the internal state of 87Rb neutral atoms in optical dipole traps using state-dependent fluorescence imaging [M. Martinez-Dorantes, W. Alt, J. Gallego, S. Ghosh, L. Ratschbacher, Y. Völzke, and D. Meschede, Phys. Rev. Lett. 119, 180503 (2017), 10.1103/PhysRevLett.119.180503]. In this paper we provide experimental procedures and interpretations to overcome the detrimental effects of heating-induced trap losses and state leakage. We present models for the dynamics of optically trapped atoms during state-dependent fluorescence imaging and verify our results by comparing Monte Carlo simulations with experimental data. Our systematic study of dipole force fluctuations heating in optical traps during near-resonant illumination shows that off-resonant light is preferable for state detection in tightly confining optical potentials.

Hyperpolarizability and Operational Magic Wavelength in an Optical Lattice Clock

NASA Astrophysics Data System (ADS)

Brown, R. C.; Phillips, N. B.; Beloy, K.; McGrew, W. F.; Schioppo, M.; Fasano, R. J.; Milani, G.; Zhang, X.; Hinkley, N.; Leopardi, H.; Yoon, T. H.; Nicolodi, D.; Fortier, T. M.; Ludlow, A. D.

2017-12-01

Optical clocks benefit from tight atomic confinement enabling extended interrogation times as well as Doppler- and recoil-free operation. However, these benefits come at the cost of frequency shifts that, if not properly controlled, may degrade clock accuracy. Numerous theoretical studies have predicted optical lattice clock frequency shifts that scale nonlinearly with trap depth. To experimentally observe and constrain these shifts in an 171Yb optical lattice clock, we construct a lattice enhancement cavity that exaggerates the light shifts. We observe an atomic temperature that is proportional to the optical trap depth, fundamentally altering the scaling of trap-induced light shifts and simplifying their parametrization. We identify an "operational" magic wavelength where frequency shifts are insensitive to changes in trap depth. These measurements and scaling analysis constitute an essential systematic characterization for clock operation at the 10-18 level and beyond.

Launch and capture of a single particle in a pulse-laser-assisted dual-beam fiber-optic trap

NASA Astrophysics Data System (ADS)

Fu, Zhenhai; She, Xuan; Li, Nan; Hu, Huizhu

2018-06-01

The rapid loading and manipulation of microspheres in optical trap is important for its applications in optomechanics and precision force sensing. We investigate the microsphere behavior under coaction of a dual-beam fiber-optic trap and a pulse laser beam, which reveals a launched microsphere can be effectively captured in a spatial region. A suitable order of pulse duration for launch is derived according to the calculated detachment energy threshold of pulse laser. Furthermore, we illustrate the effect of structural parameters on the launching process, including the spot size of pulse laser, the vertical displacement of beam waist and the initial position of microsphere. Our result will be instructive in the optimal design of the pulse-laser-assisted optical tweezers for controllable loading mechanism of optical trap.

Minimum-variance Brownian motion control of an optically trapped probe.

PubMed

Huang, Yanan; Zhang, Zhipeng; Menq, Chia-Hsiang

2009-10-20

This paper presents a theoretical and experimental investigation of the Brownian motion control of an optically trapped probe. The Langevin equation is employed to describe the motion of the probe experiencing random thermal force and optical trapping force. Since active feedback control is applied to suppress the probe's Brownian motion, actuator dynamics and measurement delay are included in the equation. The equation of motion is simplified to a first-order linear differential equation and transformed to a discrete model for the purpose of controller design and data analysis. The derived model is experimentally verified by comparing the model prediction to the measured response of a 1.87 microm trapped probe subject to proportional control. It is then employed to design the optimal controller that minimizes the variance of the probe's Brownian motion. Theoretical analysis is derived to evaluate the control performance of a specific optical trap. Both experiment and simulation are used to validate the design as well as theoretical analysis, and to illustrate the performance envelope of the active control. Moreover, adaptive minimum variance control is implemented to maintain the optimal performance in the case in which the system is time varying when operating the actively controlled optical trap in a complex environment.

Coherent Atom Optics with Optical Potentials: A Summary of New Phenomena with Bose-Einstein Condensates at the University of Arizona

DTIC Science & Technology

2009-10-08

differentially pumped two-cell vacuum system. A gas of Rb atoms, provided by SAES dispensers, fills a glass cell where laser cooling and magneto - optic ...mask [Fig. 1(b)] that was imaged onto the center of the trap . The sum of the magnetic and optical potentials created a triple-well trap , with three... Simulations of BEC growth in a toroidal trap show vortices (as in (b),(c)) and persistent currents. 4 The merging of experimental capabilities. [ongoing work

Dark optical lattice of ring traps for cold atoms

NASA Astrophysics Data System (ADS)

Courtade, Emmanuel; Houde, Olivier; Clément, Jean-François; Verkerk, Philippe; Hennequin, Daniel

2006-09-01

We propose an optical lattice for cold atoms made of a one-dimensional stack of dark ring traps. It is obtained through the interference pattern of a standard Gaussian beam with a counterpropagating hollow beam obtained using a setup with two conical lenses. The traps of the resulting lattice are characterized by a high confinement and a filling rate much larger than unity, even if loaded with cold atoms from a magneto-optical trap. We have implemented this system experimentally, and demonstrated its feasibility. Applications in statistical physics, quantum computing, and Bose-Einstein condensate dynamics are conceivable.

Optical trapping gold nanoparticles by a pulse laser

NASA Astrophysics Data System (ADS)

Liu, XiaoYu; Wang, Feng

2010-11-01

Gold nanoparticles are widely employed in nanomaterials, nanobiotechnology and health care, but generally they are considered difficult to trap stably. Compared with the continuous laser which is popular to the optical trapping, pulse laser has a relatively larger power in its work pulse, which is useful for trap particles. So this paper comprehensively analyzes the forces (the radiation forces, the gravitation, and the Brownian motion) on the gold nanoparticles in the optical tweezers formed by a pulse laser, through building up a mathematical model. Finally gets the dependence relation between the characteristics of the pulse laser and that of the gold nanoparticles.

Optical levitation measurements with intensity-modulated light beams.

PubMed

Cai, W; Li, F; Sun, S; Wang, Y

1997-10-20

Illumination of an optically levitated particle with an intensity-modulated transverse beam induces a transverse vibration of a particle in an optical trap. Based on this, the trapping force of a trap can be measured. Using an intensity-modulated longitudinal levitating beam causes a particle to move vertically, allowing for the determination of some aerodynamic parameters of a particle in air. The principles and the experimental phenomena are described and the initial results are given.

Optical stretching of giant unilamellar vesicles with an integrated dual-beam optical trap

PubMed Central

Solmaz, Mehmet E.; Biswas, Roshni; Sankhagowit, Shalene; Thompson, James R.; Mejia, Camilo A.; Malmstadt, Noah; Povinelli, Michelle L.

2012-01-01

We have integrated a dual-beam optical trap into a microfluidic platform and used it to study membrane mechanics in giant unilamellar vesicles (GUVs). We demonstrate the trapping and stretching of GUVs and characterize the membrane response to a step stress. We then measure area strain as a function of applied stress to extract the bending modulus of the lipid bilayer in the low-tension regime. PMID:23082284

Low-Power Optical Trapping of Nanoparticles and Proteins with Resonant Coaxial Nanoaperture Using 10 nm Gap.

PubMed

Yoo, Daehan; Gurunatha, Kargal L; Choi, Han-Kyu; Mohr, Daniel A; Ertsgaard, Christopher T; Gordon, Reuven; Oh, Sang-Hyun

2018-06-13

We present optical trapping with a 10 nm gap resonant coaxial nanoaperture in a gold film. Large arrays of 600 resonant plasmonic coaxial nanoaperture traps are produced on a single chip via atomic layer lithography with each aperture tuned to match a 785 nm laser source. We show that these single coaxial apertures can act as efficient nanotweezers with a sharp potential well, capable of trapping 30 nm polystyrene nanoparticles and streptavidin molecules with a laser power as low as 4.7 mW. Furthermore, the resonant coaxial nanoaperture enables real-time label-free detection of the trapping events via simple transmission measurements. Our fabrication technique is scalable and reproducible, since the critical nanogap dimension is defined by atomic layer deposition. Thus our platform shows significant potential to push the limit of optical trapping technologies.

Designing an experiment to measure cellular interaction forces

NASA Astrophysics Data System (ADS)

McAlinden, Niall; Glass, David G.; Millington, Owain R.; Wright, Amanda J.

2013-09-01

Optical trapping is a powerful tool in Life Science research and is becoming common place in many microscopy laboratories and facilities. The force applied by the laser beam on the trapped object can be accurately determined allowing any external forces acting on the trapped object to be deduced. We aim to design a series of experiments that use an optical trap to measure and quantify the interaction force between immune cells. In order to cause minimum perturbation to the sample we plan to directly trap T cells and remove the need to introduce exogenous beads to the sample. This poses a series of challenges and raises questions that need to be answered in order to design a set of effect end-point experiments. A typical cell is large compared to the beads normally trapped and highly non-uniform - can we reliably trap such objects and prevent them from rolling and re-orientating? In this paper we show how a spatial light modulator can produce a triple-spot trap, as opposed to a single-spot trap, giving complete control over the object's orientation and preventing it from rolling due, for example, to Brownian motion. To use an optical trap as a force transducer to measure an external force you must first have a reliably calibrated system. The optical trapping force is typically measured using either the theory of equipartition and observing the Brownian motion of the trapped object or using an escape force method, e.g. the viscous drag force method. In this paper we examine the relationship between force and displacement, as well as measuring the maximum displacement from equilibrium position before an object falls out of the trap, hence determining the conditions under which the different calibration methods should be applied.

Technologies for Trapped-Ion Quantum Information Systems

DTIC Science & Technology

2016-03-21

mate- rials such as graphene and indium tin oxide, integrating devices like optical fibers and mirrors, and exploring alternative ion loading and...trapping techniques. Keywords ion traps · quantum computation · quantum information · trapped ions · ion-photon interface · graphene · indium tin oxide...displays are typically made of indium tin oxide (ITO), a material that is both an elec- trical and an optical conductor. However, using ITO electrodes

A Linear Ion Trap with an Expanded Inscribed Diameter to Improve Optical Access for Fluorescence Spectroscopy

NASA Astrophysics Data System (ADS)

Rajagopal, Vaishnavi; Stokes, Chris; Ferzoco, Alessandra

2018-02-01

We report a custom-geometry linear ion trap designed for fluorescence spectroscopy of gas-phase ions at ambient to cryogenic temperatures. Laser-induced fluorescence from trapped ions is collected from between the trapping rods, orthogonal to the excitation laser that runs along the axis of the linear ion trap. To increase optical access to the ion cloud, the diameter of the round trapping rods is 80% of the inscribed diameter, rather than the roughly 110% used to approximate purely quadrupolar electric fields. To encompass as much of the ion cloud as possible, the first collection optic has a 25.4 mm diameter and a numerical aperture of 0.6. The choice of geometry and collection optics yields 107 detected photons/s from trapped rhodamine 6G ions. The trap is coupled to a closed-cycle helium refrigerator, which in combination with two 50 Ohm heaters enables temperature control to below 25 K on the rod electrodes. The purpose of the instrument is to broaden the applicability of fluorescence spectroscopy of gas-phase ions to cases where photon emission is a minority relaxation pathway. Such studies are important to understand how the microenvironment of a chromophore influences excited state charge transfer processes.

Automated motile cell capture and analysis with optical traps.

PubMed

Shao, Bing; Nascimento, Jaclyn M; Shi, Linda Z; Botvinick, Elliot L

2007-01-01

Laser trapping in the near infrared regime is a noninvasive and microfluidic-compatible biomedical tool. This chapter examines the use of optical trapping as a quantitative measure of sperm motility. The single point gradient trap is used to directly measure the swimming forces of sperm from several different species. These forces could provide useful information about the overall sperm motility and semen quality. The swimming force is measured by trapping sperm and subsequently decreasing laser power until the sperm is capable of escaping the trap. Swimming trajectories were calculated by custom built software, an automatic sperm tracking algorithm called the single sperm tracking algorithm or SSTA. A real-time automated tracking and trapping system, or RATTS, which operates at video rate, was developed to perform experiments with minimal human involvement. After the experimenter initially identifies and clicks the computer mouse on the sperm-of-interest, RATTS performs all further tracking and trapping functions without human intervention. Additionally, an annular laser trap which is potentially useful for high-throughput sperm sorting based on motility and chemotaxis was developed. This low power trap offers a more gentle way for studying the effects of laser radiation, optical force, and external obstacles on sperm swimming pattern.

Activation of water soluble amines by halogens for trapping methyl radioactive iodine from air streams

DOEpatents

Deitz, Victor R.; Blachly, Charles H.

1977-01-01

Gas adsorbent charcoals impregnated with an aqueous solution of the reaction product of a tertiary amine and elemental iodine or bromine are better than 99 per cent efficient in trapping methyl iodine.sup.131. The chemical addition of iodine or bromine to the tertiary amine molecule increases the efficiency of the impregnated charcoal as a trapping agent, and in conjunction with the high flash point of the tertiary amine raises the ignition temperature of the impregnated charcoal.

Counter-propagating optical trapping system for size and refractive index measurement of microparticles.

PubMed

Flynn, Richard A; Shao, Bing; Chachisvilis, Mirianas; Ozkan, Mihrimah; Esener, Sadik C

2006-01-15

We propose and demonstrate a novel approach to measure the size and refractive index of microparticles based on two beam optical trapping, where forward scattered light is detected to give information about the particle. The counter-propagating optical trap measurement (COTM) system exploits the capability of optical traps to measure pico-Newton forces for microparticles' refractive index and size characterization. Different from the current best technique for microparticles' refractive index measurement, refractometry, a bulk technique requiring changing the fluid composition of the sample, our optical trap technique works with any transparent fluid and enables single particle analysis without the use of biological markers. A ray-optics model is used to explore the physical operation of the COTM system, predict system performance and aid system design. Experiments demonstrate the accuracy of refractive index measurement of Deltan=0.013 and size measurement of 3% of diameter with 2% standard deviation. Present performance is instrumentation limited, and a potential improvement by more than two orders of magnitude can be expected in the future. With further development in parallelism and miniaturization, the system offers advantages for cell manipulation and bioanalysis compatible with lab-on-a-chip systems.

Investigation of HIV-1 infected and uninfected cells using the optical trapping technique

NASA Astrophysics Data System (ADS)

Ombinda-Lemboumba, S.; Malabi, R.; Lugongolo, M. Y.; Thobakgale, S. L.; Manoto, S.; Mthunzi-Kufa, P.

2017-02-01

Optical trapping has emerged as an essential tool for manipulating single biological material and performing sophisticated spectroscopy analysis on individual cell. The optical trapping technique has been used to grab and immobilize cells from a tightly focused laser beam emitted through a high numerical aperture objective lens. Coupling optical trapping with other technologies is possible and allows stable sample trapping, while also facilitating molecular, chemical and spectroscopic analysis. For this reason, we are exploring laser trapping combined with laser spectroscopy as a potential non-invasive method of interrogating individual cells with a high degree of specificity in terms of information generated. Thus, for the delivery of as much pathological information as possible, we use a home-build optical trapping and spectroscopy system for real time probing human immunodeficiency virus (HIV-1) infected and uninfected single cells. Briefly, our experimental rig comprises an infrared continuous wave laser at 1064 nm with power output of 1.5 W, a 100X high numerical aperture oil-immersion microscope objective used to capture and immobilise individual cell samples as well as an excitation source. Spectroscopy spectral patterns obtained by the 1064 nm laser beam excitation provide information on HIV-1 infected and uninfected cells. We present these preliminary findings which may be valuable for the development of an HIV-1 point of care detection system.

Radioactivity measurement of radioactive contaminated soil by using a fiber-optic radiation sensor

NASA Astrophysics Data System (ADS)

Joo, Hanyoung; Kim, Rinah; Moon, Joo Hyun

2016-06-01

A fiber-optic radiation sensor (FORS) was developed to measure the gamma radiation from radioactive contaminated soil. The FORS was fabricated using an inorganic scintillator (Lu,Y)2SiO5:Ce (LYSO:Ce), a mixture of epoxy resin and hardener, aluminum foil, and a plastic optical fiber. Before its real application, the FORS was tested to determine if it performed adequately. The test result showed that the measurements by the FORS adequately followed the theoretically estimated values. Then, the FORS was applied to measure the gamma radiation from radioactive contaminated soil. For comparison, a commercial radiation detector was also applied to measure the same soil samples. The measurement data were analyzed by using a statistical parameter, the critical level to determine if net radioactivity statistically different from background was present in the soil sample. The analysis showed that the soil sample had radioactivity distinguishable from background.

Optical trapping and binding of particles in an optofluidic stable Fabry-Pérot resonator with single-sided injection.

PubMed

Gaber, Noha; Malak, Maurine; Marty, Frédéric; Angelescu, Dan E; Richalot, Elodie; Bourouina, Tarik

2014-07-07

In this article, microparticles are manipulated inside an optofluidic Fabry-Pérot cylindrical cavity embedding a fluidic capillary tube, taking advantage of field enhancement and multiple reflections within the optically-resonant cavity. This enables trapping of suspended particles with single-side injection of light and with low optical power. A Hermite-Gaussian standing wave is developed inside the cavity, forming trapping spots at the locations of the electromagnetic field maxima with a strong intensity gradient. The particles get arranged in a pattern related to the mechanism affecting them: either optical trapping or optical binding. This is proven to eventually translate into either an axial one dimensional (1D) particle array or a cluster of particles. Numerical simulations are performed to model the field distributions inside the cavity allowing a behavioral understanding of the phenomena involved in each case.

Trapping and rotating of a metallic particle trimer with optical vortex

NASA Astrophysics Data System (ADS)

Shen, Z.; Su, L.; Yuan, X.-C.; Shen, Y.-C.

2016-12-01

We have experimentally observed the steady rotation of a mesoscopic size metallic particle trimer that is optically trapped by tightly focused circularly polarized optical vortex. Our theoretical analysis suggests that a large proportion of the radial scattering force pushes the metallic particles together, whilst the remaining portion provides the centripetal force necessary for the rotation. Furthermore, we have achieved the optical trapping and rotation of four dielectric particles with optical vortex. We found that, different from the metallic particles, instead of being pushed together by the radial scattering force, the dielectric particles are trapped just outside the maximum intensity ring of the focused field. The radial gradient force attracting the dielectric particles towards the maximum intensity ring provides the centripetal force for the rotation. The achieved steady rotation of the metallic particle trimer reported here may open up applications such as the micro-rotor.

Objective-lens-free Fiber-based Position Detection with Nanometer Resolution in a Fiber Optical Trapping System.

PubMed

Ti, Chaoyang; Ho-Thanh, Minh-Tri; Wen, Qi; Liu, Yuxiang

2017-10-13

Position detection with high accuracy is crucial for force calibration of optical trapping systems. Most existing position detection methods require high-numerical-aperture objective lenses, which are bulky, expensive, and difficult to miniaturize. Here, we report an affordable objective-lens-free, fiber-based position detection scheme with 2 nm spatial resolution and 150 MHz bandwidth. This fiber based detection mechanism enables simultaneous trapping and force measurements in a compact fiber optical tweezers system. In addition, we achieved more reliable signal acquisition with less distortion compared with objective based position detection methods, thanks to the light guiding in optical fibers and small distance between the fiber tips and trapped particle. As a demonstration of the fiber based detection, we used the fiber optical tweezers to apply a force on a cell membrane and simultaneously measure the cellular response.

Method for removing cesium from a nuclear reactor coolant

DOEpatents

Colburn, R.P.

1983-08-10

A method of and system for removing cesium from a liquid metal reactor coolant including a carbon packing trap in the primary coolant system for absorbing a major portion of the radioactive cesium from the coolant flowing therethrough at a reduced temperature. A regeneration subloop system having a secondary carbon packing trap is selectively connected to the primary system for isolating the main trap therefrom and connecting it to the regeneration system. Increasing the temperature of the sodium flowing through the primary trap diffuses a portion of the cesium inventory thereof further into the carbon matrix while simultaneously redispersing a portion into the regeneration system for absorption at a reduced temperature by the secondary trap.

Probing orientation and rotation of red blood cells in optical tweezers by digital holographic microscopy

NASA Astrophysics Data System (ADS)

Cardenas, Nelson; Yu, Lingfeng; Mohanty, Samarendra K.

2011-03-01

Interaction of red blood cells (RBC) with optical tweezers has been found to differ under varied physiological and pathological conditions as compared to its normal conditions. Earlier, we reported difference in rotation of trapped RBC in hypertonic conditions for detection of malaria infection. Disk-like RBC when trapped in optical tweezers get oriented in the vertical plane to maximize interaction with trapping beam. However, classical bright field, phase contrast or epifluorescence microscopy cannot confirm its orientation, thus leading to ambiguous conclusions such as folding of RBC during trapping by some researchers. Now, with use of digital holographic microscopy (DHM), we achieved high axial sensitivity that confirmed orientation of trapped red blood cell. Further, DHM enabled quantitative phase imaging of RBC under hypertonic condition. Dynamic changes of rotating RBC under optical tweezers at different trapping laser power were evaluated by the use of DHM. The deviation from linear dependence of rotation speed of RBC on laser power, was attributed towards deformation of RBC shape due to higher laser power (or speed).

Optical trapping reveals propulsion forces, power generation and motility efficiency of the unicellular parasites Trypanosoma brucei brucei

NASA Astrophysics Data System (ADS)

Stellamanns, Eric; Uppaluri, Sravanti; Hochstetter, Axel; Heddergott, Niko; Engstler, Markus; Pfohl, Thomas

2014-10-01

Unicellular parasites have developed sophisticated swimming mechanisms to survive in a wide range of environments. Cell motility of African trypanosomes, parasites responsible for fatal illness in humans and animals, is crucial both in the insect vector and the mammalian host. Using millisecond-scale imaging in a microfluidics platform along with a custom made optical trap, we are able to confine single cells to study trypanosome motility. From the trapping characteristics of the cells, we determine the propulsion force generated by cells with a single flagellum as well as of dividing trypanosomes with two fully developed flagella. Estimates of the dissipative energy and the power generation of single cells obtained from the motility patterns of the trypanosomes within the optical trap indicate that specific motility characteristics, in addition to locomotion, may be required for antibody clearance. Introducing a steerable second optical trap we could further measure the force, which is generated at the flagellar tip. Differences in the cellular structure of the trypanosomes are correlated with the trapping and motility characteristics and in consequence with their propulsion force, dissipative energy and power generation.

Optical trapping reveals propulsion forces, power generation and motility efficiency of the unicellular parasites Trypanosoma brucei brucei.

PubMed

Stellamanns, Eric; Uppaluri, Sravanti; Hochstetter, Axel; Heddergott, Niko; Engstler, Markus; Pfohl, Thomas

2014-10-01

Unicellular parasites have developed sophisticated swimming mechanisms to survive in a wide range of environments. Cell motility of African trypanosomes, parasites responsible for fatal illness in humans and animals, is crucial both in the insect vector and the mammalian host. Using millisecond-scale imaging in a microfluidics platform along with a custom made optical trap, we are able to confine single cells to study trypanosome motility. From the trapping characteristics of the cells, we determine the propulsion force generated by cells with a single flagellum as well as of dividing trypanosomes with two fully developed flagella. Estimates of the dissipative energy and the power generation of single cells obtained from the motility patterns of the trypanosomes within the optical trap indicate that specific motility characteristics, in addition to locomotion, may be required for antibody clearance. Introducing a steerable second optical trap we could further measure the force, which is generated at the flagellar tip. Differences in the cellular structure of the trypanosomes are correlated with the trapping and motility characteristics and in consequence with their propulsion force, dissipative energy and power generation.

Optical waveguide loop for planar trapping of blood cells and microspheres

NASA Astrophysics Data System (ADS)

Ahluwalia, Balpreet S.; Hellesø, Olav G.

2013-09-01

The evanescent field from a waveguide can be used to trap and propel a particle. An optical waveguide loop with an intentional gap at the center is used for planar transport and stable trapping of particles. The waveguide acts as a conveyor belt to trap and deliver spheres towards the gap. At the gap, the counter-diverging light fields hold the sphere at a fixed position. Numerical simulation based on the finite element method was performed in three dimensions using a computer cluster. The field distribution and optical forces for rib and strip waveguide designs are compared and discussed. The optical force on a single particle was computed for various positions of the particle in the gap. Simulation predicted stable trapping of particles in the gap. Depending on the gap separation (2-50 μm) a single or multiple spheres and red blood cells were trapped at the gap. Waveguides were made of tantalum pentaoxide material. The waveguides are only 180 nm thick and thus could be integrated with other functions on the chip.

Refractive multiple optical tweezers for parallel biochemical analysis in micro-fluidics

NASA Astrophysics Data System (ADS)

Merenda, Fabrice; Rohner, Johann; Pascoal, Pedro; Fournier, Jean-Marc; Vogel, Horst; Salathé, René-Paul

2007-02-01

We present a multiple laser tweezers system based on refractive optics. The system produces an array of 100 optical traps thanks to a refractive microlens array, whose focal plane is imaged into the focal plane of a high-NA microscope objective. This refractive multi-tweezers system is combined to micro-fluidics, aiming at performing simultaneous biochemical reactions on ensembles of free floating objects. Micro-fluidics allows both transporting the particles to the trapping area, and conveying biochemical reagents to the trapped particles. Parallel trapping in micro-fluidics is achieved with polystyrene beads as well as with native vesicles produced from mammalian cells. The traps can hold objects against fluid flows exceeding 100 micrometers per second. Parallel fluorescence excitation and detection on the ensemble of trapped particles is also demonstrated. Additionally, the system is capable of selectively and individually releasing particles from the tweezers array using a complementary steerable laser beam. Strategies for high-yield particle capture and individual particle release in a micro-fluidic environment are discussed. A comparison with diffractive optical tweezers enhances the pros and cons of refractive systems.

Extending calibration-free force measurements to optically-trapped rod-shaped samples

PubMed Central

Català, Frederic; Marsà, Ferran; Montes-Usategui, Mario; Farré, Arnau; Martín-Badosa, Estela

2017-01-01

Optical trapping has become an optimal choice for biological research at the microscale due to its non-invasive performance and accessibility for quantitative studies, especially on the forces involved in biological processes. However, reliable force measurements depend on the calibration of the optical traps, which is different for each experiment and hence requires high control of the local variables, especially of the trapped object geometry. Many biological samples have an elongated, rod-like shape, such as chromosomes, intracellular organelles (e.g., peroxisomes), membrane tubules, certain microalgae, and a wide variety of bacteria and parasites. This type of samples often requires several optical traps to stabilize and orient them in the correct spatial direction, making it more difficult to determine the total force applied. Here, we manipulate glass microcylinders with holographic optical tweezers and show the accurate measurement of drag forces by calibration-free direct detection of beam momentum. The agreement between our results and slender-body hydrodynamic theoretical calculations indicates potential for this force-sensing method in studying protracted, rod-shaped specimens. PMID:28220855

Rotating of low-refractive-index microparticles with a quasi-perfect optical vortex.

PubMed

Liang, Yansheng; Lei, Ming; Yan, Shaohui; Li, Manman; Cai, Yanan; Wang, Zhaojun; Yu, Xianghua; Yao, Baoli

2018-01-01

Low-refractive-index microparticles, such as hollow microspheres, have shown great significance in some applications, such as biomedical sensing and targeted drug delivery. However, optical trapping and manipulation of low-refractive-index microparticles are challenging, owing to the repelling force exerted by typical optical traps. In this paper, we demonstrated optical trapping and rotating of large-sized low-refractive-index microparticles by using quasi-perfect optical vortex (quasi-POV) beams, which were generated by Fourier transform of high-order quasi-Bessel beams. Numerical simulation was carried out to characterize the focusing property of the quasi-POV beams. The dynamics of low-refractive-index microparticles in the quasi-POV with various topological charges was investigated in detail. To improve the trapping and rotating performances of the vortex, a point trap was introduced at the center of the ring. Experimental results showed that the quasi-POV was preferable for manipulation of large-sized low-refractive-index microparticles, with its control of the particles' rotating velocity dependent only on the topological charge due to the unchanged orbital radius.

Cooling an Optically Trapped Ultracold Fermi Gas by Periodical Driving.

PubMed

Li, Jiaming; de Melo, Leonardo F; Luo, Le

2017-03-30

We present a cooling method for a cold Fermi gas by parametrically driving atomic motions in a crossed-beam optical dipole trap (ODT). Our method employs the anharmonicity of the ODT, in which the hotter atoms at the edge of the trap feel the anharmonic components of the trapping potential, while the colder atoms in the center of the trap feel the harmonic one. By modulating the trap depth with frequencies that are resonant with the anharmonic components, we selectively excite the hotter atoms out of the trap while keeping the colder atoms in the trap, generating parametric cooling. This experimental protocol starts with a magneto-optical trap (MOT) that is loaded by a Zeeman slower. The precooled atoms in the MOT are then transferred to an ODT, and a bias magnetic field is applied to create an interacting Fermi gas. We then lower the trapping potential to prepare a cold Fermi gas near the degenerate temperature. After that, we sweep the magnetic field to the noninteracting regime of the Fermi gas, in which the parametric cooling can be manifested by modulating the intensity of the optical trapping beams. We find that the parametric cooling effect strongly depends on the modulation frequencies and amplitudes. With the optimized frequency and amplitude, we measure the dependence of the cloud energy on the modulation time. We observe that the cloud energy is changed in an anisotropic way, where the energy of the axial direction is significantly reduced by parametric driving. The cooling effect is limited to the axial direction because the dominant anharmonicity of the crossed-beam ODT is along the axial direction. Finally, we propose to extend this protocol for the trapping potentials of large anharmonicity in all directions, which provides a promising scheme for cooling quantum gases using external driving.

Collisional Decoherence in Trapped-Atom Interferometers that use Nondegenerate Sources

DTIC Science & Technology

2009-01-22

a magneto - optical trap . The trap is switched off and the atomic cloud begins to fall due to gravity. At the time t=0, the cloud is illuminated with...model is used to find the optimal operating conditions of the interferometer and direct Monte-Carlo simulation of the interferometer is used to...A major difficulty with all trapped -atom interferometers that use optical pulses is that the residual potential along the guide causes

Efficient repumping of a Ca magneto-optical trap

NASA Astrophysics Data System (ADS)

Mills, Michael; Puri, Prateek; Yu, Yanmei; Derevianko, Andrei; Schneider, Christian; Hudson, Eric R.

2017-09-01

We investigate the limiting factors in the standard implementation of the Ca magneto-optical trap. We find that intercombination transitions from the 4 s 5 p 1P1 state used to repump the electronic population from the 3 d 4 s 1D2 state severely reduce the trap lifetime. We explore seven alternative repumping schemes theoretically and investigate five of them experimentally. We find that all five of these schemes yield a significant increase in the trap lifetime and consequently improve the number of atoms and peak atom density by as much as ˜20 times and ˜6 times, respectively. One of these transitions, at 453 nm, is shown to approach the fundamental limit for a Ca magneto-optical trap with repumping only from the dark 3 d 4 s 1D2 state, yielding a trap lifetime of ˜5 s.

Trapping force and optical lifting under focused evanescent wave illumination.

PubMed

Ganic, Djenan; Gan, Xiaosong; Gu, Min

2004-11-01

A physical model is presented to understand and calculate trapping force exerted on a dielectric micro-particle under focused evanescent wave illumination. This model is based on our recent vectorial diffraction model by a high numerical aperture objective operating under the total internal condition. As a result, trapping force in a focused evanescent spot generated by both plane wave (TEM00) and doughnut beam (TEM*01) illumination is calculated, showing an agreement with the measured results. It is also revealed by this model that unlike optical trapping in the far-field region, optical axial trapping force in an evanescent focal spot increases linearly with the size of a trapped particle. This prediction shows that it is possible to overcome the force of gravity to lift a polystyrene particle of up to 800 nm in radius with a laser beam of power 10 microW.

Coherent all-optical control of ultracold atoms arrays in permanent magnetic traps.

PubMed

Abdelrahman, Ahmed; Mukai, Tetsuya; Häffner, Hartmut; Byrnes, Tim

2014-02-10

We propose a hybrid architecture for quantum information processing based on magnetically trapped ultracold atoms coupled via optical fields. The ultracold atoms, which can be either Bose-Einstein condensates or ensembles, are trapped in permanent magnetic traps and are placed in microcavities, connected by silica based waveguides on an atom chip structure. At each trapping center, the ultracold atoms form spin coherent states, serving as a quantum memory. An all-optical scheme is used to initialize, measure and perform a universal set of quantum gates on the single and two spin-coherent states where entanglement can be generated addressably between spatially separated trapped ultracold atoms. This allows for universal quantum operations on the spin coherent state quantum memories. We give detailed derivations of the composite cavity system mediated by a silica waveguide as well as the control scheme. Estimates for the necessary experimental conditions for a working hybrid device are given.

Optical ferris wheel for ultracold atoms

NASA Astrophysics Data System (ADS)

Franke-Arnold, S.; Leach, J.; Padgett, M. J.; Lembessis, V. E.; Ellinas, D.; Wright, A. J.; Girkin, J. M.; Ohberg, P.; Arnold, A. S.

2007-07-01

We propose a versatile optical ring lattice suitable for trapping cold and quantum degenerate atomic samples. We demonstrate the realisation of intensity patterns from pairs of Laguerre-Gauss (exp(iℓө) modes with different ℓ indices. These patterns can be rotated by introducing a frequency shift between the modes. We can generate bright ring lattices for trapping atoms in red-detuned light, and dark ring lattices suitable for trapping atoms with minimal heating in the optical vortices of blue-detuned light. The lattice sites can be joined to form a uniform ring trap, making it ideal for studying persistent currents and the Mott insulator transition in a ring geometry.

A technique for individual atom delivery into a crossed vortex bottle beam trap using a dynamic 1D optical lattice.

PubMed

Dinardo, Brad A; Anderson, Dana Z

2016-12-01

We describe a system for loading a single atom from a reservoir into a blue-detuned crossed vortex bottle beam trap using a dynamic 1D optical lattice. The lattice beams are frequency chirped using acousto-optic modulators, which causes the lattice to move along its axial direction and behave like an optical conveyor belt. A stationary lattice is initially loaded with approximately 6000 atoms from a reservoir, and the conveyor belt transports them 1.1 mm from the reservoir to a bottle beam trap, where a single atom is loaded via light-assisted collisions. Photon counting data confirm that an atom can be delivered and loaded into the bottle beam trap 13.1% of the time.

Ion current as a precise measure of the loading rate of a magneto-optical trap

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, W.; Bailey, K.; Lu, Z. -T.

2014-01-01

We have demonstrated that the ion current resulting from collisions between metastable krypton atoms in a magneto-optical trap can be used to precisely measure the trap loading rate. We measured both the ion current of the abundant isotope Kr-83 (isotopic abundance = 11%) and the single-atom counting rate of the rare isotope Kr-85 (isotopic abundance similar to 1 x 10(-11)), and found the two quantities to be proportional at a precision level of 0.9%. This work results in a significant improvement in using the magneto-optical trap as an analytical tool for noble-gas isotope ratio measurements, and will benefit both atomicmore » physics studies and applications in the earth sciences. (C) 2014 Optical Society of America« less

Dynamics of optical matter creation and annihilation in colloidal liquids controlled by laser trapping power.

PubMed

Liu, Jin; Dai, Qiao-Feng; Huang, Xu-Guang; Wu, Li-Jun; Guo, Qi; Hu, Wei; Yang, Xiang-Bo; Lan, Sheng; Gopal, Achanta Venu; Trofimov, Vyacheslav A

2008-11-15

We investigate the dynamics of optical matter creation and annihilation in a colloidal liquid that was employed to construct an all-optical switch. It is revealed that the switching-on process can be characterized by the Fermi-Dirac distribution function, while the switching-off process can be described by a steady state followed by a single exponential decay. The phase transition times exhibit a strong dependence on trapping power. With an increasing trapping power, while the switching-on time decreases rapidly, the switch-off time increases significantly, indicating the effects of optical binding and van der Waals force on the lifetime of the optical matter.

Optical trapping via guided resonance modes in a Slot-Suzuki-phase photonic crystal lattice.

PubMed

Ma, Jing; Martínez, Luis Javier; Povinelli, Michelle L

2012-03-12

A novel photonic crystal lattice is proposed for trapping a two-dimensional array of particles. The lattice is created by introducing a rectangular slot in each unit cell of the Suzuki-Phase lattice to enhance the light confinement of guided resonance modes. Large quality factors on the order of 10⁵ are predicted in the lattice. A significant decrease of the optical power required for optical trapping can be achieved compared to our previous design.

Assembly of microparticles by optical trapping with a photonic crystal nanocavity

NASA Astrophysics Data System (ADS)

Renaut, C.; Dellinger, J.; Cluzel, B.; Honegger, T.; Peyrade, D.; Picard, E.; de Fornel, F.; Hadji, E.

2012-03-01

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.

Rotational dynamics and heating of trapped nanovaterite particles (Conference Presentation)

NASA Astrophysics Data System (ADS)

Arita, Yoshihiko; Richards, Joseph M.; Mazilu, Michael; Spalding, Gabriel C.; Skelton Spesyvtseva, Susan E.; Craig, Derek; Dholakia, Kishan

2016-09-01

Rotational control over optically trapped particles has gained significant prominence in recent years. The marriage between light fields possessing optical angular momentum and the material properties of microparticles has been useful to controllably spin particles in liquid, air and vacuum. The rotational degree of freedom adds new functionality to optical traps: in addition to allowing fundamental tests of optical angular momentum, the transfer of spin angular momentum in particular can allow measurements of local viscosity and exert local stresses on cellular systems. We demonstrate optical trapping and controlled rotation of nanovaterite crystals. These particles represent the smallest birefringent crystals ever trapped and set into rotation. Rotation rates of up to 5kHz in water are recorded, representing the fastest rotation to date for dielectric particles in liquid. Laser-induced heating results in the superlinear behaviour of the rotation rate as a function of trap power. We study both the rotational and translational modes of trapped nanovaterite crystals. The particle temperatures derived from those two optomechanical modes are in good agreement, which is supported by a numerical model revealing that the observed heating is dominated by absorption of light by the particles rather than by the surrounding liquid. A comparison is performed with trapped silica particles of similar size. The use of nanovaterite particles open up new studies for levitated optomechanics in vacuum as well as microrheological properties of cells or biological media. Their size and low heating offers prospects of viscosity measurements in ultra-small volumes and potentially simpler uptake by cellular media.

Measurement of elastic light scattering from two optically trapped microspheres and red blood cells in a transparent medium.

PubMed

Kinnunen, Matti; Kauppila, Antti; Karmenyan, Artashes; Myllylä, Risto

2011-09-15

Optical tweezers can be used to manipulate small objects and cells. A trap can be used to fix the position of a particle during light scattering measurements. The places of two separately trapped particles can also be changed. In this Letter we present elastic light scattering measurements as a function of scattering angle when two trapped spheres are illuminated with a He-Ne laser. This setup is suitable for trapping noncharged homogeneous spheres. We also demonstrate measurement of light scattering patterns from two separately trapped red blood cells. Two different illumination schemes are used for both samples.

Single atom array to form a Rydberg ring

NASA Astrophysics Data System (ADS)

Zhan, Mingsheng; Xu, Peng; He, Xiaodong; Liu, Min; Wang, Jin

2012-02-01

Single atom arrays are ideal quantum systems for studying few-body quantum simulation and quantum computation [1]. Towards realizing a fully controllable array we did a lot of experimental efforts, which include rotating single atoms in a ring optical lattice generated by a spatial light modulator [2], high efficient loading of two atoms into a microscopic optical trap by dynamically reshaping the trap with a spatial light modulator [3], and trapping a single atom in a blue detuned optical bottle beam trap [4]. Recently, we succeeded in trapping up to 6 atoms in a ring optical lattice with one atom in each site. Further laser cooling the array and manipulation of the inner states will provide chance to form Ryberg rings for quantum simulation. [4pt] [1] M. Saffman et al., Rev. Mod. Phys. 82, 2313 (2010)[0pt] [2] X.D. He et al., Opt. Express 17, 21014 (2009)[0pt] [3] X.D. He et al., Opt. Express 18, 13586 (2010)[0pt] [4] P. Xu et al., Opt. Lett. 35, 2164 (2010)

Effects of non-Gaussian Brownian motion on direct force optical tweezers measurements of the electrostatic forces between pairs of colloidal particles.

PubMed

Raudsepp, Allan; A K Williams, Martin; B Hall, Simon

2016-07-01

Measurements of the electrostatic force with separation between a fixed and an optically trapped colloidal particle are examined with experiment, simulation and analytical calculation. Non-Gaussian Brownian motion is observed in the position of the optically trapped particle when particles are close and traps weak. As a consequence of this motion, a simple least squares parameterization of direct force measurements, in which force is inferred from the displacement of an optically trapped particle as separation is gradually decreased, contains forces generated by the rectification of thermal fluctuations in addition to those originating directly from the electrostatic interaction between the particles. Thus, when particles are close and traps weak, simply fitting the measured direct force measurement to DLVO theory extracts parameters with modified meanings when compared to the original formulation. In such cases, however, physically meaningful DLVO parameters can be recovered by comparing the measured non-Gaussian statistics to those predicted by solutions to Smoluchowski's equation for diffusion in a potential.

Confocal micro-Raman spectroscopy of single biological cells using optical trapping and shifted excitation difference techniques

NASA Astrophysics Data System (ADS)

Xie, Changan; Li, Yong-qing

2003-03-01

We report on the study of single biological cells with a confocal micro-Raman spectroscopy system that uses optical trapping and shifted excitation Raman difference technique. A tunable diode laser was used to capture a living cell in solution, confine it in the confocal excitation volume, and then excite the Raman scattering. The optical trapping allows us to lift the cell well off the cover plate so that the fluorescence interference from the plate can be effectively reduced. In order to further remove the interference of the fluorescence and stray light from the trapped cell, we employed a shifted excitation Raman difference technique with slightly tuned laser frequencies. With this system, high-quality Raman spectra were obtained from single optically trapped biological cells including E. coli bacteria, yeast cells, and red blood cells. A significant difference between control and heat-treated E. coli B cells was observed due to the denaturation of biomolecules.

BioPhotonics workstation: A versatile setup for simultaneous optical manipulation, heat stress, and intracellular pH measurements of a live yeast cell

NASA Astrophysics Data System (ADS)

Aabo, Thomas; Banás, Andrew Raphael; Glückstad, Jesper; Siegumfeldt, Henrik; Arneborg, Nils

2011-08-01

In this study we have modified the BioPhotonics workstation (BWS), which allows for using long working distance objective for optical trapping, to include traditional epi-fluorescence microscopy, using the trapping objectives. We have also added temperature regulation of sample stage, allowing for fast temperature variations while trapping. Using this modified BWS setup, we investigated the internal pH (pHi) response and membrane integrity of an optically trapped Saccharomyces cerevisiae cell at 5 mW subject to increasing temperatures. The pHi of the cell is obtained from the emission of 5-(and-6)-carboxyfluorescein diacetate, succinimidyl ester, at 435 and 485 nm wavelengths, while the permeability is indicated by the fluorescence of propidium iodide. We present images mapping the pHi and permeability of the cell at different temperatures and with enough spatial resolution to localize these attributes within the cell. The combined capability of optical trapping, fluorescence microscopy and temperature regulation offers a versatile tool for biological research.

Introduction: Optical trapping and applications feature issue

PubMed Central

López-Mariscal, Carlos; McGloin, David

2013-01-01

The editors introduce the Biomedical Optics Express feature issue on “Optical Trapping and Applications.” The works presented in the papers within this issue include were the focus of the third OTA Topical Meeting that was held on April 14–18, 2013, in Waikoloa, Hawaii. PMID:24298428

Intensity-modulated polarizabilities and magic trapping of alkali-metal and divalent atoms in infrared optical lattices

NASA Astrophysics Data System (ADS)

Topcu, Turker; Derevianko, Andrei

2014-05-01

Long range interactions between neutral Rydberg atoms has emerged as a potential means for implementing quantum logical gates. These experiments utilize hyperfine manifold of ground state atoms to act as a qubit basis, while exploiting the Rydberg blockade mechanism to mediate conditional quantum logic. The necessity for overcoming several sources of decoherence makes magic wavelength trapping in optical lattices an indispensable tool for gate experiments. The common wisdom is that atoms in Rydberg states see trapping potentials that are essentially that of a free electron, and can only be trapped at laser intensity minima. We show that although the polarizability of a Rydberg state is always negative, the optical potential can be both attractive or repulsive at long wavelengths (up to ~104 nm). This opens up the possibility of magic trapping Rydberg states with ground state atoms in optical lattices, thereby eliminating the necessity to turn off trapping fields during gate operations. Because the wavelengths are near the CO2 laser band, the photon scattering and the ensuing motional heating is also reduced compared to conventional traps near low lying resonances, alleviating an important source of decoherence. This work was supported by the National Science Foundation (NSF) Grant No. PHY-1212482.

Trapping and dynamic manipulation of polystyrene beads mimicking circulating tumor cells using targeted magnetic/photoacoustic contrast agents

NASA Astrophysics Data System (ADS)

Wei, Chen-Wei; Xia, Jinjun; Pelivanov, Ivan; Hu, Xiaoge; Gao, Xiaohu; O'Donnell, Matthew

2012-10-01

Results on magnetically trapping and manipulating micro-scale beads circulating in a flow field mimicking metastatic cancer cells in human peripheral vessels are presented. Composite contrast agents combining magneto-sensitive nanospheres and highly optical absorptive gold nanorods were conjugated to micro-scale polystyrene beads. To efficiently trap the targeted objects in a fast stream, a dual magnet system consisting of two flat magnets to magnetize (polarize) the contrast agent and an array of cone magnets producing a sharp gradient field to trap the magnetized contrast agent was designed and constructed. A water-ink solution with an optical absorption coefficient of 10 cm-1 was used to mimic the optical absorption of blood. Magnetomotive photoacoustic imaging helped visualize bead trapping, dynamic manipulation of trapped beads in a flow field, and the subtraction of stationary background signals insensitive to the magnetic field. The results show that trafficking micro-scale objects can be effectively trapped in a stream with a flow rate up to 12 ml/min and the background can be significantly (greater than 15 dB) suppressed. It makes the proposed method very promising for sensitive detection of rare circulating tumor cells within high flow vessels with a highly absorptive optical background.

Elastic light scattering from single cells: orientational dynamics in optical trap.

PubMed

Watson, Dakota; Hagen, Norbert; Diver, Jonathan; Marchand, Philippe; Chachisvilis, Mirianas

2004-08-01

Light-scattering diagrams (phase functions) from single living cells and beads suspended in an optical trap were recorded with 30-ms time resolution. The intensity of the scattered light was recorded over an angular range of 0.5-179.5 degrees using an optical setup based on an elliptical mirror and rotating aperture. Experiments revealed that light-scattering diagrams from biological cells exhibit significant and complex time dependence. We have attributed this dependence to the cell's orientational dynamics within the trap. We have also used experimentally measured phase function information to calculate the time dependence of the optical radiation pressure force on the trapped particle and show how it changes depending on the orientation of the particle. Relevance of these experiments to potential improvement in the sensitivity of label-free flow cytometry is discussed.

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

PubMed Central

López-Quesada, C.; Fontaine, A.-S.; Farré, A.; Joseph, M.; Selva, J.; Egea, G.; Ludevid, M. D.; Martín-Badosa, E.; Montes-Usategui, M.

2014-01-01

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. PMID:25071944

Single-laser, one beam, tetrahedral magneto-optical trap.

PubMed

Vangeleyn, Matthieu; Griffin, Paul F; Riis, Erling; Arnold, Aidan S

2009-08-03

We have realized a 4-beam pyramidal magneto-optical trap ideally suited for future microfabrication. Three mirrors split and steer a single incoming beam into a tripod of reflected beams, allowing trapping in the four-beam overlap volume. We discuss the influence of mirror angle on cooling and trapping, finding optimum efficiency in a tetrahedral configuration. We demonstrate the technique using an ex-vacuo mirror system to illustrate the previously inaccessible supra-plane pyramid MOT configuration. Unlike standard pyramidal MOTs both the pyramid apex and its mirror angle are non-critical and our MOT offers improved molasses free from atomic shadows in the laser beams. The MOT scheme naturally extends to a 2-beam refractive version with high optical access. For quantum gas experiments, the mirror system could also be used for a stable 3D tetrahedral optical lattice.

A minimally invasive optical trapping system to understand cellular interactions at onset of an immune response

PubMed Central

Glass, David G.; McAlinden, Niall; Millington, Owain R.

2017-01-01

T-cells and antigen presenting cells are an essential part of the adaptive immune response system and how they interact is crucial in how the body effectively fights infection or responds to vaccines. Much of the experimental work studying interaction forces between cells has looked at the average properties of bulk samples of cells or applied microscopy to image the dynamic contact between these cells. In this paper we present a novel optical trapping technique for interrogating the force of this interaction and measuring relative interaction forces at the single-cell level. A triple-spot optical trap is used to directly manipulate the cells of interest without introducing foreign bodies such as beads to the system. The optical trap is used to directly control the initiation of cell-cell contact and, subsequently to terminate the interaction at a defined time point. The laser beam power required to separate immune cell pairs is determined and correlates with the force applied by the optical trap. As proof of concept, the antigen-specific increase in interaction force between a dendritic cell and a specific T-cell is demonstrated. Furthermore, it is demonstrated that this interaction force is completely abrogated when T-cell signalling is blocked. As a result the potential of using optical trapping to interrogate cellular interactions at the single cell level without the need to introduce foreign bodies such as beads is clearly demonstrated. PMID:29220398

Experimental and theoretical investigations on the validity of the geometrical optics model for calculating the stability of optical traps.

PubMed

Schut, T C; Hesselink, G; de Grooth, B G; Greve, J

1991-01-01

We have developed a computer program based on the geometrical optics approach proposed by Roosen to calculate the forces on dielectric spheres in focused laser beams. We have explicitly taken into account the polarization of the laser light and thd divergence of the laser beam. The model can be used to evaluate the stability of optical traps in a variety of different optical configurations. Our calculations explain the experimental observation by Ashkin that a stable single-beam optical trap, without the help of the gravitation force, can be obtained with a strongly divergent laser beam. Our calculations also predict a different trap stability in the directions orthogonal and parallel to the polarization direction of the incident light. Different experimental methods were used to test the predictions of the model for the gravity trap. A new method for measuring the radiation force along the beam axis in both the stable and instable regions is presented. Measurements of the radiation force on polystyrene spheres with diameters of 7.5 and 32 microns in a TEM00-mode laser beam showed a good qualitative correlation with the predictions and a slight quantitative difference. The validity of the geometrical approximations involved in the model will be discussed for spheres of different sizes and refractive indices.

The tug-of-war behavior of a Brownian particle in an asymmetric double optical trap with stochastic fluctuations

NASA Astrophysics Data System (ADS)

Long, Fei; Zhu, Jia-Pei

2018-07-01

A Brownian particle optically trapped in an asymmetric double potential surrounded by a thermal bath was simulated. Under the cooperative action of the resultant deterministic optical force and the stochastic fluctuations of the thermal bath, the confined particle undergoes Kramers transition, and oscillates between the two traps with a probability of trap occupancy that is asymmetrically distributed about the midpoint. The simulation results obtained at different temperatures indicate that the oscillation behavior of the particle can be treated as the result of a tug-of-war game played between the resultant deterministic force and the random force. We also employ a bistable model to explain the observed phenomena.

Observation of a single-beam gradient-force optical trap for dielectric particles in air.

PubMed

Omori, R; Kobayashi, T; Suzuki, A

1997-06-01

A single-beam gradient-force optical trap for dielectric particles, which relies solely on the radiation pressure force of a TEM(00)-mode laser light, is demonstrated in air for what is believed to be the first time. It was observed that micrometer-sized glass spheres with a refractive index of n=1.45 remained trapped in the focus region for more than 30 min, and we could transfer them three dimensionally by moving the beam focus and the microscope stage. A laser power of ~40 mW was sufficient to trap a 5- microm -diameter glass sphere. The present method has several distinct advantages over the conventional optical levitation method.

Grating-flanked plasmonic coaxial apertures for efficient fiber optical tweezers.

PubMed

Saleh, Amr A E; Sheikhoelislami, Sassan; Gastelum, Steven; Dionne, Jennifer A

2016-09-05

Subwavelength plasmonic apertures have been foundational for direct optical manipulation of nanoscale specimens including sub-100 nm polymeric beads, metallic nanoparticles and proteins. While most plasmonic traps result in two-dimensional localization, three-dimensional manipulation has been demonstrated by integrating a plasmonic aperture on an optical fiber tip. However, such 3D traps are usually inefficient since the optical mode of the fiber and the subwavelength aperture only weakly couple. In this paper we design more efficient optical-fiber-based plasmonic tweezers combining a coaxial plasmonic aperture with a plasmonic grating coupler at the fiber tip facet. Using full-field finite difference time domain analysis, we optimize the grating design for both gold and silver fiber-based coaxial tweezers such that the optical transmission through the apertures is maximized. With the optimized grating, we show that the maximum transmission efficiency increases from 2.5% to 19.6% and from 1.48% to 16.7% for the gold and silver structures respectively. To evaluate their performance as optical tweezers, we calculate the optical forces and the corresponding trapping potential on dielectric particles interacting with the apertures. We demonstrate that the enahncement in the transmission translates into an equivalent increase in the optical forces. Consequently, the optical power required to achieve stable optical trapping is significantly reduced allowing for efficient localization and 3D manipulation of sub-30 nm dielectric particles.

Symmetry dependence of holograms for optical trapping

NASA Astrophysics Data System (ADS)

Curtis, Jennifer E.; Schmitz, Christian H. J.; Spatz, Joachim P.

2005-08-01

No iterative algorithm is necessary to calculate holograms for most holographic optical trapping patterns. Instead, holograms may be produced by a simple extension of the prisms-and-lenses method. This formulaic approach yields the same diffraction efficiency as iterative algorithms for any asymmetric or symmetric but nonperiodic pattern of points while requiring less calculation time. A slight spatial disordering of periodic patterns significantly reduces intensity variations between the different traps without extra calculation costs. Eliminating laborious hologram calculations should greatly facilitate interactive holographic trapping.

Kinect the dots: 3D control of optical tweezers

NASA Astrophysics Data System (ADS)

Shaw, Lucy; Preece, Daryl; Rubinsztein-Dunlop, Halina

2013-07-01

Holographically generated optical traps confine micron- and sub-micron sized particles close to the center of focused light beams. They also provide a way of trapping multiple particles and moving them in three dimensions. However, in many systems the user interface is not always advantageous or intuitive especially for collaborative work and when depth information is required. We discuss and evaluate a set of multi-beam optical tweezers that utilize off the shelf gaming technology to facilitate user interaction. We use the Microsoft Kinect sensor bar as a way of getting the user input required to generate arbitrary optical force fields and control optically trapped particles. We demonstrate that the system can also be used for dynamic light control.

Characteristics of the annular beam using a single axicon and a pair of lens

NASA Astrophysics Data System (ADS)

Ji, Ke; Lei, Ming; Yao, Baoli; Yan, Shaohui; Yang, Yanlong; Li, Ze; Dan, Dan; Menke, Neimule

2012-10-01

In optical trapping, annular beam as a kind of hollow beam is used to increase the axial trapping efficiency as well as the trapping stability. In this paper, a method for producing an annular beam by a system consisting of a single axicon and a pair of lens is proposed. The generated beam was also used as the optical tweezers. We use the geometrical optics to describe the propagation of light in the system. The calculated intensity distribution in three-dimensional space after the system shows a good agreement with the experimental results. The advantages of this method are simplicity of operation, good stability, and high transmittance, having possible applications in fields like optical microscopic, optical manipulation and electronic acceleration, etc.

Measuring forces and dynamics for optically levitated 20μm PS particles in air using electrostatic modulation

NASA Astrophysics Data System (ADS)

Park, Haesung; LeBrun, Thomas W.

2015-08-01

We demonstrate the simultaneous measurement of optical trap stiffness and quadrant-cell photodetector (QPD) calibration of optically trapped polystyrene particle in air. The analysis is based on the transient response of particles, confined to an optical trap, subject to a pulsed electrostatic field generated by parallel indium tin oxide (ITO) coated substrates. The resonant natural frequency and damping were directly estimated by fitting the analytical solution of the transient response of an underdamped harmonic oscillator to the measured particle displacement from its equilibrium position. Because, the particle size was estimated independently with video microscopy, this approach allowed us to measure the optical force without ignoring the effects of inertia and temperature changes from absorption.

Optical trapping reveals propulsion forces, power generation and motility efficiency of the unicellular parasites Trypanosoma brucei brucei

PubMed Central

Stellamanns, Eric; Uppaluri, Sravanti; Hochstetter, Axel; Heddergott, Niko; Engstler, Markus; Pfohl, Thomas

2014-01-01

Unicellular parasites have developed sophisticated swimming mechanisms to survive in a wide range of environments. Cell motility of African trypanosomes, parasites responsible for fatal illness in humans and animals, is crucial both in the insect vector and the mammalian host. Using millisecond-scale imaging in a microfluidics platform along with a custom made optical trap, we are able to confine single cells to study trypanosome motility. From the trapping characteristics of the cells, we determine the propulsion force generated by cells with a single flagellum as well as of dividing trypanosomes with two fully developed flagella. Estimates of the dissipative energy and the power generation of single cells obtained from the motility patterns of the trypanosomes within the optical trap indicate that specific motility characteristics, in addition to locomotion, may be required for antibody clearance. Introducing a steerable second optical trap we could further measure the force, which is generated at the flagellar tip. Differences in the cellular structure of the trypanosomes are correlated with the trapping and motility characteristics and in consequence with their propulsion force, dissipative energy and power generation. PMID:25269514

Measurement of macrophage adhesion using optical tweezers with backward-scattered detection

NASA Astrophysics Data System (ADS)

Wei, Sung-Yang; Su, Yi-Jr; Shih, Po-Chen; Yang, Shih-Mo; Hsu, Long

2010-08-01

Macrophages are members of the leukocyte family. Tissue damage causes inflammation and release of vasoactive and chemotactic factors, which trigger a local increase in blood flow and capillary permeability. Then, leukocytes accumulate quickly to the infection site. The leukocyte extravasation process takes place according to a sequence of events that involve tethering, activation by a chemoattractant stimulus, adhesion by integrin binding, and migrating to the infection site. The leukocyte extravasation process reveals that adhesion is an important part of the immune system. Optical tweezers have become a useful tool with broad applications in biology and physics. In force measurement, the trapped bead as a probe usually uses a polystyrene bead of 1 μm diameter to measure adhesive force between the trapped beads and cell by optical tweezers. In this paper, using the ray-optics model calculated trapping stiffness and defined the linear displacement ranges. By the theoretical values of stiffness and linear displacement ranges, this study attempted to obtain a proper trapped particle size in measuring adhesive force. Finally, this work investigates real-time adhesion force measurements between human macrophages and trapped beads coated with lipopolysaccharides using optical tweezers with backscattered detection.

Scattering of a Tightly Focused Beam by an Optically Trapped Particle

NASA Technical Reports Server (NTRS)

Lock, James A.; Wrbanek, Susan Y.; Weiland, Kenneth E.

2006-01-01

Near-forward scattering of an optically trapped 5 m radius polystyrene latex sphere by the trapping beam was examined both theoretically and experimentally. Since the trapping beam is tightly focused, the beam fields superpose and interfere with the scattered fields in the forward hemisphere. The observed light intensity consists of a series of concentric bright and dark fringes centered about the forward scattering direction. Both the number of fringes and their contrast depend on the position of the trapping beam focal waist with respect to the sphere. The fringes are caused by diffraction due to the truncation of the tail of the trapping beam as the beam is transmitted through the sphere.

A Surface-Coupled Optical Trap with 1-bp Precision via Active Stabilization

PubMed Central

Okoniewski, Stephen R.; Carter, Ashley R.; Perkins, Thomas T.

2017-01-01

Optical traps can measure bead motions with Å-scale precision. However, using this level of precision to infer 1-bp motion of molecular motors along DNA is difficult, since a variety of noise sources degrade instrumental stability. In this chapter, we detail how to improve instrumental stability by (i) minimizing laser pointing, mode, polarization, and intensity noise using an acousto-optical-modulator mediated feedback loop and (ii) minimizing sample motion relative to the optical trap using a 3-axis piezo-electric-stage mediated feedback loop. These active techniques play a critical role in achieving a surface stability of 1 Å in 3D over tens of seconds and a 1-bp stability and precision in a surface-coupled optical trap over a broad bandwidth (Δf = 0.03–2 Hz) at low force (6 pN). These active stabilization techniques can also aid other biophysical assays that would benefit from improved laser stability and/or Å-scale sample stability, such as atomic force microscopy and super-resolution imaging. PMID:27844426

Alternative laser system for cesium magneto-optical trap via optical injection locking to sideband of a 9-GHz current-modulated diode laser.

PubMed

Diao, Wenting; He, Jun; Liu, Zhi; Yang, Baodong; Wang, Junmin

2012-03-26

By optical injection of an 852-nm extended-cavity diode laser (master laser) to lock the + 1-order sideband of a ~9-GHz-current-modulated diode laser (slave laser), we generate a pair of phase-locked lasers with a frequency difference up to ~9-GHz for a cesium (Cs) magneto-optical trap (MOT) with convenient tuning capability. For a cesium MOT, the master laser acts as repumping laser, locked to the Cs 6S₁/₂ (F = 3) - 6P₃/₂ (F' = 4) transition. When the + 1-order sideband of the 8.9536-GHz-current-modulated slave laser is optically injection-locked, the carrier operates on the Cs 6S₁/₂ (F = 4) - 6P₃/₂ (F' = 5) cooling cycle transition with -12 MHz detuning and acts as cooling/trapping laser. When carrying a 9.1926-GHz modulation signal, this phase-locked laser system can be applied in the fields of coherent population trapping and coherent manipulation of Cs atomic ground states.

Contact Electrification of Individual Dielectric Microparticles Measured by Optical Tweezers in Air.

PubMed

Park, Haesung; LeBrun, Thomas W

2016-12-21

We measure charging of single dielectric microparticles after interaction with a glass substrate using optical tweezers to control the particle, measure its charge with a sensitivity of a few electrons, and precisely contact the particle with the substrate. Polystyrene (PS) microparticles adhered to the substrate can be selected based on size, shape, or optical properties and repeatedly loaded into the optical trap using a piezoelectric (PZT) transducer. Separation from the substrate leads to charge transfer through contact electrification. The charge on the trapped microparticles is measured from the response of the particle motion to a step excitation of a uniform electric field. The particle is then placed onto a target location of the substrate in a controlled manner. Thus, the triboelectric charging profile of the selected PS microparticle can be measured and controlled through repeated cycles of trap loading followed by charge measurement. Reversible optical trap loading and manipulation of the selected particle leads to new capabilities to study and control successive and small changes in surface interactions.

Optical trapping studies of acto-myosin motor proteins

NASA Astrophysics Data System (ADS)

Farrow, Rachel E.; Rosenthal, Peter B.; Mashanov, Gregory I.; Holder, Anthony A.; Molloy, Justin E.

2007-09-01

Optical tweezers have been used extensively to measure the mechanical properties of individual biological molecules. Over the past 10-15 years optical trapping studies have revealed important information about the way in which motor proteins convert chemical energy to mechanical work. This paper focuses on studies of the acto-myosin motor system that is responsible for muscle contraction and a host of other cellular motilities. Myosin works by binding to filamentous actin, pulling and then releasing. Each cycle of interaction produces a few nanometres movement and a few piconewtons force. Individual interactions can be observed directly by holding an individual actin filament between two optically trapped microspheres and positioning it in the immediate vicinity of a single myosin motor. When the chemical fuel (adenosine triphosphate or ATP) is present the myosin undergoes repeated cycles of interaction with the actin filament producing square-wave like displacements and forces. Analysis of optical trapping data sets enables the size and timing of the molecular motions to be deduced.

Dual-beam optical trapping of cells in an optofluidic device fabricated by femtosecond lasers

NASA Astrophysics Data System (ADS)

Bellini, N.; Bragheri, F.; Vishnubhatla, K. C.; Ferrara, L.; Minzioni, P.; Cerullo, G.; Ramponi, R.; Cristiani, I.; Osellame, R.

2010-02-01

We present design and optimization of an optofluidic monolithic chip, able to provide optical trapping and controlled stretching of single cells. The chip is fabricated in a fused silica glass substrate by femtosecond laser micromachining, which can produce both optical waveguides and microfluidic channels with great accuracy. Versatility and three-dimensional capabilities of this fabrication technology provide the possibility to fabricate circular cross-section channels with enlarged access holes for an easy connection with an external fluidic circuit. Moreover, a new fabrication procedure adopted allows the demonstration of microchannels with a square cross-section, thus guaranteeing an improved quality of the trapped cell images. Optical trapping and stretching of single red blood cells are demonstrated, thus proving the effectiveness of the proposed device as a monolithic optical stretcher. We believe that femtosecond laser micromachining represents a promising technique for the development of multifunctional integrated biophotonic devices that can be easily coupled to a microscope platform, thus enabling a complete characterization of the cells under test.

A Scalable Microfabricated Ion Trap for Quantum Information Processing

NASA Astrophysics Data System (ADS)

Maunz, Peter; Haltli, Raymond; Hollowell, Andrew; Lobser, Daniel; Mizrahi, Jonathan; Rembetski, John; Resnick, Paul; Sterk, Jonathan D.; Stick, Daniel L.; Blain, Matthew G.

2016-05-01

Trapped Ion Quantum Information Processing (QIP) relies on complex microfabricated trap structures to enable scaling of the number of quantum bits. Building on previous demonstrations of surface-electrode ion traps, we have designed and characterized the Sandia high-optical-access (HOA-2) microfabricated ion trap. This trap features high optical access, high trap frequencies, low heating rates, and negligible charging of dielectric trap components. We have observed trap lifetimes of more than 100h, measured trap heating rates for ytterbium of less than 40quanta/s, and demonstrated shuttling of ions from a slotted to an above surface region and through a Y-junction. Furthermore, we summarize demonstrations of high-fidelity single and two-qubit gates realized in this trap. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000. This work was supported by the Intelligence Advanced Research Projects Activity (IARPA).

Studies of lipid vesicle mechanics using an optical fiber dual-beam trap

NASA Astrophysics Data System (ADS)

Pinon, Tessa M.; Hirst, Linda S.; Sharping, Jay E.

2011-03-01

Fiber-based optical traps can be used for manipulating micron-sized dielectric particles such as microspheres and biological cells. Here we study the mechanics of giant unilamellar vesicles (GUVs) which are held and stretched by light forces in a fiber-based dual-beam optical trap. Our GUVs are suspended in a buffer solution and encapsulate various concentrations and molecular weights of poly(ethylene glycol) (PEG) polymer yielding a range of refractive index contrasts and trapping conditions. We find that we can trap GUVs in solution with index contrasts of less than 0.01. We explore the mechanical response of the GUV membrane to a range of forces which are proportional to laser power and refractive index contrast. Our trapping system is a compact and inexpensive platform and trapping is viewed in real time under a microscope. We hypothesize that forces within the high-tension regime will induce a linear response in vesicle surface area. This project sets the stage for membrane mechanics and lipid phase change studies. Grant: NSF award #DMR 0852791, ``CAREER: Self-Assembly of Polyunsaturated Lipids and Cholesterol in the Cell Membrane.''

Scanning holographic optical tweezers.

PubMed

Shaw, L A; Panas, Robert M; Spadaccini, C M; Hopkins, J B

2017-08-01

The aim of this Letter is to introduce a new optical tweezers approach, called scanning holographic optical tweezers (SHOT), which drastically increases the working area (WA) of the holographic-optical tweezers (HOT) approach, while maintaining tightly focused laser traps. A 12-fold increase in the WA is demonstrated. The SHOT approach achieves its utility by combining the large WA of the scanning optical tweezers (SOT) approach with the flexibility of the HOT approach for simultaneously moving differently structured optical traps in and out of the focal plane. This Letter also demonstrates a new heuristic control algorithm for combining the functionality of the SOT and HOT approaches to efficiently allocate the available laser power among a large number of traps. The proposed approach shows promise for substantially increasing the number of particles that can be handled simultaneously, which would enable optical tweezers additive fabrication technologies to rapidly assemble microgranular materials and structures in reasonable build times.

Spectrally reconfigurable integrated multi-spot particle trap.

PubMed

Leake, Kaelyn D; Olson, Michael A B; Ozcelik, Damla; Hawkins, Aaron R; Schmidt, Holger

2015-12-01

Optical manipulation of small particles in the form of trapping, pushing, or sorting has developed into a vast field with applications in the life sciences, biophysics, and atomic physics. Recently, there has been increasing effort toward integration of particle manipulation techniques with integrated photonic structures on self-contained optofluidic chips. Here, we use the wavelength dependence of multi-spot pattern formation in multimode interference (MMI) waveguides to create a new type of reconfigurable, integrated optical particle trap. Interfering lateral MMI modes create multiple trapping spots in an intersecting fluidic channel. The number of trapping spots can be dynamically controlled by altering the trapping wavelength. This novel, spectral reconfigurability is utilized to deterministically move single and multiple particles between different trapping locations along the channel. This fully integrated multi-particle trap can form the basis of high throughput biophotonic assays on a chip.

Cold Trap Dismantling and Sodium Removal at a Fast Breeder Reactor - 12327

DOE Office of Scientific and Technical Information (OSTI.GOV)

Graf, A.; Petrick, H.; Stutz, U.

2012-07-01

The first German prototype Fast Breeder Nuclear Reactor (KNK) is currently being dismantled after being the only operating Fast Breeder-type reactor in Germany. As this reactor type used sodium as a coolant in its primary and secondary circuit, seven cold traps containing various amounts of partially activated sodium needed to be disposed of as part of the dismantling. The resulting combined difficulties of radioactive contamination and high chemical reactivity were handled by treating the cold traps differently depending on their size and the amount of sodium contained inside. Six small cold traps were processed onsite by cutting them up intomore » small parts using a band saw under a protective atmosphere. The sodium was then converted to sodium hydroxide by using water. The remaining large cold trap could not be handled in the same way due to its dimensions (2.9 m x 1.1 m) and the declared amount of sodium inside (1,700 kg). It was therefore manually dismantled inside a large box filled with a protective atmosphere, while the resulting pieces were packaged for later burning in a special facility. The experiences gained by KNK during this process may be advantageous for future dismantling projects in similar sodium-cooled reactors worldwide. The dismantling of a prototype fast breeder reactor provides the challenge not only to dismantle radioactive materials but also to handle sodium-contaminated or sodium-containing components. The treatment of sodium requires additional equipment and installations to ensure a safe handling. Since it is not permitted to bring sodium into a repository, all sodium has to be neutralized either through a controlled reaction with water or by incinerating. The resulting components can be disposed of as normal radioactive waste with no further conditions. The handling of sodium needs skilled and experienced workers to minimize the inherent risks. And the example of the disposal of the large KNK cold trap shows the interaction with others and also foreign decommissioning projects can provide solutions with were unknown before. (authors)« less

A Compact, High-Flux Cold Atom Beam Source

NASA Technical Reports Server (NTRS)

Kellogg, James R.; Kohel, James M.; Thompson, Robert J.; Aveline, David C.; Yu, Nan; Schlippert, Dennis

2012-01-01

The performance of cold atom experiments relying on three-dimensional magneto-optical trap techniques can be greatly enhanced by employing a highflux cold atom beam to obtain high atom loading rates while maintaining low background pressures in the UHV MOT (ultra-high vacuum magneto-optical trap) regions. Several techniques exist for generating slow beams of cold atoms. However, one of the technically simplest approaches is a two-dimensional (2D) MOT. Such an atom source typically employs at least two orthogonal trapping beams, plus an additional longitudinal "push" beam to yield maximum atomic flux. A 2D atom source was created with angled trapping collimators that not only traps atoms in two orthogonal directions, but also provides a longitudinal pushing component that eliminates the need for an additional push beam. This development reduces the overall package size, which in turn, makes the 2D trap simpler, and requires less total optical power. The atom source is more compact than a previously published effort, and has greater than an order of magnitude improved loading performance.

Photoluminescence, optically stimulated luminescence, and thermoluminescence study of RbMgF3:Eu2+

NASA Astrophysics Data System (ADS)

Dotzler, C.; Williams, G. V. M.; Rieser, U.; Robinson, J.

2009-01-01

Optically stimulated luminescence (OSL) and thermoluminescence are observed in polycrystalline RbMgF3:Eu2+ after x-ray, γ-ray, or β irradiation. The main electron traps are F-centers but there are other unidentified traps. The main hole traps at room temperature are probably Eu3+ and thermal or optical stimulation leads to electron-hole recombination at the Eu3+ site and Eu2+ emissions arising from P6J to S87/2 and 4f5d(Eg) to S87/2 transitions. We find that some of the electron traps can be emptied by infrared stimulation and all of the electron traps can be emptied by white light stimulation. The OSL dark decay is long and exceeds 5 days for traps that are emptied by white light stimulation after initial infrared bleaching. Our results show that this compound can be used as a radiation dosimeter for intermediate dose levels where the R87b self-dose does not significantly affect the dose reading.

Atom chip apparatus for experiments with ultracold rubidium and potassium gases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ivory, M. K.; Ziltz, A. R.; Fancher, C. T.

2014-04-15

We present a dual chamber atom chip apparatus for generating ultracold {sup 87}Rb and {sup 39}K atomic gases. The apparatus produces quasi-pure Bose-Einstein condensates of 10{sup 4} {sup 87}Rb atoms in an atom chip trap that features a dimple and good optical access. We have also demonstrated production of ultracold {sup 39}K and subsequent loading into the chip trap. We describe the details of the dual chamber vacuum system, the cooling lasers, the magnetic trap, the multicoil magnetic transport system, the atom chip, and two optical dipole traps. Due in part to the use of light-induced atom desorption, the lasermore » cooling chamber features a sufficiently good vacuum to also support optical dipole trap-based experiments. The apparatus is well suited for studies of atom-surface forces, quantum pumping and transport experiments, atom interferometry, novel chip-based traps, and studies of one-dimensional many-body systems.« less

Micro particle launcher/cleaner based on optical trapping technology.

PubMed

Liu, Zhihai; Liang, Peibo; Zhang, Yu; Zhang, Yaxun; Zhao, Enming; Yang, Jun; Yuan, Libo

2015-04-06

Efficient and controllable launching function of an optical tweezers is a challenging task. We present and demonstrate a novel single fiber optical tweezers which can trap and launch (clean) a target polystyrene (PS) microsphere (diameter~10μm) with independent control by using two wavelengths beams: 980nm and 1480nm. We employ 980nm laser beam to trap the target PS microsphere by molding the fiber tip into a special tapered-shape; and we employ 1480nm laser beam to launch the trapped PS microsphere with a certain velocity by using the thermophoresis force generated from the thermal effect due to the high absorption of the 1480nm laser beams in water. When the launching force is smaller than the trapping force, the PS microsphere will be trapped near the fiber tip, and the launching force will blow away other PS microspheres in the workspace realizing the cleaning function; When the launching force is larger than the trapping force, the trapped PS microsphere will be launched away from the fiber tip with a certain velocity and towards a certain direction, realizing the launching function. The launching velocity, acceleration and the distance can be measured by detecting the interference signals generated from the PS microsphere surface and the fiber tip end-face. This PS microsphere launching and cleaning functions expanded new features of single fiber optical tweezers, providing for the possibility of more practical applications in the micro manipulation research fields.

Three-dimensional image and spatial spectrum analysis of behavior of small animal erythrocytes in optical tweezers

NASA Astrophysics Data System (ADS)

Chen, Hui Chi; Shen, Wen-Tai; Kong, Yu-Han; Chuang, Chun-Hao

2008-02-01

Because of the softness of membrane, erythrocytes (red blood cell, RBC) have different shapes while being immersed in buffer with different osmotic pressure. While affecting by different viruses and illnesses, RBC may change its shape, or its membrane may become rigid. Moreover, RBC will ford and stretch when it is trapped by optical tweezers. Therefore, the behaviors of RBC in optical tweezers raise more discussion. In this report, we set up an optical tweezers to trap RBC of small animals like feline and canine. By adding a long working distance objective to collect the side-viewing image, a 3-D image system was constructed to detect the motion of trapped RBC. To improve the image quality for side-view, an aperture and narrow glass plate were used. From the video of these images and their spatial spectrum, the shape of trapped RBC was studied.

Experimental nonlinear dynamical studies in cesium magneto-optical trap using time-series analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anwar, M., E-mail: mamalik2000@gmail.com; Islam, R.; Faisal, M.

2015-03-30

A magneto-optical trap of neutral atoms is essentially a dissipative quantum system. The fast thermal atoms continuously dissipate their energy to the environment via spontaneous emissions during the cooling. The atoms are, therefore, strongly coupled with the vacuum reservoir and the laser field. The vacuum fluctuations as well as the field fluctuations are imparted to the atoms as random photon recoils. Consequently, the external and internal dynamics of atoms becomes stochastic. In this paper, we have investigated the stochastic dynamics of the atoms in a magneto-optical trap during the loading process. The time series analysis of the fluorescence signal showsmore » that the dynamics of the atoms evolves, like all dissipative systems, from deterministic to the chaotic regime. The subsequent disappearance and revival of chaos was attributed to chaos synchronization between spatially different atoms in the magneto-optical trap.« less

Hexapole-compensated magneto-optical trap on a mesoscopic atom chip

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joellenbeck, S.; Mahnke, J.; Randoll, R.

2011-04-15

Magneto-optical traps on atom chips are usually restricted to small atomic samples due to a limited capture volume caused primarily by distorted field configurations. Here we present a magneto-optical trap based on a millimeter-sized wire structure which generates a magnetic field with minimized distortions. Together with the loading from a high-flux two-dimensional magneto-optical trap, we achieve a loading rate of 8.4x10{sup 10} atoms/s and maximum number of 8.7x10{sup 9} captured atoms. The wire structure is placed outside of the vacuum to enable a further adaptation to new scientific objectives. Since all magnetic fields are applied locally without the need formore » external bias fields, the presented setup will facilitate parallel generation of Bose-Einstein condensates on a conveyor belt with a cycle rate above 1 Hz.« less

FDTD simulations of forces on particles during holographic assembly.

PubMed

Benito, David C; Simpson, Stephen H; Hanna, Simon

2008-03-03

We present finite-difference time-domain (FDTD) calculations of the forces and torques on dielectric particles of various shapes, held in one or many Gaussian optical traps, as part of a study of the physical limitations involved in the construction of micro- and nanostructures using a dynamic holographic assembler (DHA). We employ a full 3-dimensional FDTD implementation, which includes a complete treatment of optical anisotropy. The Gaussian beams are sourced using a multipole expansion of a fifth order Davis beam. Force and torques are calculated for pairs of silica spheres in adjacent traps, for silica cylinders trapped by multiple beams and for oblate silica spheroids and calcite spheres in both linearly and circularly polarized beams. Comparisons are drawn between the magnitudes of the optical forces and the Van der Waals forces acting on the systems. The paper also considers the limitations of the FDTD approach when applied to optical trapping.

Ultracold molecules for the masses: Evaporative cooling and magneto-optical trapping

NASA Astrophysics Data System (ADS)

Stuhl, B. K.

While cold molecule experiments are rapidly moving towards their promised benefits of precision spectroscopy, controllable chemistry, and novel condensed phases, heretofore the field has been greatly limited by a lack of methods to cool and compress chemically diverse species to temperatures below ten millikelvin. While in atomic physics these needs are fulfilled by laser cooling, magneto-optical trapping, and evaporative cooling, until now none of these techniques have been applicable to molecules. In this thesis, two major breakthroughs are reported. The first is the observation of evaporative cooling in magnetically trapped hydroxyl (OH) radicals, which potentially opens a path all the way to Bose-Einstein condensation of dipolar radicals, as well as allowing cold- and ultracold-chemistry studies of fundamental reaction mechanisms. Through the combination of an extremely high gradient magnetic quadrupole trap and the use of the OH Λ-doublet transition to enable highly selective forced evaporation, cooling by an order of magnitude in temperature was achieved and yielded a final temperature no higher than 5mK. The second breakthrough is the successful application of laser cooling and magneto-optical trapping to molecules. Motivated by a proposal in this thesis, laser cooling of molecules is now known to be technically feasible in a select but substantial pool of diatomic molecules. The demonstration of not only Doppler cooling but also two-dimensional magneto-optical trapping in yttrium (II) oxide, YO, is expected to enable rapid growth in the availability of ultracold molecules—just as the invention of the atomic magneto-optical trap stimulated atomic physics twenty-five years ago.

Raman spectra and optical trapping of highly refractive and nontransparent particles

NASA Astrophysics Data System (ADS)

Xie, Changan; Li, Yong-qing

2002-08-01

We measured the Raman spectra of single optically trapped highly refractive and nontransparent microscopic particles suspended in a liquid using an inverted confocal laser-tweezers-Raman-spectroscopy system. A low-power diode-laser beam of TEM00 mode was used both for optical trapping and Raman excitation of refractive, absorptive, and reflective metal particles. To form a stable trap for a nontransparent particle, the beam focus was located near the top of the particle and the particle was pushed against a glass plate by the axial repulsive force. Raman spectra from single micron-sized crystals with high index of refraction including silicon, germanium, and KNbO3, and from absorptive particles of black and color paints were recorded. Surface-enhanced Raman scattering of R6G and phenylalanine molecules absorbed on the surface of a trapped cluster of silver particles was also demonstrated.

An optical conveyor for molecules.

PubMed

Weinert, Franz M; Braun, Dieter

2009-12-01

Trapping single ions under vacuum allows for precise spectroscopy in atomic physics. The confinement of biological molecules in bulk water is hindered by the lack of comparably strong forces. Molecules have been immobilized to surfaces, however often with detrimental effects on their function. Here, we optically trap molecules by creating the microscale analogue of a conveyor belt: a bidirectional flow is combined with a perpendicular thermophoretic molecule drift. Arranged in a toroidal geometry, the conveyor accumulates a hundredfold excess of 5-base DNA within seconds. The concentrations of the trapped DNA scale exponentially with length, reaching trapping potential depths of 14 kT for 50 bases. The mechanism does not require microfluidics, electrodes, or surface modifications. As a result, the trap can be dynamically relocated. The optical conveyor can be used to enhance diffusion-limited surface reactions, redirect cellular signaling, observe individual biomolecules over a prolonged time, or approach single-molecule chemistry in bulk water.

Concentric Circular Grating Generated by the Patterning Trapping of Nanoparticles in an Optofluidic Chip

PubMed Central

Dai, Hailang; Cao, Zhuangqi; Wang, Yuxing; Li, Honggen; Sang, Minghuang; Yuan, Wen; Chen, Fan; Chen, Xianfeng

2016-01-01

Due to the field enhancement effect of the hollow-core metal-cladded optical waveguide chip, massive nanoparticles in a solvent are effectively trapped via exciting ultrahigh order modes. A concentric ring structure of the trapped nanoparticles is obtained since the excited modes are omnidirectional at small incident angle. During the process of solvent evaporation, the nanoparticles remain well trapped since the excitation condition of the optical modes is still valid, and a concentric circular grating consisting of deposited nanoparticles can be produced by this approach. Experiments via scanning electron microscopy, atomic force microscopy and diffraction of a probe laser confirmed the above hypothesis. This technique provides an alternative strategy to enable effective trapping of dielectric particles with low-intensity nonfocused illumination, and a better understanding of the correlation between the guided modes in an optical waveguide and the nanoparticles in a solvent. PMID:27550743

Cavity-enhanced optical bottle beam as a mechanical amplifier

NASA Astrophysics Data System (ADS)

Freegarde, Tim; Dholakia, Kishan

2002-07-01

We analyze the resonant cavity enhancement of a hollow ``optical bottle beam'' for the dipole-force trapping of dark-field-seeking species. We first improve upon the basic bottle beam by adding further Laguerre-Gaussian components to deepen the confining potential. Each of these components itself corresponds to a superposition of transverse cavity modes, which are then enhanced simultaneously in a confocal cavity to produce a deep optical trap needing only a modest incident power. The response of the trapping field to displacement of the cavity mirrors offers an unusual form of mechanical amplifier in which the Gouy phase shift produces an optical Vernier scale between the Laguerre-Gaussian beam components.

Graded-index fiber tip optical tweezers: numerical simulation and trapping experiment.

PubMed

Gong, Yuan; Ye, Ai-Yan; Wu, Yu; Rao, Yun-Jiang; Yao, Yao; Xiao, Song

2013-07-01

Optical fiber tweezers based on a graded-index multimode fiber (GIMMF) tip is proposed. Light propagation characteristics and gradient force distribution near the GIMMF tip are numerically investigated, which are further compared with that of optical fiber tips based on conventional single mode fibers. The simulated results indicated that by selecting optimal GIMMF length, the gradient force of the GIMMF tip tweezers is about 4 times higher than that of the SMF tip tweezers with a same shape. To prove the feasibility of such a new concept, optical trapping of yeast cells with a diameter of ~5 μm using the chemically-etched GIMMF tip is experimentally demonstrated and the trapping force is also calculated.

Narrow-line magneto-optical cooling and trapping of strongly magnetic atoms.

PubMed

Berglund, Andrew J; Hanssen, James L; McClelland, Jabez J

2008-03-21

Laser cooling on weak transitions is a useful technique for reaching ultracold temperatures in atoms with multiple valence electrons. However, for strongly magnetic atoms a conventional narrow-line magneto-optical trap (MOT) is destabilized by competition between optical and magnetic forces. We overcome this difficulty in Er by developing an unusual narrow-line MOT that balances optical and magnetic forces using laser light tuned to the blue side of a narrow (8 kHz) transition. The trap population is spin polarized with temperatures reaching below 2 muK. Our results constitute an alternative method for laser cooling on weak transitions, applicable to rare-earth-metal and metastable alkaline earth elements.

The Laser Cooling and Magneto-Optical Trapping of the YO Molecule

NASA Astrophysics Data System (ADS)

Yeo, Mark

Laser cooling and magneto-optical trapping of neutral atoms has revolutionized the field of atomic physics by providing an elegant and efficient method to produce cold dense samples of ultracold atoms. Molecules, with their strong anisotropic dipolar interaction promises to unlock even richer phenomenon. However, due to their additional vibrational and rotational degrees of freedom, laser cooling techniques have only been extended to a small set of diatomic molecules. In this thesis, we demonstrate the first magneto-optical trapping of a diatomic molecule using a quasi-cycling transition and an oscillating quadrupole magnetic field. The transverse temperature of a cryogenically produced YO beam was reduced from 25 mK to 10 mK via doppler cooling and further reduced to 2 mK with the addition of magneto-optical trapping forces. The optical cycling in YO is complicated by the presence of an intermediate electronic state, as decays through this state lead to optical pumping into dark rotational states. Thus, we also demonstrate the mixing of rotational states in the ground electronic state using microwave radiation. This technique greatly enhances optical cycling, leading to a factor of 4 increase in the YO beam fluorescence and is used in conjunction with a frequency modulated and chirped continuous wave laser to longitudinally slow the YO beam. We generate YO molecules below 10 m/s that are directly loadable into a three-dimensional magneto-optical trap. This mixing technique provides an alternative to maintaining rotational closure and should extend laser cooling to a larger set of molecules.

Electro-optic deflectors deliver advantages over acousto-optical deflectors in a high resolution, ultra-fast force-clamp optical trap.

PubMed

Woody, Michael S; Capitanio, Marco; Ostap, E Michael; Goldman, Yale E

2018-04-30

We characterized experimental artifacts arising from the non-linear response of acousto-optical deflectors (AODs) in an ultra-fast force-clamp optical trap and have shown that using electro-optical deflectors (EODs) instead eliminates these artifacts. We give an example of the effects of these artifacts in our ultra-fast force clamp studies of the interaction of myosin with actin filaments. The experimental setup, based on the concept of Capitanio et al. [Nat. Methods 9, 1013-1019 (2012)] utilizes a bead-actin-bead dumbbell held in two force-clamped optical traps which apply a load to the dumbbell to move it at a constant velocity. When myosin binds to actin, the filament motion stops quickly as the total force from the optical traps is transferred to the actomyosin attachment. We found that in our setup, AODs were unsuitable for beam steering due to non-linear variations in beam intensity and deflection angle as a function of driving frequency, likely caused by low-amplitude standing acoustic waves in the deflectors. These aberrations caused instability in the force feedback loops leading to artifactual jumps in the trap position. We demonstrate that beam steering with EODs improves the performance of our instrument. Combining the superior beam-steering capability of the EODs, force acquisition via back-focal-plane interferometry, and dual high-speed FPGA-based feedback loops, we apply precise and constant loads to study the dynamics of interactions between actin and myosin. The same concept applies to studies of other biomolecular interactions.

Precision force sensing with optically-levitated nanospheres

NASA Astrophysics Data System (ADS)

Geraci, Andrew

2017-04-01

In high vacuum, optically-trapped dielectric nanospheres achieve excellent decoupling from their environment and experience minimal friction, making them ideal for precision force sensing. We have shown that 300 nm silica spheres can be used for calibrated zeptonewton force measurements in a standing-wave optical trap. In this optical potential, the known spacing of the standing wave anti-nodes can serve as an independent calibration tool for the displacement spectrum of the trapped particle. I will describe our progress towards using these sensors for tests of the Newtonian gravitational inverse square law at micron length scales. Optically levitated dielectric objects also show promise for a variety of other precision sensing applications, including searches for gravitational waves and other experiments in quantum optomechanics. National Science Foundation PHY-1205994, PHY-1506431, PHY-1509176.

Doughnut shape atom traps with arbitrary inclination

NASA Astrophysics Data System (ADS)

Masegosa, R. R. Y.; Moya-Cessa, H.; Chavez-Cerda, S.

2006-02-01

Since the invention of magneto-optical trap (MOT), there have been several experimental and theoretical studies of the density distribution in these devices. To the best of our knowledge, only horizontal orbital traps have been observed, perpendicular to the coil axis. In this work we report the observation of distributions of trapped atoms in pure circular orbits without a nucleus whose orbital plane is tilted up to 90 degrees with respect to the horizontal plane. We have used a stabilized time phase optical array in our experiments and conventional equipment used for MOT.

A dynamic magneto-optical trap for atom chips

NASA Astrophysics Data System (ADS)

Rushton, Jo; Roy, Ritayan; Bateman, James; Himsworth, Matt

2016-11-01

We describe a dynamic magneto-optical trap (MOT) suitable for the use with vacuum systems in which optical access is limited to a single window. This technique facilitates the long-standing desire of producing integrated atom chips, many of which are likely to have severely restricted optical access compared with conventional vacuum chambers. This ‘switching-MOT’ relies on the synchronized pulsing of optical and magnetic fields at audio frequencies. The trap’s beam geometry is obtained using a planar mirror surface, and does not require a patterned substrate or bulky optics inside the vacuum chamber. Central to the design is a novel magnetic field geometry that requires no external quadrupole or bias coils which leads toward a very compact system. We have implemented the trap for 85Rb and shown that it is capable of capturing 2 million atoms and directly cooling below the Doppler temperature.

Cost effective flat plate photovoltaic modules using light trapping

NASA Technical Reports Server (NTRS)

Bain, C. N.; Gordon, B. A.; Knasel, T. M.; Malinowski, R. L.

1981-01-01

Work in optical trapping in 'thick films' is described to form a design guide for photovoltaic engineers. A thick optical film can trap light by diffusive reflection and total internal reflection. Light can be propagated reasonably long distances compared with layer thicknesses by this technique. This makes it possible to conduct light from inter-cell and intra-cell areas now not used in photovoltaic modules onto active cell areas.

Cooperative effects between color centers in diamond: applications to optical tweezers and optomechanics

NASA Astrophysics Data System (ADS)

Bradac, Carlo; Prasanna Venkatesh, B.; Besga, Benjamin; Johnsson, Mattias; Brennen, Gavin; Molina-Terriza, Gabriel; Volz, Thomas; Juan, Mathieu L.

2017-08-01

Since the early work by Ashkin in 1970,1 optical trapping has become one of the most powerful tools for manipulating small particles, such as micron sized beads2 or single atoms.3 Interestingly, both an atom and a lump of dielectric material can be manipulated through the same mechanism: the interaction energy of a dipole and the electric field of the laser light. In the case of atom trapping, the dominant contribution typically comes from the allowed optical transition closest to the laser wavelength while it is given by the bulk polarisability for mesoscopic particles. This difference lead to two very different contexts of applications: one being the trapping of small objects mainly in biological settings,4 the other one being dipole traps for individual neutral atoms5 in the field of quantum optics. In this context, solid state artificial atoms present the interesting opportunity to combine these two aspects of optical manipulation. We are particularly interested in nanodiamonds as they constitute a bulk dielectric object by themselves, but also contain artificial atoms such as nitrogen-vacancy (NV) or silicon-vacancy (SiV) colour centers. With this system, both regimes of optical trapping can be observed at the same time even at room temperature. In this work, we demonstrate that the resonant force from the optical transition of NV centres at 637 nm can be measured in a nanodiamond trapped in water. This additional contribution to the total force is significant, reaching up to 10%. In addition, due to the very large density of NV centres in a sub-wavelength crystal, collective effects between centres have an important effect on the magnitude of the resonant force.6 The possibility to observe such cooperatively enhanced optical force at room temperature is also theoretically confirmed.7 This approach may enable the study of cooperativity in various nanoscale solid-state systems and the use of atomic physics techniques in the field of nano-manipulation and opto-mechanics.

Quantum memory with optically trapped atoms.

PubMed

Chuu, Chih-Sung; Strassel, Thorsten; Zhao, Bo; Koch, Markus; Chen, Yu-Ao; Chen, Shuai; Yuan, Zhen-Sheng; Schmiedmayer, Jörg; Pan, Jian-Wei

2008-09-19

We report the experimental demonstration of quantum memory for collective atomic states in a far-detuned optical dipole trap. Generation of the collective atomic state is heralded by the detection of a Raman scattered photon and accompanied by storage in the ensemble of atoms. The optical dipole trap provides confinement for the atoms during the quantum storage while retaining the atomic coherence. We probe the quantum storage by cross correlation of the photon pair arising from the Raman scattering and the retrieval of the atomic state stored in the memory. Nonclassical correlations are observed for storage times up to 60 mus.

Trapping of a micro-bubble by non-paraxial Gaussian beam: computation using the FDTD method.

PubMed

Sung, Seung-Yong; Lee, Yong-Gu

2008-03-03

Optical forces on a micro-bubble were computed using the Finite Difference Time Domain method. Non-paraxial Gaussian beam equation was used to represent the incident laser with high numerical aperture, common in optical tweezers. The electromagnetic field distribution around a micro-bubble was computed using FDTD method and the electromagnetic stress tensor on the surface of a micro-bubble was used to compute the optical forces. By the analysis of the computational results, interesting relations between the radius of the circular trapping ring and the corresponding stability of the trap were found.

How the stiffness of the optical trap depends on the proximity of the dielectric interface

NASA Astrophysics Data System (ADS)

Jákl, Petr; Šerý, Mojmír; Liška, Miroslav; Zemánek, Pavel

2005-09-01

When a probe confined in a single focused laser beam approaches the surface, it is getting more influenced by the retroreflected beam. This beam interferes with the incident one and a weak standing wave (SW) is created, which slightly modulates the incident beam. We studied experimentally how this phenomena influences the optical trap properties if SW is created using surfaces of two different reflectivities. We used polystyrene probes of diameters 690 nm and 820 nm, tracked their positions with quadrant photodiode (QPD) and analysed their thermal motion to get the axial trap stiffness along optical axis.

The design and fabrication of an inverted IR optical trap

NASA Astrophysics Data System (ADS)

Zhu, Tianchun; Feng, Xiuzhou; Fang, Jianxing

2005-02-01

Optical tweezers offer the unique ability to manipulate particles dispersed in a liquid medium without any mechanical contact. It can trap, move and position a wide variety of living cells and sub-cellular particles. The nature of the technique has led to its predominant use in the fields of medicine and microbiology. On the other hand, different biomedical experiments require the traps with different structures and characteristics. Commercial optical tweezers are very expensive and they can"t meet the demands of some special experiments. In this paper, the authors describe a detailed recipe for fabrication of an inverted optical trap. The system uses a single mode laser with the wavelength of 1064 nm so as not to damage the living organisms. The system has a platform whose temperature is tunable at a range of 20-40°C and can be stabilized by a controller. The system is also has a video device. The significant advantage of the system is low cost and easy to be operated. It especially fits the labs that are short of fund but interested in the application of optical trap in research of living cells. By means of the system, the authors do the experiments on control over the neuronal growth successfully.

Higher order microfibre modes for dielectric particle trapping and propulsion

PubMed Central

Maimaiti, Aili; Truong, Viet Giang; Sergides, Marios; Gusachenko, Ivan; Nic Chormaic, Síle

2015-01-01

Optical manipulation in the vicinity of optical micro- and nanofibres has shown potential across several fields in recent years, including microparticle control, and cold atom probing and trapping. To date, most work has focussed on the propagation of the fundamental mode through the fibre. However, along the maximum mode intensity axis, higher order modes have a longer evanescent field extension and larger field amplitude at the fibre waist compared to the fundamental mode, opening up new possibilities for optical manipulation and particle trapping. We demonstrate a microfibre/optical tweezers compact system for trapping and propelling dielectric particles based on the excitation of the first group of higher order modes at the fibre waist. Speed enhancement of polystyrene particle propulsion was observed for the higher order modes compared to the fundamental mode for particles ranging from 1 μm to 5 μm in diameter. The optical propelling velocity of a single, 3 μm polystyrene particle was found to be 8 times faster under the higher order mode than the fundamental mode field for a waist power of 25 mW. Experimental data are supported by theoretical calculations. This work can be extended to trapping and manipulation of laser-cooled atoms with potential for quantum networks. PMID:25766925

Laser Cooling and Trapping of Neutral Strontium for Spectroscopic Measurements of Casimir-Polder Potentials

NASA Astrophysics Data System (ADS)

Cook, Eryn C.

Casimir and Casimir-Polder effects are forces between electrically neutral bodies and particles in vacuum, arising entirely from quantum fluctuations. The modification to the vacuum electromagnetic-field modes imposed by the presence of any particle or surface can result in these mechanical forces, which are often the dominant interaction at small separations. These effects play an increasingly critical role in the operation of micro- and nano-mechanical systems as well as miniaturized atomic traps for precision sensors and quantum-information devices. Despite their fundamental importance, calculations present theoretical and numeric challenges, and precise atom-surface potential measurements are lacking in many geometric and distance regimes. The spectroscopic measurement of Casimir-Polder-induced energy level shifts in optical-lattice trapped atoms offers a new experimental method to probe atom-surface interactions. Strontium, the current front-runner among optical frequency metrology systems, has demonstrated characteristics ideal for such precision measurements. An alkaline earth atom possessing ultra-narrow intercombination transitions, strontium can be loaded into an optical lattice at the "magic" wavelength where the probe transition is unperturbed by the trap light. Translation of the lattice will permit controlled transport of tightly-confined atomic samples to well-calibrated atom-surface separations, while optical transition shifts serve as a direct probe of the Casimir-Polder potential. We have constructed a strontium magneto-optical trap (MOT) for future Casimir-Polder experiments. This thesis will describe the strontium apparatus, initial trap performance, and some details of the proposed measurement procedure.

Optical trapping and Raman spectroscopy of solid particles.

PubMed

Rkiouak, L; Tang, M J; Camp, J C J; McGregor, J; Watson, I M; Cox, R A; Kalberer, M; Ward, A D; Pope, F D

2014-06-21

The heterogeneous interactions of gas molecules on solid particles are crucial in many areas of science, engineering and technology. Such interactions play a critical role in atmospheric chemistry and in heterogeneous catalysis, a key technology in the energy and chemical industries. Investigating heterogeneous interactions upon single levitated particles can provide significant insight into these important processes. Various methodologies exist for levitating micron sized particles including: optical, electrical and acoustic techniques. Prior to this study, the optical levitation of solid micron scale particles has proved difficult to achieve over timescales relevant to the above applications. In this work, a new vertically configured counter propagating dual beam optical trap was optimized to levitate a range of solid particles in air. Silica (SiO2), α-alumina (Al2O3), titania (TiO2) and polystyrene were stably trapped with a high trapping efficiency (Q = 0.42). The longest stable trapping experiment was conducted continuously for 24 hours, and there are no obvious constraints on trapping time beyond this period. Therefore, the methodology described in this paper should be of major benefit to various research communities. The strength of the new technique is demonstrated by the simultaneous levitation and spectroscopic interrogation of silica particles by Raman spectroscopy. In particular, the adsorption of water upon silica was investigated under controlled relative humidity environments. Furthermore, the collision and coagulation behaviour of silica particles with microdroplets of sulphuric acid was followed using both optical imaging and Raman spectroscopy.

A Minimal Optical Trapping and Imaging Microscopy System

PubMed Central

Hernández Candia, Carmen Noemí; Tafoya Martínez, Sara; Gutiérrez-Medina, Braulio

2013-01-01

We report the construction and testing of a simple and versatile optical trapping apparatus, suitable for visualizing individual microtubules (∼25 nm in diameter) and performing single-molecule studies, using a minimal set of components. This design is based on a conventional, inverted microscope, operating under plain bright field illumination. A single laser beam enables standard optical trapping and the measurement of molecular displacements and forces, whereas digital image processing affords real-time sample visualization with reduced noise and enhanced contrast. We have tested our trapping and imaging instrument by measuring the persistence length of individual double-stranded DNA molecules, and by following the stepping of single kinesin motor proteins along clearly imaged microtubules. The approach presented here provides a straightforward alternative for studies of biomaterials and individual biomolecules. PMID:23451216

On-chip particle trapping and manipulation

NASA Astrophysics Data System (ADS)

Leake, Kaelyn Danielle

The ability to control and manipulate the world around us is human nature. Humans and our ancestors have used tools for millions of years. Only in recent years have we been able to control objects at such small levels. In order to understand the world around us it is frequently necessary to interact with the biological world. Optical trapping and manipulation offer a non-invasive way to move, sort and interact with particles and cells to see how they react to the world around them. Optical tweezers are ideal in their abilities but they require large, non-portable, and expensive setups limiting how and where we can use them. A cheap portable platform is required in order to have optical manipulation reach its full potential. On-chip technology offers a great solution to this challenge. We focused on the Liquid-Core Anti-Resonant Reflecting Optical Waveguide (liquid-core ARROW) for our work. The ARROW is an ideal platform, which has anti-resonant layers which allow light to be guided in liquids, allowing for particles to easily be manipulated. It is manufactured using standard silicon manufacturing techniques making it easy to produce. The planner design makes it easy to integrate with other technologies. Initially I worked to improve the ARROW chip by reducing the intersection losses and by reducing the fluorescence and background on the ARROW chip. The ARROW chip has already been used to trap and push particles along its channel but here I introduce several new methods of particle trapping and manipulation on the ARROW chip. Traditional two beam traps use two counter propagating beams. A trapping scheme that uses two orthogonal beams which counter to first instinct allow for trapping at their intersection is introduced. This scheme is thoroughly predicted and analyzed using realistic conditions. Simulations of this method were done using a program which looks at both the fluidics and optical sources to model complex situations. These simulations were also used to model and predict a sorting method which combines fluid flow with a single optical source to automatically sort dielectric particles by size in waveguide networks. These simulations were shown to be accurate when repeated on-chip. Lastly I introduce a particle trapping technique that uses Multimode Interference(MMI) patterns in order to trap multiple particles at once. The location of the traps can be adjusted as can the number of trapping location by changing the input wavelength. By changing the wavelength back and forth between two values this MMI can be used to pass a particle down the channel like a conveyor belt.

A Surface-Coupled Optical Trap with 1-bp Precision via Active Stabilization.

PubMed

Okoniewski, Stephen R; Carter, Ashley R; Perkins, Thomas T

2017-01-01

Optical traps can measure bead motions with Å-scale precision. However, using this level of precision to infer 1-bp motion of molecular motors along DNA is difficult, since a variety of noise sources degrade instrumental stability. In this chapter, we detail how to improve instrumental stability by (1) minimizing laser pointing, mode, polarization, and intensity noise using an acousto-optical-modulator mediated feedback loop and (2) minimizing sample motion relative to the optical trap using a three-axis piezo-electric-stage mediated feedback loop. These active techniques play a critical role in achieving a surface stability of 1 Å in 3D over tens of seconds and a 1-bp stability and precision in a surface-coupled optical trap over a broad bandwidth (Δf = 0.03-2 Hz) at low force (6 pN). These active stabilization techniques can also aid other biophysical assays that would benefit from improved laser stability and/or Å-scale sample stability, such as atomic force microscopy and super-resolution imaging.

Quantitative photothermal heating and cooling measurements of engineered nanoparticles in an optical trap

NASA Astrophysics Data System (ADS)

Roder, Paden Bernard

Laser tweezers and optical trapping has provided scientists and engineers a unique way to study the wealth of phenomena that materials exhibit at the micro- and nanoscale, much of which remains mysterious. Of particular interest is the interplay between light absorption and subsequent heat generation of laser-irradiated materials, especially due to recent interest in developing nanoscale materials for use as agents for photothermal cancer treatments. An introduction to optical trapping physics and laser tweezers are given in Chapter 1 and 2 of this thesis, respectively. The remaining chapters, summarized below, describe the theoretical basis of laser heating of one-dimensional nanostructures and experiments in which optically-trapped nanostructures are studied using techniques developed for a laser tweezer. In Chapter 3, we delve into the fundamentals of laser heating of one-dimensional materials by developing an analytical model of pulsed laser heating of uniform and tapered supported nanowires and compare calculations with experimental data to comment on the effects that the material's physical, optical, and thermal parameters have on its heating and cooling rates. We then consider closed-form analytical solutions for the temperature rise within infinite circular cylinders with nanometer-scale diameters irradiated at right angles by TM-polarized continuous-wave laser sources, which allows for analysis of laser-heated nanowires in a solvated environment. The infinite nanowire analysis will then be extended to the optical heating of laser-irradiated finite nanowires in the framework of a laser tweezer, which enables predictive capabilities and direct comparison with laser trapping experiments. An effective method for determining optically-trapped particle temperatures as well as the temperature gradient in the surrounding medium will be discussed in Chapter 4. By combining laser tweezer calibration techniques, forward-scattered light power spectrum analysis, and hot Brownian motion theory, we attempt to measure realistic temperatures at the surface of an optically-trapped particle while properly accounting for inhomogeneous temperature fields generated by the optical trap. In Chapter 5, this technique is then applied to measure the temperature of engineered gold- and silicon-implanted silicon nanowires to rigorously study the effect ion implantation has on silicon nanowire photothermal efficiencies. Silicon nanowire photothermal efficiencies are shown to drastically increase by implanting with gold ions and cause superheating of water of over 200 C at the trap site, suggesting potential application as agents for photothermal cancer therapies. Chapter 6 describes the hydrothermal synthesis and optical trapping of engineered YLF nanoparticles doped with Yb(III) ions. Laser tweezer experiments using the developed temperature extraction techniques and hot Brownian motion analysis show the first observation of particles undergoing recently hypothesized cold Brownian motion and local laser refrigeration in a condensed phase via anti-Stokes photoluminescence. Furthermore, YLF nanoparticles codoped with Er(III) and Yb(III) ions are also developed and their intense visible upconversion of the NIR trapping laser is used to monitor its internal lattice temperature using ratiometric thermography. The results suggest the potential of these materials to investigate kinetics and temperature sensitivity of basic cellular processes, or to act as simultaneous theranostic-hypothermia agents to identify and treat cancerous tissues. Finally, Chapter 7 presents a summary of the salient conclusions of the reported studies. The chapter concludes with a short discussion of my personal experience with being a member of a new research group and setting up the Pauzauskie laboratory.

Optical Trap Methods to Determine the Viscoelastic Properties of Biological Materials | NCI Technology Transfer Center | TTC

Cancer.gov

The National Cancer Institute seeks licensees and/or co-development partners for methods that provide significant improvements in examining clinically relevant tissue samples, by improving spatial resolution and tissue depth using optical trapping. 

Cavity-enhanced optical trapping of bacteria using a silicon photonic crystal.

PubMed

van Leest, Thijs; Caro, Jacob

2013-11-21

On-chip optical trapping and manipulation of cells based on the evanescent field of photonic structures is emerging as a promising technique, both in research and for applications in broader context. Relying on mass fabrication techniques, the involved integration of photonics and microfluidics allows control of both the flow of light and water on the scale of interest in single cell microbiology. In this paper, we demonstrate for the first time optical trapping of single bacteria (B. subtilis and E. coli) using photonic crystal cavities for local enhancement of the evanescent field, as opposed to the synthetic particles used so far. Three types of cavities (H0, H1 and L3) are studied, embedded in a planar photonic crystal and optimized for coupling to two collinear photonic crystal waveguides. The photonic crystals are fabricated on a silicon-on-insulator chip, onto which a fluidic channel is created as well. For each of the cavities, when pumped at the resonance wavelength (around 1550 nm), we clearly demonstrate optical trapping of bacteria, in spite of their low index contrast w.r.t. water. By tracking the confined Brownian motion of B. subtilis spores in the traps using recorded microscope observations, we derive strong in-plane trap stiffnesses of about 7.6 pN nm(-1) W(-1). The values found agree very well with calculations based on the Maxwell stress tensor for the force and finite-difference time-domain simulations of the fields for the fabricated cavity geometries. We envision that our lab-on-a-chip with photonic crystal traps opens up new application directions, e.g. immobilization of single bio-objects such as mammalian cells and bacteria under controlled conditions for optical microscopy studies.

Cooling optically levitated dielectric nanoparticles via parametric feedback

NASA Astrophysics Data System (ADS)

Neukirch, Levi; Rodenburg, Brandon; Bhattacharya, Mishkatul; Vamivakas, Nick

2015-05-01

The inability to leverage resonant scattering processes involving internal degrees of freedom differentiates optical cooling experiments performed with levitated dielectric nanoparticles, from similar atomic and molecular traps. Trapping in optical cavities or the application of active feedback techniques have proven to be effective ways to circumvent this limitation. We present our nanoparticle optical cooling apparatus, which is based on parametric feedback modulation of a single-beam gradient force optical trap. This scheme allows us to achieve effective center-of-mass temperatures well below 1 kelvin for our ~ 1 ×10-18 kg particles, at modest vacuum pressures. The method provides a versatile platform, with parameter tunability not found in conventional tethered nanomechanical systems. Potential applications include investigations of nonequilibrium nanoscale thermodynamics, ultra-sensitive force metrology, and mesoscale quantum mechanics and hybrid systems. Supported by the office of Naval Research award number N000141410442.

All-optical patterning of Au nanoparticles on surfaces using optical traps.

PubMed

Guffey, Mason J; Scherer, Norbert F

2010-11-10

The fabrication of nanoscale devices would be greatly enhanced by "nanomanipulators" that can position single and few objects rapidly with nanometer precision and without mechanical damage. Here, we demonstrate the feasibility and precision of an optical laser tweezer, or optical trap, approach to place single gold (Au) nanoparticles on surfaces with high precision (approximately 100 nm standard deviation). The error in the deposition process is rather small but is determined to be larger than the thermal fluctuations of single nanoparticles within the optical trap. Furthermore, areas of tens of square micrometers could be patterned in a matter of minutes. Since the method does not rely on lithography, scanning probes or a specialized surface, it is versatile and compatible with a variety of systems. We discuss active feedback methods to improve positioning accuracy and the potential for multiplexing and automation.

Electrodynamic multiple-scattering method for the simulation of optical trapping atop periodic metamaterials

NASA Astrophysics Data System (ADS)

Yannopapas, Vassilios; Paspalakis, Emmanuel

2018-07-01

We present a new theoretical tool for simulating optical trapping of nanoparticles in the presence of an arbitrary metamaterial design. The method is based on rigorously solving Maxwell's equations for the metamaterial via a hybrid discrete-dipole approximation/multiple-scattering technique and direct calculation of the optical force exerted on the nanoparticle by means of the Maxwell stress tensor. We apply the method to the case of a spherical polystyrene probe trapped within the optical landscape created by illuminating of a plasmonic metamaterial consisting of periodically arranged tapered metallic nanopyramids. The developed technique is ideally suited for general optomechanical calculations involving metamaterial designs and can compete with purely numerical methods such as finite-difference or finite-element schemes.

Multiplexed fluctuation-dissipation-theorem calibration of optical tweezers inside living cells

NASA Astrophysics Data System (ADS)

Yan, Hao; Johnston, Jessica F.; Cahn, Sidney B.; King, Megan C.; Mochrie, Simon G. J.

2017-11-01

In order to apply optical tweezers-based force measurements within an uncharacterized viscoelastic medium such as the cytoplasm of a living cell, a quantitative calibration method that may be applied in this complex environment is needed. We describe an improved version of the fluctuation-dissipation-theorem calibration method, which has been developed to perform in situ calibration in viscoelastic media without prior knowledge of the trapped object. Using this calibration procedure, it is possible to extract values of the medium's viscoelastic moduli as well as the force constant describing the optical trap. To demonstrate our method, we calibrate an optical trap in water, in polyethylene oxide solutions of different concentrations, and inside living fission yeast (S. pombe).

Near-Field, On-Chip Optical Brownian Ratchets.

PubMed

Wu, Shao-Hua; Huang, Ningfeng; Jaquay, Eric; Povinelli, Michelle L

2016-08-10

Nanoparticles in aqueous solution are subject to collisions with solvent molecules, resulting in random, Brownian motion. By breaking the spatiotemporal symmetry of the system, the motion can be rectified. In nature, Brownian ratchets leverage thermal fluctuations to provide directional motion of proteins and enzymes. In man-made systems, Brownian ratchets have been used for nanoparticle sorting and manipulation. Implementations based on optical traps provide a high degree of tunability along with precise spatiotemporal control. Here, we demonstrate an optical Brownian ratchet based on the near-field traps of an asymmetrically patterned photonic crystal. The system yields over 25 times greater trap stiffness than conventional optical tweezers. Our technique opens up new possibilities for particle manipulation in a microfluidic, lab-on-chip environment.

Progress towards a rapidly rotating ultracold Fermi gas

NASA Astrophysics Data System (ADS)

Hu, Ming-Guang; van de Graaff, Michael; Cornell, Eric; Jin, Deborah

2015-05-01

We are designing an experiment with the goal of creating a rapidly rotating ultracold Fermi gas, which is promising system in which to study quantum Hall physics. We propose to use selective evaporation of a gas that has been initialized with a modest rotation rate to increase the angular momentum per particle in order to reach rapid rotation. We have performed simulations of this evaporation process for a model optical trap potential. Achieving rapid rotation will require a very smooth, very harmonic, and dynamically variable optical trap. We plan to use a setup consisting of two acousto-optical modulators to ``paint'' an optical dipole trapping potential that can be made smooth, radially symmetric, and harmonic. This project is supported by NSF, NIST, NASA.

Laser-induced rotation and cooling of a trapped microgyroscope in vacuum

PubMed Central

Arita, Yoshihiko; Mazilu, Michael; Dholakia, Kishan

2013-01-01

Quantum state preparation of mesoscopic objects is a powerful playground for the elucidation of many physical principles. The field of cavity optomechanics aims to create these states through laser cooling and by minimizing state decoherence. Here we demonstrate simultaneous optical trapping and rotation of a birefringent microparticle in vacuum using a circularly polarized trapping laser beam—a microgyroscope. We show stable rotation rates up to 5 MHz. Coupling between the rotational and translational degrees of freedom of the trapped microgyroscope leads to the observation of positional stabilization in effect cooling the particle to 40 K. We attribute this cooling to the interaction between the gyroscopic directional stabilization and the optical trapping field. PMID:23982323

Ion-neutral-atom sympathetic cooling in a hybrid linear rf Paul and magneto-optical trap

NASA Astrophysics Data System (ADS)

Goodman, D. S.; Sivarajah, I.; Wells, J. E.; Narducci, F. A.; Smith, W. W.

2012-09-01

Long-range polarization forces between ions and neutral atoms result in large elastic scattering cross sections (e.g., ˜106a.u. for Na-Na+ or Na-Ca+ at cold and ultracold temperatures). This suggests that a hybrid ion-neutral trap should offer a general means for significant sympathetic cooling of atomic or molecular ions. We present simion 7.0 simulation results concerning the advantages and limitations of sympathetic cooling within a hybrid trap apparatus consisting of a linear rf Paul trap concentric with a Na magneto-optical trap (MOT). This paper explores the impact of various heating mechanisms on the hybrid system and how parameters related to the MOT, Paul trap, number of ions, and ion species affect the efficiency of the sympathetic cooling.

Stability and instability for low refractive-index-contrast particle trapping in a dual-beam optical trap.

PubMed

Huff, Alison; Melton, Charles N; Hirst, Linda S; Sharping, Jay E

2015-10-01

A dual-beam optical trap is used to trap and manipulate dielectric particles. When the refractive index of these particles is comparable to that of the surrounding medium, equilibrium trapping locations within the system shift from stable to unstable depending on fiber separation and particle size. This is due to to the relationship between gradient and scattering forces. We experimentally and computationally study the transitions between stable and unstable trapping of poly(methyl methacrylate) beads for a range of parameters relevant to experimental setups involving giant unilamellar vesicles. We present stability maps for various fiber separations and particle sizes, and find that careful attention to particle size and configuration is necessary to obtain reproducible quantitative results for soft matter stretching experiments.

Stability and instability for low refractive-index-contrast particle trapping in a dual-beam optical trap

PubMed Central

Huff, Alison; Melton, Charles N.; Hirst, Linda S.; Sharping, Jay E.

2015-01-01

A dual-beam optical trap is used to trap and manipulate dielectric particles. When the refractive index of these particles is comparable to that of the surrounding medium, equilibrium trapping locations within the system shift from stable to unstable depending on fiber separation and particle size. This is due to to the relationship between gradient and scattering forces. We experimentally and computationally study the transitions between stable and unstable trapping of poly(methyl methacrylate) beads for a range of parameters relevant to experimental setups involving giant unilamellar vesicles. We present stability maps for various fiber separations and particle sizes, and find that careful attention to particle size and configuration is necessary to obtain reproducible quantitative results for soft matter stretching experiments. PMID:26504632

A dark-line two-dimensional magneto-optical trap of 85Rb atoms with high optical depth.

PubMed

Zhang, Shanchao; Chen, J F; Liu, Chang; Zhou, Shuyu; Loy, M M T; Wong, G K L; Du, Shengwang

2012-07-01

We describe the apparatus of a dark-line two-dimensional (2D) magneto-optical trap (MOT) of (85)Rb cold atoms with high optical depth (OD). Different from the conventional configuration, two (of three) pairs of trapping laser beams in our 2D MOT setup do not follow the symmetry axes of the quadrupole magnetic field: they are aligned with 45° angles to the longitudinal axis. Two orthogonal repumping laser beams have a dark-line volume in the longitudinal axis at their cross over. With a total trapping laser power of 40 mW and repumping laser power of 18 mW, we obtain an atomic OD up to 160 in an electromagnetically induced transparency (EIT) scheme, which corresponds to an atomic-density-length product NL = 2.05 × 10(15) m(-2). In a closed two-state system, the OD can become as large as more than 600. Our 2D MOT configuration allows full optical access of the atoms in its longitudinal direction without interfering with the trapping and repumping laser beams spatially. Moreover, the zero magnetic field along the longitudinal axis allows the cold atoms maintain a long ground-state coherence time without switching off the MOT magnetic field, which makes it possible to operate the MOT at a high repetition rate and a high duty cycle. Our 2D MOT is ideal for atomic-ensemble-based quantum optics applications, such as EIT, entangled photon pair generation, optical quantum memory, and quantum information processing.

Ion traps for precision experiments at rare-isotope-beam facilities

NASA Astrophysics Data System (ADS)

Kwiatkowski, Anna

2016-09-01

Ion traps first entered experimental nuclear physics when the ISOLTRAP team demonstrated Penning trap mass spectrometry of radionuclides. From then on, the demand for ion traps has grown at radioactive-ion-beam (RIB) facilities since beams can be tailored for the desired experiment. Ion traps have been deployed for beam preparation, from bunching (thereby allowing time coincidences) to beam purification. Isomerically pure beams needed for nuclear-structure investigations can be prepared for trap-assisted or in-trap decay spectroscopy. The latter permits studies of highly charged ions for stellar evolution, which would be impossible with traditional experimental nuclear-physics methods. Moreover, the textbook-like conditions and advanced ion manipulation - even of a single ion - permit high-precision experiments. Consequently, the most accurate and precise mass measurements are now performed in Penning traps. After a brief introduction to ion trapping, I will focus on examples which showcase the versatility and utility of the technique at RIB facilities. I will demonstrate how this atomic-physics technique has been integrated into nuclear science, accelerator physics, and chemistry. DOE.

An Optical Trap for Relativistic Plasma

NASA Astrophysics Data System (ADS)

Zhang, Ping

2002-11-01

Optical traps have achieved remarkable success recently in confining ultra-cold matter.Traps capable of confining ultra-hot matter, or plasma, have also been built for applications such as basic plasma research and thermonuclear fusion. For instance, low-density plasmas with temperature less than 1 keV have been confined with static magnetic fields in Malmberg-Penning traps. Low-density 10-50 keV plasmas are confined in magnetic mirrors and tokamaks. High density plasmas have been trapped in optical traps with kinetic energies up to 10 keV [J. L. Chaloupka and D. D. Meyerhofer, Phys. Rev. Lett. 83, 4538 (1999)]. We present the results of experiment, theory and numerical simulation on an optical trap capable of confining relativistic plasma. A stationary interference grating with submicron spacing is created when two high-power (terawatt) laser pulses of equal wavelength (1-micron) are focused from orthogonal directions to the same point in space and time in high density underdense plasma. Light pressure gradients bunch electrons into sheets located at the minima of the interference pattern. The density of the bunched electrons is found to be up to ten times the background density, which is orders-of-magnitude above that previously reported for other optical traps or plasma waves. The amplitudes and frequencies of multiple satellites in the scattered spectrum also indicate the presence of a highly nonlinear ion wave and an electron temperature about 100 keV. Energy transfer from the stronger beam to the weaker beam is also observed. Potential applications include a test-bed for detailed studies of relativistic nonlinear scattering, a positron source and an electrostatic wiggler. This research is also relevant to fast igniter fusion or ion acceleration experiments, in which laser pulses with intensities comparable to those used in the experiment may also potentially beat [Y. Sentoku, et al., Appl. Phys. B 74, 207215 (2002)]. The details of a specific application, the injection of electrons into laser-driven plasma waves, will also be presented. With crossed beams, the energy of a laser-accelerated electron beam is increased and its emittance is decreased compared with a single beam, potentially paving the way towards an all-optical monoenergetic electron injector.

Fourier optics along a hybrid optical fiber for Bessel-like beam generation and its applications in multiple-particle trapping.

PubMed

Kim, Jongki; Jeong, Yoonseob; Lee, Sejin; Ha, Woosung; Shin, Jeon-Soo; Oh, Kyunghwan

2012-02-15

Highly efficient Bessel-like beam generation was achieved based on a new all-fiber method that implements Fourier transformation of a micro annular aperture along a concatenated composite optical fiber. The beam showed unique characteristics of tilted washboard optical potential in the transverse plane and sustained a nondiffracting length over 400 μm along the axial direction. Optical trapping of multiple dielectric particles and living Jurkat cells were successfully demonstrated along the axial direction of the beam in the water.

Optical Traps to Study Properties of Molecular Motors

PubMed Central

Spudich, James A.; Rice, Sarah E.; Rock, Ronald S.; Purcell, Thomas J.; Warrick, Hans M.

2016-01-01

In vitro motility assays enabled the analysis of coupling between ATP hydrolysis and movement of myosin along actin filaments or kinesin along microtubules. Single-molecule assays using laser trapping have been used to obtain more detailed information about kinesins, myosins, and processive DNA enzymes. The combination of in vitro motility assays with laser-trap measurements has revealed detailed dynamic structural changes associated with the ATPase cycle. This article describes the use of optical traps to study processive and nonprocessive molecular motor proteins, focusing on the design of the instrument and the assays to characterize motility. PMID:22046048

Atomization efficiency and photon yield in laser-induced breakdown spectroscopy analysis of single nanoparticles in an optical trap

NASA Astrophysics Data System (ADS)

Purohit, Pablo; Fortes, Francisco J.; Laserna, J. Javier

2017-04-01

Laser-induced breakdown spectroscopy (LIBS) was employed for investigating the influence of particle size on the dissociation efficiency and the absolute production of photons per mass unit of airborne solid graphite spheres under single-particle regime. Particles of average diameter of 400 nm were probed and compared with 2 μm particles. Samples were first catapulted into aerosol form and then secluded in an optical trap set by a 532 nm laser. Trap stability was quantified before subjecting particles to LIBS analysis. Fine alignment of the different lines comprising the optical catapulting-optical trapping-laser-induced breakdown spectroscopy instrument and tuning of excitation parameters conditioning the LIBS signal such as fluence and acquisition delay are described in detail with the ultimate goal of acquiring clear spectroscopic data on masses as low as 75 fg. The atomization efficiency and the photon yield increase as the particle size becomes smaller. Time-resolved plasma imaging studies were conducted to elucidate the mechanisms leading to particle disintegration and excitation.

Stable optical trapping and sensitive characterization of nanostructures using standing-wave Raman tweezers

PubMed Central

Wu, Mu-ying; Ling, Dong-xiong; Ling, Lin; Li, William; Li, Yong-qing

2017-01-01

Optical manipulation and label-free characterization of nanoscale structures open up new possibilities for assembly and control of nanodevices and biomolecules. Optical tweezers integrated with Raman spectroscopy allows analyzing a single trapped particle, but is generally less effective for individual nanoparticles. The main challenge is the weak gradient force on nanoparticles that is insufficient to overcome the destabilizing effect of scattering force and Brownian motion. Here, we present standing-wave Raman tweezers for stable trapping and sensitive characterization of single isolated nanostructures with a low laser power by combining a standing-wave optical trap with confocal Raman spectroscopy. This scheme has stronger intensity gradients and balanced scattering forces, and thus can be used to analyze many nanoparticles that cannot be measured with single-beam Raman tweezers, including individual single-walled carbon nanotubes (SWCNT), graphene flakes, biological particles, SERS-active metal nanoparticles, and high-refractive semiconductor nanoparticles. This would enable sorting and characterization of specific SWCNTs and other nanoparticles based on their increased Raman fingerprints. PMID:28211526

Tomographic active optical trapping of arbitrarily shaped objects by exploiting 3D refractive index maps

NASA Astrophysics Data System (ADS)

Kim, Kyoohyun; Park, Yongkeun

2017-05-01

Optical trapping can manipulate the three-dimensional (3D) motion of spherical particles based on the simple prediction of optical forces and the responding motion of samples. However, controlling the 3D behaviour of non-spherical particles with arbitrary orientations is extremely challenging, due to experimental difficulties and extensive computations. Here, we achieve the real-time optical control of arbitrarily shaped particles by combining the wavefront shaping of a trapping beam and measurements of the 3D refractive index distribution of samples. Engineering the 3D light field distribution of a trapping beam based on the measured 3D refractive index map of samples generates a light mould, which can manipulate colloidal and biological samples with arbitrary orientations and/or shapes. The present method provides stable control of the orientation and assembly of arbitrarily shaped particles without knowing a priori information about the sample geometry. The proposed method can be directly applied in biophotonics and soft matter physics.

Final Report: Laser-Based Optical Trap for Remote Sampling of Interplanetary and Atmospheric Particulate Matter

NASA Technical Reports Server (NTRS)

Stysley, Paul

2016-01-01

Applicability to Early Stage Innovation NIAC Cutting edge and innovative technologies are needed to achieve the demanding requirements for NASA origin missions that require sample collection as laid out in the NRC Decadal Survey. This proposal focused on fully understanding the state of remote laser optical trapping techniques for capturing particles and returning them to a target site. In future missions, a laser-based optical trapping system could be deployed on a lander that would then target particles in the lower atmosphere and deliver them to the main instrument for analysis, providing remote access to otherwise inaccessible samples. Alternatively, for a planetary mission the laser could combine ablation and trapping capabilities on targets typically too far away or too hard for traditional drilling sampling systems. For an interstellar mission, a remote laser system could gather particles continuously at a safe distance; this would avoid the necessity of having a spacecraft fly through a target cloud such as a comet tail. If properly designed and implemented, a laser-based optical trapping system could fundamentally change the way scientists designand implement NASA missions that require mass spectroscopy and particle collection.

Optical trapping, pulling, and Raman spectroscopy of airborne absorbing particles based on negative photophoretic force

NASA Astrophysics Data System (ADS)

Chen, Gui-hua; He, Lin; Wu, Mu-ying; Yang, Guang; Li, Y. Q.

2017-08-01

Optical pulling is the attraction of objects back to the light source by the use of optically induced "negative forces". The light-induced photophoretic force is generated by the momentum transfer between the heating particles and surrounding gas molecules and can be several orders of magnitude larger than the radiation force and gravitation force. Here, we demonstrate that micron-sized absorbing particles can be optically pulled and manipulated towards the light source over a long distance in air with a collimated Gaussian laser beam based on a negative photophoretic force. A variety of airborne absorbing particles can be pulled by this optical pipeline to the region where they are optically trapped with another focused laser beam and their chemical compositions are characterized with Raman spectroscopy. We found that micron-sized particles are pulled over a meter-scale distance in air with a pulling speed of 1-10 cm/s in the optical pulling pipeline and its speed can be controlled by changing the laser intensity. When an aerosol particle is optically trapped with a focused Gaussian beam, we measured its rotation motion around the laser propagation direction and measured its Raman spectroscopy for chemical identification by molecular fingerprints. The centripetal acceleration of the trapped particle as high as 20 times the gravitational acceleration was observed. Optical pulling over large distances with lasers in combination with Raman spectroscopy opens up potential applications for the collection and identification of atmospheric particles.

Semiclassical theory of sub-Doppler forces in an asymmetric magneto-optical trap with unequal laser detunings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Noh, Heung-Ryoul; Jhe, Wonho

We present a semiclassical theory of the sub-Doppler forces in an asymmetric magneto-optical trap where the trap-laser frequencies are unequal to one another. To solve the optical Bloch equations, which contain explicit time dependence, unlike in the symmetric case of equal laser detunings, we have developed a convenient and efficient method to calculate the atomic forces at various oscillating frequencies for each atomic density matrix element. In particular, the theory provides a qualitative understanding of the array of sub-Doppler traps (SDTs) recently observed in such an asymmetric trap. We find that the distances between SDTs are proportional to the relativemore » detuning differences, in good agreement with experimental results. The theory presented here can be applied to a dynamic system with multiple laser frequencies involved; the number of coupled equations to solve is much reduced and the resulting numerical calculation can be performed rather simply and efficiently.« less

Optical trapping using cascade conical refraction of light.

PubMed

O'Dwyer, D P; Ballantine, K E; Phelan, C F; Lunney, J G; Donegan, J F

2012-09-10

Cascade conical refraction occurs when a beam of light travels through two or more biaxial crystals arranged in series. The output beam can be altered by varying the relative azimuthal orientation of the two biaxial crystals. For two identical crystals, in general the output beam comprises a ring beam with a spot at its centre. The relative intensities of the spot and ring can be controlled by varying the azimuthal angle between the refracted cones formed in each crystal. We have used this beam arrangement to trap one microsphere within the central spot and a second microsphere on the ring. Using linearly polarized light, we can rotate the microsphere on the ring with respect to the central sphere. Finally, using a half wave-plate between the two crystals, we can create a unique beam profile that has two intensity peaks on the ring, and thereby trap two microspheres on diametrically opposite points on the ring and rotate them around the central sphere. Such a versatile optical trap should find application in optical trapping setups.

Direct measurement of interaction forces between a single bacterium and a flat plate.

PubMed

Klein, Jonah D; Clapp, Aaron R; Dickinson, Richard B

2003-05-15

A technique for precisely measuring the equilibrium and viscous interaction forces between a single bacterium and a flat surface as functions of separation distance is described. A single-beam gradient optical trap was used to micromanipulate the bacterium against a flat surface while evanescent wave light scattering was used to measure separation distances. Calibrating the optical trap far from the surface allowed the trapped bacterium to be used as a force probe. Equilibrium force-distance profiles were determined by measuring the deflection of the cell from the center of the optical trap at various trap positions. Simultaneously, viscous forces were determined by measuring the relaxation time for the fluctuating bacterium. Absolute distances were determined using a best-fit approximation to the theoretical prediction for the hindered mobility of a diffusing sphere near a wall. Using this approach, forces in the range from 0.01 to 4 pN were measured at near-nanometer resolution between Staphylococcus aureus and glass that was bare or coated with adsorbed protein.

Plasmonic non-concentric nanorings array as an unidirectional nano-optical conveyor belt actuated by polarization rotation.

PubMed

Jiang, Min; Wang, Guanghui; Jiao, Wenxiang; Ying, Zhoufeng; Zou, Ningmu; Ho, Ho-Pui; Sun, Tianyu; Zhang, Xuping

2017-01-15

We report a nano-optical conveyor belt containing an array of gold plasmonic non-concentric nanorings (PNNRs) for the realization of trapping and unidirectional transportation of nanoparticles through rotating the polarization of an excitation beam. The location of hot spots within an asymmetric plasmonic nanostructure is polarization dependent, thus making it possible to manipulate a trapped target by rotating the incident polarization state. In the case of PNNR, the two poles have highly unbalanced trap potential. This greatly enhances the chance of transferring trapped particles between adjacent PNNRs in a given direction through rotating the polarization. As confirmed by three-dimensional finite-difference time-domain analysis, an array of PNNRs forms an unidirectional nano-optical conveyor belt, which delivers target nanoparticles or biomolecules over a long distance with nanometer accuracy. With the capacity to trap and to transfer, our design offers a versatile scheme for conducting mechanical sample manipulation in many on-chip optofluidic applications.

Pulsed laser manipulation of an optically trapped bead: averaging thermal noise and measuring the pulsed force amplitude.

PubMed

Lindballe, Thue B; Kristensen, Martin V G; Berg-Sørensen, Kirstine; Keiding, Søren R; Stapelfeldt, Henrik

2013-01-28

An experimental strategy for post-eliminating thermal noise on position measurements of optically trapped particles is presented. Using a nanosecond pulsed laser, synchronized to the detection system, to exert a periodic driving force on an optically trapped 10 μm polystyrene bead, the laser pulse-bead interaction is repeated hundreds of times. Traces with the bead position following the prompt displacement from equilibrium, induced by each laser pulse, are averaged and reveal the underlying deterministic motion of the bead, which is not visible in a single trace due to thermal noise. The motion of the bead is analyzed from the direct time-dependent position measurements and from the power spectrum. The results show that the bead is on average displaced 208 nm from the trap center and exposed to a force amplitude of 71 nanoNewton, more than five orders of magnitude larger than the trapping forces. Our experimental method may have implications for microrheology.

Improved atom number with a dual color magneto—optical trap

NASA Astrophysics Data System (ADS)

Cao, Qiang; Luo, Xin-Yu; Gao, Kui-Yi; Wang, Xiao-Rui; Chen, Dong-Min; Wang, Ru-Quan

2012-04-01

We demonstrate a novel dual color magneto—optical trap (MOT), which uses two sets of overlapping laser beams to cool and trap 87Rb atoms. The volume of cold cloud in the dual color MOT is strongly dependent on the frequency difference of the laser beams and can be significantly larger than that in the normal MOT with single frequency MOT beams. Our experiment shows that the dual color MOT has the same loading rate as the normal MOT, but much longer loading time, leading to threefold increase in the number of trapped atoms. This indicates that the larger number is caused by reduced light induced loss. The dual color MOT is very useful in experiments where both high vacuum level and large atom number are required, such as single chamber quantum memory and Bose—Einstein condensation (BEC) experiments. Compared to the popular dark spontaneous-force optical trap (dark SPOT) technique, our approach is technically simpler and more suitable to low power laser systems.

Induced dual EIT and EIA resonances with optical trapping phenomenon in near/far fields in the N-type four-level system

NASA Astrophysics Data System (ADS)

Osman, Kariman I.; Joshi, Amitabh

2017-01-01

The optical trapping phenomenon is investigated in the probe absorptive susceptibility spectra, during the interaction of four-level N-type atomic system with three transverse Gaussian fields, in a Doppler broadened medium. The system was studied under different temperature settings of 87Rb atomic vapor as well as different non-radiative decay rate. The system exhibits a combination of dual electromagnetically induced transparency with electromagnetically induced absorption (EIA) or transparency (EIT) resonances simultaneously in near/far field. Also, the optical trapping phenomenon is considerably affected by the non-radiative decay rate.

Highly efficient, versatile, self-Q-switched, high-repetition-rate microchip laser generating Ince-Gaussian modes for optical trapping

NASA Astrophysics Data System (ADS)

Dong, Jun; He, Yu; Zhou, Xiao; Bai, Shengchuang

2016-03-01

Lasers operating in the Ince-Gaussian (IG) mode have potential applications for optical manipulation of microparticles and formation of optical vortices, as well as for optical trapping and optical tweezers. Versatile, self-Q-switched, high-peak-power, high-repetition-rate Cr, Nd:YAG microchip lasers operating in the IG mode are implemented under tilted, tightly focused laser-diode pumping. An average output power of over 2 W is obtained at an absorbed pump power of 6.4 W. The highest optical-to-optical efficiency of 33.2% is achieved at an absorbed pump power of 3.9 W. Laser pulses with a pulse energy of 7.5 μJ, pulse width of 3.5 ns and peak power of over 2 kW are obtained. A repetition rate up to 335 kHz is reached at an absorbed pump power of 5.8 W. Highly efficient, versatile, IG-mode lasers with a high repetition rate and a high peak power ensure a better flexibility in particle manipulation and optical trapping.

Highly efficient, versatile, self-Q-switched, high-repetition-rate microchip laser generating Ince–Gaussian modes for optical trapping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jun Dong; Yu He; Xiao Zhou

2016-03-31

Lasers operating in the Ince-Gaussian (IG) mode have potential applications for optical manipulation of microparticles and formation of optical vortices, as well as for optical trapping and optical tweezers. Versatile, self-Q-switched, high-peak-power, high-repetition-rate Cr, Nd:YAG microchip lasers operating in the IG mode are implemented under tilted, tightly focused laser-diode pumping. An average output power of over 2 W is obtained at an absorbed pump power of 6.4 W. The highest optical-to-optical efficiency of 33.2% is achieved at an absorbed pump power of 3.9 W. Laser pulses with a pulse energy of 7.5 μJ, pulse width of 3.5 ns and peakmore » power of over 2 kW are obtained. A repetition rate up to 335 kHz is reached at an absorbed pump power of 5.8 W. Highly efficient, versatile, IG-mode lasers with a high repetition rate and a high peak power ensure a better flexibility in particle manipulation and optical trapping. (control of laser radiation parameters)« less

Multispectral optical tweezers for molecular diagnostics of single biological cells

NASA Astrophysics Data System (ADS)

Butler, Corey; Fardad, Shima; Sincore, Alex; Vangheluwe, Marie; Baudelet, Matthieu; Richardson, Martin

2012-03-01

Optical trapping of single biological cells has become an established technique for controlling and studying fundamental behavior of single cells with their environment without having "many-body" interference. The development of such an instrument for optical diagnostics (including Raman and fluorescence for molecular diagnostics) via laser spectroscopy with either the "trapping" beam or secondary beams is still in progress. This paper shows the development of modular multi-spectral imaging optical tweezers combining Raman and Fluorescence diagnostics of biological cells.

Spectroscopy, Manipulation and Trapping of Neutral Atoms, Molecules, and Other Particles Using Optical Nanofibers: A Review

PubMed Central

Morrissey, Michael J.; Deasy, Kieran; Frawley, Mary; Kumar, Ravi; Prel, Eugen; Russell, Laura; Truong, Viet Giang; Chormaic, Síle Nic

2013-01-01

The use of tapered optical fibers, i.e., optical nanofibers, for spectroscopy and the detection of small numbers of particles, such as neutral atoms or molecules, has been gaining interest in recent years. In this review, we briefly introduce the optical nanofiber, its fabrication, and optical mode propagation within. We discuss recent progress on the integration of optical nanofibers into laser-cooled atom and vapor systems, paying particular attention to spectroscopy, cold atom cloud characterization, and optical trapping schemes. Next, a natural extension of this work to molecules is introduced. Finally, we consider several alternatives to optical nanofibers that display some advantages for specific applications. PMID:23945738

Photoionization of radiation-induced traps in quartz and alkali feldspars.

PubMed

Hütt, G; Jaek, I; Vasilchenko, V

2001-01-01

For the optimization of luminescence dating and dosimetry techniques on the basis of the optically stimulated luminescence, the stimulation spectra of quartz and alkali feldspars were measured in the spectral region of 250-1100 nm using optically stimulated afterglow. Optically stimulated luminescence in all studied spectral regions is induced by the same kind of deep traps, that produce thermoluminescence in the regions of palaeodosimetric peaks for both minerals. The mechanism for photoionization of deep traps was proposed as being due to delocalization of the excited state of the corresponding lattice defects. The excited state overlaps the zone states; i.e. is situated in the conduction band. Because of the high quantum yield of deep electron trap ionization in the UV spectral region, the present aim was to study the possibility of using UV-stimulation for palaeodose reconstruction.

Trapping two types of particles using a double-ring-shaped radially polarized beam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang Yaoju; Ding Biaofeng; Suyama, Taikei

An optical-trap method based on the illumination of a double-ring-shaped radially polarized beam (R-TEM{sub 11}*) is proposed. The numerical results based on the vector diffraction theory show that a highly focused R-TEM{sub 11}* beam not only can produce a bright spot but also can form an optical cage in the focal region by changing the truncation parameter {beta}, defined as the ratio of the radius of the aperture to the waist of the beam. The radiation forces acting on Rayleigh particles are calculated by using the Rayleigh scattering theory. The bright spot generated by the R-TEM{sub 11}* beam with amore » {beta} value close to 2 can three-dimensionally trap a particle with a refractive index larger than that of the ambient. An optical cage or three-dimensional dark spot generated by the R-TEM{sub 11}* beam with a {beta} value close to 1.3 can three-dimensionally trap a particle with refractive index smaller than that of the ambient. Because the adjustment of the truncation parameter can be actualized by simply changing the radius of a circular aperture inserted in the front of the lens, only one optical-trap system in the present method can be used to three-dimensionally trap two types of particles with different refractive indices.« less

Ultraviolet laser spectroscopy of neutral mercury in a one-dimensional optical lattice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mejri, S.; McFerran, J. J.; Yi, L.

2011-09-15

We present details on the ultraviolet lattice spectroscopy of the (6s{sup 2}) {sup 1}S{sub 0}{r_reversible} (6s6p) {sup 3}P{sub 0} transition in neutral mercury, specifically {sup 199}Hg. Mercury atoms are loaded into a one-dimensional vertically aligned optical lattice from a magneto-optical trap with an rms temperature of {approx}60 {mu}K. We describe aspects of the magneto-optical trapping, the lattice cavity design, and the techniques employed to trap and detect mercury in an optical lattice. The clock-line frequency dependence on lattice depth is measured at a range of lattice wavelengths. We confirm the magic wavelength to be 362.51(0.16) nm. Further observations to thosemore » reported by Yi et al.[Phys. Rev. Lett. 106, 073005 (2011)] are presented regarding the laser excitation of a Wannier-Stark ladder of states.« less

Radiation pressure on a biconcave human Red Blood Cell and the resulting deformation in a pair of parallel optical traps.

PubMed

Liao, Guan-Bo; Chen, Yin-Quan; Bareil, Paul B; Sheng, Yunlong; Chiou, Arthur; Chang, Ming-Shien

2014-10-01

We calculated the three-dimensional optical stress distribution and the resulting deformation on a biconcave human red blood cell (RBC) in a pair of parallel optical trap. We assumed a Gaussian intensity distribution with a spherical wavefront for each trapping beam and calculated the optical stress from the momentum transfer associated with the reflection and refraction of the incident photons at each interface. The RBC was modelled as a biconcave thin elastic membrane with uniform elasticity and a uniform thickness of 0.25 μm. The resulting cell deformation was determined from the optical stress distribution by finite element software, Comsol Structure Mechanics Module, with Young's modulus (E) as a fitting parameter in order to fit the theoretical results for cell elongation to our experimental data. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dynamics analysis of microsphere in a dual-beam fiber-optic trap with transverse offset.

PubMed

Chen, Xinlin; Xiao, Guangzong; Luo, Hui; Xiong, Wei; Yang, Kaiyong

2016-04-04

A comprehensive dynamics analysis of microsphere has been presented in a dual-beam fiber-optic trap with transverse offset. As the offset distance between two counterpropagating beams increases, the motion type of the microsphere starts with capture, then spiral motion, then orbital rotation, and ends with escape. We analyze the transformation process and mechanism of the four motion types based on ray optics approximation. Dynamic simulations show that the existence of critical offset distances at which different motion types transform. The result is an important step toward explaining physical phenomena in a dual-beam fiber-optic trap with transverse offset, and is generally applicable to achieving controllable motions of microspheres in integrated systems, such as microfluidic systems and lab-on-a-chip systems.

Design and characterization of an integrated surface ion trap and micromirror optical cavity.

PubMed

Van Rynbach, Andre; Schwartz, George; Spivey, Robert F; Joseph, James; Vrijsen, Geert; Kim, Jungsang

2017-08-10

We have fabricated and characterized laser-ablated micromirrors on fused silica substrates for constructing stable Fabry-Perot optical cavities. We highlight several design features which allow these cavities to have lengths in the 250-300 μm range and be integrated directly with surface ion traps. We present a method to calculate the optical mode shape and losses of these micromirror cavities as functions of cavity length and mirror shape, and confirm that our simulation model is in good agreement with experimental measurements of the intracavity optical mode at a test wavelength of 780 nm. We have designed and tested a mechanical setup for dampening vibrations and stabilizing the cavity length, and explore applications for these cavities as efficient single-photon sources when combined with trapped Yb171 + ions.

Micromanipulation and microfabrication for optical microrobotics

NASA Astrophysics Data System (ADS)

Palima, Darwin; Bañas, Andrew Rafael; Vizsnyiczai, Gaszton; Kelemen, Lóránd; Aabo, Thomas; Ormos, Pál.; Glückstad, Jesper

2012-10-01

Robotics can use optics feedback in vision-based control of intelligent robotic guidance systems. With light's miniscule momentum, shrinking robots down to the microscale regime creates opportunities for exploiting optical forces and torques in microrobotic actuation and control. Indeed, the literature on optical trapping and micromanipulation attests to the possibilities for optical microrobotics. This work presents an optical microrobotics perspective on the optical microfabrication and micromanipulation work that we performed. We designed different three-dimensional microstructures and fabricated them by two-photon polymerization. These microstructures were then handled using our biophotonics workstation (BWS) for proof-of-principle demonstrations of optical actuation, akin to 6DOF actuation of robotic micromanipulators. Furthermore, we also show an example of dynamic behavior of the trapped microstructure that can be achieved when using static traps in the BWS. This can be generalized, in the future, towards a structural shaping optimization strategy for optimally controlling microstructures to complement approaches based on lightshaping. We also show that light channeled to microfabricated, free-standing waveguides can be used not only to redirect light for targeted delivery of optical energy but can also for targeted delivery of optical force, which can serve to further extend the manipulation arms in optical robotics. Moreover, light deflection with waveguide also creates a recoil force on the waveguide, which can be exploited for controlling the optical force.

Tapered fiber optical tweezers for microscopic particle trapping: fabrication and application

NASA Astrophysics Data System (ADS)

Liu, Zhihai; Guo, Chengkai; Yang, Jun; Yuan, Libo

2006-12-01

A novel single tapered fiber optical tweezers is proposed and fabricated by heating and drawing technology. The microscopic particle tapping performance of this special designed tapered fiber probe is demonstrated and investigated. The distribution of the optical field emerging from the tapered fiber tip is numerically calculated based on the beam propagation method. The trapping force FDTD analysis results, both axial and transverse, are also given.

Simultaneous trapping of rubidium-85 and rubidium-87 in a far off resonant trap

NASA Astrophysics Data System (ADS)

Gorges, Anthony R.

The experiments described in this thesis were focused on the physics of simultaneous trapping of 85Rb and 87 Rb into a Far Off Resonant Trap (FORT), with a view towards the implementation of a nonevaporative cooling scheme. Atoms were first trapped in a Magneto Optical Trap (MOT) and from there loaded into the FORT. We investigated the effects of loading the FORT from a MOT vs. an optical molasses; observing that the molasses significantly improved the trapped atom number. The ultimate number of atoms trapped is determined by a balance between efficient laser cooling into the FORT and light-assisted collisional losses from the FORT. We have studied and measured the loss rates associated with light-assisted collisions for our FORT, measuring both heteronuclear and homonuclear collisions. It was discovered that induced long range dipole-dipole interactions between 85Rb and 87Rb have a significant impact on FORT loading. This interaction interferes with the loading into the trap and thus limits the number of atoms which can be trapped in the FORT under simultaneous load conditions. Despite this limitation, all required experimental parameters for our future measurements have been met. In addition to these FORT studies, we have found a technique which can successfully mitigate the effects of reabsorption in optically thick clouds, which is a limitation to the ultimate temperature an atom cloud will reach during light-based cooling. Planned future measurements for this project include the creation of a variable aspect ratio FORT; along with investigating collision assisted Zeeman cooling.

Optical force and torque on a dielectric Rayleigh particle by a circular Airy vortex beam

NASA Astrophysics Data System (ADS)

Chen, Musheng; Huang, Sujuan; Shao, Wei; Liu, Xianpeng

2018-03-01

Optical force and torque exerted on the Rayleigh particles by tightly focused circularly polarized circular Airy vortex beams (CAVB) in the far field are studied in this paper. The relation between parameters of circularly polarized CAVB and the trapping properties is numerically analyzed based on Rayleigh models and the Debye diffraction theory. The results show that both the high refractive index and low refractive index particles can be fully stably trapped in three dimensions by circularly polarized CAVB. The parameters of circularly polarized CAVB greatly affect the optical force. The longitudinal and transverse gradient force increase with the increase of decay factor and scaling factor, and decrease with the increase of the radius of the first primary ring and topological charges. The positions of the longitudinal stable equilibrium move toward the high numerical aperture lens when the scaling factor and the radius of the primary ring increase. The trapping range is broadened with the decrease of scaling factor. The optical orbital torque (OOT) of circularly polarized CAVB has circular symmetry and remains positive or negative. With the increase of topological charges, the peak value of OOT first increases and then decreases after reaches a maximum. These results are useful for optical trapping, optical levitation and particle acceleration.

Optical Trapping and Manipulation in the Single- and Many-Body Limits

NASA Astrophysics Data System (ADS)

Spalding, Gabriel

2007-03-01

Analysis of optical dipole/scattering forces can be done at a variety of levels, some of which are appropriate to the undergraduate curriculum. The addition of simple holographic techniques has extended the basic capabilities of optical tweezing, making it a more viable tool for the assembly of micro-systems and organization of specimens into user-defined structures. In 2D, we have demonstrated an approach that allows optical forces alone to assemble microparticles over macroscopic areas. 3D structures pose greater challenges, but also significant opportunities. Our early efforts at filling a 3D lattice of optical traps led to an appreciation for the dynamics of injected microparticle streams, which yield a surprisingly successful method of sorting or re- routing within microfludic environments. We will discuss the status of efforts using optical trapping to create static many-body structures (both simple and complex), as well as recent results on dynamic interactions. At the same time, some of these techniques have clear pedagogical value, as will be emphasized.

The ATTA-Hefei Instrument for Radioactive Noble-gas Dating

NASA Astrophysics Data System (ADS)

Hu, S.; Cheng, C.; Cheng, G.; Sun, Y. R.; Tu, L.; Yang, G.

2013-12-01

Long-lived noble-gas isotopes 85Kr (10.8 y), 39Ar (269 y) and 81Kr (229 ky) are ideal tracers for dating environmental samples such as groundwater and ice. Together with 14C, these nuclides can be used to cover the whole range of 100-106 y. Atom Trap Trace Analysis (ATTA) is an emerging method for the analysis of these isotopes at an isotopic abundance level as low as 10^-16 [1,2]. The ATTA instrument built in Hefei, China, can determine the isotopic abundances of 85Kr and 81Kr with typically 5-10% accuracy using krypton gas samples of a few micro-liters (STP) krypton gas [3]. The krypton gas sample can be extracted from several liters of air using a distillation-chromatograph setup with a typical efficiency of 85%, while the air sample can be extracted from groundwater or ices. The typical sample size for ATTA measurement is 100L groundwater or 40Kg ices. One such ATTA beamline can handle about 100 samples per year. [1] Chen, C. Y. et al. Ultrasensitive isotope trace analyses with a magneto-optical trap. Science 286, 1139-1141 (1999). [2] Jiang, W. et al. 39Ar detection at the 10-16 isotopic abundance level with atom trap trace analysis. Phys. Rev. Lett. 106, 103001 (2011). [3] Yang, G. -M. et al. Analysis of 85Kr: a comparison at the 10-14 level using micro-liter samples, Sci. Rep. 3, 1596 (2013). Relative uncertainty of the determined 85Kr abundance by the ATTA-Hefei instrument.

Evolution of colloidal dispersions in novel time-varying optical potentials

NASA Astrophysics Data System (ADS)

Koss, Brian Alan

Optical traps use forces exerted by a tightly focused light beam to trap objects from tens of nanometers to tens of micrometers in size. Since their introduction in 1986, optical tweezers have become very useful to biology, chemistry, and soft condensed-matter physics. Work presented here, promises to advance optical tweezers not only in fundamental scientific research, but also in applications outside of the laboratory and into the mainstream of miniaturized manufacturing and diagnostics. By providing unprecedented access to the mesoscopic world, a new generation of optical traps, called Dynamic Holographic Optical Tweezers (HOTs) offers revolutionary new opportunities for fundamental and applied research. To demonstrate this technique, HOTs will be used to pump particles via a new method of transport called Optical Peristalsis (OP). OP is efficient method for transporting mesoscopic objects in three dimensions using short repetitive sequences of holographic optical trapping patterns. Transport in this process is analogous to peristaltic pumping, with the configurations of optical traps mimicking states of a peristaltic pump. While not limited to the deterministic particle transport, OP, can also be a platform to investigate the stochastic limit of particle transport. Advances in recent years have demonstrated that a variety of time-varying perturbations can induce drift in a diffusive system without exerting an overall force. Among these, are thermal ratchet models in which the system is subjected to time-varying energy landscapes that break spatiotemporal symmetry and thereby induce drift. Typically, the potential energy landscape is chosen to be the sawtooth potential. This work describes an alternate class of symmetric thermal ratchet models, that are not sawtooth, and demonstrates their efficacy in biasing the diffusion of colloidal spheres in both the stochastic and deterministic limits. Unlike previous models, each state in this thermal ratchet consists of discrete spatially-symmetric potential wells, which are implemented with an array of HOTs.

A trap potential model investigation of the optical activity induced in dye-DNA intercalation complexes

NASA Astrophysics Data System (ADS)

Kamiya, Mamoru

1988-02-01

The fundamental features of the optical activity induced in dye-DNA intercalation complexes are studied by application of the trap potential model which is useful to evaluate the induced rotational strength without reference to detailed geometrical information about the intercalation complexes. The specific effect of the potential depth upon the induced optical activity is explained in terms of the relative magnitudes of the wave-phase and helix-phase variations in the path of an electron moving on a restricted helical segment just like an exciton trapped around the dye intercalation site. The parallel and perpendicular components of the induced rotational strength well reflect basic properties of the helicity effects about the longitudinal and tangential axes of the DNA helical cylinder. The trap potential model is applied to optimize the potential parameters so as to reproduce the ionic strength effect upon the optical activity induced to proflavine-DNA intercalation complexes. From relationships between the optimized potential parameters and ionic strengths, it is inferred that increase in the ionic strength contributes to the optical activity induced by the nearest-neighbour interaction between intercalated proflavine and DNA base pairs.

Optical Tweezer Assembly and Calibration

NASA Technical Reports Server (NTRS)

Collins, Timothy M.

2004-01-01

An Optical Tweezer, as the name implies, is a useful tool for precision manipulation of micro and nano scale objects. Using the principle of electromagnetic radiation pressure, an optical tweezer employs a tightly focused laser beam to trap and position objects of various shapes and sizes. These devices can trap micrometer and nanometer sized objects. An exciting possibility for optical tweezers is its future potential to manipulate and assemble micro and nano sized sensors. A typical optical tweezer makes use of the following components: laser, mirrors, lenses, a high quality microscope, stage, Charge Coupled Device (CCD) camera, TV monitor and Position Sensitive Detectors (PSDs). The laser wavelength employed is typically in the visible or infrared spectrum. The laser beam is directed via mirrors and lenses into the microscope. It is then tightly focused by a high magnification, high numerical aperture microscope objective into the sample slide, which is mounted on a translating stage. The sample slide contains a sealed, small volume of fluid that the objects are suspended in. The most common objects trapped by optical tweezers are dielectric spheres. When trapped, a sphere will literally snap into and center itself in the laser beam. The PSD s are mounted in such a way to receive the backscatter after the beam has passed through the trap. PSD s used with the Differential Interference Contrast (DIC) technique provide highly precise data. Most optical tweezers employ lasers with power levels ranging from 10 to 100 miliwatts. Typical forces exerted on trapped objects are in the pico-newton range. When PSDs are employed, object movement can be resolved on a nanometer scale in a time range of milliseconds. Such accuracy, however, can only by utilized by calibrating the optical tweezer. Fortunately, an optical tweezer can be modeled accurately as a simple spring. This allows Hook s Law to be used. My goal this summer at NASA Glenn Research Center is the assembly and calibration of an optical tweezer setup in the Instrumentation and Controls Division (5520). I am utilizing a custom LabVIEW Virtual Instrument program for data collection and microscope stage control. Helping me in my assignment are the following people: Mentor Susan Wrbanek (5520), Dr. Baha Jassemnejad (UCO) and Technicians Ken Weiland (7650) and James Williams (7650). Without their help, my task would not be possible.

Radioactivity observed in scintillation counters during the HEAO-1 mission

NASA Technical Reports Server (NTRS)

Gruber, D. E.; Jung, G. V.; Matteson, J. L.

1989-01-01

Results are reported from an analysis of radioactivity induced in the NaI medium-energy detector of the hard X-ray and low-energy gamma-ray experiment during the HEAO-1 satellite mission (1977-1978). Consideration is given to the instrument characteristics, the origin and variability of background, and the separation of cosmic-ray activity from the internal activity due to South Atlantic Anomaly trapped protons. Energy spectra and tables listing the nuclide identifications are provided.

Induced radioactivity in LDEF components

NASA Technical Reports Server (NTRS)

Harmon, B. A.; Fishman, G. J.; Parnell, T. A.; Laird, C. E.

1992-01-01

A systematic study of the induced radioactivity of the Long Duration Exposure Facility (LDEF) is being carried out in order to gather information about the low earth orbit radiation environment and its effects on materials. The large mass of the LDEF spacecraft, its stabilized configuration, and long mission duration have presented an opportunity to determine space radiation-induced radioactivities with a precision not possible before. Data presented include preliminary activities for steel and aluminum structural samples, and activation subexperiment foils. Effects seen in the data show a clear indication of the trapped proton anisotropy in the South Atlantic Anomaly and suggest contributions from different sources of external radiation fluxes.

Radioactivity observed in the sodium iodide gamma-ray spectrometer returned on the Apollo 17 mission

NASA Technical Reports Server (NTRS)

Dyer, C. S.; Trombka, J. I.; Schmadebeck, R. L.; Eller, E.; Bielefeld, M. J.; Okelley, G. D.; Eldridge, J. S.; Northcutt, K. J.; Metzger, A. E.; Reedy, R. C.

1975-01-01

In order to obtain information on radioactive background induced in the Apollo 15 and 16 gamma-ray spectrometers (7 cm x 7 cm NaI) by particle irradiation during spaceflight, and identical detector was flown and returned to earth on the Apollo 17 mission. The induced radioactivity was monitored both internally and externally from one and a half hours after splashdown. When used in conjunction with a computation scheme for estimating induced activation from calculated trapped proton and cosmic-ray fluences, these results show an important contribution resulting from both thermal and energetic neutrons produced in the heavy spacecraft by cosmic-ray interactions.

Secondary scattering on the intensity dependence of the capture velocity in a magneto-optical trap

NASA Astrophysics Data System (ADS)

Loos, M. R.; Massardo, S. B.; de S. Zanon, R. A.; de Oliveira, A. L.

2005-08-01

In this work, we consider a three-dimensional model to simulate the capture velocity behavior in a sample of cold-trapped sodium atoms as a function of the trapping laser intensity. We expand on previous work [V. S. Bagnato, L. G. Marcassa, S. G. Miranda, S. R. Muniz, and A. L. de Oliveira, Phys. Rev. A 62, 013404 (2000)] by calculating the capture velocity over a broad range of light intensities considering the secondary scattering in a magneto-optical trap. Our calculations are in a good agreement with recent measured values [S. R. Muniz , Phys. Rev. A 65, 015402 (2001)].

Digital holography applications in ophthalmology, biometry, and optical trapping characterization

NASA Astrophysics Data System (ADS)

Potcoava, Mariana Camelia

This dissertation combines various holographic techniques with application on the two- and three-dimensional imaging of ophthalmic tissue, fingerprints, and microsphere samples with micrometer resolution. Digital interference holography (DIH) uses scanned wavelengths to synthesize short-coherence interference tomographic images. We used DIH for in vitro imaging of human optic nerve head and retina. Tomographic images were produced by superposition of holograms. Holograms were obtained with a signal-to-noise ratio of approximately 50 dB. Optic nerve head characteristics (shape, diameter, cup depth, and cup width) were quantified with a few micron resolution (4.06--4.8mum). Multiple layers were distinguishable in cross-sectional images of the macula. To our knowledge, this is the first report of DIH use to image human macular and optic nerve tissue. Holographic phase microscopy is used to produce images of thin film patterns left by latent fingerprints. Two or more holographic phase images with different wavelengths are combined for optical phase unwrapping of images of patent prints. We demonstrated digital interference holography images of a plastic print, and latent prints. These demonstrations point to significant contributions to biometry by using digital interference holography to identify and quantify Level 1 (pattern), Level 2 (minutia points), and Level 3 (pores and ridge contours). Quantitative studies of physical and biological processes and precise non-contact manipulation of nanometer/micrometer trapped objects can be effectuated with nanometer accuracy due to the development of optical tweezers. A three-dimensional gradient trap is produced at the focus position of a high NA microscope objective. Particles are trapped axially and laterally due to the gradient force. The particle is confined in a potential well and the trap acts as a harmonic spring. The elastic constant or the stiffness along any axis is determined from the particle displacements in time along each specific axis. Thus, we report the sensing of small particles using optical trapping in combination with the digital Gabor holography to calibrate the optical force and the position and of the copolymer microsphere in the x, y, z direction with nm precision.

Trapping and Propelling Microparticles at Long Range by Using an Entirely Stripped and Slightly Tapered No-Core Optical Fiber

PubMed Central

Sheu, Fang-Wen; Huang, Yen-Si

2013-01-01

A stripped no-core optical fiber with a 125 μm diameter was transformed into a symmetric and unbroken optical fiber that tapers slightly to a 45-μm-diameter waist. The laser light can be easily launched into the no-core optical fiber. The enhanced evanescent wave of the slightly tapered no-core optical fiber can attract nearby 5-μm-diameter polystyrene microparticles onto the surface of the tapered multimode optical fiber within fast flowing fluid and propel the trapped particles in the direction of the light propagation to longer delivery range than is possible using a slightly tapered telecom single-mode optical fiber. PMID:23449118

Nano-optomechanics with optically levitated nanoparticles

NASA Astrophysics Data System (ADS)

Neukirch, Levi P.; Vamivakas, A. Nick

2015-01-01

Nano-optomechanics is a vibrant area of research that continues to push the boundary of quantum science and measurement technology. Recently, it has been realised that the optical forces experienced by polarisable nanoparticles can provide a novel platform for nano-optomechanics with untethered mechanical oscillators. Remarkably, these oscillators are expected to exhibit quality factors approaching ?. The pronounced quality factors are a direct result of the mechanical oscillator being freed from a supporting substrate. This review provides an overview of the basic optical physics underpinning optical trapping and optical levitation experiments, it discusses a number of experimental approaches to optical trapping and finally outlines possible applications of this nano-optomechanics modality in hybrid quantum systems and nanoscale optical metrology.

Trapping and propelling microparticles at long range by using an entirely stripped and slightly tapered no-core optical fiber.

PubMed

Sheu, Fang-Wen; Huang, Yen-Si

2013-02-28

A stripped no-core optical fiber with a 125 µm diameter was transformed into a symmetric and unbroken optical fiber that tapers slightly to a 45-µm-diameter waist. The laser light can be easily launched into the no-core optical fiber. The enhanced evanescent wave of the slightly tapered no-core optical fiber can attract nearby 5-µm-diameter polystyrene microparticles onto the surface of the tapered multimode optical fiber within fast flowing fluid and propel the trapped particles in the direction of the light propagation to longer delivery range than is possible using a slightly tapered telecom single-mode optical fiber.

Trapping of a microsphere pendulum resonator in an optical potential

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ward, J. M.; Photonics Centre, Tyndall National Institute, Prospect Row, Cork; Wu, Y.

We propose a method to spatially confine or corral the movements of a micropendulum via the optical forces produced by two simultaneously excited optical modes of a photonic molecule comprising two microspherical cavities. We discuss how the cavity-enhanced optical force generated in the photonic molecule can create an optomechanical potential of about 10 eV deep and 30 pm wide, which can be used to trap the pendulum at any given equilibrium position by a simple choice of laser frequencies. This result presents opportunities for very precise all-optical self-alignment of microsystems.

Quantitative phase imaging for enhanced assessment of optomechanical cancer cell properties

NASA Astrophysics Data System (ADS)

Kastl, Lena; Kemper, Björn; Schnekenburger, Jürgen

2018-02-01

Optical cell stretching provides label-free investigations of cells by measuring their biomechanical properties based on deformability determination in a fiber optical two-beam trap. However, the stretching forces in this two-beam laser trap depend on the optical properties of the investigated specimen. Therefore, we characterized in parallel four cancer cell lines with varying degree of differentiation utilizing quantitative phase imaging (QPI) and optical cell stretching. The QPI data allowed enhanced assessment of the mechanical cell properties measured with the optical cell stretcher and demonstrates the high potential of cell phenotyping when both techniques are combined.

Quantum correlated pulse-pair generation during pulse-trapping propagation in optical fibers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hirosawa, Kenichi; Kannari, Fumihiko; Takeoka, Masahiro

2007-10-15

We study a different scheme for generating photon number correlation and squeezing for two copropagating pulses, a soliton and a trapped pulse, in an optical fiber. When the center wavelength of a trapped pulse is close to that of a soliton pulse, the two pulses interact with each other through the third-order optical nonlinear process and exchange photons between the two pulses. The soliton pulse exhibits photon number squeezing. When the center wavelengths of the two pulses are sufficiently separated and no photon-number exchange takes place, the strong negative correlation in the photon number between the parts of the trappedmore » pulse and the soliton pulse is formed via cross-phase modulation. By measuring the photon number of the negatively correlated part of the trapped pulse, we can obtain the photon number of the soliton pulse with a variance less than the shot-noise limit.« less

Euler buckling-induced folding and rotation of red blood cells in an optical trap

NASA Astrophysics Data System (ADS)

Ghosh, A.; Sinha, Supurna; Dharmadhikari, J. A.; Roy, S.; Dharmadhikari, A. K.; Samuel, J.; Sharma, S.; Mathur, D.

2006-03-01

We investigate the physics of an optically driven micromotor of biological origin. When a single, live red blood cell (RBC) is placed in an optical trap, the normal biconcave disc shape of the cell is observed to fold into a rod-like shape. If the trapping laser beam is circularly polarized, the folded RBC rotates. A model based on geometric considerations, using the concept of buckling instabilities, captures the folding phenomenon; the rotation of the cell is rationalized using the Poincaré sphere. Our model predicts that (i) at a critical power of the trapping laser beam the RBC shape undergoes large fluctuations, and (ii) the torque that is generated is proportional to the power of the laser beam. These predictions are verified experimentally. We suggest a possible mechanism for the emergence of birefringent properties in the RBC in the folded state.

Independent polarisation control of multiple optical traps

PubMed Central

Preece, Daryl; Keen, Stephen; Botvinick, Elliot; Bowman, Richard; Padgett, Miles; Leach, Jonathan

2009-01-01

We present a system which uses a single spatial light modulator to control the spin angular momentum of multiple optical traps. These traps may be independently controlled both in terms of spatial location and in terms of their spin angular momentum content. The system relies on a spatial light modulator used in a “split-screen” configuration to generate beams of orthogonal polarisation states which are subsequently combined at a polarising beam splitter. Defining the phase difference between the beams with the spatial light modulator enables control of the polarisation state of the light. We demonstrate the functionality of the system by controlling the rotation and orientation of birefringent vaterite crystals within holographic optical tweezers. PMID:18825226

Surface transport and stable trapping of particles and cells by an optical waveguide loop.

PubMed

Hellesø, Olav Gaute; Løvhaugen, Pål; Subramanian, Ananth Z; Wilkinson, James S; Ahluwalia, Balpreet Singh

2012-09-21

Waveguide trapping has emerged as a useful technique for parallel and planar transport of particles and biological cells and can be integrated with lab-on-a-chip applications. However, particles trapped on waveguides are continuously propelled forward along the surface of the waveguide. This limits the practical usability of the waveguide trapping technique with other functions (e.g. analysis, imaging) that require particles to be stationary during diagnosis. In this paper, an optical waveguide loop with an intentional gap at the centre is proposed to hold propelled particles and cells. The waveguide acts as a conveyor belt to transport and deliver the particles/cells towards the gap. At the gap, the diverging light fields hold the particles at a fixed position. The proposed waveguide design is numerically studied and experimentally implemented. The optical forces on the particle at the gap are calculated using the finite element method. Experimentally, the method is used to transport and trap micro-particles and red blood cells at the gap with varying separations. The waveguides are only 180 nm thick and thus could be integrated with other functions on the chip, e.g. microfluidics or optical detection, to make an on-chip system for single cell analysis and to study the interaction between cells.

Enumerating virus-like particles in an optically concentrated suspension by fluorescence correlation spectroscopy.

PubMed

Hu, Yi; Cheng, Xuanhong; Daniel Ou-Yang, H

2013-01-01

Fluorescence correlation spectroscopy (FCS) is one of the most sensitive methods for enumerating low concentration nanoparticles in a suspension. However, biological nanoparticles such as viruses often exist at a concentration much lower than the FCS detection limit. While optically generated trapping potentials are shown to effectively enhance the concentration of nanoparticles, feasibility of FCS for enumerating field-enriched nanoparticles requires understanding of the nanoparticle behavior in the external field. This paper reports an experimental study that combines optical trapping and FCS to examine existing theoretical predictions of particle concentration. Colloidal suspensions of polystyrene (PS) nanospheres and HIV-1 virus-like particles are used as model systems. Optical trapping energies and statistical analysis are used to discuss the applicability of FCS for enumerating nanoparticles in a potential well produced by a force field.

Spin angular momentum transfer from TEM00 focused Gaussian beams to negative refractive index spherical particles

PubMed Central

Ambrosio, Leonardo A.; Hernández-Figueroa, Hugo E.

2011-01-01

We investigate optical torques over absorbent negative refractive index spherical scatterers under the influence of linear and circularly polarized TEM00 focused Gaussian beams, in the framework of the generalized Lorenz-Mie theory with the integral localized approximation. The fundamental differences between optical torques due to spin angular momentum transfer in positive and negative refractive index optical trapping are outlined, revealing the effect of the Mie scattering coefficients in one of the most fundamental properties in optical trapping systems. PMID:21833372

Cavity cooling a single charged levitated nanosphere.

PubMed

Millen, J; Fonseca, P Z G; Mavrogordatos, T; Monteiro, T S; Barker, P F

2015-03-27

Optomechanical cavity cooling of levitated objects offers the possibility for laboratory investigation of the macroscopic quantum behavior of systems that are largely decoupled from their environment. However, experimental progress has been hindered by particle loss mechanisms, which have prevented levitation and cavity cooling in a vacuum. We overcome this problem with a new type of hybrid electro-optical trap formed from a Paul trap within a single-mode optical cavity. We demonstrate a factor of 100 cavity cooling of 400 nm diameter silica spheres trapped in vacuum. This paves the way for ground-state cooling in a smaller, higher finesse cavity, as we show that a novel feature of the hybrid trap is that the optomechanical cooling becomes actively driven by the Paul trap, even for singly charged nanospheres.

Cavity Cooling a Single Charged Levitated Nanosphere

NASA Astrophysics Data System (ADS)

Millen, J.; Fonseca, P. Z. G.; Mavrogordatos, T.; Monteiro, T. S.; Barker, P. F.

2015-03-01

Optomechanical cavity cooling of levitated objects offers the possibility for laboratory investigation of the macroscopic quantum behavior of systems that are largely decoupled from their environment. However, experimental progress has been hindered by particle loss mechanisms, which have prevented levitation and cavity cooling in a vacuum. We overcome this problem with a new type of hybrid electro-optical trap formed from a Paul trap within a single-mode optical cavity. We demonstrate a factor of 100 cavity cooling of 400 nm diameter silica spheres trapped in vacuum. This paves the way for ground-state cooling in a smaller, higher finesse cavity, as we show that a novel feature of the hybrid trap is that the optomechanical cooling becomes actively driven by the Paul trap, even for singly charged nanospheres.

Cooling the center-of-mass motion of a diamond nanocrystal in a magneto-gravitational trap

NASA Astrophysics Data System (ADS)

Hsu, Jen-Feng

A magneto-gravitational trap for micro/nanometer sized diamagnetic particles, such as diamond nanocrystals, is tested and characterized. After exploring various other systems, such as a suspended graphene beam and an optical trap, this magneto-gravitational nanomechanical trapping system for diamond with nitrogen-vacancy (NV) centers presents unique advantages for experiments in fundamental quantum mechanics. Those include, for example, the generation of large quantum superposition states and tests of quantum gravity. Features are demonstrated for this system, such as stable and passive levitation from atmospheric pressure to high vacuum, low resonant frequencies and damping rates, and cooling of the center-of-mass motions to below 1 K. The construction of the trap, vacuum system, optics, and motion detection electronics are described in detail.

Improving the trapping capability using radially polarized narrow-width annular beam

NASA Astrophysics Data System (ADS)

Xu, Hua-Feng; Zhang, Wei-Jun; Qu, Jun; Huang, Wei

2016-03-01

A novel optical-trap method for improving the trapping capability using a radially polarized narrow-width annular beam (NWAB) has been proposed. In this paper, we theoretically study the tight focusing properties of a radially polarized NWAB, formed by subtly blocking the central portion of a radially polarized Bessel-Gaussian beam (the original doughnut beam), through a high-numerical aperture objective. It is shown that a sub-wavelength focal spot (?) with a quite long depth of focus (about ?) can be formed in the vicinity of the focus. Furthermore, the optical trapping forces acting on a metallic Rayleigh particle are calculated for the case where a radially polarized annular beam is applied. Numerical results show that the radially polarized NWAB can largely enhance the transverse trap stiffness and broaden the longitudinal trap range compared with the usage of the original doughnut beam. The influence of the annular factor δ on the focusing properties and the trap stiffness is investigated in detail.

Paul Trapping of Radioactive {sup 6}He{sup +} Ions and Direct Observation of Their {beta} Decay

DOE Office of Scientific and Technical Information (OSTI.GOV)

Flechard, X.; Lienard, E.; Mery, A.

2008-11-21

We demonstrate that abundant quantities of short-lived {beta} unstable ions can be trapped in a novel transparent Paul trap and that their decay products can directly be detected in coincidence. Low energy {sup 6}He{sup +} (807 ms half-life) ions were extracted from the SPIRAL source at GANIL, then decelerated, cooled, and bunched by means of the buffer gas cooling technique. More than 10{sup 8} ions have been stored over a measuring period of six days, and about 10{sup 5} decay coincidences between the beta particles and the {sup 6}Li{sup ++} recoiling ions have been recorded. The technique can be extendedmore » to other short-lived species, opening new possibilities for trap assisted decay experiments.« less

An automated two-dimensional optical force clamp for single molecule studies.

PubMed Central

Lang, Matthew J; Asbury, Charles L; Shaevitz, Joshua W; Block, Steven M

2002-01-01

We constructed a next-generation optical trapping instrument to study the motility of single motor proteins, such as kinesin moving along a microtubule. The instrument can be operated as a two-dimensional force clamp, applying loads of fixed magnitude and direction to motor-coated microscopic beads moving in vitro. Flexibility and automation in experimental design are achieved by computer control of both the trap position, via acousto-optic deflectors, and the sample position, using a three-dimensional piezo stage. Each measurement is preceded by an initialization sequence, which includes adjustment of bead height relative to the coverslip using a variant of optical force microscopy (to +/-4 nm), a two-dimensional raster scan to calibrate position detector response, and adjustment of bead lateral position relative to the microtubule substrate (to +/-3 nm). During motor-driven movement, both the trap and stage are moved dynamically to apply constant force while keeping the trapped bead within the calibrated range of the detector. We present details of force clamp operation and preliminary data showing kinesin motor movement subject to diagonal and forward loads. PMID:12080136

Motion Control and Optical Interrogation of a Levitating Single Nitrogen Vacancy in Vacuum.

PubMed

Conangla, Gerard P; Schell, Andreas W; Rica, Raúl A; Quidant, Romain

2018-05-24

Levitation optomechanics exploits the unique mechanical properties of trapped nano-objects in vacuum to address some of the limitations of clamped nanomechanical resonators. In particular, its performance is foreseen to contribute to a better understanding of quantum decoherence at the mesoscopic scale as well as to lead to novel ultrasensitive sensing schemes. While most efforts have focused so far on the optical trapping of low-absorption silica particles, further opportunities arise from levitating objects with internal degrees of freedom, such as color centers. Nevertheless, inefficient heat dissipation at low pressures poses a challenge because most nano-objects, even with low-absorption materials, experience photodamage in an optical trap. Here, by using a Paul trap, we demonstrate levitation in vacuum and center-of-mass feedback cooling of a nanodiamond hosting a single nitrogen-vacancy center. The achieved level of motion control enables us to optically interrogate and characterize the emitter response. The developed platform is applicable to a wide range of other nano-objects and represents a promising step toward coupling internal and external degrees of freedom.

Millikelvin cooling of an optically trapped microsphere in vacuum

NASA Astrophysics Data System (ADS)

Li, Tongcang; Kheifets, Simon; Raizen, Mark G.

2011-07-01

Cooling of micromechanical resonators towards the quantum mechanical ground state in their centre-of-mass motion has advanced rapidly in recent years. This work is an important step towards the creation of `Schrödinger cats', quantum superpositions of macroscopic observables, and the study of their destruction by decoherence. Here we report optical trapping of glass microspheres in vacuum with high oscillation frequencies, and cooling of the centre-of-mass motion from room temperature to a minimum temperature of about 1.5mK. This new system eliminates the physical contact inherent to clamped cantilevers, and can allow ground-state cooling from room temperature. More importantly, the optical trap can be switched off, allowing a microsphere to undergo free-fall in vacuum after cooling. This is ideal for studying the gravitational state reduction, a manifestation of the apparent conflict between general relativity and quantum mechanics. A cooled optically trapped object in vacuum can also be used to search for non-Newtonian gravity forces at small scales, measure the impact of a single air molecule and even produce Schrödinger cats of living organisms.

Role of Hole Trap Sites in MoS2 for Inconsistency in Optical and Electrical Phenomena.

PubMed

Tran, Minh Dao; Kim, Ji-Hee; Kim, Hyun; Doan, Manh Ha; Duong, Dinh Loc; Lee, Young Hee

2018-03-28

Because of strong Coulomb interaction in two-dimensional van der Waals-layered materials, the trap charges at the interface strongly influence the scattering of the majority carriers and thus often degrade their electrical properties. However, the photogenerated minority carriers can be trapped at the interface, modulate the electron-hole recombination, and eventually influence the optical properties. In this study, we report the role of the hole trap sites on the inconsistency in the electrical and optical phenomena between two systems with different interfacial trap densities, which are monolayer MoS 2 -based field-effect transistors (FETs) on hexagonal boron nitride (h-BN) and SiO 2 substrates. Electronic transport measurements indicate that the use of h-BN as a gate insulator can induce a higher n-doping concentration of the monolayer MoS 2 by suppressing the free-electron transfer from the intrinsically n-doped MoS 2 to the SiO 2 gate insulator. Nevertheless, optical measurements show that the electron concentration in MoS 2 /SiO 2 is heavier than that in MoS 2 /h-BN, manifested by the relative red shift of the A 1g Raman peak. The inconsistency in the evaluation of the electron concentration in MoS 2 by electrical and optical measurements is explained by the trapping of the photogenerated holes in the spatially modulated valence band edge of the monolayer MoS 2 caused by the local strain from the SiO 2 /Si substrate. This photoinduced electron doping in MoS 2 /SiO 2 is further confirmed by the development of the trion component in the power-dependent photoluminescence spectra and negative shift of the threshold voltage of the FET after illumination.

Analysis of the influence of manufacturing and alignment related errors on an optical tweezer system

NASA Astrophysics Data System (ADS)

Kampmann, R.; Sinzinger, S.

2014-12-01

In this work we present the design process as well as experimental results of an optical system for trapping particles in air. For positioning applications of micro-sized objects onto a glass wafer we developed a highly efficient optical tweezer. The focus of this paper is the iterative design process where we combine classical optics design software with a ray optics based force simulation tool. Thus we can find the best compromise which matches the optical systems restrictions with stable trapping conditions. Furthermore we analyze the influence of manufacturing related tolerances and errors in the alignment process of the optical elements on the optical forces. We present the design procedure for the necessary optical elements as well as experimental results for the aligned system.

Fabrication and Operation of a Nano-Optical Conveyor Belt

PubMed Central

Ryan, Jason; Zheng, Yuxin; Hansen, Paul; Hesselink, Lambertus

2015-01-01

The technique of using focused laser beams to trap and exert forces on small particles has enabled many pivotal discoveries in the nanoscale biological and physical sciences over the past few decades. The progress made in this field invites further study of even smaller systems and at a larger scale, with tools that could be distributed more easily and made more widely available. Unfortunately, the fundamental laws of diffraction limit the minimum size of the focal spot of a laser beam, which makes particles smaller than a half-wavelength in diameter hard to trap and generally prevents an operator from discriminating between particles which are closer together than one half-wavelength. This precludes the optical manipulation of many closely-spaced nanoparticles and limits the resolution of optical-mechanical systems. Furthermore, manipulation using focused beams requires beam-forming or steering optics, which can be very bulky and expensive. To address these limitations in the system scalability of conventional optical trapping our lab has devised an alternative technique which utilizes near-field optics to move particles across a chip. Instead of focusing laser beams in the far-field, the optical near field of plasmonic resonators produces the necessary local optical intensity enhancement to overcome the restrictions of diffraction and manipulate particles at higher resolution. Closely-spaced resonators produce strong optical traps which can be addressed to mediate the hand-off of particles from one to the next in a conveyor-belt-like fashion. Here, we describe how to design and produce a conveyor belt using a gold surface patterned with plasmonic C-shaped resonators and how to operate it with polarized laser light to achieve super-resolution nanoparticle manipulation and transport. The nano-optical conveyor belt chip can be produced using lithography techniques and easily packaged and distributed. PMID:26381708

Fabrication and Operation of a Nano-Optical Conveyor Belt.

PubMed

Ryan, Jason; Zheng, Yuxin; Hansen, Paul; Hesselink, Lambertus

2015-08-26

The technique of using focused laser beams to trap and exert forces on small particles has enabled many pivotal discoveries in the nanoscale biological and physical sciences over the past few decades. The progress made in this field invites further study of even smaller systems and at a larger scale, with tools that could be distributed more easily and made more widely available. Unfortunately, the fundamental laws of diffraction limit the minimum size of the focal spot of a laser beam, which makes particles smaller than a half-wavelength in diameter hard to trap and generally prevents an operator from discriminating between particles which are closer together than one half-wavelength. This precludes the optical manipulation of many closely-spaced nanoparticles and limits the resolution of optical-mechanical systems. Furthermore, manipulation using focused beams requires beam-forming or steering optics, which can be very bulky and expensive. To address these limitations in the system scalability of conventional optical trapping our lab has devised an alternative technique which utilizes near-field optics to move particles across a chip. Instead of focusing laser beams in the far-field, the optical near field of plasmonic resonators produces the necessary local optical intensity enhancement to overcome the restrictions of diffraction and manipulate particles at higher resolution. Closely-spaced resonators produce strong optical traps which can be addressed to mediate the hand-off of particles from one to the next in a conveyor-belt-like fashion. Here, we describe how to design and produce a conveyor belt using a gold surface patterned with plasmonic C-shaped resonators and how to operate it with polarized laser light to achieve super-resolution nanoparticle manipulation and transport. The nano-optical conveyor belt chip can be produced using lithography techniques and easily packaged and distributed.

Cell identification using Raman spectroscopy in combination with optical trapping and microfluidics

NASA Astrophysics Data System (ADS)

Krafft, Christoph; Dochow, Sebastian; Beleites, Claudia; Popp, Jürgen

2014-03-01

Cell identification by Raman spectroscopy has evolved to be an attractive complement to established optical techniques. Raman activated cell sorting (RACS) offers prospects to complement the widely applied fluorescence activated cell sorting. RACS can be realized by combination with optical traps and microfluidic devices. The progress of RACS is reported for a cellular model system that can be found in peripheral blood of tumor patients. Lymphocytes and erythrocytes were extracted from blood samples. Breast carcinoma derived tumor cells (MCF-7, BT-20) and acute myeloid leukemia cells (OCI-AML3) were grown in cell cultures. First, Raman images were collected from dried cells on calcium fluoride slides. Support vector machines (SVM) classified 99.7% of the spectra to the correct cell type. Second, a 785 nm laser was used for optical trapping of single cells in aqueous buffer and for excitation of the Raman spectrum. SVM distinguished 1210 spectra of tumor and normal cells with a sensitivity of >99.7% and a specificity of >99.5%. Third, a microfluidic glass chip was designed to inject single cells, modify the flow speed, accommodate fibers of an optical trap and sort single cells after Raman based identification with 514 nm for excitation. Forth, the microfluidic chip was fabricated by quartz which improved cell identification results with 785 nm excitation. Here, partial least squares discriminant analysis gave classification rates of 98%. Finally, a Raman-on-chip approach was developed that integrates fibers for trapping, Raman excitation and signal detection in a single compact unit.

Effects of viscosity on sperm motility studied with optical tweezers

NASA Astrophysics Data System (ADS)

Hyun, Nicholas; Chandsawangbhuwana, Charlie; Zhu, Qingyuan; Shi, Linda Z.; Yang-Wong, Collin; Berns, Michael W.

2012-02-01

The purpose of this study is to analyze human sperm motility and energetics in media with different viscosities. Multiple experiments were performed to collect motility parameters using customized computer tracking software that measures the curvilinear velocity (VCL) and the minimum laser power (Pesc) necessary to hold an individual sperm in an optical trap. The Pesc was measured by using a 1064 nm Nd:YVO4 continuous wave laser that optically traps motile sperm at a power of 450 mW in the focused trap spot. The VCL was measured frame by frame before trapping. In order to study sperm energetics under different viscous conditions sperm were labeled with the fluorescent dye DiOC6(3) to measure membrane potentials of mitochondria in the sperm midpiece. Fluorescence intensity was measured before and during trapping. The results demonstrate a decrease in VCL but an increase in Pesc with increasing viscosity. Fluorescent intensity is the same regardless of the viscosity level indicating no change in sperm energetics. The results suggest that, under the conditions tested, viscosity physically affects the mechanical properties of sperm motility rather than the chemical pathways associated with energetics.

Influence of shallow traps on time-resolved optically stimulated luminescence measurements of Al2O3:C,Mg

NASA Astrophysics Data System (ADS)

Denis, G.; Akselrod, M. S.; Yukihara, E. G.

2011-05-01

The objective of this paper is to investigate the influence of shallow traps on the signals from Al2O3:C,Mg obtained using time-resolved optically stimulated luminescence (TR-OSL) measurements through experiments and numerical simulations. TR-OSL measurements of Al2O3:C,Mg were carried out and the resulting optically stimulated luminescence (OSL) curves were investigated as a function of the temperature. The numerical simulations were carried out using the rate-equations for a simplified model of Al2O3:C,Mg containing two types of luminescence centers with different luminescence lifetimes and three types of electron traps (a shallow trap, a main dosimetric trap, and a thermally disconnected deep trap). Both experimental results and simulations show that the OSL signals during and between the stimulation pulses are affected by the presence of shallow traps. However, with an appropriate choice of timing parameters, the influence of shallow traps can be reduced by calculating the difference between the signals during and between stimulation pulses. Therefore, TR-OSL can be useful in dosimetry using materials having a large concentration of shallow traps and OSL components with short luminescence lifetimes, for example Al2O3:C,Mg and BeO. Our results also show that the presence of shallow traps has to be taken into account when using the TR-OSL for discrimination between luminescence centers with different luminescence lifetimes, or separation between the OSL from different materials based on their characteristic luminescence lifetimes. The experimental results also show evidence of thermal assistance in the OSL process of Al2O3:C,Mg.

Hg(+) Frequency Standards

NASA Technical Reports Server (NTRS)

Prestage, John D.; Tjoelker, Robert L.; Maleki, Lute

2000-01-01

In this paper we review the development of Hg(+) microwave frequency standards for use in high reliability and continuous operation applications. In recent work we have demonstrated short-term frequency stability of 3 x 10(exp -14)/nu(sub tau) when a cryogenic oscillator of stability 2-3 x 10(exp 15) was used a the local oscillator. The trapped ion frequency standard employs a Hg-202 discharge lamp to optically pump the trapped Hg(+)-199 clock ions and a helium buffer gas to cool the ions to near room temperature. We describe a small Hg(+) ion trap based frequency standard with an extended linear ion trap (LITE) architecture which separates the optical state selection region from the clock resonance region. This separation allows the use of novel trap configurations in the resonance region since no optical pumping is carried out there. A method for measuring the size of an ion cloud inside a linear trap with a 12-rod trap is currently being investigated. At approx. 10(exp -12), the 2nd order Doppler shift for trapped mercury ion frequency standards is one of the largest frequency offsets and its measurement to the 1% level would represent an advance in insuring the very long-term stability of these standards to the 10(exp -14) or better level. Finally, we describe atomic clock comparison experiments that can probe for a time variation of the fine structure constant, alpha = e(exp 2)/2(pi)hc, at the level of 10(exp -20)/year as predicted in some Grand Unified String Theories.

Trapping of Individual Airborne Absorbing Particles Using a Counterflow Nozzle and Photophoretic Trap for Continuous Sampling and Analysis

DTIC Science & Technology

2014-03-19

particles from air. The key parts of the system are a conical photophoretic optical trap and a counter-flow coaxial-double- nozzle that concentrates and then...distribution is unlimited. Trapping of individual airborne absorbing particles using a counterflow nozzle and photophoretic trap for continuous...airborne absorbing particles using a counterflow nozzle and photophoretic trap for continuous sampling and analysis Report Title We describe an

Optical Forces on Non-Spherical Nanoparticles Trapped by Optical Waveguides

NASA Astrophysics Data System (ADS)

Hasan Ahmed, Dewan; Sung, Hyung Jin

2011-07-01

Numerical simulations of a solid-core polymer waveguide structure were performed to calculate the trapping efficiencies of particles with nanoscale dimensions smaller than the wavelength of the trapping beam. A three-dimensional (3-D) finite element method was employed to calculate the electromagnetic field. The inlet and outlet boundary conditions were obtained using an eigenvalue solver to determine the guided and evanescent mode profiles. The Maxwell stress tensor was considered for the calculation of the transverse and downward trapping efficiencies. A particle at the center of the waveguide showed minimal transverse trapping efficiency and maximal downward trapping efficiency. This trend gradually reversed as the particle moved away from the center of the waveguide. Particles with larger surface areas exhibited higher trapping efficiencies and tended to be trapped near the waveguide. Particles displaced from the wave input tended to be trapped at the waveguide surface. Simulation of an ellipsoidal particle showed that the orientation of the major axis along the waveguide's lateral z-coordinate significantly influenced the trapping efficiency. The particle dimensions along the z-coordinate were more critical than the gap distance (vertical displacement from the floor of the waveguide) between the ellipsoid particle and the waveguide. The present model was validated using the available results reported in the literature for different trapping efficiencies.

An in-vacuo optical levitation trap for high-intensity laser interaction experiments with isolated microtargets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Price, C. J., E-mail: c.price10@imperial.ac.uk; Giltrap, S.; Stuart, N. H.

2015-03-15

We report on the design, construction, and characterisation of a new class of in-vacuo optical levitation trap optimised for use in high-intensity, high-energy laser interaction experiments. The system uses a focused, vertically propagating continuous wave laser beam to capture and manipulate micro-targets by photon momentum transfer at much longer working distances than commonly used by optical tweezer systems. A high speed (10 kHz) optical imaging and signal acquisition system was implemented for tracking the levitated droplets position and dynamic behaviour under atmospheric and vacuum conditions, with ±5 μm spatial resolution. Optical trapping of 10 ± 4 μm oil droplets inmore » vacuum was demonstrated, over timescales of >1 h at extended distances of ∼40 mm from the final focusing optic. The stability of the levitated droplet was such that it would stay in alignment with a ∼7 μm irradiating beam focal spot for up to 5 min without the need for re-adjustment. The performance of the trap was assessed in a series of high-intensity (10{sup 17} W cm{sup −2}) laser experiments that measured the X-ray source size and inferred free-electron temperature of a single isolated droplet target, along with a measurement of the emitted radio-frequency pulse. These initial tests demonstrated the use of optically levitated microdroplets as a robust target platform for further high-intensity laser interaction and point source studies.« less

An in-vacuo optical levitation trap for high-intensity laser interaction experiments with isolated microtargets

NASA Astrophysics Data System (ADS)

Price, C. J.; Donnelly, T. D.; Giltrap, S.; Stuart, N. H.; Parker, S.; Patankar, S.; Lowe, H. F.; Drew, D.; Gumbrell, E. T.; Smith, R. A.

2015-03-01

We report on the design, construction, and characterisation of a new class of in-vacuo optical levitation trap optimised for use in high-intensity, high-energy laser interaction experiments. The system uses a focused, vertically propagating continuous wave laser beam to capture and manipulate micro-targets by photon momentum transfer at much longer working distances than commonly used by optical tweezer systems. A high speed (10 kHz) optical imaging and signal acquisition system was implemented for tracking the levitated droplets position and dynamic behaviour under atmospheric and vacuum conditions, with ±5 μm spatial resolution. Optical trapping of 10 ± 4 μm oil droplets in vacuum was demonstrated, over timescales of >1 h at extended distances of ˜40 mm from the final focusing optic. The stability of the levitated droplet was such that it would stay in alignment with a ˜7 μm irradiating beam focal spot for up to 5 min without the need for re-adjustment. The performance of the trap was assessed in a series of high-intensity (1017 W cm-2) laser experiments that measured the X-ray source size and inferred free-electron temperature of a single isolated droplet target, along with a measurement of the emitted radio-frequency pulse. These initial tests demonstrated the use of optically levitated microdroplets as a robust target platform for further high-intensity laser interaction and point source studies.

Wave front engineering by means of diffractive optical elements for applications in microscopy

NASA Astrophysics Data System (ADS)

Cojoc, Dan; Ferrari, Enrico; Garbin, Valeria; Cabrini, Stefano; Carpentiero, Alessandro; Prasciolu, Mauro; Businaro, Luca; Kaulich, Burchard; Di Fabrizio, Enzo

2006-05-01

We present a unified view regarding the use of diffractive optical elements (DOEs) for microscopy applications a wide range of electromagnetic spectrum. The unified treatment is realized through the design and fabrication of DOE through which wave front beam shaping is obtained. In particular we show applications ranging from micromanipulation using optical tweezers to X-ray differential interference contrast (DIC) microscopy. We report some details on the design and physical implementation of diffractive elements that beside focusing perform also other optical functions: beam splitting, beam intensity and phase redistribution or mode conversion. Laser beam splitting is used for multiple trapping and independent manipulation of spherical micro beads and for direct trapping and manipulation of biological cells with non-spherical shapes. Another application is the Gauss to Laguerre-Gaussian mode conversion, which allows to trap and transfer orbital angular momentum of light to micro particles with high refractive index and to trap and manipulate low index particles. These experiments are performed in an inverted optical microscope coupled with an infrared laser beam and a spatial light modulator for DOEs implementation. High resolution optics, fabricated by means of e-beam lithography, are demonstrated to control the intensity and the phase of the sheared beams in X-ray DIC microscopy. DIC experiments with phase objects reveal a dramatic increase in image contrast compared to bright-field X-ray microscopy.

Two-species five-beam magneto-optical trap for erbium and dysprosium

NASA Astrophysics Data System (ADS)

Ilzhöfer, P.; Durastante, G.; Patscheider, A.; Trautmann, A.; Mark, M. J.; Ferlaino, F.

2018-02-01

We report on the first realization of a two-species magneto-optical trap (MOT) for the highly magnetic erbium and dysprosium atoms. The MOT operates on an intercombination line for the respective species. Owing to the narrow-line character of such a cooling transition and the action of gravity, we demonstrate a trap geometry employing only five beams in the orthogonal configuration. We observe that the mixture is cooled and trapped very efficiently, with up to 5 ×108 Er atoms and 109 Dy atoms at temperatures of about 10 μ K . Our results offer an ideal starting condition for the creation of a dipolar quantum mixture of highly magnetic atoms.

Optical trapping and rotation of airborne absorbing particles with a single focused laser beam

NASA Astrophysics Data System (ADS)

Lin, Jinda; Li, Yong-qing

2014-03-01

We measure the periodic circular motion of single absorbing aerosol particles that are optically trapped with a single focused Gaussian beam and rotate around the laser propagation direction. The scattered light from the trapped particle is observed to be directional and change periodically at 0.4-20 kHz. The instantaneous positions of the moving particle within a rotation period are measured by a high-speed imaging technique using a charge coupled device camera and a repetitively pulsed light-emitting diode illumination. The centripetal acceleration of the trapped particle as high as ˜20 times the gravitational acceleration is observed and is attributed to the photophoretic forces.

Calculation of the force acting on a micro-sized particle with optical vortex array laser beam tweezers

NASA Astrophysics Data System (ADS)

Kuo, Chun-Fu; Chu, Shu-Chun

2013-03-01

Optical vortices possess several special properties, including carrying optical angular momentum (OAM) and exhibiting zero intensity. Vortex array laser beams have attracts many interests due to its special mesh field distributions, which show great potential in the application of multiple optical traps and dark optical traps. Previously study developed an Ince-Gaussian Mode (IGM)-based vortex array laser beam1. This study develops a simulation model based on the discrete dipole approximation (DDA) method for calculating the resultant force acting on a micro-sized spherical dielectric particle that situated at the beam waist of the IGM-based vortex array laser beams1.

Dual-Mode Operation of an Optical Lattice Clock Using Strontium and Ytterbium Atoms.

PubMed

Akamatsu, Daisuke; Kobayashi, Takumi; Hisai, Yusuke; Tanabe, Takehiko; Hosaka, Kazumoto; Yasuda, Masami; Hong, Feng-Lei

2018-06-01

We have developed an optical lattice clock that can operate in dual modes: a strontium (Sr) clock mode and an ytterbium (Yb) clock mode. Dual-mode operation of the Sr-Yb optical lattice clock is achieved by alternately cooling and trapping 87 Sr and 171 Yb atoms inside the vacuum chamber of the clock. Optical lattices for Sr and Yb atoms were arranged with horizontal and vertical configurations, respectively, resulting in a small distance of the order of between the trapped Sr and Yb atoms. The 1 S 0 - 3 P 0 clock transitions in the trapped atoms were interrogated in turn and the clock lasers were stabilized to the transitions. We demonstrated the frequency ratio measurement of the Sr and Yb clock transitions by using the dual-mode operation of the Sr-Yb optical lattice clock. The dual-mode operation can reduce the uncertainty of the blackbody radiation shift in the frequency ratio measurement, because both Sr and Yb atoms share the same blackbody radiation.

Multiple Optical Traps with a Single-Beam Optical Tweezer Utilizing Surface Micromachined Planar Curved Grating

NASA Astrophysics Data System (ADS)

Kuo, Ju-Nan; Chen, Kuan-Yu

2010-11-01

In this paper, we present a single-beam optical tweezer integrated with a planar curved diffraction grating for microbead manipulation. Various curvatures of the surface micromachined planar curved grating are systematically investigated. The planar curved grating was fabricated using multiuser micro-electro-mechanical-system (MEMS) processes (MUMPs). The angular separation and the number of diffracted orders were determined. Experimental results indicate that the diffraction patterns and curvature of the planar curved grating are closely related. As the curvature of the planar curved grating increases, the vertical diffraction angle increases, resulting in the strip patterns of the planar curved grating. A single-beam optical tweezer integrated with a planar curved diffraction grating was developed. We demonstrate a technique for creating multiple optical traps from a single laser beam using the developed planar curved grating. The strip patterns of the planar curved grating that resulted from diffraction were used to trap one row of polystyrene beads.

Stiffness of RBC optical confinement affected by optical clearing

NASA Astrophysics Data System (ADS)

Grishin, Oleg V.; Fedosov, Ivan V.; Tuchin, Valery V.

2017-03-01

In vivo optical trapping is a novel applied direction of an optical manipulation, which enables one to noninvasive measurement of mechanical properties of cells and tissues in living animals directly. But an application area of this direction is limited because strong scattering of many biological tissues. An optical clearing enables one to decrease the scattering and therefore increase a depth of light penetration, decrease a distortion of light beam, improve a resolution in imaging applications. Now novel methods had appeared for a measurement an optical clearing degree at a cellular level. But these methods aren't applicable in vivo. In this paper we present novel measurement method of estimate of the optical clearing, which are based on a measurement of optical trap stiffness. Our method may be applicable in vivo.

Single-atom trapping and transport in DMD-controlled optical tweezers

NASA Astrophysics Data System (ADS)

Stuart, Dustin; Kuhn, Axel

2018-02-01

We demonstrate the trapping and manipulation of single neutral atoms in reconfigurable arrays of optical tweezers. Our approach offers unparalleled speed by using a Texas instruments digital micro-mirror device as a holographic amplitude modulator with a frame rate of 20 000 per second. We show the trapping of static arrays of up to 20 atoms, as well as transport of individually selected atoms over a distance of 25 μm with laser cooling and 4 μm without. We discuss the limitations of the technique and the scope for technical improvements.

Coherent control of a single nitrogen-vacancy center spin in optically levitated nanodiamond

DOE PAGES

Pettit, Robert M.; Neukirch, Levi Patrick; Zhang, Yi; ...

2017-05-12

Here, we report the first observation, to the best of our knowledge, of electron spin transients in single negatively charged nitrogen-vacancy (NV -) centers, contained within optically trapped nanodiamonds, in both atmospheric pressure and low vacuum. It is shown that, after an initial exposure to low vacuum, the trapped nanodiamonds remain at temperatures near room temperature even in low vacuum. Furthermore, the transverse coherence time of the NV - center spin, measured to be T 2=101.4 ns, is robust over the range of trapping powers considered in this study.

Influence of trapping potentials on the phase diagram of bosonic atoms in optical lattices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giampaolo, S.M.; Illuminati, F.; Mazzarella, G.

2004-12-01

We study the effect of external trapping potentials on the phase diagram of bosonic atoms in optical lattices. We introduce a generalized Bose-Hubbard Hamiltonian that includes the structure of the energy levels of the trapping potential, and show that these levels are in general populated both at finite and zero temperature. We characterize the properties of the superfluid transition for this situation and compare them with those of the standard Bose-Hubbard description. We briefly discuss similar behaviors for fermionic systems.

Rydberg-Dressed Magneto-optical Trap

NASA Astrophysics Data System (ADS)

Bounds, A. D.; Jackson, N. C.; Hanley, R. K.; Faoro, R.; Bridge, E. M.; Huillery, P.; Jones, M. P. A.

2018-05-01

We propose and demonstrate the laser cooling and trapping of Rydberg-dressed Sr atoms. By off-resonantly coupling the excited state of a narrow (7 kHz) cooling transition to a high-lying Rydberg state, we transfer Rydberg properties such as enhanced electric polarizability to a stable magneto-optical trap operating at <1 μ K . Simulations show that it is possible to reach a regime where the long-range interaction between Rydberg-dressed atoms becomes comparable to the kinetic energy, opening a route to combining laser cooling with tunable long-range interactions.

FDTD approach to optical forces of tightly focused vector beams on metal particles.

PubMed

Qin, Jian-Qi; Wang, Xi-Lin; Jia, Ding; Chen, Jing; Fan, Ya-Xian; Ding, Jianping; Wang, Hui-Tian

2009-05-11

We propose an improved FDTD method to calculate the optical forces of tightly focused beams on microscopic metal particles. Comparison study on different kinds of tightly focused beams indicates that trapping efficiency can be altered by adjusting the polarization of the incident field. The results also show the size-dependence of trapping forces exerted on metal particles. Transverse tapping forces produced by different illumination wavelengths are also evaluated. The numeric simulation demonstrates the possibility of trapping moderate-sized metal particles whose radii are comparable to wavelength.

Understanding Optical Trapping Phenomena: A Simulation for Undergraduates

ERIC Educational Resources Information Center

Mas, J.; Farre, A.; Cuadros, J.; Juvells, I.; Carnicer, A.

2011-01-01

Optical trapping is an attractive and multidisciplinary topic that has become the center of attention to a large number of researchers. Moreover, it is a suitable subject for advanced students that requires a knowledge of a wide range of topics. As a result, it has been incorporated into some syllabuses of both undergraduate and graduate programs.…

Kinematic cooling of molecules in a magneto-optical trap

NASA Astrophysics Data System (ADS)

Takase, Ken; Chandler, David W.; Strecker, Kevin E.

2008-05-01

We will present our current progress on a new experimental technique aimed at slowing and cooling hot molecules using a single collision with magneto-optically trapped atoms. Kinematic cooling, unlike buffer gas and sympathetic cooling, relies only on a single collision between the molecule and atom to stop the molecule in the laboratory frame. This technique has recently been demonstrated in a crossed atomic and molecular beam machine to produce 35mK samples of nitric oxide via a single collision with argon [1]. In this technique we replace the atomic beam with a sample magneto-optically trapped atoms. We are currently designing and building a new apparatus to attempt these experiments. [1] Kevin E. Strecker and David W. Chandler (to be published)

Optical trapping inside living organisms

NASA Astrophysics Data System (ADS)

Hansen, Poul M.; Oddershede, Lene B.

2005-08-01

We use optical tweezers to investigate processes happening inside ving cells. In a previous study, we trapped naturally occurring lipid granules inside living yeast cells, and used them to probe the viscoelastic properties of the cytoplasm. However, we prefer to use probes which can be specifically attached to various organelles within the living cells in order to optically quantify the forces acting on these organelles. Therefore, we have chosen to use nanometer sized gold beads as probes. These gold beads can be conjugated and attached chemically to the organelles of interest. Only Rayleigh metallic particles can be optically trapped and for these it is the case that the larger the beads, the larger the forces which can be exerted and thus measured using optical tweezers. The gold nanoparticles are injected into the cytoplasm using micropipettes. The very rigid cell wall of the S. pombe yeast cells poses a serious obstacle to this injection. In order to be able to punch a hole in the cell, first, the cells have to be turned into protoplasts, where only a lipid bilayer separates the cytoplasm from the surrounding media. We show how to perform micropipette delivery into the protoplasts and also how the protoplasts can be ablated using the trapping laserlight. Finally, we demonstrate that we can transform the protoplasts back to normal yeast cells.

Hg-201 (+) CO-Magnetometer for HG-199(+) Trapped Ion Space Atomic Clocks

NASA Technical Reports Server (NTRS)

Burt, Eric A. (Inventor); Taghavi, Shervin (Inventor); Tjoelker, Robert L. (Inventor)

2011-01-01

Local magnetic field strength in a trapped ion atomic clock is measured in real time, with high accuracy and without degrading clock performance, and the measurement is used to compensate for ambient magnetic field perturbations. First and second isotopes of an element are co-located within the linear ion trap. The first isotope has a resonant microwave transition between two hyperfine energy states, and the second isotope has a resonant Zeeman transition. Optical sources emit ultraviolet light that optically pump both isotopes. A microwave radiation source simultaneously emits microwave fields resonant with the first isotope's clock transition and the second isotope's Zeeman transition, and an optical detector measures the fluorescence from optically pumping both isotopes. The second isotope's Zeeman transition provides the measure of magnetic field strength, and the measurement is used to compensate the first isotope's clock transition or to adjust the applied C-field to reduce the effects of ambient magnetic field perturbations.

Optical trapping for complex fluid microfluidics

NASA Astrophysics Data System (ADS)

Vestad, Tor; Oakey, John; Marr, David W. M.

2004-10-01

Many proposed applications of microfluidics involve the manipulation of complex fluid mixtures such as blood or bacterial suspensions. To sort and handle the constituent particles within these suspensions, we have developed a miniaturized automated cell sorter using optical traps. This microfluidic cell sorter offers the potential to perform chip-top microbiology more rapidly and with less associated hardware and preparation time than other techniques currently available. To realize the potential of this technology in practical clinical and consumer lab-on-a-chip devices however, microscale control of not only particulates but also the fluid phase must be achieved. To address this, we have developed a mechanical fluid control scheme that integrates well with our optical separations approach. We demonstrate here a combined technique, one that employs both mechanical actuation and optical trapping for the precise control of complex suspensions. This approach enables both cell and particle separations as well as the subsequent fluid control required for the completion of complex analyses.

Creation of quantum-degenerate gases of ytterbium in a compact 2D-/3D-magneto-optical trap setup

DOE Office of Scientific and Technical Information (OSTI.GOV)

Doerscher, Soeren; Thobe, Alexander; Hundt, Bastian

2013-04-15

We report on the first experimental setup based on a 2D-/3D-magneto-optical trap (MOT) scheme to create both Bose-Einstein condensates and degenerate Fermi gases of several ytterbium isotopes. Our setup does not require a Zeeman slower and offers the flexibility to simultaneously produce ultracold samples of other atomic species. Furthermore, the extraordinary optical access favors future experiments in optical lattices. A 2D-MOT on the strong {sup 1}S{sub 0}{yields}{sup 1}P{sub 1} transition captures ytterbium directly from a dispenser of atoms and loads a 3D-MOT on the narrow {sup 1}S{sub 0}{yields}{sup 3}P{sub 1} intercombination transition. Subsequently, atoms are transferred to a crossed opticalmore » dipole trap and cooled evaporatively to quantum degeneracy.« less

The study of thin films on solid aerosol particles using optical trapping and Mie scattering from a broadband white LED

NASA Astrophysics Data System (ADS)

Jones, Stephanie H.; King, Martin D.; Ward, Andrew D.

2014-09-01

A counter-propagating optical trap has been used to study thin organic films on the surface of solid particles levitated in air. Micron sized silica spheres have been trapped in air between opposed 1064 nm laser beams, and illuminated with a broadband white LED. Backscattered light from the trapped particle was collected to obtain a Mie spectrum over the 495-670 nm wavelength range and this was used to determine particle radius and wavelength dependent refractive index (Jones et al., 2013). The trapped particle was coated using a flow of organic vapour and the resultant thin film analysed using a coated sphere model. Resonance positions in the Mie spectrum were monitored with time in order to determine film formation, thickness and refractive index. Whilst thin films are believed to form naturally on atmospheric aerosols (Tervahattu et al., 2002), a debate remains as to whether the organic component completely coats the aerosol surface or partially engulfs it. Such films are readily oxidised in the atmosphere causing a change in aerosol properties and knowledge of aerosol properties is required to understand their effect on the climate. The use of optical trapping combined with Mie spectra acquisition to study and characterise coated solid particles is therefore an important step in atmospheric science.

Numerical study of the properties of optical vortex array laser tweezers.

PubMed

Kuo, Chun-Fu; Chu, Shu-Chun

2013-11-04

Chu et al. constructed a kind of Ince-Gaussian modes (IGM)-based vortex array laser beams consisting of p x p embedded optical vortexes from Ince-Gaussian modes, IG(e)(p,p) modes [Opt. Express 16, 19934 (2008)]. Such an IGM-based vortex array laser beams maintains its vortex array profile during both propagation and focusing, and is applicable to optical tweezers. This study uses the discrete dipole approximation (DDA) method to study the properties of the IGM-based vortex array laser tweezers while it traps dielectric particles. This study calculates the resultant force exerted on the spherical dielectric particles of different sizes situated at the IGM-based vortex array laser beam waist. Numerical results show that the number of trapping spots of a structure light (i.e. IGM-based vortex laser beam), is depended on the relation between the trapped particle size and the structure light beam size. While the trapped particle is small comparing to the beam size of the IGM-based vortex array laser beams, the IGM-based vortex array laser beams tweezers are suitable for multiple traps. Conversely, the tweezers is suitable for single traps. The results of this study is useful to the future development of the vortex array laser tweezers applications.

Enzymatic determination of carbon-14 labeled L-alanine in biological samples

DOE Office of Scientific and Technical Information (OSTI.GOV)

Serra, F.; Palou, A.; Pons, A.

A method for determination of L-alanine-specific radioactivity in biological samples is presented. This method is based on the specific enzymatic transformation of L-alanine to pyruvic acid hydrazone catalyzed by the enzyme L-alanine dehydrogenase, formation of the pyruvic acid 2,4-dinitrophenylhydrazone derivative, and quantitative trapping in Amberlite XAD-7 columns, followed by radioactivity counting of the lipophilic eluate. No interferences from other UC-labeled materials such as D-glucose, glycerol, L-lactate, L-serine, L-glutamate, L-phenylalanine, glycine, L-leucine, and L-arginine were observed. This inexpensive and high-speed method is applicable to the simultaneous determination of L-alanine-specific radioactivity for a large number of samples.

Factors affecting the transverse force measurements of an optical trap: I

NASA Astrophysics Data System (ADS)

Wood, Tiffany A.; Wright, Amanda; Gleeson, Helen F.; Dickenson, Mark; Mullin, Tom; Murray, Andrew

2002-03-01

The transverse force of an optical trap is usually measured by equating the trapping force to the viscous drag force applied to the trapped particle according to Stokes' Law. Under normal conditions, the viscous drag force on a trapped particle is proportional to the fluid velocity of the medium. In this paper we show that an increase of particle concentration within the medium affects force measurements. In order to trap the particle, 1064 nm light from a Nd:YVO4 laser was brought to a focus in a sample slide, of thickness around 380 microns, by using an inverted Zeiss microscope objective, with NA equals 1.3. The slide was filled with distilled water containing 6 micron diameter polystyrene spheres. Measurements were taken at a fluid velocity of 0.75 microns/sec, achieved by moving the sample stage with a piezo-electric transducer whilst a particle was held stationary in the trap. The laser power required to hold a sphere at different trap depths for various concentrations was measured. Significant weakening of the trap was found for concentrations >0.03% solids by weight, becoming weaker for higher trap depths. These results are explained in terms of aberrations, particle-particle interactions and distortion of the beam due to particle-light interactions.

Optical Manipulation of Symbiotic Chlorella in Paramecium Bursaria Using a Fiber Axicon Microlens

NASA Astrophysics Data System (ADS)

Taguchi, K.; Hirota, S.; Nakayama, H.; Kunugihara, D.; Mihara, Y.

2012-03-01

In this paper, chemically etched axicon fiber was proposed for laser trapping of symbiotic chlorella from paramecium bursaria. We fabricated axicon micro lenses on a single-mode bare optical fiber by selective chemical etching technique. The laser beam from fiber axicon microlens was strongly focused and optical forces were sufficient to move a symbiotic chlorella. From experimental results, it was found that our proposed fiber axicon microlens was a promising tool for cell trapping without physical contact.

Particle trapping in 3-D using a single fiber probe with an annular light distribution.

PubMed

Taylor, R; Hnatovsky, C

2003-10-20

A single optical fiber probe has been used to trap a solid 2 ìm diameter glass bead in 3-D in water. Optical confinement in 2-D was produced by the annular light distribution emerging from a selectively chemically etched, tapered, hollow tipped metalized fiber probe. Confinement of the bead in 3-D was achieved by balancing an electrostatic force of attraction towards the tip and the optical scattering force pushing the particle away from the tip.

Magnus force effect in optical manipulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cipparrone, Gabriella; Pagliusi, Pasquale; Istituto per i Processi Chimici e Fisici, Consiglio Nazionale delle Ricerche, Ponte P. Bucci, Cubo 33B, I-87036 Rende

2011-07-15

The effect of the Magnus force in optical micromanipulation has been observed. An ad hoc experiment has been designed based on a one-dimensional optical trap that carries angular momentum. The observed particle dynamics reveals the occurrence of this hydrodynamic force, which is neglected in the common approach. Its measured value is larger than the one predicted by the existing theoretical models for micrometric particles and low Reynolds number, showing that the Magnus force can contribute to unconventional optohydrodynamic trapping and manipulation.

Quasi-optical simulation of the electron cyclotron plasma heating in a mirror magnetic trap

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shalashov, A. G., E-mail: ags@appl.sci-nnov.ru; Balakin, A. A.; Khusainov, T. A.

The resonance microwave plasma heating in a large-scale open magnetic trap is simulated taking into account all the basic wave effects during the propagation of short-wavelength wave beams (diffraction, dispersion, and aberration) within the framework of the consistent quasi-optical approximation of Maxwell’s equations. The quasi-optical method is generalized to the case of inhomogeneous media with absorption dispersion, a new form of the quasi-optical equation is obtained, the efficient method for numerical integration is found, and simulation results are verified on the GDT facility (Novosibirsk).

Local x-ray structure analysis of optically manipulated biological micro-objects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cojoc, Dan; Ferrari, Enrico; Santucci, Silvia C.

2010-12-13

X-ray diffraction using micro- and nanofocused beams is well suited for nanostructure analysis at different sites of a biological micro-object. To conduct in vitro studies without mechanical contact, we developed object manipulation by optical tweezers in a microfluidic cell. Here we report x-ray microdiffraction analysis of a micro-object optically trapped in three dimensions. We revealed the nanostructure of a single starch granule at different points and investigated local radiation damage induced by repeated x-ray exposures at the same position, demonstrating high stability and full control of the granule orientation by multiple optical traps.

Integrating a high-force optical trap with gold nanoposts and a robust gold-DNA bond.

PubMed

Paik, D Hern; Seol, Yeonee; Halsey, Wayne A; Perkins, Thomas T

2009-08-01

Gold-thiol chemistry is widely used in nanotechnology but has not been exploited in optical-trapping experiments due to laser-induced ablation of gold. We circumvented this problem by using an array of gold nanoposts (r = 50-250 nm, h approximately 20 nm) that allowed for quantitative optical-trapping assays without direct irradiation of the gold. DNA was covalently attached to the gold via dithiol phosphoramidite (DTPA). By using three DTPAs, the gold-DNA bond was not cleaved in the presence of excess thiolated compounds. This chemical robustness allowed us to reduce nonspecific sticking by passivating the unreacted gold with methoxy-(polyethylene glycol)-thiol. We routinely achieved single beads anchored to the nanoposts by single DNA molecules. We measured DNA's elasticity and its overstretching transition, demonstrating moderate- and high-force optical-trapping assays using gold-thiol chemistry. Force spectroscopy measurements were consistent with the rupture of the strepavidin-biotin bond between the bead and the DNA. This implied that the DNA remained anchored to the surface due to the strong gold-thiol bond. Consistent with this conclusion, we repeatedly reattached the trapped bead to the same individual DNA molecule. Thus, surface conjugation of biomolecules onto an array of gold nanostructures by chemically and mechanically robust bonds provides a unique way to carry out spatially controlled, repeatable measurements of single molecules.

Mathematical model of a DIC position sensing system within an optical trap

NASA Astrophysics Data System (ADS)

Wulff, Kurt D.; Cole, Daniel G.; Clark, Robert L.

2005-08-01

The quantitative study of displacements and forces of motor proteins and processes that occur at the microscopic level and below require a high level of sensitivity. For optical traps, two techniques for position sensing have been accepted and used quite extensively: quadrant photodiodes and an interferometric position sensing technique based on DIC imaging. While quadrant photodiodes have been studied in depth and mathematically characterized, a mathematical characterization of the interferometric position sensor has not been presented to the authors' knowledge. The interferometric position sensing method works off of the DIC imaging capabilities of a microscope. Circularly polarized light is sent into the microscope and the Wollaston prism used for DIC imaging splits the beam into its orthogonal components, displacing them by a set distance determined by the user. The distance between the axes of the beams is set so the beams overlap at the specimen plane and effectively share the trapped microsphere. A second prism then recombines the light beams and the exiting laser light's polarization is measured and related to position. In this paper we outline the mathematical characterization of a microsphere suspended in an optical trap using a DIC position sensing method. The sensitivity of this mathematical model is then compared to the QPD model. The mathematical model of a microsphere in an optical trap can serve as a calibration curve for an experimental setup.

Preliminary constraints on the kinetics of OSL thermochronology

NASA Astrophysics Data System (ADS)

Guralnik, B.; Herman, F.; Lowick, S.; Preusser, F.; Rhodes, E. J.

2010-12-01

Utilizing the fact that temperature exerts a strong control on the retention of radiogenic products at their production sites (and hence their rate of accumulation), thermochronology is an extension of geochronology used to elucidate the cooling histories (t-T trajectories) of rocks over time (Dodson, 1973). Here we present a potential thermochronometer based on the optically stimulated luminescence (OSL) signal of bedrock quartz, with an estimated “closure” temperature of ~25-40°C (-dT/dt=10°C/Ma). In this method, the radiogenic “products” measured are electrons trapped at the naturally occurring lattice defects (electrically unbalanced sites). These electrons can be subsequently released back into the conduction band by exposure to heat and/or light. The mean lifetime of an electron in a particular trapping site is well described by an Arrhenius relationship of the form τ=s-1exp(-E/kT), where E and s are activation energy and frequency factors, respectively, and k is Boltzmann’s constant. Reported lifetimes of the major trap types at 20°C are well beyond Ma-timescale, but for typical natural radioactivity dose rates, these traps saturate well before ~0.5 Ma. In the current work, we analyzed the OSL signals of bedrock quartz from the KTB-VB drillhole (Southern Germany), where long-term stable temperature conditions provide a natural isothermal holding experiment at a Ma-timescale. Eleven core samples from a depth range of 560 m - 2335 m (22°C - 71°C, respectively), were processed to obtain an unbleached quartz fraction of 180-250 µm. Natural and regenerated luminescence signals were measured by stimulation with infrared and then blue light using a single-aliquot regeneration (SAR) protocol. As a function of sample depth, the measured OSL signal varies from a saturated signal at shallow depths to reset signals below a depth of 1 km (i.e., ambient rock temperature higher than 40°C). Several unstable trapping sites with potentially different closure temperatures are suggested by comparison of the natural to regenerated signals.

Holographic spectrum-splitting optical systems for solar photovoltaics

NASA Astrophysics Data System (ADS)

Zhang, Deming

Solar energy is the most abundant source of renewable energy available. The relatively high cost prevents solar photovoltaic (PV) from replacing fossil fuel on a larger scale. In solar PV power generation the cost is reduced with more efficient PV technologies. In this dissertation, methods to improve PV conversion efficiency with holographic optical components are discussed. The tandem multiple-junction approach has achieved very high conversion efficiency. However it is impossible to manufacture tandem PV cells at a low cost due to stringent fabrication standards and limited material types that satisfy lattice compatibility. Current produced by the tandem multi-junction PV cell is limited by the lowest junction due to series connection. Spectrum-splitting is a lateral multi-junction concept that is free of lattice and current matching constraints. Each PV cell can be optimized towards full absorption of a spectral band with tailored light-trapping schemes. Holographic optical components are designed to achieve spectrum-splitting PV energy conversion. The incident solar spectrum is separated onto multiple PV cells that are matched to the corresponding spectral band. Holographic spectrum-splitting can take advantage of existing and future low-cost technologies that produces high efficiency thin-film solar cells. Spectrum-splitting optical systems are designed and analyzed with both transmission and reflection holographic optical components. Prototype holograms are fabricated and high optical efficiency is achieved. Light-trapping in PV cells increases the effective optical path-length in the semiconductor material leading to improved absorption and conversion efficiency. It has been shown that the effective optical path length can be increased by a factor of 4n2 using diffusive surfaces. Ultra-light-trapping can be achieved with optical filters that limit the escape angle of the diffused light. Holographic reflection gratings have been shown to act as angle-wavelength selective filters that can function as ultra-light-trapping filters. Results from an experimental reflection hologram are used to model the absorption enhancement factor for a silicon solar cell and light-trapping filter. The result shows a significant improvement in current generation for thin-film silicon solar cells under typical operating conditions.

Reduction of Trapped-Ion Anomalous Heating by in situ Surface Plasma Cleaning

DTIC Science & Technology

2015-04-29

the trap chip temperature. To load ions, we initially cool 88Sr atoms into a remotely-located magneto - optical trap (MOT), then use a resonant push beam... trap heating rates [10]. Furthermore, some previous experiments have shown an improvement in the heating rates of surface-electrode ion traps after...rate when the trap chip is held at 4 K is not significantly improved by the plasma cleaning. While the observed frequency scaling is not the same in

Optimized coupling of cold atoms into a fiber using a blue-detuned hollow-beam funnel

NASA Astrophysics Data System (ADS)

Poulin, Jerome; Light, Philip S.; Kashyap, Raman; Luiten, Andre N.

2011-11-01

We theoretically investigate the process of coupling cold atoms into the core of a hollow-core photonic-crystal optical fiber using a blue-detuned Laguerre-Gaussian beam. In contrast to the use of a red-detuned Gaussian beam to couple the atoms, the blue-detuned hollow beam can confine cold atoms to the darkest regions of the beam, thereby minimizing shifts in the internal states and making the guide highly robust to heating effects. This single optical beam is used as both a funnel and a guide to maximize the number of atoms into the fiber. In the proposed experiment, Rb atoms are loaded into a magneto-optical trap (MOT) above a vertically oriented optical fiber. We observe a gravito-optical trapping effect for atoms with high orbital momentum around the trap axis, which prevents atoms from coupling to the fiber: these atoms lack the kinetic energy to escape the potential and are thus trapped in the laser funnel indefinitely. We find that by reducing the dipolar force to the point at which the trapping effect just vanishes, it is possible to optimize the coupling of atoms into the fiber. Our simulations predict that by using a low-power (2.5 mW) and far-detuned (300 GHz) Laguerre-Gaussian beam with a 20-μm-radius core hollow fiber, it is possible to couple 11% of the atoms from a MOT 9 mm away from the fiber. When the MOT is positioned farther away, coupling efficiencies over 50% can be achieved with larger core fibers.

Single-cell isolation using a DVD optical pickup

PubMed Central

Kasukurti, A.; Potcoava, M.; Desai, S.A.; Eggleton, C.; Marr, D. W. M.

2011-01-01

A low-cost single-cell isolation system incorporating a digital versatile disc burner (DVD RW) optical pickup has been developed. We show that these readily available modules have the required laser power and focusing optics to provide a steady Gaussian beam capable of optically trapping micron-sized colloids and red blood cells. Utility of the pickup is demonstrated through the non-destructive isolation of such particles in a laminar-flow based microfluidic device that captures and translates single microscale objects across streamlines into designated channel exits. In this, the integrated objective lens focusing coils are used to steer the optical trap across the channel, resulting in the isolation of colloids and red blood cells using a very inexpensive off-the-shelf optical component. PMID:21643294

Blue-detuned optical ring trap for Bose-Einstein condensates based on conical refraction.

PubMed

Turpin, A; Polo, J; Loiko, Yu V; Küber, J; Schmaltz, F; Kalkandjiev, T K; Ahufinger, V; Birkl, G; Mompart, J

2015-01-26

We present a novel approach for the optical manipulation of neutral atoms in annular light structures produced by the phenomenon of conical refraction occurring in biaxial optical crystals. For a beam focused to a plane behind the crystal, the focal plane exhibits two concentric bright rings enclosing a ring of null intensity called the Poggendorff ring. We demonstrate both theoretically and experimentally that the Poggendorff dark ring of conical refraction is confined in three dimensions by regions of higher intensity. We derive the positions of the confining intensity maxima and minima and discuss the application of the Poggendorff ring for trapping ultra-cold atoms using the repulsive dipole force of blue-detuned light. We give analytical expressions for the trapping frequencies and potential depths along both the radial and the axial directions. Finally, we present realistic numerical simulations of the dynamics of a ⁸⁷Rb Bose-Einstein condensate trapped inside the Poggendorff ring which are in good agreement with corresponding experimental results.

Optical tweezers for the measurement of binding forces: system description and application for the study of E. coli adhesion

NASA Astrophysics Data System (ADS)

Fallman, Erik G.; Schedin, Staffan; Andersson, Magnus J.; Jass, Jana; Axner, Ove

2003-06-01

Optical tweezers together with a position sensitive detection system allows measurements of forces in the pN range between micro-sized biological objects. A prototype force measurement system has been constructed around in inverted microscope with an argon-ion pumped Ti:sapphire laser as light source for optical trapping. A trapped particle in the focus of the high numerical aperture microscope-objective behaves like an omni-directional mechanical spring if an external force displaces it. The displacement from the equilibrium position is a measure of the exerted force. For position detection of the trapped particle (polystyrene beads), a He-Ne laser beam is focused a small distance below the trapping focus. An image of the bead appears as a distinct spot in the far field, monitored by a photosensitive detector. The position data is converted to a force measurement by a calibration procedure. The system has been used for measuring the binding forces between E-coli bacterial adhesin and their receptor sugars.

Stiffness measurement of a biomaterial by optical manipulation of microparticle

NASA Astrophysics Data System (ADS)

Kim, Jung-Dae; Waleed, Muhammad; Lee, Yong-Gu

2013-02-01

Since the discovery of the trapping nature of laser beam, optical tweezers have been extensively employed to measure various parameters at micro/nano level. Optical tweezers show exceptional sensitivity to weak forces making it one of the most sensitive force measurement devices. In this work, we present a technique to measure the stiffness of a biomaterial at different points. For this purpose, a microparticle stuck at the bottom of the dish is illuminated by the trapping laser and respective QPD signal as a function of the distance between the focus of the laser and the center of the microparticle is monitored. After this, microparticle is trapped and manipulated towards the target biomaterial and when it touches the cell membrane, QPD signal shows variation. By comparing two different QPD signals and measuring the trap stiffness, a technique is described to measure the stiffness of the biomaterial at a particular point. We believe that this parameter can be used as a tool to identify and classify different biomaterials.

In situ calibration of position detection in an optical trap for active microrheology in viscous materials

PubMed Central

Staunton, Jack R.; Blehm, Ben; Devine, Alexus; Tanner, Kandice

2017-01-01

In optical trapping, accurate determination of forces requires calibration of the position sensitivity relating displacements to the detector readout via the V-nm conversion factor (β). Inaccuracies in measured trap stiffness (k) and dependent calculations of forces and material properties occur if β is assumed to be constant in optically heterogeneous materials such as tissue, necessitating calibration at each probe. For solid-like samples in which probes are securely positioned, calibration can be achieved by moving the sample with a nanopositioning stage and stepping the probe through the detection beam. However, this method may be applied to samples only under select circumstances. Here, we introduce a simple method to find β in any material by steering the detection laser beam while the probe is trapped. We demonstrate the approach in the yolk of living Danio rerio (zebrafish) embryos and measure the viscoelastic properties over an order of magnitude of stress-strain amplitude. PMID:29519028

Transverse acoustic trapping using a Gaussian focused ultrasound

PubMed Central

Lee, Jungwoo; Teh, Shia-Yen; Lee, Abraham; Kim, Hyung Ham; Lee, Changyang; Shung, K. Kirk

2009-01-01

The optical tweezer has become a popular device to manipulate particles in nanometer scales, and to study the underlying principles of many cellular or molecular interactions. Theoretical analysis was previously carried out at the authors’ laboratory, to show that similar acoustic trapping of microparticles may be possible with a single beam ultrasound. This paper experimentally presents the transverse trapping of 125 μm lipid droplets under an acoustically transparent mylar film, which is an intermediate step toward achieving acoustic tweezers in 3D. Despite the lack of axial trapping capability in the current experimental arrangement, it was found that a 30 MHz focused beam could be used to laterally direct the droplets towards the focus. The spatial range within which acoustic traps may guide droplet motion was in the range of hundreds of micrometers, much greater than that of optical traps. This suggests that this acoustic device may offer an alternative for manipulating microparticles in a wider spatial range. PMID:20045590

Photophoretic trapping of absorbing particles in air and measurement of their single-particle Raman spectra.

PubMed

Pan, Yong-Le; Hill, Steven C; Coleman, Mark

2012-02-27

A new method is demonstrated for optically trapping micron-sized absorbing particles in air and obtaining their single-particle Raman spectra. A 488-nm Gaussian beam from an Argon ion laser is transformed by conical lenses (axicons) and other optics into two counter-propagating hollow beams, which are then focused tightly to form hollow conical beams near the trapping region. The combination of the two coaxial conical beams, with focal points shifted relative to each other along the axis of the beams, generates a low-light-intensity biconical region totally enclosed by the high-intensity light at the surface of the bicone, which is a type of bottle beam. Particles within this region are trapped by the photophoretic forces that push particles toward the low-intensity center of this region. Raman spectra from individual trapped particles made from carbon nanotubes are measured. This trapping technique could lead to the development of an on-line real-time single-particle Raman spectrometer for characterization of absorbing aerosol particles.

A versatile electrostatic trap with open optical access

NASA Astrophysics Data System (ADS)

Li, Sheng-Qiang; Yin, Jian-Ping

2018-04-01

A versatile electrostatic trap with open optical access for cold polar molecules in weak-field-seeking state is proposed in this paper. The trap is composed of a pair of disk electrodes and a hexapole. With the help of a finite element software, the spatial distribution of the electrostatic field is calculated. The results indicate that a three-dimensional closed electrostatic trap is formed. Taking ND3 molecules as an example, the dynamic process of loading and trapping is simulated. The results show that when the velocity of the molecular beam is 10 m/s and the loading time is 0.9964 ms, the maximum loading efficiency reaches 94.25% and the temperature of the trapped molecules reaches about 30.3 mK. A single well can be split into two wells, which is of significant importance to the precision measurement and interference of matter waves. This scheme, in addition, can be further miniaturized to construct one-dimensional, two-dimensional, and three-dimensional spatial electrostatic lattices.

Optical binding of two microparticles levitated in vacuum

NASA Astrophysics Data System (ADS)

Arita, Yoshihiko; Wright, Ewan M.; Dholakia, Kishan

2017-04-01

Optical binding refers to an optically mediated inter-particle interaction that creates new equilibrium positions for closely spaced particles [1-5]. Optical binding of mesoscopic particles levitated in vacuum can pave the way towards the realisation of a large scale quantum bound array in cavity-optomechanics [6-9]. Recently we have demonstrated trapping and rotation of two mesoscopic particles in vacuum using a spatial-light-modulator-based approach to trap more than one particle, induce controlled rotation of individual particles, and mediate interparticle separation [10]. By trapping and rotating two vaterite particles, we observe intensity modulation of the scattered light at the sum and difference frequencies with respect to the individual rotation rates. This first demonstration of optical interference between two microparticles in vacuum has lead to a platform to explore optical binding. Here we demonstrate for the first time optically bound two microparticles mediated by light scattering in vacuum. We investigate autocorrelations between the two normal modes of oscillation, which are determined by the centre-of-mass and the relative positions of the two-particle system. In situ determination of the optical restoring force acting on the bound particles are based on measurement of the oscillation frequencies of the autocorrelation functions of the two normal modes, thereby providing a powerful and original platform to explore multiparticle entanglement in cavity-optomechanics.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ribezzi-Crivellari, M.; Huguet, J. M.; Ritort, F.

We present a dual-trap optical tweezers setup which directly measures forces using linear momentum conservation. The setup uses a counter-propagating geometry, which allows momentum measurement on each beam separately. The experimental advantages of this setup include low drift due to all-optical manipulation, and a robust calibration (independent of the features of the trapped object or buffer medium) due to the force measurement method. Although this design does not attain the high-resolution of some co-propagating setups, we show that it can be used to perform different single molecule measurements: fluctuation-based molecular stiffness characterization at different forces and hopping experiments on molecularmore » hairpins. Remarkably, in our setup it is possible to manipulate very short tethers (such as molecular hairpins with short handles) down to the limit where beads are almost in contact. The setup is used to illustrate a novel method for measuring the stiffness of optical traps and tethers on the basis of equilibrium force fluctuations, i.e., without the need of measuring the force vs molecular extension curve. This method is of general interest for dual trap optical tweezers setups and can be extended to setups which do not directly measure forces.« less

Localised and delocalised optically induced conversion of composite glow peak 5 in LiF:Mg,Ti (TLD-100) to glow peak 4 as a function of postirradiation annealing temperature.

PubMed

Horowitz, Y S; Einav, Y; Biderman, S; Oster, L

2002-01-01

The composite structure of glow peak 5 in LiF:Mg,Ti (TLD-100) has been investigated using optical bleaching by 310 nm (4 eV) light. The glow peak conversion efficiency of peak 5a (Tm = 187 degrees C) to peak 4 traps is very high at a value of 3+/-0.5 (1 SD) whereas the glow peak conversion efficiency of peak 5 (Tm = 205 degrees C) to peak 4 traps is 0.0026+/-0.0012 (1 SD). The high conversion efficiency of peak 5a to peak 4 arises from direct optical ionisation of the electron in the electron-hole pair. leaving behind a singly-trapped hole (peak 4), a direct mechanism, relatively free of competitive mechanisms. Optical ionisation of the 'singly-trapped' electron (peak 5), however, can lead to peak 4 only via multi-stage mechanisms involving charge carrier transport in the valence and conduction bands, a mechanism subject to competitive processes. The conduction/valence band competitive processes lead to the factor of one thousand decrease in the conversion efficiency of peak 5 compared to peak 5a.

Selectively transporting small chiral particles with circularly polarized Airy beams.

PubMed

Lu, Wanli; Chen, Huajin; Guo, Sandong; Liu, Shiyang; Lin, Zhifang

2018-05-01

Based on the full wave simulation, we demonstrate that a circularly polarized vector Airy beam can selectively transport small chiral particles along a curved trajectory via the chirality-tailored optical forces. The transverse optical forces can draw the chiral particles with different particle chirality towards or away from the intensity maxima of the beam, leading to the selective trapping in the transverse plane. The transversely trapped chiral particles are then accelerated along a curved trajectory of the Airy beam by the chirality-tailored longitudinal scattering force, rendering an alternative way to sort and/or transport chiral particles with specified helicity. Finally, the underlying physics of the chirality induced transverse trap and de-trap phenomena are examined by the analytical theory within the dipole approximation.

Building one molecule from a reservoir of two atoms

NASA Astrophysics Data System (ADS)

Liu, L. R.; Hood, J. D.; Yu, Y.; Zhang, J. T.; Hutzler, N. R.; Rosenband, T.; Ni, K.-K.

2018-05-01

Chemical reactions typically proceed via stochastic encounters between reactants. Going beyond this paradigm, we combined exactly two atoms in a single, controlled reaction. The experimental apparatus traps two individual laser-cooled atoms [one sodium (Na) and one cesium (Cs)] in separate optical tweezers and then merges them into one optical dipole trap. Subsequently, photoassociation forms an excited-state NaCs molecule. The discovery of previously unseen resonances near the molecular dissociation threshold and measurement of collision rates are enabled by the tightly trapped ultracold sample of atoms. As laser-cooling and trapping capabilities are extended to more elements, the technique will enable the study of more diverse, and eventually more complex, molecules in an isolated environment, as well as synthesis of designer molecules for qubits.

Measuring the Temperature of the Ithaca College MOT Cloud using a CMOS Camera

NASA Astrophysics Data System (ADS)

Smucker, Jonathan; Thompson, Bruce

2015-03-01

We present our work on measuring the temperature of Rubidium atoms cooled using a magneto-optical trap (MOT). The MOT uses laser trapping methods and Doppler cooling to trap and cool Rubidium atoms to form a cloud that is visible to a CMOS Camera. The Rubidium atoms are cooled further using optical molasses cooling after they are released from the trap (by removing the magnetic field). In order to measure the temperature of the MOT we take pictures of the cloud using a CMOS camera as it expands and calculate the temperature based on the free expansion of the cloud. Results from the experiment will be presented along with a summary of the method used.

Note: Real time optical sensing of alpha-radiation emitting radioactive aerosols based on solid state nuclear track detector.

PubMed

Kulkarni, A; Ha, S; Joshirao, P; Manchanda, V; Bak, M S; Kim, T

2015-06-01

A sensitive radioactive aerosols sensor has been designed and developed. Its design guidance is based on the need for a low operational cost and reliable measurements to provide daily aerosol monitoring. The exposure of diethylene-glycol bis (allylcarbonate) to radiation causes modification of its physico-chemical properties like surface roughness and reflectance. In the present study, optical sensor based on the reflectance measurement has been developed with an aim to monitor real time presence of alpha radioactive aerosols emitted from thorium nitrate hydrate. The results shows that the fabricated sensor can detect 0.0157 kBq to 0.1572 kBq of radio activity by radioactive aerosols generated from (Th(NO3)4 ⋅ 5H2O) at 0.1 ml/min flow rate. The proposed instrument will be helpful to monitor radioactive aerosols in/around a nuclear facility, building construction sites, mines, and granite polishing factories.

High accuracy indirect optical manipulation of live cells with functionalized microtools

NASA Astrophysics Data System (ADS)

Vizsnyiczai, Gaszton; Aekbote, Badri L.; Buzás, András.; Grexa, István.; Ormos, Pál.; Kelemen, Lóránd

2016-09-01

Optical micro manipulation of live cells has been extensively used to study a wide range of cellular phenomena with relevance in basic research or in diagnostics. The approaches span from manipulation of many cells for high throughput measurement or sorting, to more elaborated studies of intracellular events on trapped single cells when coupled with modern imaging techniques. In case of direct cell trapping the damaging effects of light-cell interaction must be minimized, for instance with the choice of proper laser wavelength. Microbeads have already been used for trapping cells indirectly thereby reducing the irradiation damage and increasing trapping efficiency with their high refractive index contrast. We show here that such intermediate objects can be tailor-made for indirect cell trapping to further increase cell-to-focal spot distance while maintaining their free and fast maneuverability. Carefully designed structures were produced with two-photon polymerization with shapes optimized for effective manipulation and cell attachment. Functionalization of the microstructures is also presented that enables cell attachment to them within a few seconds with strength much higher that the optical forces. Fast cell actuation in 6 degrees of freedom is demonstrated with the outlook to possible applications in cell imaging.

Geometrical effect characterization of femtosecond-laser manufactured glass microfluidic chips based on optical manipulation of submicroparticles

NASA Astrophysics Data System (ADS)

Kotsifaki, Domna G.; Mackenzie, Mark D.; Polydefki, Georgia; Kar, Ajoy K.; Makropoulou, Mersini; Serafetinides, Alexandros A.

2017-12-01

Microfluidic devices provide a platform with wide ranging applications from environmental monitoring to disease diagnosis. They offer substantive advantages but are often not optimized or designed to be used by nonexpert researchers. Microchannels of a microanalysis platform and their geometrical characterization are of eminent importance when designing such devices. We present a method that is used to optimize each microchannel within a device using high-throughput particle manipulation. For this purpose, glass-based microfluidic devices, with three-dimensional channel networks of several geometrical sizes, were fabricated by employing laser fabrication techniques. The effect of channel geometry was investigated by employing an optical tweezer. The optical trapping force depends on the flow velocity that is associated with the dimensions of the microchannel. We observe a linear dependence of the trapping efficiency and of the fluid flow velocity, with the channel dimensions. We determined that the highest trapping efficiency was achieved for microchannels with aspect ratio equal to one. Numerical simulation validated the impact of the device design dimensions on the trapping efficiency. This investigation indicates that the geometrical characteristics, the flow velocity, and trapping efficiency are crucial and should be considered when fabricating microfluidic devices for cell studies.

3-dimensional dark traps for low refractive index bio-cells using a single optical fiber Bessel beam.

PubMed

Zhang, Yu; Tang, Xiaoyun; Zhang, Yaxun; Su, Wenjie; Liu, Zhihai; Yang, Xinghua; Zhang, Jianzhong; Yang, Jun; Oh, Kyunghwan; Yuan, Libo

2018-06-15

We proposed and experimentally demonstrated 3-dimensional dark traps for low refractive index bio-cells using a single optical fiber Bessel beam. The Bessel beam was produced by concatenating single-mode fiber and a step index multimode fiber, which was then focused by a high refractive index glass microsphere integrated on the fiber end facet. The focused Bessel beam provided two dark fields along the axial direction, where stable trapping of low refractive index bio-cells was realized in a high refractive index liquid bath. The all-fiber and seamlessly integrated structure of the proposed scheme can find ample potential as a micro-optical probe in in situ characterization and manipulation of multiple bio-cells with refractive indices lower than that of the liquid bath.

Spectroscopy and optical imaging of coalescing droplets

NASA Astrophysics Data System (ADS)

Ivanov, Maksym; Viderström, Michel; Chang, Kelken; Ramírez Contreras, Claudia; Mehlig, Bernhard; Hanstorp, Dag

2016-09-01

We report on experimental investigations of the dynamics of colliding liquid droplets by combining optical trapping, spectroscopy and high-speed color imaging. Two droplets with diameters between 5 and 50 microns are suspended in quiescent air by optical traps. The traps allows us to control the initial positions, and hence the impact parameter and the relative velocity of the colliding droplets. Movies of the droplet dynamics are recorded using high-speed digital movie cameras at a frame rate of up to 63000 frames per second. A fluorescent dye is added to one of the colliding droplets. We investigate the temporal evolution of the scattered and fluorescence light from the colliding droplets with concurrent spectroscopy and color imaging. This technique can be used to detect the exchange of molecules between a pair of neutral or charged droplets.

Nanophotonic light-trapping theory for solar cells

NASA Astrophysics Data System (ADS)

Yu, Zongfu; Raman, Aaswath; Fan, Shanhui

2011-11-01

Conventional light-trapping theory, based on a ray-optics approach, was developed for standard thick photovoltaic cells. The classical theory established an upper limit for possible absorption enhancement in this context and provided a design strategy for reaching this limit. This theory has become the foundation for light management in bulk silicon PV cells, and has had enormous influence on the optical design of solar cells in general. This theory, however, is not applicable in the nanophotonic regime. Here we develop a statistical temporal coupled-mode theory of light trapping based on a rigorous electromagnetic approach. Our theory reveals that the standard limit can be substantially surpassed when optical modes in the active layer are confined to deep-subwavelength scale, opening new avenues for highly efficient next-generation solar cells.

Millikelvin cooling of the center-of-mass motion of a levitated nanoparticle

NASA Astrophysics Data System (ADS)

Bullier, Nathanaël. P.; Pontin, Antonio; Barker, Peter F.

2017-08-01

Cavity optomechanics has been used to cool the center-of-mass motion of levitated nanospheres to millikelvin temperatures. Trapping the particle in the cavity field enables high mechanical frequencies bringing the system close to the resolved-sideband regime. Here we describe a Paul trap constructed from a printed circuit board that is small enough to fit inside the optical cavity and which should enable an accurate positioning of the particle inside the cavity field. This will increase the optical damping and therefore reduce the final temperature by at least one order of magnitude. Simulations of the potential inside the trap enable us to estimate the charge- to-mass ratio of trapped particles by measuring the secular frequencies as a function of the trap parameters. Lastly, we show the importance of reducing laser noise to reach lower temperatures and higher sensitivity in the phase-sensitive readout.

Toolkit for the Automated Characterization of Optical Trapping Forces on Microscopic Particles

NASA Astrophysics Data System (ADS)

Glaser, Joseph; Hoeprich, David; Resnick, Andrew

2014-03-01

Optical traps have been in use in microbiological studies for the past 40 years to obtain noninvasive control of microscopic particles. However, the magnitude of the applied forces is often unknown. Therefore, we have developed an automated data acquisition and processing system which characterizes trap properties for known particle geometries. Extensive experiments and measurements utilizing well-characterized objects were performed and compared to literature to confirm the system's performance. This system will enable the future analysis of a trapped primary cilium, a slender rod-shaped organelle with aspect ratio L/R >30, where `L' is the cilium length and `R' the cilium diameter. The trapping of cilia is of primary importance, as it will lead to the precise measurements of mechanical properties of the organelle and its significance to the epithelial cell. Support from the National Institutes of Health, 1R15DK092716 is gratefully acknowledged.

Microfabricated Waveguide Atom Traps.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jau, Yuan-Yu

A nanoscale , microfabricated waveguide structure can in - principle be used to trap atoms in well - defined locations and enable strong photon-atom interactions . A neutral - atom platform based on this microfabrication technology will be prealigned , which is especially important for quantum - control applications. At present, there is still no reported demonstration of evanescent - field atom trapping using a microfabricated waveguide structure. We described the capabilities established by our team for future development of the waveguide atom - trapping technology at SNL and report our studies to overcome the technical challenges of loading coldmore » atoms into the waveguide atom traps, efficient and broadband optical coupling to a waveguide, and the waveguide material for high - power optical transmission. From the atomic - physics and the waveguide modeling, w e have shown that a square nano-waveguide can be utilized t o achieve better atomic spin squeezing than using a nanofiber for first time.« less

Synchronization of a self-sustained cold-atom oscillator

NASA Astrophysics Data System (ADS)

Heimonen, H.; Kwek, L. C.; Kaiser, R.; Labeyrie, G.

2018-04-01

Nonlinear oscillations and synchronization phenomena are ubiquitous in nature. We study the synchronization of self-oscillating magneto-optically trapped cold atoms to a weak external driving. The oscillations arise from a dynamical instability due the competition between the screened magneto-optical trapping force and the interatomic repulsion due to multiple scattering of light. A weak modulation of the trapping force allows the oscillations of the cloud to synchronize to the driving. The synchronization frequency range increases with the forcing amplitude. The corresponding Arnold tongue is experimentally measured and compared to theoretical predictions. Phase locking between the oscillator and drive is also observed.

Particle trapping and manipulation using hollow beam with tunable size generated by thermal nonlinear optical effect

NASA Astrophysics Data System (ADS)

He, Bo; Cheng, Xuemei; Zhang, Hui; Chen, Haowei; Zhang, Qian; Ren, Zhaoyu; Ding, Shan; Bai, Jintao

2018-05-01

We report micron-sized particle trapping and manipulation using a hollow beam of tunable size, which was generated by cross-phase modulation via the thermal nonlinear optical effect in an ethanol medium. The results demonstrated that the particle can be trapped stably in air for hours and manipulated in millimeter range with micrometer-level accuracy by modulating the size of the hollow beam. The merits of flexibility in tuning the beam size and simplicity in operation give this method great potential for the in situ study of individual particles in air.

Manipulation of Micro Scale Particles in Optical Traps Using Programmable Spatial Light Modulation

NASA Technical Reports Server (NTRS)

Seibel, Robin E.; Decker, Arthur J. (Technical Monitor)

2003-01-01

1064 nm light, from an Nd:YAG laser, was polarized and incident upon a programmable parallel aligned liquid crystal spatial light modulator (PAL-SLM), where it was phase modulated according to the program controlling the PAL-SLM. Light reflected from the PAL-SLM was injected into a microscope and focused. At the focus, multiple optical traps were formed in which 9.975 m spheres were captured. The traps and the spheres were moved by changing the program of the PAL-SLM. The motion of ordered groups of micro particles was clearly demonstrated.

Development of a dual joystick-controlled laser trapping and cutting system for optical micromanipulation of chromosomes inside living cells.

PubMed

Harsono, Marcellinus S; Zhu, Qingyuan; Shi, Linda Z; Duquette, Michelle; Berns, Michael W

2013-02-01

A multi-joystick robotic laser microscope system used to control two optical traps (tweezers) and one laser scissors has been developed for subcellular organelle manipulation. The use of joysticks has provided a "user-friendly" method for both trapping and cutting of organelles such as chromosomes in live cells. This innovative design has enabled the clean severing of chromosome arms using the laser scissors as well as the ability to easily hold and pull the severed arm using the laser tweezers. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Avalanches and plasticity for colloids in a time dependent optical trap

DOE PAGES

Olson Reichhardt, Cynthia Jane; McDermott, Danielle Marie; Reichhardt, Charles

2015-08-25

Here, with the use of optical traps it is possible to confine assemblies of colloidal particles in two-dimensional and quasi-one-dimensional arrays. Here we examine how colloidal particles rearrange in a quasi-one-dimensional trap with a time dependent confining potential. The particle motion occurs both through slow elastic uniaxial distortions as well as through abrupt large-scale two-dimensional avalanches associated with plastic rearrangements. During the avalanches the particle velocity distributions extend over a broad range and can be fit to a power law consistent with other studies of plastic events mediated by dislocations.

Three dimensional touch and vision for the micro-world

NASA Astrophysics Data System (ADS)

Bowman, Richard W.

This thesis describes advances in the holographic technology used to control multiple optical traps (and hence many trapped particles), and improved methods for monitoring the positions and forces involved. The speed with which multiple holographic optical traps can be moved has traditionally been limited by the time taken to calculate holograms, but by using consumer graphics cards and high speed Spatial Light Modulators (SLMs) I have implemented holographic systems fast enough to react to the Brownian motion of trapped particles. Brownian motion can, to some extent, be suppressed by this approach, and it also allows the trap's stiffness to be engineered to balance sensitivity against tight constraint of position. Feedback control using an SLM, rather than the other beam steering technologies that have been employed, is able to react to motion in three dimensions. This requires 3D position measurement, which is provided by the stereo microscopy technique described in Chapter 2. By illuminating and viewing the sample from two different angles it is possible to reconstruct the depth of objects. This is accomplished through a single high numerical aperture microscope objective, the same lens used to focus the trapping laser. In conjunction with a fast CMOS camera, it is possible to track particles with an accuracy of 2-3nm at several thousand frames per second. This allows measurement of forces and displacements within the control loop, that can be fed back to influence the position of the optical traps. This force information can also be relayed to the operator using a force-feedback joystick as detailed in Chapter 7. Interface design is an important part of making technology accessible to scientists from other disciplines; to this end I have also developed a multi-touch tablet application to control optical tweezers. By creating simple, reliable systems and coupling them to an intuitive interface, I have endeavoured to produce developments which are of use to the non-specialist as well as to experts in optical tweezers-a number of which are now available commercially (Section 8.7). These technologies form the basis of a toolkit for working with multi-part probes in optical tweezers, and they should bear fruit in the coming years as a new form of scanning-probe microscopy emerges.

Radiological Air Sampling. Protocol Development for the Canadian Forces

DTIC Science & Technology

2003-03-01

samplers trap these airborne radon daughters . Because radon is ubiquitous, all air samplers will catch these radioactive radon daughters in the...environment is complicated because all air sampler filters are radioactive because of the radon daughters . ’Actually, D will often depend on the isotope that...simply as "radon". 2 DRDC Ottawa TM 2003-149 -28 - 22 R_ 211p0 214pb 3.8 d 3.0 m 27 m 214Bi 210TI Radon Daughters 20 m ŕ.3 m (Uranium Decay Chain

Chernobyl radioactivity found in mid-water sediment interceptors in the N. Pacific and Bering Sea

NASA Astrophysics Data System (ADS)

Kusakabe, M.; Ku, T.-L.; Harada, K.; Taguchi, K.; Tsunogai, S.

1988-01-01

Fission-product nuclides 134Cs, 137Cs and 103Ru originated from the Chernobyl accident have been detected in sediment traps deployed at mid-water depths ranging from 110 to 780 m in the N. Pacific and the Bering Sea. The detected radioactivities, originally associated with fine airborne particles, have apparently been incorporated into much larger aggregates of predominantly biogenic material formed in the surface ocean, and transferred downward through the water column with velocities of the order of 100 m/day.

An Orthotropic Oven for Loading Vapor Traps

NASA Astrophysics Data System (ADS)

Maddi, J.; Dinneen, T.; Gould, H.

1998-05-01

Orthotropic ovens(T. Dinneen, A. Ghiorso, and H. Gould, Rev. Sci. Inst. 67, 752 (1996) ) produce collimated beams of alkali atoms with high efficiency. They are useful for producing beams of rare species such as short-lived radioactive atoms. We describe the design and operation of the UHV orthotropic oven used in vapor-capture trapping and cooling(Z.-T. Lu, K.L. Corwin, K.R. Vogel, C.E. Wieman, T.P. Dinneen, J. Maddi, and H. Gould, Phys. Rev. Lett. 79, 994 (1997)) of ^221Fr, and recent improvments in its design.

LDEF satellite radiation study

NASA Technical Reports Server (NTRS)

Armstrong, T. W.; Colborn, B. L.

1994-01-01

Some early results are summarized from a program under way to utilize LDEF satellite data for evaluating and improving current models of the space radiation environment in low earth orbit. Reported here are predictions and comparisons with some of the LDEF dose and induced radioactivity data, which are used to check the accuracy of current models describing the magnitude and directionality of the trapped proton environment. Preliminary findings are that the environment models underestimate both dose and activation from trapped protons by a factor of about two, and the observed anisotropy is higher than predicted.

In situ microparticle analysis of marine phytoplankton cells with infrared laser-based optical tweezers

NASA Astrophysics Data System (ADS)

Sonek, G. J.; Liu, Y.; Iturriaga, R. H.

1995-11-01

We describe the application of infrared optical tweezers to the in situ microparticle analysis of marine phytoplankton cells. A Nd:YAG laser (lambda=3D 1064 nm) trap is used to confine and manipulate single Nannochloris and Synechococcus cells in an enriched seawater medium while spectral fluorescence and Lorenz-Mie backscatter signals are simultaneously acquired under a variety of excitation and trapping conditions. Variations in the measured fluorescence intensities of chlorophyll a (Chl a) and phycoerythrin pigments in phytoplankton cells are observed. These variations are related, in part, to basic intrasample variability, but they also indicate that increasing ultraviolet-exposure time and infrared trapping power may have short-term effects on cellular physiology that are related to Chl a photobleaching and laser-induced heating, respectively. The use of optical tweezers to study the factors that affect marine cell physiology and the processes of absorption, scattering, and attenuation by individual cells, organisms, and particulate matter that contribute to optical closure on a microscopic scale are also described. (c)1995 Optical Society of America

Nano-optical conveyor belt with waveguide-coupled excitation.

PubMed

Wang, Guanghui; Ying, Zhoufeng; Ho, Ho-pui; Huang, Ying; Zou, Ningmu; Zhang, Xuping

2016-02-01

We propose a plasmonic nano-optical conveyor belt for peristaltic transport of nano-particles. Instead of illumination from the top, waveguide-coupled excitation is used for trapping particles with a higher degree of precision and flexibility. Graded nano-rods with individual dimensions coded to have resonance at specific wavelengths are incorporated along the waveguide in order to produce spatially addressable hot spots. Consequently, by switching the excitation wavelength sequentially, particles can be transported to adjacent optical traps along the waveguide. The feasibility of this design is analyzed using three-dimensional finite-difference time-domain and Maxwell stress tensor methods. Simulation results show that this system is capable of exciting addressable traps and moving particles in a peristaltic fashion with tens of nanometers resolution. It is the first, to the best of our knowledge, report about a nano-optical conveyor belt with waveguide-coupled excitation, which is very important for scalability and on-chip integration. The proposed approach offers a new design direction for integrated waveguide-based optical manipulation devices and its application in large scale lab-on-a-chip integration.

Radiation effects and defects in lithium borate crystals

NASA Astrophysics Data System (ADS)

Ogorodnikov, Igor N.; Poryvay, Nikita E.; Pustovarov, Vladimir A.

2010-11-01

The paper presents the results of a study of the formation and decay of lattice defects in wide band-gap optical crystals of LiB3O5 (LBO), Li2B4O7 (LTB) and Li6Gd(BO3)3 (LGBO) with a sublattice of mobile lithium cations. By means of thermoluminescence techniques, and luminescent and absorption optical spectroscopy with a nanosecond time resolution under excitation with an electron beam, it was revealed that the optical absorption in these crystals in the visible and ultraviolet spectral ranges is produced by optical hole-transitions from the local defect level to the valence band states. The valence band density of the states determines mainly the optical absorption spectral profile, and the relaxation kinetics is rated by the interdefect non-radiative tunnel recombination between the trapped-hole center and the Li0 trapped-electron centers. At 290 K, the Li0 centers are subject to thermally stimulated migration. Based on experimental results, the overall picture of thermally stimulated recombination processes with the participation of shallow traps was established for these crystals.

Optical manipulation of microparticles and biological structures

NASA Astrophysics Data System (ADS)

Gahagan, Kevin Thomas

1998-06-01

We report experimental and theoretical investigations of the trapping of microparticles and biological objects using radiation pressure. Part I of this thesis presents a technique for trapping both low and high index microparticles using a single, stationary focused laser beam containing an optical vortex. Advantages of this vortex trap include the ease of implementation, a lower exposure level for high-index particles compared to a standard Gaussian beam trap, and the ability to isolate individual low-index particles in concentrated dispersions. The vortex trap is modeled using ray-tracing methods and a more precise electromagnetic model, which is accurate for particles less than 10 μm in diameter. We have measured the stable equilibrium position for two low-index particle systems (e.g., hollow glass spheres (HGS) in water, and water droplets in acetophenone (W/A)). The strength of the trap was measured for the HGS system along the longitudinal and transverse directions. We also demonstrate simultaneous trapping of a low and high index particle with a vortex beam. The stability of this dual-particle trap is found to depend on the relative particle size, the divergence angle of the beam, and the depth of the particles within the trapping chamber. Part II presents results from an interdisciplinary and collaborative investigation of an all-optical genetic engineering technique whereby Agrobacterium rhizogenes were inserted through a laser-ablated hole in the cell wall of the plant, Gingko biloba. We describe a protocol which includes the control of osmotic conditions, culturing procedures, viability assays and laser microsurgery. We succeeded in placing up to twelve viable bacteria into a single plant cell using this technique. The bacteria are believed to be slightly heated by the Gaussian beam trap. A numerical model is presented predicting a temperature rise of just a few degrees. Whereas G. biloba and A. rhitogenes were chosen for this study because of Ginkgo's pharmaceutical importance, only slight modification of the protocol is needed for other plant species.

Motion of Cesium Atoms in the One-Dimensional Magneto-Optical Trap

NASA Technical Reports Server (NTRS)

Li, Yimin; Chen, Xuzong; Wang, Qingji; Wang, Yiqiu

1996-01-01

The force to which Cs atoms are subjected in the one-dimensional magneto-optical trap (lD-MOT) is calculated, and properties of this force are discussed. Several methods to increase the number of Cs atoms in the lD-MOT are presented on the basis of the analysis of the capture and escape of Cs atoms in the ID-MOT.

Optimal quantum control of multimode couplings between trapped ion qubits for scalable entanglement.

PubMed

Choi, T; Debnath, S; Manning, T A; Figgatt, C; Gong, Z-X; Duan, L-M; Monroe, C

2014-05-16

We demonstrate entangling quantum gates within a chain of five trapped ion qubits by optimally shaping optical fields that couple to multiple collective modes of motion. We individually address qubits with segmented optical pulses to construct multipartite entangled states in a programmable way. This approach enables high-fidelity gates that can be scaled to larger qubit registers for quantum computation and simulation.

Improved Linear-Ion-Trap Frequency Standard

NASA Technical Reports Server (NTRS)

Prestage, John D.

1995-01-01

Improved design concept for linear-ion-trap (LIT) frequency-standard apparatus proposed. Apparatus contains lengthened linear ion trap, and ions processed alternately in two regions: ions prepared in upper region of trap, then transported to lower region for exposure to microwave radiation, then returned to upper region for optical interrogation. Improved design intended to increase long-term frequency stability of apparatus while reducing size, mass, and cost.

Measuring the Kinetic and Mechanical Properties of Non-Processive Myosins using Optical Tweezers

PubMed Central

Greenberg, Michael J.; Shuman, Henry; Ostap, E. Michael

2017-01-01

The myosin superfamily of molecular motors utilizes energy from ATP hydrolysis to generate force and motility along actin filaments in a diverse array of cellular processes. These motors are structurally, kinetically, and mechanically tuned to their specific molecular roles in the cell. Optical trapping techniques have played a central role in elucidating the mechanisms by which myosins generate force and in exposing the remarkable diversity of myosin functions. Here, we present thorough methods for measuring and analyzing interactions between actin and non-processive myosins using optical trapping techniques. PMID:27844441

Origin and Future of Plasmonic Optical Tweezers

PubMed Central

Huang, Jer-Shing; Yang, Ya-Tang

2015-01-01

Plasmonic optical tweezers can overcome the diffraction limits of conventional optical tweezers and enable the trapping of nanoscale objects. Extension of the trapping and manipulation of nanoscale objects with nanometer position precision opens up unprecedented opportunities for applications in the fields of biology, chemistry and statistical and atomic physics. Potential applications include direct molecular manipulation, lab-on-a-chip applications for viruses and vesicles and the study of nanoscale transport. This paper reviews the recent research progress and development bottlenecks and provides an overview of possible future directions in this field. PMID:28347051

Origin and Future of Plasmonic Optical Tweezers.

PubMed

Huang, Jer-Shing; Yang, Ya-Tang

2015-06-12

Plasmonic optical tweezers can overcome the diffraction limits of conventional optical tweezers and enable the trapping of nanoscale objects. Extension of the trapping and manipulation of nanoscale objects with nanometer position precision opens up unprecedented opportunities for applications in the fields of biology, chemistry and statistical and atomic physics. Potential applications include direct molecular manipulation, lab-on-a-chip applications for viruses and vesicles and the study of nanoscale transport. This paper reviews the recent research progress and development bottlenecks and provides an overview of possible future directions in this field.

Manufacturing a thin wire electrostatic trap for ultracold polar molecules.

PubMed

Kleinert, J; Haimberger, C; Zabawa, P J; Bigelow, N P

2007-11-01

We present a detailed description on how to build a thin wire electrostatic trap (TWIST) for ultracold polar molecules. It is the first design of an electrostatic trap that can be superimposed directly onto a magneto-optical trap (MOT). We can thus continuously produce ultracold polar molecules via photoassociation from a two species MOT and instantaneously trap them in the TWIST without the need for complex transfer schemes. Despite the spatial overlap of the TWIST and the MOT, the two traps can be operated and optimized completely independently due to the complementary nature of the utilized trapping mechanisms.

Trapping of ultracold polar molecules with a thin-wire electrostatic trap.

PubMed

Kleinert, J; Haimberger, C; Zabawa, P J; Bigelow, N P

2007-10-05

We describe the realization of a dc electric-field trap for ultracold polar molecules, the thin-wire electrostatic trap (TWIST). The thin wires that form the electrodes of the TWIST allow us to superimpose the trap onto a magneto-optical trap (MOT). In our experiment, ultracold polar NaCs molecules in their electronic ground state are created in the MOT via photoassociation, achieving a continuous accumulation in the TWIST of molecules in low-field seeking states. Initial measurements show that the TWIST trap lifetime is limited only by the background pressure in the chamber.

OAT3-mediated extrusion of the 99mTc-ECD metabolite in the mouse brain

PubMed Central

Kikuchi, Tatsuya; Okamura, Toshimitsu; Wakizaka, Hidekatsu; Okada, Maki; Odaka, Kenichi; Yui, Joji; Tsuji, Atsushi B; Fukumura, Toshimitsu; Zhang, Ming-Rong

2014-01-01

After administration of the 99mTc complex with N,N'-1,2-ethylenediylbis-L-cysteine diethyl ester (99mTc-ECD), a brain perfusion imaging agent, the radioactive metabolite is trapped in primate brain, but not in mouse and rat. Here, we investigate the involvement of metabolite extrusion by organic anion transporter 3 (OAT3), which is highly expressed at the blood–brain barrier in mice, in this species difference. The efflux rate of radioactivity in the cerebrum of Oat3−/− mice at later phase was 20% of that of control mice. Thus, organic anion transporters in mouse brain would be involved in the low brain retention of radioactivity after 99mTc-ECD administration. PMID:24496177

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kleinert, J.; Haimberger, C.; Zabawa, P. J.

We present a detailed description on how to build a thin wire electrostatic trap (TWIST) for ultracold polar molecules. It is the first design of an electrostatic trap that can be superimposed directly onto a magneto-optical trap (MOT). We can thus continuously produce ultracold polar molecules via photoassociation from a two species MOT and instantaneously trap them in the TWIST without the need for complex transfer schemes. Despite the spatial overlap of the TWIST and the MOT, the two traps can be operated and optimized completely independently due to the complementary nature of the utilized trapping mechanisms.

Systematic optimization of laser cooling of dysprosium

NASA Astrophysics Data System (ADS)

Mühlbauer, Florian; Petersen, Niels; Baumgärtner, Carina; Maske, Lena; Windpassinger, Patrick

2018-06-01

We report on an apparatus for cooling and trapping of neutral dysprosium. We characterize and optimize the performance of our Zeeman slower and 2D molasses cooling of the atomic beam by means of Doppler spectroscopy on a 136 kHz broad transition at 626 nm. Furthermore, we demonstrate the characterization and optimization procedure for the loading phase of a magneto-optical trap (MOT) by increasing the effective laser linewidth by sideband modulation. After optimization of the MOT compression phase, we cool and trap up to 10^9 atoms within 3 seconds in the MOT at temperatures of 9 μK and phase space densities of 1.7 \\cdot 10^{-5}, which constitutes an ideal starting point for loading the atoms into an optical dipole trap and for subsequent forced evaporative cooling.

Optical trapping/modification of nano-(micro)particles by gradient and photorefractive forces during laser illumination

NASA Astrophysics Data System (ADS)

Kukhtarev, N.; Kukhtareva, T.; Okafor, F.

2010-08-01

In this paper we describe photo-induced trapping/redistribution of silver nano-(micro) particles near the surface of photorefractive crystal LiNbO3:Fe. This type of optical trapping is due to combined forces of direct gradient-force trapping and asymmetric photorefractive forces of electro-phoresis and dielectro-phoresis. The silver nanoparticles were produced through extracellular biosynthesis on exposure to the fungus, Fusarium oxysporum (FO) and to the plant extracts. Pulsed and CW visible laser radiation lead to significant modification of nanoparticle clusters. This study indicates that extracellular biosynthesis can constitute a possible viable alternative method for the production of nanoparticles. In addition, the theoretical modeling of asymmetric photorefractive electric field grating has been presented and compared with the experimental results.

Optical patterning of trapped charge in nitrogen-doped diamond

NASA Astrophysics Data System (ADS)

Jayakumar, Harishankar; Henshaw, Jacob; Dhomkar, Siddharth; Pagliero, Daniela; Laraoui, Abdelghani; Manson, Neil B.; Albu, Remus; Doherty, Marcus W.; Meriles, Carlos A.

2016-08-01

The nitrogen-vacancy (NV) centre in diamond is emerging as a promising platform for solid-state quantum information processing and nanoscale metrology. Of interest in these applications is the manipulation of the NV charge, which can be attained by optical excitation. Here, we use two-colour optical microscopy to investigate the dynamics of NV photo-ionization, charge diffusion and trapping in type-1b diamond. We combine fixed-point laser excitation and scanning fluorescence imaging to locally alter the concentration of negatively charged NVs, and to subsequently probe the corresponding redistribution of charge. We uncover the formation of spatial patterns of trapped charge, which we qualitatively reproduce via a model of the interplay between photo-excited carriers and atomic defects. Further, by using the NV as a probe, we map the relative fraction of positively charged nitrogen on localized optical excitation. These observations may prove important to transporting quantum information between NVs or to developing three-dimensional, charge-based memories.

Monolayer optical memory cells based on artificial trap-mediated charge storage and release

NASA Astrophysics Data System (ADS)

Lee, Juwon; Pak, Sangyeon; Lee, Young-Woo; Cho, Yuljae; Hong, John; Giraud, Paul; Shin, Hyeon Suk; Morris, Stephen M.; Sohn, Jung Inn; Cha, Seungnam; Kim, Jong Min

2017-03-01

Monolayer transition metal dichalcogenides are considered to be promising candidates for flexible and transparent optoelectronics applications due to their direct bandgap and strong light-matter interactions. Although several monolayer-based photodetectors have been demonstrated, single-layered optical memory devices suitable for high-quality image sensing have received little attention. Here we report a concept for monolayer MoS2 optoelectronic memory devices using artificially-structured charge trap layers through the functionalization of the monolayer/dielectric interfaces, leading to localized electronic states that serve as a basis for electrically-induced charge trapping and optically-mediated charge release. Our devices exhibit excellent photo-responsive memory characteristics with a large linear dynamic range of ~4,700 (73.4 dB) coupled with a low OFF-state current (<4 pA), and a long storage lifetime of over 104 s. In addition, the multi-level detection of up to 8 optical states is successfully demonstrated. These results represent a significant step toward the development of future monolayer optoelectronic memory devices.

Optical patterning of trapped charge in nitrogen-doped diamond.

PubMed

Jayakumar, Harishankar; Henshaw, Jacob; Dhomkar, Siddharth; Pagliero, Daniela; Laraoui, Abdelghani; Manson, Neil B; Albu, Remus; Doherty, Marcus W; Meriles, Carlos A

2016-08-30

The nitrogen-vacancy (NV) centre in diamond is emerging as a promising platform for solid-state quantum information processing and nanoscale metrology. Of interest in these applications is the manipulation of the NV charge, which can be attained by optical excitation. Here, we use two-colour optical microscopy to investigate the dynamics of NV photo-ionization, charge diffusion and trapping in type-1b diamond. We combine fixed-point laser excitation and scanning fluorescence imaging to locally alter the concentration of negatively charged NVs, and to subsequently probe the corresponding redistribution of charge. We uncover the formation of spatial patterns of trapped charge, which we qualitatively reproduce via a model of the interplay between photo-excited carriers and atomic defects. Further, by using the NV as a probe, we map the relative fraction of positively charged nitrogen on localized optical excitation. These observations may prove important to transporting quantum information between NVs or to developing three-dimensional, charge-based memories.

Optical patterning of trapped charge in nitrogen-doped diamond

PubMed Central

Jayakumar, Harishankar; Henshaw, Jacob; Dhomkar, Siddharth; Pagliero, Daniela; Laraoui, Abdelghani; Manson, Neil B.; Albu, Remus; Doherty, Marcus W.; Meriles, Carlos A.

2016-01-01

The nitrogen-vacancy (NV) centre in diamond is emerging as a promising platform for solid-state quantum information processing and nanoscale metrology. Of interest in these applications is the manipulation of the NV charge, which can be attained by optical excitation. Here, we use two-colour optical microscopy to investigate the dynamics of NV photo-ionization, charge diffusion and trapping in type-1b diamond. We combine fixed-point laser excitation and scanning fluorescence imaging to locally alter the concentration of negatively charged NVs, and to subsequently probe the corresponding redistribution of charge. We uncover the formation of spatial patterns of trapped charge, which we qualitatively reproduce via a model of the interplay between photo-excited carriers and atomic defects. Further, by using the NV as a probe, we map the relative fraction of positively charged nitrogen on localized optical excitation. These observations may prove important to transporting quantum information between NVs or to developing three-dimensional, charge-based memories. PMID:27573190

The First Hours of the GW170817 Kilonova and the Importance of Early Optical and Ultraviolet Observations for Constraining Emission Models

NASA Astrophysics Data System (ADS)

Arcavi, Iair

2018-03-01

The kilonova associated with GW170817 displayed early blue emission, which has been interpreted as a signature of either radioactive decay in low-opacity ejecta, relativistic boosting of radioactive decay in high-velocity ejecta, the cooling of material heated by a wind or by a “cocoon” surrounding a jet, or a combination thereof. Distinguishing between these mechanisms is important for constraining the ejecta components and their parameters, which tie directly into the physics we can learn from these events. I compile published ultraviolet, optical, and infrared light curves of the GW170817 kilonova and examine whether the combined data set can be used to distinguish between early-emission models. The combined optical data show an early rise consistent with radioactive decay of low-opacity ejecta as the main emission source, but the subsequent decline is fit well by all models. A lack of constraints on the ultraviolet flux during the first few hours after discovery allows for both radioactive decay and other cooling mechanisms to explain the early bolometric light curve. This analysis demonstrates that early (few hours after merger) high-cadence optical and ultraviolet observations will be critical for determining the source of blue emission in future kilonovae.

Shaping of nested potentials for electron cooling of highly-charged ions in a cooler Penning trap

NASA Astrophysics Data System (ADS)

Paul, Stefan; Kootte, Brian; Lascar, Daniel; Gwinner, Gerald; Dilling, Jens; Titan Collaboration

2016-09-01

TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN) is dedicated to mass spectrometry and decay spectroscopy of short-lived radioactive nuclides in a series of ion traps including a precision Penning trap. In order to boost the achievable precision of mass measurements TITAN deploys an Electron Beam Ion Trap (EBIT) providing Highly-Charged Ions (HCI). However, the charge breeding process in the EBIT leads to an increase in the ion bunch's energy spread which is detrimental to the overall precision gain. To reduce this effect a new cylindrical Cooler PEnning Trap (CPET) is being commissioned to sympathetically cool the HCI via a simultaneously trapped electron plasma. Simultaneous trapping of ions and electrons requires a high level of control over the nested potential landscape and sophisticated switching schemes for the voltages on CPET's multiple ring electrodes. For this purpose, we are currently setting up a new experimental control system for multi-channel voltage switching. The control system employs a Raspberry Pi communicating with a digital-to-analog board via a serial peripheral interface. We report on the implementation of the voltage control system and its performance with respect to electron and ion manipulation in CPET. University of British Columbia, Vancouver, BC, Canada.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kleinert, J.; Haimberger, C.; Zabawa, P. J.

We describe the realization of a dc electric-field trap for ultracold polar molecules, the thin-wire electrostatic trap (TWIST). The thin wires that form the electrodes of the TWIST allow us to superimpose the trap onto a magneto-optical trap (MOT). In our experiment, ultracold polar NaCs molecules in their electronic ground state are created in the MOT via photoassociation, achieving a continuous accumulation in the TWIST of molecules in low-field seeking states. Initial measurements show that the TWIST trap lifetime is limited only by the background pressure in the chamber.

Dynamics of optically levitated microparticles in vacuum placed in 2D and 3D optical potentials possessing orbital angular momentum

NASA Astrophysics Data System (ADS)

Arita, Yoshihiko; Mazilu, Michael; Chen, Mingzhou; Vettenburg, Tom; Auñón, Juan M.; Wright, Ewan M.; Dholakia, Kishan

2017-04-01

We demonstrate the transfer of orbital angular momentum to optically levitated microparticles in vacuum [1]. We prepare two-dimensional and three-dimensional optical potentials. In the former case the microparticle is placed within a Laguerre-Gaussian beam and orbits the annular beam profile with increasing angular velocity as the air drag coefficient is reduced. We explore the particle dynamics as a function of the topological charge of the levitating beam. Our results reveal that there is a fundamental limit to the orbital angular momentum that may be transferred to a trapped particle, dependent upon the beam parameters and inertial forces present. This effect was predicted theoretically [2] and can be understood considering the underlying dynamics arising from the link between the magnitude of the azimuthal index and the beam radius [3]. Whilst a Laguerre-Gaussian beam scales in size with azimuthal index `, recently we have created a "perfect" vortex beam whose radial intensity profile and radius are both independent of topological charge [4, 5]. As the Fourier transform of a perfect vortex yields a Bessel beam. Imaging a perfect vortex, with its subsequent propagation thus realises a complex three dimensional optical field. In this scenario we load individual silica microparticles into this field and observe their trajectories. The optical gradient and scattering forces interplay with the inertial and gravitational forces acting on the trapped particle, including the rotational degrees of freedom. As a result the trapped microparticle exhibits a complex three dimensional motion that includes a periodic orbital motion between the Bessel and the perfect vortex beam. We are able to determine the three dimensional optical potential in situ by tracking the particle. This first demonstration of trapping microparticles within a complex three dimensional optical potential in vacuum opens up new possibilities for fundamental studies of many-body dynamics, mesoscopic entanglement [6, 7], and optical binding [8, 9].

Simulation of single-molecule trapping in a nanochannel

PubMed Central

Robinson, William Neil; Davis, Lloyd M.

2010-01-01

The detection and trapping of single fluorescent molecules in solution within a nanochannel is studied using numerical simulations. As optical forces are insufficient for trapping molecules much smaller than the optical wavelength, a means for sensing a molecule’s position along the nanochannel and adjusting electrokinetic motion to compensate diffusion is assessed. Fluorescence excitation is provided by two adjacently focused laser beams containing temporally interleaved laser pulses. Photon detection is time-gated, and the displacement of the molecule from the middle of the two foci alters the count rates collected in the two detection channels. An algorithm for feedback control of the electrokinetic motion in response to the timing of photons, to reposition the molecule back toward the middle for trapping and to rapidly reload the trap after a molecule photobleaches or escapes, is evaluated. While accommodating the limited electrokinetic speed and the finite latency of feedback imposed by experimental hardware, the algorithm is shown to be effective for trapping fast-diffusing single-chromophore molecules within a micron-sized confocal region. Studies show that there is an optimum laser power for which loss of molecules from the trap due to either photobleaching or shot-noise fluctuations is minimized. PMID:20799801

Trapping of thulium atoms in a cavity-enhanced optical lattice near a magic wavelength of 814.5 nm

NASA Astrophysics Data System (ADS)

Kalganova, E. S.; Golovizin, A. A.; Shevnin, D. O.; Tregubov, D. O.; Khabarova, K. Yu; Sorokin, V. N.; Kolachevsky, N. N.

2018-05-01

A cavity-enhanced optical lattice at a wavelength of 814.5 nm for thulium atoms is designed and its characteristics are investigated. The parametric resonances at the vibrational frequencies of the trap are measured. The enhancement cavity will be applied to search for the magic wavelength of the clock transition at 1.14 μm in thulium atoms.

Determining the unique refractive index properties of solid polystyrene aerosol using broadband Mie scattering from optically trapped beads.

PubMed

Jones, Stephanie H; King, Martin D; Ward, Andrew D

2013-12-21

A method is described to measure the refractive index dispersion with wavelength of optically trapped solid particles in air. Knowledge of the refraction properties of solid particles is critical for the study of aerosol; both in the laboratory and in the atmosphere for climate studies. Single micron-sized polystyrene beads were optically trapped in air using a vertically aligned counter-propagating configuration of focussed laser beams. Each bead was illuminated using white light from a broadband light emitting diode (LED) and elastic scattering within the bead was collected onto a spectrograph. The resulting Mie spectra were analysed to accurately determine polystyrene bead radii to ±0.4 nm and values of the refractive index to ±0.0005 over a wavelength range of 480-700 nm. We demonstrate that optical trapping combined with elastic scattering can be used to both accurately size polystyrene beads suspended in air and determine their wavelength dependent refractive index. The refractive index dispersions are in close agreement with reported values for polystyrene beads in aqueous dispersion. Our results also demonstrate a variation in the refractive index of polystyrene, from bead to bead, in a commercial sample. The measured variation highlights that care must be taken when using polystyrene beads as a calibration aerosol.

Black thin film silicon

NASA Astrophysics Data System (ADS)

Koynov, Svetoslav; Brandt, Martin S.; Stutzmann, Martin

2011-08-01

"Black etching" has been proposed previously as a method for the nanoscale texturing of silicon surfaces, which results in an almost complete suppression of reflectivity in the spectral range of absorption relevant for photovoltaics. The method modifies the topmost 150 to 300 nm of the material and thus also is applicable for thin films of silicon. The present work is focused on the optical effects induced by the black-etching treatment on hydrogenated amorphous and microcrystalline silicon thin films, in particular with respect to their application in solar cells. In addition to a strong reduction of the reflectivity, efficient light trapping within the modified thin films is found. The enhancement of the optical absorption due to the light trapping is investigated via photometric measurements and photothermal deflection spectroscopy. The correlation of the texture morphology (characterized via atomic force microscopy) with the optical effects is discussed in terms of an effective medium with gradually varying optical density and in the framework of the theory of statistical light trapping. Photoconductivity spectra directly show that the light trapping causes a significant prolongation of the light path within the black silicon films by up to 15 μm for ˜1 μm thick films, leading to a significant increase of the absorption in the red.

Dual-wavelength excited photoluminescence spectroscopy of deep-level hole traps in Ga(In)NP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dagnelund, D.; Huang, Y. Q.; Buyanova, I. A.

2015-01-07

By employing photoluminescence (PL) spectroscopy under dual-wavelength optical excitation, we uncover the presence of deep-level hole traps in Ga(In)NP alloys grown by molecular beam epitaxy (MBE). The energy level positions of the traps are determined to be at 0.56 eV and 0.78 eV above the top of the valance band. We show that photo-excitation of the holes from the traps, by a secondary light source with a photon energy below the bandgap energy, can lead to a strong enhancement (up to 25%) of the PL emissions from the alloys under a primary optical excitation above the bandgap energy. We further demonstrate thatmore » the same hole traps can be found in various MBE-grown Ga(In)NP alloys, regardless of their growth temperatures, chemical compositions, and strain. The extent of the PL enhancement induced by the hole de-trapping is shown to vary between different alloys, however, likely reflecting their different trap concentrations. The absence of theses traps in the GaNP alloy grown by vapor phase epitaxy suggests that their incorporation could be associated with a contaminant accompanied by the N plasma source employed in the MBE growth, possibly a Cu impurity.« less

Scanning dimensional measurement using laser-trapped microsphere with optical standing-wave scale

NASA Astrophysics Data System (ADS)

Michihata, Masaki; Ueda, Shin-ichi; Takahashi, Satoru; Takamasu, Kiyoshi; Takaya, Yasuhiro

2017-06-01

We propose a laser trapping-based scanning dimensional measurement method for free-form surfaces. We previously developed a laser trapping-based microprobe for three-dimensional coordinate metrology. This probe performs two types of measurements: a tactile coordinate and a scanning measurement in the same coordinate system. The proposed scanning measurement exploits optical interference. A standing-wave field is generated between the laser-trapped microsphere and the measured surface because of the interference from the retroreflected light. The standing-wave field produces an effective length scale, and the trapped microsphere acts as a sensor to read this scale. A horizontal scan of the trapped microsphere produces a phase shift of the standing wave according to the surface topography. This shift can be measured from the change in the microsphere position. The dynamics of the trapped microsphere within the standing-wave field was estimated using a harmonic model, from which the measured surface can be reconstructed. A spherical lens was measured experimentally, yielding a radius of curvature of 2.59 mm, in agreement with the nominal specification (2.60 mm). The difference between the measured points and a spherical fitted curve was 96 nm, which demonstrates the scanning function of the laser trapping-based microprobe for free-form surfaces.

Manipulation of Micro Scale Particles in an Optical Trap Using Interferometry

NASA Technical Reports Server (NTRS)

Seibel, Robin

2002-01-01

This research shows that micro particles can be manipulated via interferometric patterns superimposed on an optical tweezers beam. Interferometry allows the manipulation of intensity distributions, and thus, force distributions on a trapped particle. To demonstrate the feasibility of such manipulation, 458 nm light, from an argon-ion laser, was injected into a Mach Zender interferometer. One mirror in the interferometer was oscillated with a piezoelectric phase modulator. The light from the interferometer was then injected into a microscope to trap a 9.75 micron polystyrene sphere. By varying the phase modulation, the sphere was made to oscillate in a controlled fashion.

Influence of the finite linewidth of the laser radiation spectrum on the shape of the coherent population trapping resonance line in an optically dense medium with a buffer gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barantsev, K. A., E-mail: kostmann@yandex.ru; Popov, E. N.; Litvinov, A. N., E-mail: andrey.litvinov@mail.ru

2015-11-15

The theory of coherent population trapping resonance is developed for the finite linewidth of the laser radiation spectrum in an optically dense medium of Λ atoms in a cell with a buffer gas. Equations are derived for the atomic density matrix and laser emission spectrum transfer in a cell with working and buffer gases at a finite temperature. The dependence of the quality factor of coherent population trapping resonance on the linewidth of the laser radiation spectrum is studied by measuring transmitted radiation and fluorescence signals.

Use of an optical trap for study of host-pathogen interactions for dynamic live cell imaging.

PubMed

Tam, Jenny M; Castro, Carlos E; Heath, Robert J W; Mansour, Michael K; Cardenas, Michael L; Xavier, Ramnik J; Lang, Matthew J; Vyas, Jatin M

2011-07-28

Dynamic live cell imaging allows direct visualization of real-time interactions between cells of the immune system(1, 2); however, the lack of spatial and temporal control between the phagocytic cell and microbe has rendered focused observations into the initial interactions of host response to pathogens difficult. Historically, intercellular contact events such as phagocytosis(3) have been imaged by mixing two cell types, and then continuously scanning the field-of-view to find serendipitous intercellular contacts at the appropriate stage of interaction. The stochastic nature of these events renders this process tedious, and it is difficult to observe early or fleeting events in cell-cell contact by this approach. This method requires finding cell pairs that are on the verge of contact, and observing them until they consummate their contact, or do not. To address these limitations, we use optical trapping as a non-invasive, non-destructive, but fast and effective method to position cells in culture. Optical traps, or optical tweezers, are increasingly utilized in biological research to capture and physically manipulate cells and other micron-sized particles in three dimensions(4). Radiation pressure was first observed and applied to optical tweezer systems in 1970(5, 6), and was first used to control biological specimens in 1987(7). Since then, optical tweezers have matured into a technology to probe a variety of biological phenomena(8-13). We describe a method(14) that advances live cell imaging by integrating an optical trap with spinning disk confocal microscopy with temperature and humidity control to provide exquisite spatial and temporal control of pathogenic organisms in a physiological environment to facilitate interactions with host cells, as determined by the operator. Live, pathogenic organisms like Candida albicans and Aspergillus fumigatus, which can cause potentially lethal, invasive infections in immunocompromised individuals(15, 16) (e.g. AIDS, chemotherapy, and organ transplantation patients), were optically trapped using non-destructive laser intensities and moved adjacent to macrophages, which can phagocytose the pathogen. High resolution, transmitted light and fluorescence-based movies established the ability to observe early events of phagocytosis in living cells. To demonstrate the broad applicability in immunology, primary T-cells were also trapped and manipulated to form synapses with anti-CD3 coated microspheres in vivo, and time-lapse imaging of synapse formation was also obtained. By providing a method to exert fine spatial control of live pathogens with respect to immune cells, cellular interactions can be captured by fluorescence microscopy with minimal perturbation to cells and can yield powerful insight into early responses of innate and adaptive immunity.

Optical trapping and Raman spectroscopy of single nanostructures using standing-wave Raman tweezers

NASA Astrophysics Data System (ADS)

Wu, Mu-ying; He, Lin; Chen, Gui-hua; Yang, Guang; Li, Yong-qing

2017-08-01

Optical tweezers integrated with Raman spectroscopy allows analyzing a single trapped micro-particle, but is generally less effective for individual nano-sized objects in the 10-100 nm range. The main challenge is the weak gradient force on nanoparticles that is insufficient to overcome the destabilizing effect of scattering force and Brownian motion. Here, we present standing-wave Raman tweezers for stable trapping and sensitive characterization of single isolated nanostructures with a low laser power by combining a standing-wave optical trap (SWOT) with confocal Raman spectroscopy. This scheme has stronger intensity gradients and balanced scattering forces, and thus is more stable and sensitive in measuring nanoparticles in liquid with 4-8 fold increase in the Raman signals. It can be used to analyze many nanoparticles that cannot be measured with single-beam Raman tweezers, including individual single-walled carbon nanotubes (SWCNT), graphene flakes, biological particles, polystyrene beads (100 nm), SERS-active metal nanoparticles, and high-refractive semiconductor nanoparticles with a low laser power of a few milliwatts. This would enable sorting and characterization of specific SWCNTs and other nanoparticles based on their increased Raman fingerprints.

Raman Spectroscopy of Single Light-Absorbing Carbonaceous Particles Levitated in Air Using an Annular Laser Beam.

PubMed

Uraoka, Masaru; Maegawa, Keisuke; Ishizaka, Shoji

2017-12-05

A laser trapping technique is a powerful means to investigate the physical and chemical properties of single aerosol particles in a noncontact manner. However, optical trapping of strongly light-absorbing particles such as black carbon or soot is quite difficult because the repulsive force caused by heat is orders of magnitude larger than the attractive force of radiation pressure. In this study, a laser trapping and Raman microspectroscopy system using an annular laser beam was constructed to achieve noncontact levitation of single light-absorbing particles in air. Single acetylene carbon black or candle soot particles were arbitrarily selected with a glass capillary connected to a three-axis oil hydraulic micromanipulator and introduced into a minute space surrounded by a repulsive force at the focal point of an objective lens. Using the developed system, we achieved optical levitation of micrometer-sized carbonaceous particles and observation of their Raman spectra in air. Furthermore, we demonstrated in situ observations of changes in the morphology and chemical composition of optically trapped carbonaceous particles in air, which were induced by heterogeneous oxidation reactions with ozone and hydroxyl radicals.

Improving the lifetime in optical microtraps by using elliptically polarized dipole light

NASA Astrophysics Data System (ADS)

Garcia, Sébastien; Reichel, Jakob; Long, Romain

2018-02-01

Tightly focused optical dipole traps induce vector light shifts ("fictitious magnetic fields") which complicate their use for single-atom trapping and manipulation. The problem can be mitigated by adding a larger, real magnetic field, but this solution is not always applicable; in particular, it precludes fast switching to a field-free configuration. Here we show that this issue can be addressed elegantly by deliberately adding a small elliptical polarization component to the dipole trap beam. In our experiments with single 87Rb atoms laser-cooled in a chopped trap, we observe improvements up to a factor of 11 of the trap lifetime compared to the standard, seemingly ideal linear polarization. This effect results from a modification of heating processes via spin-state diffusion in state-dependent trapping potentials. We develop Monte Carlo simulations of the evolution of the atom's internal and motional states and find that they agree quantitatively with the experimental data. The method is general and can be applied in all experiments where the longitudinal polarization component is non-negligible.

High Speed Video Measurements of a Magneto-optical Trap

NASA Astrophysics Data System (ADS)

Horstman, Luke; Graber, Curtis; Erickson, Seth; Slattery, Anna; Hoyt, Chad

2016-05-01

We present a video method to observe the mechanical properties of a lithium magneto-optical trap. A sinusoidally amplitude-modulated laser beam perturbed a collection of trapped ce7 Li atoms and the oscillatory response was recorded with a NAC Memrecam GX-8 high speed camera at 10,000 frames per second. We characterized the trap by modeling the oscillating cold atoms as a damped, driven, harmonic oscillator. Matlab scripts tracked the atomic cloud movement and relative phase directly from the captured high speed video frames. The trap spring constant, with magnetic field gradient bz = 36 G/cm, was measured to be 4 . 5 +/- . 5 ×10-19 N/m, which implies a trap resonant frequency of 988 +/- 55 Hz. Additionally, at bz = 27 G/cm the spring constant was measured to be 2 . 3 +/- . 2 ×10-19 N/m, which corresponds to a resonant frequency of 707 +/- 30 Hz. These properties at bz = 18 G/cm were found to be 8 . 8 +/- . 5 ×10-20 N/m, and 438 +/- 13 Hz. NSF #1245573.

Single-cell adhesion probed in-situ using optical tweezers: A case study with Saccharomyces cerevisiae

NASA Astrophysics Data System (ADS)

Castelain, Mickaël; Rouxhet, Paul G.; Pignon, Frédéric; Magnin, Albert; Piau, Jean-Michel

2012-06-01

A facile method of using optical trapping to measure cell adhesion forces is presented and applied to the adhesion of Saccharomyces cerevisiae on glass, in contact with solutions of different compositions. Trapping yeast cells with optical tweezers (OT) is not perturbed by cell wall deformation or cell deviation from a spherical shape. The trapping force calibration requires correction not only for the hydrodynamic effect of the neighboring wall but also for spherical aberrations affecting the focal volume and the trap stiffness. Yeast cells trapped for up to 5 h were still able to undergo budding but showed an increase of doubling time. The proportion of adhering cells showed the expected variation according to the solution composition. The detachment force varied in the same way. This observation and the fact that the detachment stress was exerted parallel to the substrate surface point to the role of interactions involving solvated macromolecules. Both the proportion of adhering cells and the removal force showed a distribution which, in our experimental conditions, must be attributed to a heterogeneity of surface properties at the cell level or at the subcellular scale. As compared with magnetic tweezers, atomic force microscopy, and more conventional ways of studying cell adhesion (shear-flow cells), OT present several advantages that are emphasized in this paper.

Temperature control and measurement with tunable femtosecond optical tweezers

NASA Astrophysics Data System (ADS)

Mondal, Dipankar; Goswami, Debabrata

2016-09-01

We present the effects of wavelength dependent temperature rise in a femtosecond optical tweezers. Our experiments involve the femtosecond trapping laser tunable from 740-820 nm at low power 25 mW to cause heating in the trapped volume within a homogeneous solution of sub micro-molar concentration of IR dye. The 780 nm high repetition rate laser acts as a resonant excitation source which helps to create the local heating effortlessly within the trapping volume. We have used both position autocorrelation and equipartion theorem to evaluate temperature at different wavelength having different absorption coefficient. Fixing the pulse width in the temporal domain gives constant bandwidth at spatial domain, which makes our system behave as a tunable temperature rise device with high precision. This observation leads us to calculate temperature as well as viscosity within the vicinity of the trapping zone. A mutual energy transfer occurs between the trapped bead and solvents that leads to transfer the thermal energy of solvents into the kinetic energy of the trap bead and vice-versa. Thus hot solvated molecules resulting from resonant and near resonant excitation of trapping wavelength can continuously dissipate heat to the trapped bead which will be reflected on frequency spectrum of Brownian noise exhibited by the bead. Temperature rise near the trapping zone can significantly change the viscosity of the medium. We observe temperature rise profile according to its Gaussian shaped absorption spectrum with different wavelength.

Scheme for generating the singlet state of three atoms trapped in distant cavities coupled by optical fibers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Dong-Yang; Wen, Jing-Ji; Bai, Cheng-Hua

2015-09-15

An effective scheme is proposed to generate the singlet state with three four-level atoms trapped in three distant cavities connected with each other by three optical fibers, respectively. After a series of appropriate atom–cavity interactions, which can be arbitrarily controlled via the selective pairing of Raman transitions and corresponding optical switches, a three-atom singlet state can be successfully generated. The influence of atomic spontaneous decay, photon leakage of cavities and optical fibers on the fidelity of the state is numerically simulated showing that the three-atom singlet state can be generated with high fidelity by choosing the experimental parameters appropriately.

Plasmonic graded nano-disks as nano-optical conveyor belt.

PubMed

Kang, Zhiwen; Lu, Haifei; Chen, Jiajie; Chen, Kun; Xu, Fang; Ho, Ho-Pui

2014-08-11

We propose a plasmonic system consisting of nano-disks (NDs) with graded diameters for the realization of nano-optical conveyor belt. The system contains a couple of NDs with individual elements coded with different resonant wavelengths. By sequentially switching the wavelength and polarization of the excitation source, optically trapped target nano-particle can be transferred from one ND to another. The feasibility of such function is verified based on the three-dimensional finite-difference time-domain technique and the Maxwell stress tensor method. Our design may provide an alternative way to construct nano-optical conveyor belt with which target molecules can be delivered between trapping sites, thus enabling many on-chip optofluidic applications.

Bespoke optical springs and passive force clamps from shaped dielectric particles

NASA Astrophysics Data System (ADS)

Simpson, S. H.; Phillips, D. B.; Carberry, D. M.; Hanna, S.

2013-09-01

By moulding optical fields, holographic optical tweezers are able to generate structured force fields with magnitudes and length scales of great utility for experiments in soft matter and biological physics. It has recently been noted that optically induced force fields are determined not only by the incident optical field, but by the shape and composition of the particles involved [Gluckstad J. Optical manipulation: sculpting the object. Nat Photonics 2011;5:7-8]. Indeed, there are desirable but simple attributes of a force field, such as orientational control, that cannot be introduced by sculpting optical fields alone. With this insight in mind, we show, theoretically, how relationships between force and displacement can be controlled by optimizing particle shapes. We exhibit a constant force optical spring, made from a tapered microrod and discuss methods by which it could be fabricated. In addition, we investigate the optical analogue of streamlining, and show how objects can be shaped so as to reduce the effects of radiation pressure, and hence switch from non-trapping to trapping regimes.

Dynamic measurements and simulations of airborne picolitre-droplet coalescence in holographic optical tweezers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bzdek, Bryan R.; Reid, Jonathan P., E-mail: j.p.reid@bristol.ac.uk; Collard, Liam

We report studies of the coalescence of pairs of picolitre aerosol droplets manipulated with holographic optical tweezers, probing the shape relaxation dynamics following coalescence by simultaneously monitoring the intensity of elastic backscattered light (EBL) from the trapping laser beam (time resolution on the order of 100 ns) while recording high frame rate camera images (time resolution <10 μs). The goals of this work are to: resolve the dynamics of droplet coalescence in holographic optical traps; assign the origin of key features in the time-dependent EBL intensity; and validate the use of the EBL alone to precisely determine droplet surface tensionmore » and viscosity. For low viscosity droplets, two sequential processes are evident: binary coalescence first results from the overlap of the optical traps on the time scale of microseconds followed by the recapture of the composite droplet in an optical trap on the time scale of milliseconds. As droplet viscosity increases, the relaxation in droplet shape eventually occurs on the same time scale as recapture, resulting in a convoluted evolution of the EBL intensity that inhibits quantitative determination of the relaxation time scale. Droplet coalescence was simulated using a computational framework to validate both experimental approaches. The results indicate that time-dependent monitoring of droplet shape from the EBL intensity allows for robust determination of properties such as surface tension and viscosity. Finally, the potential of high frame rate imaging to examine the coalescence of dissimilar viscosity droplets is discussed.« less

High-refractive index particles in counter-propagating optical tweezers - manipulation and forces

NASA Astrophysics Data System (ADS)

van der Horst, Astrid

2006-09-01

With a tightly focused single laser beam, also called optical tweezers, particles of a few nanometers up to several micrometers in size can be trapped and manipulated in 3D. The size, shape and refractive index of such colloidal particles are of influence on the optical forces exerted on them in the trap. A higher refractive-index difference between a particle and the surrounding medium will increase the forces. The destabilizing scattering force, however, pushing the particle in the direction of the beam, increases more than the gradient force, directed towards the focus. As a consequence, particles with a certain refractive index cannot be trapped in a single-beam gradient trap, and a limit is set to the force that can be exerted. We developed an experimental setup with two opposing high-numerical objectives. By splitting the laser beam, we created counter-propagating tweezers in which the scattering forces were canceled in the axial direction and high-refractive index and metallic particles could also be trapped. With the use of a separate laser beam combined with a quadrant photodiode, accurate position detection on a trapped particle in the counter-propagating tweezers is possible. We used this to determine trap stiffnesses, and show, with measurements and calculations, an enhancement in trap stiffness of at least 3 times for high-index 1.1-micrometer-diameter titania particles as compared to 1.4-micrometer-diameter silica particles under the same conditions. The ability to exert higher forces with lower laser power finds application in biophysical experiments, where laser damage and heating play a role. The manipulation of high-index and metallic particles also has applications in materials and colloid science, for example to incorporate high-index defects in colloidal photonic crystals. We demonstrate the patterning of high-index particles onto a glass substrate. The sample cell was mounted on a high-accuracy piezo stage combined with a long-range stage with motorized actuators. Because we used image analysis of the patterned structure to accurately find back the starting position and compensate for drift of the sample, we could move far away from the patterning region. This enabled us to select particles from a separate reservoir of a mixture of particles, and, one-by-one, position them at chosen locations. By time-sharing the laser beam using acousto-optic deflectors, we created multiple counter-propagating tweezers. We trapped an array of high-refractive index particles, and were able to move those particles individually. We used such a dynamic array of counter-propagating tweezers to create line-optical tweezers in which we trapped semi-conducting high-refractive index nanorods in three dimensions. We demonstrate full 3D translational and in-plane rotational control over the rods, which could not be held in single-beam line-tweezers. The configuration of two opposing objectives was also used for simultaneous trapping with one objective and confocal imaging of the fluorescently labeled particles using the other objective. By trapping particles with a refractive index contrast in a dispersion of index-matched particles, crystallization could be induced, which was imaged in three dimensions using confocal microscopy.

Extracting the potential-well of a near-field optical trap using the Helmholtz-Hodge decomposition

NASA Astrophysics Data System (ADS)

Zaman, Mohammad Asif; Padhy, Punnag; Hansen, Paul C.; Hesselink, Lambertus

2018-02-01

The non-conservative nature of the force field generated by a near-field optical trap is analyzed. A plasmonic C-shaped engraving on a gold film is considered as the trap. The force field is calculated using the Maxwell stress tensor method. The Helmholtz-Hodge decomposition is used to extract the conservative and the non-conservative component of the force. Due to the non-negligible non-conservative component, it is found that the conventional approach of extracting the potential by direct integration of the force is not accurate. Despite the non-conservative nature of the force field, it is found that the statistical properties of a trapped nanoparticle can be estimated from the conservative component of the force field alone. Experimental and numerical results are presented to support the claims.

Electrical and Optical Studies of Deep Levels in Nominally Undoped Thallium Bromide

NASA Astrophysics Data System (ADS)

Smith, Holland M.; Haegel, Nancy M.; Phillips, David J.; Cirignano, Leonard; Ciampi, Guido; Kim, Hadong; Chrzan, Daryl C.; Haller, Eugene E.

2014-02-01

Photo-induced conductivity transient spectroscopy (PICTS) and cathodoluminescence (CL) measurements were performed on nominally undoped detector grade samples of TlBr. In PICTS measurements, nine traps were detected in the temperature range 80-250 K using four-gate analysis. Five of the traps are tentatively identified as electron traps, and four as hole traps. CL measurements yielded two broad peaks common to all samples and most likely associated with defects. Correlations between the optically and electrically detected deep levels are considered. Above 250 K, the photoconductivity transients measured in the PICTS experiments exhibited anomalous transient behavior, indicated by non-monotonic slope variations as a function of time. The origin of the transients is under further investigation, but their presence precludes the accurate determination of trap parameters in TlBr above 250 K with traditional PICTS analysis. Their discovery was made possible by the use of a PICTS system that records whole photoconductivity transients, as opposed to reduced and processed signals.

Rotation of an optically trapped vaterite microsphere measured using rotational Doppler effect

NASA Astrophysics Data System (ADS)

Chen, Xinlin; Xiao, Guangzong; Xiong, Wei; Yang, Kaiyong; Luo, Hui; Yao, Baoli

2018-03-01

The angular velocity of a vaterite microsphere spinning in the optical trap is measured using rotational Doppler effect. The perfectly spherical vaterite microspheres are synthesized via coprecipitation in the presence of silk fibroin nanospheres. When trapped by a circularly polarized beam, the vaterite microsphere is uniformly rotated in the trap center. The probe beams containing two Laguerre-Gaussian beams of opposite topological charge l = ± 7, l = ± 8, and l = ± 9 are illuminated on the spinning vaterite. By analyzing the backscattered light, a frequency shift is observed scaling with the rotation rate of the vaterite microsphere. The multiplicative enhancement of the frequency shift proportion to the topological charge has greatly improved the measurement precision. The reliability and practicability of this approach are verified through varying the topological charge of the probe beam and the trapping laser power. In consideration of the excellent measurement precision of the rotation frequency, this technique might be generally applicable in studying the torsional properties of micro-objects.

Plasmonic nanotweezers: strong influence of adhesion layer and nanostructure orientation on trapping performance.

PubMed

Roxworthy, Brian J; Toussaint, Kimani C

2012-04-23

Using Au bowtie nanoantennas arrays (BNAs), we demonstrate that the performance and capability of plasmonic nanotweezers is strongly influenced by both the material comprising the thin adhesion layer used to fix Au to a glass substrate and the nanostructure orientation with respect to incident illumination. We find that a Ti adhesion layer provides up to 30% larger trap stiffness and efficiency compared to a Cr layer of equal thickness. Orientation causes the BNAs to operate as either (1) a 2D optical trap capable of efficient trapping and manipulation of particles as small as 300 nm in diameter, or (2) a quasi-3D trap, with the additional capacity for size-dependent particle sorting utilizing axial Rayleigh-Bénard convection currents caused by heat generation. We show that heat generation is not necessarily deleterious to plasmonic nanotweezers and achieve dexterous manipulation of nanoparticles with non-resonant illumination of BNAs. © 2012 Optical Society of America

Purple sea urchin Strongylocentrotus purpuratus gamete manipulation using optical trapping and microfluidics

NASA Astrophysics Data System (ADS)

Chandsawangbhuwana, Charlie; Shi, Linda Z.; Zhu, Qingyuan; Berns, Michael W.

2013-04-01

A system has been developed that allows for optical and fluidic manipulation of gametes. The optical manipulation is performed by using a single-point gradient trap with a 40× oil immersion PH3 1.3 NA objective on a Zeiss inverted microscope. The fluidic manipulation is performed by using a custom microfluidic chamber designed to fit into the short working distance between the condenser and objective. The system is validated using purple sea urchin Strongylocentrotus purpuratus gametes and has the potential to be used for mammalian in vitro fertilization and animal husbandry.

France's State of the Art Distributed Optical Fibre Sensors Qualified for the Monitoring of the French Underground Repository for High Level and Intermediate Level Long Lived Radioactive Wastes.

PubMed

Delepine-Lesoille, Sylvie; Girard, Sylvain; Landolt, Marcel; Bertrand, Johan; Planes, Isabelle; Boukenter, Aziz; Marin, Emmanuel; Humbert, Georges; Leparmentier, Stéphanie; Auguste, Jean-Louis; Ouerdane, Youcef

2017-06-13

This paper presents the state of the art distributed sensing systems, based on optical fibres, developed and qualified for the French Cigéo project, the underground repository for high level and intermediate level long-lived radioactive wastes. Four main parameters, namely strain, temperature, radiation and hydrogen concentration are currently investigated by optical fibre sensors, as well as the tolerances of selected technologies to the unique constraints of the Cigéo's severe environment. Using fluorine-doped silica optical fibre surrounded by a carbon layer and polyimide coating, it is possible to exploit its Raman, Brillouin and Rayleigh scattering signatures to achieve the distributed sensing of the temperature and the strain inside the repository cells of radioactive wastes. Regarding the dose measurement, promising solutions are proposed based on Radiation Induced Attenuation (RIA) responses of sensitive fibres such as the P-doped ones. While for hydrogen measurements, the potential of specialty optical fibres with Pd particles embedded in their silica matrix is currently studied for this gas monitoring through its impact on the fibre Brillouin signature evolution.

France’s State of the Art Distributed Optical Fibre Sensors Qualified for the Monitoring of the French Underground Repository for High Level and Intermediate Level Long Lived Radioactive Wastes

PubMed Central

Delepine-Lesoille, Sylvie; Girard, Sylvain; Landolt, Marcel; Bertrand, Johan; Planes, Isabelle; Boukenter, Aziz; Marin, Emmanuel; Humbert, Georges; Leparmentier, Stéphanie; Auguste, Jean-Louis; Ouerdane, Youcef

2017-01-01

This paper presents the state of the art distributed sensing systems, based on optical fibres, developed and qualified for the French Cigéo project, the underground repository for high level and intermediate level long-lived radioactive wastes. Four main parameters, namely strain, temperature, radiation and hydrogen concentration are currently investigated by optical fibre sensors, as well as the tolerances of selected technologies to the unique constraints of the Cigéo’s severe environment. Using fluorine-doped silica optical fibre surrounded by a carbon layer and polyimide coating, it is possible to exploit its Raman, Brillouin and Rayleigh scattering signatures to achieve the distributed sensing of the temperature and the strain inside the repository cells of radioactive wastes. Regarding the dose measurement, promising solutions are proposed based on Radiation Induced Attenuation (RIA) responses of sensitive fibres such as the P-doped ones. While for hydrogen measurements, the potential of specialty optical fibres with Pd particles embedded in their silica matrix is currently studied for this gas monitoring through its impact on the fibre Brillouin signature evolution. PMID:28608831

Sub-mm Scale Fiber Guided Deep/Vacuum Ultra-Violet Optical Source for Trapped Mercury Ion Clocks

NASA Technical Reports Server (NTRS)

Yi, Lin; Burt, Eric A.; Huang, Shouhua; Tjoelker, Robert L.

2013-01-01

We demonstrate the functionality of a mercury capillary lamp with a diameter in the sub-mm range and deep ultraviolet (DUV)/ vacuum ultraviolet (VUV) radiation delivery via an optical fiber integrated with the capillary. DUV spectrum control is observed by varying the fabrication parameters such as buffer gas type and pressure, capillary diameter, electrical resonator design, and temperature. We also show spectroscopic data of the 199Hg+ hyper-fine transition at 40.5GHz when applying the above fiber optical design. We present efforts toward micro-plasma generation in hollow-core photonic crystal fiber with related optical design and theoretical estimations. This new approach towards a more practical DUV optical interface could benefit trapped ion clock developments for future ultra-stable frequency reference and time-keeping applications.

Observing single protein binding by optical transmission through a double nanohole aperture in a metal film

PubMed Central

Al Balushi, Ahmed A.; Zehtabi-Oskuie, Ana; Gordon, Reuven

2013-01-01

We experimentally demonstrate protein binding at the single particle level. A double nanohole (DNH) optical trap was used to hold onto a 20 nm biotin-coated polystyrene (PS) particle which subsequently is bound to streptavidin. Biotin-streptavidin binding has been detected by an increase in the optical transmission through the DNH. Similar optical transmission behavior was not observed when streptavidin binding sites where blocked by mixing streptavidin with excess biotin. Furthermore, interaction of non-functionalized PS particles with streptavidin did not induce a change in the optical transmission through the DNH. These results are promising as the DNH trap can make an excellent single molecule resolution sensor which would enable studying biomolecular interactions and dynamics at a single particle/molecule level. PMID:24049672

Scalable Multiplexed Ion Trap (SMIT) Program

DTIC Science & Technology

2010-12-08

an integrated micromirror . The symmetric cross and the mirror trap had a number of complex design features. Both traps shaped the electrodes in...genetic algorithm. 6. Integrated micromirror . The Gen II linear trap (as well as the linear sections of the mirror and the cross) had a number of new...conventional imaging system constructed by off-the-shelf optical components and a micromirror located very close to the ion. A large fraction of photons

Dynamics of primary and secondary microbubbles created by laser-induced breakdown of an optically trapped nanoparticle

PubMed Central

Arita, Y.; Antkowiak, M.; Venugopalan, V.; Gunn-Moore, F. J.; Dholakia, K.

2012-01-01

Laser-induced breakdown of an optically trapped nanoparticle is a unique system for studying cavitation dynamics. It offers additional degrees of freedom, namely the nanoparticle material, its size, and the relative position between the laser focus and the center of the optically trapped nanoparticle. We quantify the spatial and temporal dynamics of the cavitation and secondary bubbles created in this system and use hydrodynamic modeling to quantify the observed dynamic shear stress of the expanding bubble. In the final stage of bubble collapse, we visualize the formation of multiple submicrometer secondary bubbles around the toroidal bubble on the substrate. We show that the pattern of the secondary bubbles typically has its circular symmetry broken along an axis whose unique angle rotates over time. This is a result of vorticity along the jet towards the boundary upon bubble collapse near solid boundaries. PMID:22400669

Scalable ion-photon quantum interface based on integrated diffractive mirrors

NASA Astrophysics Data System (ADS)

Ghadimi, Moji; Blūms, Valdis; Norton, Benjamin G.; Fisher, Paul M.; Connell, Steven C.; Amini, Jason M.; Volin, Curtis; Hayden, Harley; Pai, Chien-Shing; Kielpinski, David; Lobino, Mirko; Streed, Erik W.

2017-12-01

Quantum networking links quantum processors through remote entanglement for distributed quantum information processing and secure long-range communication. Trapped ions are a leading quantum information processing platform, having demonstrated universal small-scale processors and roadmaps for large-scale implementation. Overall rates of ion-photon entanglement generation, essential for remote trapped ion entanglement, are limited by coupling efficiency into single mode fibers and scaling to many ions. Here, we show a microfabricated trap with integrated diffractive mirrors that couples 4.1(6)% of the fluorescence from a 174Yb+ ion into a single mode fiber, nearly triple the demonstrated bulk optics efficiency. The integrated optic collects 5.8(8)% of the π transition fluorescence, images the ion with sub-wavelength resolution, and couples 71(5)% of the collected light into the fiber. Our technology is suitable for entangling multiple ions in parallel and overcomes mode quality limitations of existing integrated optical interconnects.

Towards a Quantum Interface between Diamond Spin Qubits and Phonons in an Optical Trap

NASA Astrophysics Data System (ADS)

Ji, Peng; Momeen, M. Ummal; Hsu, Jen-Feng; D'Urso, Brian; Dutt, Gurudev

2014-05-01

We introduce a method to optically levitate a pre-selected nanodiamond crystal in air or vacuum. The nanodiamond containing nitrogen-vacancy (NV) centers is suspended on a monolayer of graphene transferred onto a patterned substrate. Laser light is focused onto the sample, using a home-built confocal microscope with a high numerical aperture (NA = 0.9) objective, simultaneously burning the graphene and creating a 3D optical trap that captures the falling nano-diamond at the beam waist. The trapped diamond is an ultra-high-Q mechanical oscillator, allowing us to engineer strong linear and quadratic coupling between the spin of the NV center and the phonon mode. The system could result in an ideal quantum interface between a spin qubit and vibrational phonon mode, potentially enabling applications in quantum information processing and sensing the development of quantum information storage and processing.

Microwave-mediated magneto-optical trap for polar molecules

NASA Astrophysics Data System (ADS)

Dizhou, Xie; Wenhao, Bu; Bo, Yan

2016-05-01

Realizing a molecular magneto-optical trap has been a dream for cold molecular physicists for a long time. However, due to the complex energy levels and the small effective Lande g-factor of the excited states, the traditional magneto-optical trap (MOT) scheme does not work very well for polar molecules. One way to overcome this problem is the switching MOT, which requires very fast switching of both the magnetic field and the laser polarizations. Switching laser polarizations is relatively easy, but fast switching of the magnetic field is experimentally challenging. Here we propose an alternative approach, the microwave-mediated MOT, which requires a slight change of the current experimental setup to solve the problem. We calculate the MOT force and compare it with the traditional MOT and the switching MOT scheme. The results show that we can operate a good MOT with this simple setup. Project supported by the Fundamental Research Funds for the Central Universities of China.

Nonlinear force dependence on optically bound micro-particle arrays in the evanescent fields of fundamental and higher order microfibre modes

PubMed Central

Maimaiti, Aili; Holzmann, Daniela; Truong, Viet Giang; Ritsch, Helmut; Nic Chormaic, Síle

2016-01-01

Particles trapped in the evanescent field of an ultrathin optical fibre interact over very long distances via multiple scattering of the fibre-guided fields. In ultrathin fibres that support higher order modes, these interactions are stronger and exhibit qualitatively new behaviour due to the coupling of different fibre modes, which have different propagation wave-vectors, by the particles. Here, we study one dimensional longitudinal optical binding interactions of chains of 3 μm polystyrene spheres under the influence of the evanescent fields of a two-mode microfibre. The observation of long-range interactions, self-ordering and speed variation of particle chains reveals strong optical binding effects between the particles that can be modelled well by a tritter scattering-matrix approach. The optical forces, optical binding interactions and the velocity of bounded particle chains are calculated using this method. Results show good agreement with finite element numerical simulations. Experimental data and theoretical analysis show that higher order modes in a microfibre offer a promising method to not only obtain stable, multiple particle trapping or faster particle propulsion speeds, but that they also allow for better control over each individual trapped object in particle ensembles near the microfibre surface. PMID:27451935

Optical Levitation of Micro-Scale Particles in Air

NASA Technical Reports Server (NTRS)

Wrbanek, Susan Y.; Weiland, Kenneth E.

2004-01-01

Success has been achieved using a radiation pressure gradient to levitate microscale particles in air for as long as four hours. This work is performed as a precursor to the development of a vacuum based optical tweezers interrogation tool for nanotechnology research. It was decided to first proceed with solving the problem of achieving optical levitation of a micro-scale particle in air before trying the same in a vacuum environment. This successful optical levitation in air confirms the work of Ashkin and Dziedzic. Levitation of 10 and 13.8 microns diameter polystyrene spheres was achieved, as well as the levitation of 10 and 100 microns diameter glass spheres. Particles were raised and lowered. A modicum of success was achieved translating particles horizontally. Trapping of multiple particles in one laser beam has been photographed. Also, it has been observed that particles, that may be conglomerates or irregular in shape, can also be trapped by a focused laser beam. Levitated glass beads were photographed using laser light scattered from the beads. The fact that there is evidence of optical traps in air containing irregular and conglomerate particles provides hope that future tool particles need not be perfect spheres.

Silver oxide nanocrystals anchored on titanate nanotubes and nanofibers: promising candidates for entrapment of radioactive iodine anions.

PubMed

Yang, Dongjiang; Liu, Hongwei; Liu, Long; Sarina, Sarina; Zheng, Zhanfeng; Zhu, Huaiyong

2013-11-21

Iodine radioisotopes are released into the environment by the nuclear industry and medical research institutions using radioactive materials. The (129)I(-) anion is one of the more mobile radioactive species due to a long half-life, and it is a great challenge to design long-term management solutions for such radioactive waste. In this study, a new adsorbent structure with the potential to efficiently remove radioactive iodine anions (I(-)) from water is devised: silver oxide (Ag2O) nanocrystals firmly anchored on the surface of titanate nanotubes and nanofibers via coherent interfaces between Ag2O and titanate phases. I(-) anions in fluids can easily access the Ag2O nanocrystals and be efficiently trapped by forming AgI precipitate that firmly attaches to the adsorbent. Due to their one-dimensional morphology, the new adsorbents can be readily dispersed in liquids and easily separated after purification; and the adsorption beds loaded with the adsorbents can permit high flux. This significantly enhances the adsorption efficiency and reduces the separation costs. The proposed structure reveals a new direction in developing efficient adsorbents for the removal of radioactive anions from wastewater.

Optical trapping for analytical biotechnology.

PubMed

Ashok, Praveen C; Dholakia, Kishan

2012-02-01

We describe the exciting advances of using optical trapping in the field of analytical biotechnology. This technique has opened up opportunities to manipulate biological particles at the single cell or even at subcellular levels which has allowed an insight into the physical and chemical mechanisms of many biological processes. The ability of this technique to manipulate microparticles and measure pico-Newton forces has found several applications such as understanding the dynamics of biological macromolecules, cell-cell interactions and the micro-rheology of both cells and fluids. Furthermore we may probe and analyse the biological world when combining trapping with analytical techniques such as Raman spectroscopy and imaging. Copyright © 2011 Elsevier Ltd. All rights reserved.

Optical coupling of cold atoms to a levitated nanosphere

NASA Astrophysics Data System (ADS)

Montoya, Cris; Witherspoon, Apryl; Fausett, Jacob; Lim, Jason; Kitching, John; Geraci, Andrew

2017-04-01

Cooling mechanical oscillators to their quantum ground state enables the study of quantum phenomena at macroscopic levels. In many cases, the temperature required to cool a mechanical mode to the ground state is below what current cryogenic systems can achieve. As an alternative to cooling via cryogenic systems, it has been shown theoretically that optically trapped nanospheres could reach the ground state by sympathetically cooling the spheres via cold atoms. Such cooled spheres can be used in quantum limited sensing and matter-wave interferometry, and could also enable new hybrid quantum systems where mechanical oscillators act as transducers. In our setup, optical fields are used to couple a sample of cold Rubidium atoms to a nanosphere. The sphere is optically levitated in a separate vacuum chamber, while the atoms are trapped in a 1-D optical lattice and cooled using optical molasses. This work is partially supported by NSF, Grant No. PHY-1506431.

Optical patterning of trapped charge in nitrogen-doped diamond

NASA Astrophysics Data System (ADS)

Dhomkar, Siddharth; Jayakumar, Harishankar; Pagliero, Daniela; Laraoui, Abdelghani; Albu, Remus; Manson, Neil; Doherty, Marcus; Henshaw, Jacob; Meriles, Carlos

The nitrogen-vacancy (NV) center in diamond is emerging as a promising platform for solid-state quantum information processing and nanoscale metrology. Of interest in these applications is the manipulation of the NV charge state, which can be attained by optical illumination. Here we use two-color optical microscopy to investigate the dynamics of NV photo-ionization, charge diffusion, and trapping in type-1b diamond. We combine fixed-point laser excitation and scanning fluorescence imaging to locally alter the concentration of negatively charged NVs and to subsequently probe the corresponding redistribution of charge. We uncover the formation of various spatial patterns of trapped charge, which we semi-quantitatively reproduce via a model of the interplay between photo-excited carriers and atomic defects in the diamond lattice. Further, by using the NV as a local probe, we map the relative fraction of positively charged nitrogen upon localized optical excitation. These observations may prove important to various technologies, including the transport of quantum information between remote NVs and the development of three-dimensional, charge-based memories. We acknowledge support from the National Science Foundation through Grant NSF-1314205.

Optical manipulation and catalytic activity enhanced by surface plasmon effect

NASA Astrophysics Data System (ADS)

Zou, Ningmu; Min, Jiang; Jiao, Wenxiang; Wang, Guanghui

2017-02-01

For optical manipulation, a nano-optical conveyor belt consisting of an array of gold plasmonic non-concentric nano-rings (PNNRs) is demonstrated for the realization of trapping and unidirectional transportation of nanoparticles by polarization rotation of excitation beam. These hot spots of an asymmetric plasmonic nanostructure are polarization dependent, therefore, one can use the incident polarization state to manipulate the trapped targets. Trapped particles could be transferred between adjacent PNNRs in a given direction just by rotating the polarization of incident beam due to unbalanced potential. The angular dependent distribution of electric field around PNNR has been solved using the three- dimensional finite-difference time-domain (FDTD) technique. For optical enhanced catalytic activity, the spectral properties of dimers of Au nanorod-Au nanorod nanostructures under the excitation of 532nm photons have been investigated. With a super-resolution catalytic mapping technique, we identified the existence of "hot spot" in terms of catalytic reactivity at the gap region within the twined plasmonic nanostructure. Also, FDTD calculation has revealed an intrinsic correlation between hot electron transfer.

Optical Manipulation of Single Magnetic Beads in a Microwell Array on a Digital Microfluidic Chip.

PubMed

Decrop, Deborah; Brans, Toon; Gijsenbergh, Pieter; Lu, Jiadi; Spasic, Dragana; Kokalj, Tadej; Beunis, Filip; Goos, Peter; Puers, Robert; Lammertyn, Jeroen

2016-09-06

The detection of single molecules in magnetic microbead microwell array formats revolutionized the development of digital bioassays. However, retrieval of individual magnetic beads from these arrays has not been realized until now despite having great potential for studying captured targets at the individual level. In this paper, optical tweezers were implemented on a digital microfluidic platform for accurate manipulation of single magnetic beads seeded in a microwell array. Successful optical trapping of magnetic beads was found to be dependent on Brownian motion of the beads, suggesting a 99% chance of trapping a vibrating bead. A tailor-made experimental design was used to screen the effect of bead type, ionic buffer strength, surfactant type, and concentration on the Brownian activity of beads in microwells. With the optimal conditions, the manipulation of magnetic beads was demonstrated by their trapping, retrieving, transporting, and repositioning to a desired microwell on the array. The presented platform combines the strengths of digital microfluidics, digital bioassays, and optical tweezers, resulting in a powerful dynamic microwell array system for single molecule and single cell studies.

Escherichia coli Fiber Sensors Using Concentrated Dielectrophoretic Force with Optical Defocusing Method.

PubMed

Tai, Yi-Hsin; Lee, Chia-Wei; Chang, Dao-Ming; Lai, Yu-Sheng; Huang, Ding-Wei; Wei, Pei-Kuen

2018-05-25

A sensitive tapered optical fiber tip combined with dielectrophoretic (DEP) trapping was used for rapid and label-free detection of bacteria in water. The angular spectrum of the optical field at the fiber tip was changed with the surrounding refractive index (RI). By measuring far-field intensity change at the defocus plane, the intensity sensitivity was up to 95 200%/RIU (RI unit), and the detection limit was 5.2 × 10 -6 RIU at 0.5% intensity stability. By applying an AC voltage to a Ti/Al coated fiber tip and an indium-tin-oxide glass, the DEP force effectively trapped the Escherichia coli ( E. coli) near the fiber tip. Those bacteria can be directly measured from optical intensity change due to the increase of surrounding RI. By immobilizing the antibody on the Ti/Al fiber tip, the tests for specific K12 bacteria and nonspecific BL21 bacteria verified the specificity. The antibody-immobilized Ti/Al coated fiber tip with DEP trapping can detect bacteria at a concentration about 100 CFU/mL.

Coherence Preservation of a Single Neutral Atom Qubit Transferred between Magic-Intensity Optical Traps.

PubMed

Yang, Jiaheng; He, Xiaodong; Guo, Ruijun; Xu, Peng; Wang, Kunpeng; Sheng, Cheng; Liu, Min; Wang, Jin; Derevianko, Andrei; Zhan, Mingsheng

2016-09-16

We demonstrate that the coherence of a single mobile atomic qubit can be well preserved during a transfer process among different optical dipole traps (ODTs). This is a prerequisite step in realizing a large-scale neutral atom quantum information processing platform. A qubit encoded in the hyperfine manifold of an ^{87}Rb atom is dynamically extracted from the static quantum register by an auxiliary moving ODT and reinserted into the static ODT. Previous experiments were limited by decoherences induced by the differential light shifts of qubit states. Here, we apply a magic-intensity trapping technique which mitigates the detrimental effects of light shifts and substantially enhances the coherence time to 225±21  ms. The experimentally demonstrated magic trapping technique relies on the previously neglected hyperpolarizability contribution to the light shifts, which makes the light shift dependence on the trapping laser intensity parabolic. Because of the parabolic dependence, at a certain "magic" intensity, the first order sensitivity to trapping light-intensity variations over ODT volume is eliminated. We experimentally demonstrate the utility of this approach and measure hyperpolarizability for the first time. Our results pave the way for constructing scalable quantum-computing architectures with single atoms trapped in an array of magic ODTs.

Optically detected, single nanoparticle mass spectrometer with pre-filtered electrospray nanoparticle source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Howder, Collin R.; Bell, David M.; Anderson, Scott L.

2014-01-15

An instrument designed for non-destructive mass analysis of single trapped nanoparticles is described. The heart of the instrument is a 3D quadrupole (Paul) trap constructed to give optical access to the trap center along ten directions, allowing passage of lasers for particle heating and detection, particle injection, collection of scattered or fluorescent photons for particle detection and mass analysis, and collection of particles on TEM grids for analysis, as needed. Nanoparticles are injected using an electrospray ionization (ESI) source, and conditions are described for spraying and trapping polymer particles, bare metal particles, and ligand stabilized particles with masses ranging frommore » 200 kDa to >3 GDa. Conditions appropriate to ESI and injection of different types of particles are described. The instrument is equipped with two ion guides separating the ESI source and nanoparticle trap. The first ion guide is mostly to allow desolvation and differential pumping before the particles enter the trap section of the instrument. The second is a linear quadrupole guide, which can be operated in mass selective or mass band-pass modes to limit transmission to species with mass-to-charge ratios in the range of interest. With a little experience, the design allows injection of single particles into the trap upon demand.« less

Direct Optical Measurement of Vorticity in Fluid Flow

DTIC Science & Technology

2015-12-11

was later employed to measure the angular velocity of a microparticle trapped and spinning in an optical trap [7]. II. Objectives We believe it...known theoretically. Two sets of experiments are presented. In the first, the signal from a group of 6 μm microparticles is integrated to obtain the...vorticity is known precisely. In one experiment measurements with a group of 6 μm microparticles is used to obtain the average fluid rotation rate about the

Sympathetic Cooling of Lattice Atoms by a Bose-Einstein Condensate

DTIC Science & Technology

2010-08-13

average out to zero net change in momentum. This type of cooling is the basis for techniques such as Zeeman slowing and Magneto - optical traps . On a...change in momentum. This type of cooling is the basis for techniques such as Zeeman slowing and Magneto - optical traps . On a more basic level, an excited...cause stimulated emission of a second excitation. A quantitative explanation requires the use of the density fluctuation operator . This operator

Fundamentals of negative refractive index optical trapping: forces and radiation pressures exerted by focused Gaussian beams using the generalized Lorenz-Mie theory

PubMed Central

Ambrosio, Leonardo A.; Hernández-Figueroa, Hugo E.

2010-01-01

Based on the generalized Lorenz-Mie theory (GLMT), this paper reveals, for the first time in the literature, the principal characteristics of the optical forces and radiation pressure cross-sections exerted on homogeneous, linear, isotropic and spherical hypothetical negative refractive index (NRI) particles under the influence of focused Gaussian beams in the Mie regime. Starting with ray optics considerations, the analysis is then extended through calculating the Mie coefficients and the beam-shape coefficients for incident focused Gaussian beams. Results reveal new and interesting trapping properties which are not observed for commonly positive refractive index particles and, in this way, new potential applications in biomedical optics can be devised. PMID:21258549

Fundamentals of negative refractive index optical trapping: forces and radiation pressures exerted by focused Gaussian beams using the generalized Lorenz-Mie theory.

PubMed

Ambrosio, Leonardo A; Hernández-Figueroa, Hugo E

2010-11-04

Based on the generalized Lorenz-Mie theory (GLMT), this paper reveals, for the first time in the literature, the principal characteristics of the optical forces and radiation pressure cross-sections exerted on homogeneous, linear, isotropic and spherical hypothetical negative refractive index (NRI) particles under the influence of focused Gaussian beams in the Mie regime. Starting with ray optics considerations, the analysis is then extended through calculating the Mie coefficients and the beam-shape coefficients for incident focused Gaussian beams. Results reveal new and interesting trapping properties which are not observed for commonly positive refractive index particles and, in this way, new potential applications in biomedical optics can be devised.

Moiré deflectometry-based position detection for optical tweezers.

PubMed

Khorshad, Ali Akbar; Reihani, S Nader S; Tavassoly, Mohammad Taghi

2017-09-01

Optical tweezers have proven to be indispensable tools for pico-Newton range force spectroscopy. A quadrant photodiode (QPD) positioned at the back focal plane of an optical tweezers' condenser is commonly used for locating the trapped object. In this Letter, for the first time, to the best of our knowledge, we introduce a moiré pattern-based detection method for optical tweezers. We show, both theoretically and experimentally, that this detection method could provide considerably better position sensitivity compared to the commonly used detection systems. For instance, position sensitivity for a trapped 2.17 μm polystyrene bead is shown to be 71% better than the commonly used QPD-based detection method. Our theoretical and experimental results are in good agreement.

Building one molecule from a reservoir of two atoms.

PubMed

Liu, L R; Hood, J D; Yu, Y; Zhang, J T; Hutzler, N R; Rosenband, T; Ni, K-K

2018-05-25

Chemical reactions typically proceed via stochastic encounters between reactants. Going beyond this paradigm, we combined exactly two atoms in a single, controlled reaction. The experimental apparatus traps two individual laser-cooled atoms [one sodium (Na) and one cesium (Cs)] in separate optical tweezers and then merges them into one optical dipole trap. Subsequently, photoassociation forms an excited-state NaCs molecule. The discovery of previously unseen resonances near the molecular dissociation threshold and measurement of collision rates are enabled by the tightly trapped ultracold sample of atoms. As laser-cooling and trapping capabilities are extended to more elements, the technique will enable the study of more diverse, and eventually more complex, molecules in an isolated environment, as well as synthesis of designer molecules for qubits. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Finding trap stiffness of optical tweezers using digital filters.

PubMed

Almendarez-Rangel, Pedro; Morales-Cruzado, Beatriz; Sarmiento-Gómez, Erick; Pérez-Gutiérrez, Francisco G

2018-02-01

Obtaining trap stiffness and calibration of the position detection system is the basis of a force measurement using optical tweezers. Both calibration quantities can be calculated using several experimental methods available in the literature. In most cases, stiffness determination and detection system calibration are performed separately, often requiring procedures in very different conditions, and thus confidence of calibration methods is not assured due to possible changes in the environment. In this work, a new method to simultaneously obtain both the detection system calibration and trap stiffness is presented. The method is based on the calculation of the power spectral density of positions through digital filters to obtain the harmonic contributions of the position signal. This method has the advantage of calculating both trap stiffness and photodetector calibration factor from the same dataset in situ. It also provides a direct method to avoid unwanted frequencies that could greatly affect calibration procedure, such as electric noise, for example.

Stable switching among high-order modes in polariton condensates

NASA Astrophysics Data System (ADS)

Sun, Yongbao; Yoon, Yoseob; Khan, Saeed; Ge, Li; Steger, Mark; Pfeiffer, Loren N.; West, Ken; Türeci, Hakan E.; Snoke, David W.; Nelson, Keith A.

2018-01-01

We report multistate optical switching among high-order bouncing-ball modes ("ripples") and whispering-gallery modes ("petals") of exciton-polariton condensates in a laser-generated annular trap. By tailoring the diameter and power of the annular trap, the polariton condensate can be switched among different trapped modes, accompanied by redistribution of spatial densities and superlinear increase in the emission intensities, implying that polariton condensates in this geometry could be exploited for an all-optical multistate switch. A model based on non-Hermitian modes of the generalized Gross-Pitaevskii equation reveals that this mode switching arises from competition between pump-induced gain and in-plane polariton loss. The parameters for reproducible switching among trapped modes have been measured experimentally, giving us a phase diagram for mode switching. Taken together, the experimental result and theoretical modeling advance our fundamental understanding of the spontaneous emergence of coherence and move us toward its practical exploitation.

Charge Transport and the Nature of Traps in Oxygen Deficient Tantalum Oxide.

PubMed

Gritsenko, Vladimir A; Perevalov, Timofey V; Voronkovskii, Vitalii A; Gismatulin, Andrei A; Kruchinin, Vladimir N; Aliev, Vladimir Sh; Pustovarov, Vladimir A; Prosvirin, Igor P; Roizin, Yakov

2018-01-31

Optical and transport properties of nonstoichiometric tantalum oxide thin films grown by ion beam deposition were investigated in order to understand the dominant charge transport mechanisms and reveal the nature of traps. The TaO x films composition was analyzed by X-ray photoelectron spectroscopy and by quantum-chemistry simulation. From the optical absorption and photoluminescence measurements and density functional theory simulations, it was concluded that the 2.75 eV blue luminescence excited in a TaO x by 4.45 eV photons, originates from oxygen vacancies. These vacancies are also responsible for TaO x conductivity. The thermal trap energy of 0.85 eV determined from the transport experiments coincides with the half of the Stokes shift of the blue luminescence band. It is argued that the dominant charge transport mechanism in TaO x films is phonon-assisted tunneling between the traps.

Combining optical trapping in a microfluidic channel with simultaneous micro-Raman spectroscopy and motion detection

NASA Astrophysics Data System (ADS)

Lawton, Penelope F.; Saunter, Christopher D.; Girkin, John M.

2014-03-01

Since their invention by Ashkin optical tweezers have demonstrated their ability and versatility as a non-invasive tool for micromanipulation. One of the most useful additions to the basic optical tweezers system is micro-Raman spectroscopy, which permits highly sensitive analysis of single cells or particles. We report on the development of a dual laser system combining two spatial light modulators to holographically manipulate multiple traps (at 1064nm) whilst undertaking Raman spectroscopy using a 532nm laser. We can thus simultaneously trap multiple particles and record their Raman spectra, without perturbing the trapping system. The dual beam system is built around micro-fluidic channels where crystallisation of calcium carbonate occurs on polymethylmethacrylate (PMMA) beads. The setup is designed to simulate at a microscopic level the reactions that occur on items in a dishwasher, where permanent filming of calcium carbonate on drinking glasses is a problem. Our system allows us to monitor crystal growth on trapped particles in which the Raman spectrum and changes in movement of the bead are recorded. Due to the expected low level of crystallisation on the bead surfaces this allows us to obtain results quickly and with high sensitivity. The long term goal is to study the development of filming on samples in-situ with the microfl.uidic system acting as a model dishwasher.

Ion cyclotron resonance cell

DOEpatents

Weller, Robert R.

1995-01-01

An ion cyclotron resonance cell having two adjacent sections separated by a center trapping plate. The first section is defined by the center trapping plate, a first end trapping plate, and excitation and detector electrodes. The second section includes a second end trapping plate spaced apart from the center plate, a mirror, and an analyzer. The analyzer includes a wavelength-selective light detector, such as a detector incorporating an acousto-optical device (AOD) and a photodetector. One or more ion guides, grounded plates with holes for the ion beam, are positioned within the vacuum chamber of the mass spectrometer between the ion source and the cell. After ions are trapped and analyzed by ion cyclotron resonance techniques in the first section, the ions of interest are selected according to their mass and passed into the second section for optical spectroscopic studies. The trapped ions are excited by light from a laser and caused thereby to fluoresce. The fluorescent light emitted by the excited ions is reflected by the mirror and directed onto the detector. The AOD is scanned, and the photodetector output is recorded and analyzed. The ions remain in the second section for an extended period, enabling multiple studies to be carried out on the same ensemble of ions.

High-resolution detection of Brownian motion for quantitative optical tweezers experiments.

PubMed

Grimm, Matthias; Franosch, Thomas; Jeney, Sylvia

2012-08-01

We have developed an in situ method to calibrate optical tweezers experiments and simultaneously measure the size of the trapped particle or the viscosity of the surrounding fluid. The positional fluctuations of the trapped particle are recorded with a high-bandwidth photodetector. We compute the mean-square displacement, as well as the velocity autocorrelation function of the sphere, and compare it to the theory of Brownian motion including hydrodynamic memory effects. A careful measurement and analysis of the time scales characterizing the dynamics of the harmonically bound sphere fluctuating in a viscous medium directly yields all relevant parameters. Finally, we test the method for different optical trap strengths, with different bead sizes and in different fluids, and we find excellent agreement with the values provided by the manufacturers. The proposed approach overcomes the most commonly encountered limitations in precision when analyzing the power spectrum of position fluctuations in the region around the corner frequency. These low frequencies are usually prone to errors due to drift, limitations in the detection, and trap linearity as well as short acquisition times resulting in poor statistics. Furthermore, the strategy can be generalized to Brownian motion in more complex environments, provided the adequate theories are available.

Long range magnetic ordering of ultracold fermions in an optical lattice

NASA Astrophysics Data System (ADS)

Duarte, P. M.; Hart, R. A.; Yang, T.-L.; Hulet, R. G.

2013-05-01

We present progress towards the observation of long range antiferromagnetic (AFM) ordering of fermionic 6Li atoms in an optical lattice. We prepare a two spin state mixture of 106 atoms at T /TF = 0 . 1 by evaporatively cooling in an optical dipole trap. The sample is then transferred to a dimple trap formed by three retroreflected laser beams at 1064 nm that propagate in orthogonal directions. The polarization of the retroreflected light is controlled using liquid crystal retarders, which allow us to adiabatically transform the dimple trap into a 3D lattice. Overlapped with each of the three dimple/lattice beams is a beam at 532 nm, which can cancel the harmonic confinement and flatten the band structure in the lattice. This setup offers the possibility of implementing proposed schemes which enlarge the size of the AFM phase in the trap. As a probe for AFM we use Bragg scattering of light. We have observed Bragg scattering off of the (100) lattice planes, and using an off-angle probe we can see the diffuse scattering from the sample which serves as background for the small signals expected before the onset of AFM ordering. Supported by NSF, ONR, DARPA, and the Welch Foundation.

Single molecule RNA folding studied with optical trapping

NASA Astrophysics Data System (ADS)

Vieregg, Jeffrey Robert

The RNA folding problem (predicting the equilibrium structure and folding pathway of an RNA molecule from its sequence) is one of the classic problems of biophysics. Recent discoveries of many new functions for RNA have increased its importance, and new instrumental techniques have provided new ways to characterize molecular behavior. In particular, optical trapping (optical tweezers) allows controlled mechanical force to be applied to single RNA molecules while their end-to-end extension is monitored in real time. This enables characterization of RNA folding dynamics at a level unreachable by traditional bulk methods. Furthermore, recent advances in statistical mechanics make it possible to recover equilibrium quantities such as free energy from reactions which occur away from equilibrium. This dissertation describes the application of optical trapping and non-equilibrium statistical mechanics to quantitatively characterize folding of RNA secondary structures. By measuring the folding free energy of several specially designed hairpins in solutions containing various amounts of sodium and potassium, we were able to determine that RNA secondary structure thermodynamics depends not only on monovalent cation concentration but also surprisingly, on species. We also investigated the temperature dependence of hairpin folding thermodynamics and kinetics, which provided a direct measurement of enthalpy and entropy for RNA folding at physiological temperatures. We found that the folding pathway was quite sensitive to both salt and temperature, as measured by the folding success rate of a biologically important hairpin from the HIV-1 viral genome. Finally, I discuss modeling of force-induced RNA folding and unfolding, as well as a series of efforts which have dramatically improved the performance of our optical trapping instrument.

Elegant Gaussian beams for enhanced optical manipulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alpmann, Christina, E-mail: c.alpmann@uni-muenster.de; Schöler, Christoph; Denz, Cornelia

2015-06-15

Generation of micro- and nanostructured complex light beams attains increasing impact in photonics and laser applications. In this contribution, we demonstrate the implementation and experimental realization of the relatively unknown, but highly versatile class of complex-valued Elegant Hermite- and Laguerre-Gaussian beams. These beams create higher trapping forces compared to standard Gaussian light fields due to their propagation changing properties. We demonstrate optical trapping and alignment of complex functional particles as nanocontainers with standard and Elegant Gaussian light beams. Elegant Gaussian beams will inspire manifold applications in optical manipulation, direct laser writing, or microscopy, where the design of the point-spread functionmore » is relevant.« less

Strain-assisted optomechanical coupling of polariton condensate spin to a micromechanical resonator

NASA Astrophysics Data System (ADS)

Be'er, O.; Ohadi, H.; del Valle-Inclan Redondo, Y.; Ramsay, A. J.; Tsintzos, S. I.; Hatzopoulos, Z.; Savvidis, P. G.; Baumberg, J. J.

2017-12-01

We report spin and intensity coupling of an exciton-polariton condensate to the mechanical vibrations of a circular membrane microcavity. We optically drive the microcavity resonator at the lowest mechanical resonance frequency while creating an optically trapped spin-polarized polariton condensate in different locations on the microcavity and observe spin and intensity oscillations of the condensate at the vibration frequency of the resonator. Spin oscillations are induced by vibrational strain driving, whilst the modulation of the optical trap due to the displacement of the membrane causes intensity oscillations in the condensate emission. Our results demonstrate spin-phonon coupling in a macroscopically coherent condensate.

Cold atoms as a coolant for levitated optomechanical systems

NASA Astrophysics Data System (ADS)

Ranjit, Gambhir; Montoya, Cris; Geraci, Andrew A.

2015-01-01

Optically trapped dielectric objects are well suited for reaching the quantum regime of their center-of-mass motion in an ultrahigh-vacuum environment. We show that ground-state cooling of an optically trapped nanosphere is achievable when starting at room temperature, by sympathetic cooling of a cold-atomic gas optically coupled to the nanoparticle. Unlike cavity cooling in the resolved-sideband limit, this system requires only a modest cavity finesse and it allows the cooling to be turned off, permitting subsequent observation of strongly coupled dynamics between the atoms and sphere. Nanospheres cooled to their quantum ground state could have applications in quantum information science or in precision sensing.

An ultra-fast EOD-based force-clamp detects rapid biomechanical transitions

NASA Astrophysics Data System (ADS)

Woody, Michael S.; Capitanio, Marco; Ostap, E. Michael; Goldman, Yale E.

2017-08-01

We assembled an ultra-fast infrared optical trapping system to detect mechanical events that occur less than a millisecond after a ligand binds to its filamentous substrate, such as myosin undergoing its 5 - 10 nm working stroke after actin binding. The instrument is based on the concept of Capitanio et al.1, in which a polymer bead-actin-bead dumbbell is held in two force-clamped optical traps. A force applied by the traps causes the filament to move at a constant velocity as hydrodynamic drag balances the applied load. When the ligand binds, the filament motion stops within 100 μs as the total force from the optical traps is transferred to the attachment. Subsequent translations signal active motions, such as the magnitude and timing of the motor's working stroke. In our instrument, the beads defining the dumbbell are held in independent force clamps utilizing a field-programmable gate array (FPGA) to update the trap beam positions at 250 kHz. We found that in our setup, acousto-optical deflectors (AODs) steering the beams were unsuitable for this purpose due to a slightly non-linear response in the beam intensity and deflection angle vs. the AOD ultra-sound wavelength, likely caused by low-amplitude standing acoustic waves in the deflectors. These aberrations caused instability in the force feedback loops leading to artefactual 20 nm jumps in position. This type of AOD non-linearity has been reported to be absent in electro-optical deflectors (EODs)2. We demonstrate that replacement of the AODs with EODs improves the performance of our instrument. Combining the superior beam-steering capability of the EODs, force acquisition via back-plane interferometry, and the dual high-speed FPGA-based feedback loops, we smoothly and precisely apply constant loads to study the dynamics of interactions between biological molecules such as actin and myosin.

The REX-ISOLDE charge breeder as an operational machine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wenander, F.; Delahaye, P.; Scrivens, R.

2006-03-15

The charge breeding system of radioactive beam experiment at ISOLDE (REX-ISOLDE), consisting of a large Penning trap in combination with an electron-beam ion source (EBIS), is now a mature concept after having delivered radioactive beams for postacceleration to a number of experiments for three years. The system, preparing ions prior to injection into a compact linear accelerator, has shown to be versatile in terms of the ion species and energies that can be delivered. During the experimental periods 2004 and 2005 a significant part of the ISOLDE beam time was dedicated to REX-ISOLDE experiments. Ion masses in the range betweenmore » A=7 and 153 have been handled with record efficiencies. High-intensity as well as very-short-lived isotope beams were proven to be feasible. Continuous injection into the EBIS has also been successfully tested. Two means of suppressing unwanted beam contaminations were tested and are now in use. In addition, the experience gained from the trap-EBIS concept from a machine operational point of view will be discussed and the limitations described.« less

Utilization of Plasmonic and Photonic Crystal Nanostructures for Enhanced Micro- and Nanoparticle Manipulation

PubMed Central

Simmons, Cameron S.; Knouf, Emily Christine; Tewari, Muneesh; Lin, Lih Y.

2011-01-01

A method to manipulate the position and orientation of submicron particles nondestructively would be an incredibly useful tool for basic biological research. Perhaps the most widely used physical force to achieve noninvasive manipulation of small particles has been dielectrophoresis(DEP).1 However, DEP on its own lacks the versatility and precision that are desired when manipulating cells since it is traditionally done with stationary electrodes. Optical tweezers, which utilize a three dimensional electromagnetic field gradient to exert forces on small particles, achieve this desired versatility and precision.2 However, a major drawback of this approach is the high radiation intensity required to achieve the necessary force to trap a particle which can damage biological samples.3 A solution that allows trapping and sorting with lower optical intensities are optoelectronic tweezers (OET) but OET's have limitations with fine manipulation of small particles; being DEP-based technology also puts constraint on the property of the solution.4,5 This video article will describe two methods that decrease the intensity of the radiation needed for optical manipulation of living cells and also describe a method for orientation control. The first method is plasmonic tweezers which use a random gold nanoparticle (AuNP) array as a substrate for the sample as shown in Figure 1. The AuNP array converts the incident photons into localized surface plasmons (LSP) which consist of resonant dipole moments that radiate and generate a patterned radiation field with a large gradient in the cell solution. Initial work on surface plasmon enhanced trapping by Righini et al and our own modeling have shown the fields generated by the plasmonic substrate reduce the initial intensity required by enhancing the gradient field that traps the particle.6,7,8 The plasmonic approach allows for fine orientation control of ellipsoidal particles and cells with low optical intensities because of more efficient optical energy conversion into mechanical energy and a dipole-dependent radiation field. These fields are shown in figure 2 and the low trapping intensities are detailed in figures 4 and 5. The main problems with plasmonic tweezers are that the LSP's generate a considerable amount of heat and the trapping is only two dimensional. This heat generates convective flows and thermophoresis which can be powerful enough to expel submicron particles from the trap.9,10 The second approach that we will describe is utilizing periodic dielectric nanostructures to scatter incident light very efficiently into diffraction modes, as shown in figure 6.11 Ideally, one would make this structure out of a dielectric material to avoid the same heating problems experienced with the plasmonic tweezers but in our approach an aluminum-coated diffraction grating is used as a one-dimensional periodic dielectric nanostructure. Although it is not a semiconductor, it did not experience significant heating and effectively trapped small particles with low trapping intensities, as shown in figure 7. Alignment of particles with the grating substrate conceptually validates the proposition that a 2-D photonic crystal could allow precise rotation of non-spherical micron sized particles.10 The efficiencies of these optical traps are increased due to the enhanced fields produced by the nanostructures described in this paper. PMID:21988841

Optical scanning apparatus

DOEpatents

Villarreal, R.A.

1985-11-06

An optical scanner employed in a radioactive environment for reading indicia imprinted about a cylindrical surface of an article by means of an optical system including metallic reflective and mirror surfaces resistant to degradation and discoloration otherwise imparted to glass surfaces exposed to radiation is described.

Acoustical and optical radiation pressure and the development of single beam acoustical tweezers

NASA Astrophysics Data System (ADS)

Thomas, Jean-Louis; Marchiano, Régis; Baresch, Diego

2017-07-01

Studies on radiation pressure in acoustics and optics have enriched one another and have a long common history. Acoustic radiation pressure is used for metrology, levitation, particle trapping and actuation. However, the dexterity and selectivity of single-beam optical tweezers are still to be matched with acoustical devices. Optical tweezers can trap, move and position micron size particles, biological samples or even atoms with subnanometer accuracy in three dimensions. One limitation of optical tweezers is the weak force that can be applied without thermal damage due to optical absorption. Acoustical tweezers overcome this limitation since the radiation pressure scales as the field intensity divided by the speed of propagation of the wave. However, the feasibility of single beam acoustical tweezers was demonstrated only recently. In this paper, we propose a historical review of the strong similarities but also the specificities of acoustical and optical radiation pressures, from the expression of the force to the development of single-beam acoustical tweezers.

Cold Atom Source Containing Multiple Magneto-Optical Traps

NASA Technical Reports Server (NTRS)

Ramirez-Serrano, Jaime; Kohel, James; Kellogg, James; Lim, Lawrence; Yu, Nan; Maleki, Lute

2007-01-01

An apparatus that serves as a source of a cold beam of atoms contains multiple two-dimensional (2D) magneto-optical traps (MOTs). (Cold beams of atoms are used in atomic clocks and in diverse scientific experiments and applications.) The multiple-2D-MOT design of this cold atom source stands in contrast to single-2D-MOT designs of prior cold atom sources of the same type. The advantages afforded by the present design are that this apparatus is smaller than prior designs.

Normal and system lupus erythematosus red blood cell interactions studied by double trap optical tweezers: direct measurements of aggregation forces

NASA Astrophysics Data System (ADS)

Khokhlova, Maria D.; Lyubin, Eugeny V.; Zhdanov, Alexander G.; Rykova, Sophia Yu.; Sokolova, Irina A.; Fedyanin, Andrey A.

2012-02-01

Direct measurements of aggregation forces in piconewton range between two red blood cells in pair rouleau are performed under physiological conditions using double trap optical tweezers. Aggregation and disaggregation properties of healthy and pathologic (system lupus erythematosis) blood samples are analyzed. Strong difference in aggregation speed and behavior is revealed using the offered method which is proposed to be a promising tool for SLE monitoring at single cell level.

Measurements of the force fields within an acoustic standing wave using holographic optical tweezers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bassindale, P. G.; Drinkwater, B. W.; Phillips, D. B.

2014-04-21

Direct measurement of the forces experienced by micro-spheres in an acoustic standing wave device have been obtained using calibrated optical traps generated with holographic optical tweezers. A micro-sphere, which is optically trapped in three dimensions, can be moved through the acoustic device to measure forces acting upon it. When the micro-sphere is subjected to acoustic forces, it's equilibrium position is displaced to a position where the acoustic forces and optical forces are balanced. Once the optical trapping stiffness has been calibrated, observation of this displacement enables a direct measurement of the forces acting upon the micro-sphere. The measured forces aremore » separated into a spatially oscillating component, attributed to the acoustic radiation force, and a constant force, attributed to fluid streaming. As the drive conditions of the acoustic device were varied, oscillating forces (>2.5 pN{sub pp}) and streaming forces (<0.2 pN) were measured. A 5 μm silica micro-sphere was used to characterise a 6.8 MHz standing wave, λ = 220 μm, to a spatial resolution limited by the uncertainty in the positioning of the micro-sphere (here to within 2 nm) and with a force resolution on the order of 10 fN. The results have application in the design and testing of acoustic manipulation devices.« less

EDITORIAL: Award for Patrick Gill

NASA Astrophysics Data System (ADS)

Hauptmann, Peter

2007-12-01

On behalf of the journal I would like to congratulate Professor Patrick Gill, a long-serving member of the Editorial Board for Measurement Science and Technology, who has been awarded the prestigious Institute of Physics Young medal and prize for world-leading contributions to optical frequency metrology. He is recognized as the UK leader in the quest for very accurate optical clocks. Professor Gill's work is concerned with the development of cold trapped ion systems as optical frequency standards with potential for future redefinition of the SI second, and the frequency metrology needed to relate optical and microwave standards to high accuracy. Interested readers may wish to read a short review of the wider state-of-the-art development of single cold trapped ion frequency standards, coupled with a more detailed account of results achieved at the National Physical Laboratory, written by Professor Gill and co-workers from NPL: ''Trapped ion optical frequency standards'' by P Gill, G P Barwood, H A Klein, G Huang, S A Webster, P J Blythe, K Hosaka, S N Lea and H S Margolis 2003 Meas. Sci. Technol. 14 (8) 1174-86 He was one of the very early developers of the frequency comb idea, and in 2004 he led an experiment where the femtosecond laser frequency comb measured the prototype optical clock frequency, based on a strontium-ion optical transition, with accuracy close to the capability of the best caesium microwave clocks. Once again I congratulate Professor Gill and wish him every success for his future work.

Monitoring xenon purity in the LUX detector with a mass spectrometry system

NASA Astrophysics Data System (ADS)

Balajthy, Jon; LUX Experiment Collaboration

2015-04-01

The LUX dark matter search experiment is a 350 kg two-phase liquid/gas xenon time projection chamber located at the 4850 ft level of the Sanford Underground Research Facility in Lead, SD. To monitor for radioactive impurities such as krypton and impurities which limit charge yield such as oxygen, LUX uses a xenon sampling system consisting of a mass spectrometer and a liquid nitrogen cold trap. The cold trap separates the gaseous impurities from a small sample of xenon and allows them to pass to the mass spectrometer for analysis. We report here on results from the LUX xenon sampling program. We also report on methods to enhance the sensitivity of the cold trap technique in preparation for the next-generation LUX-ZEPLIN experiment which will have even more stringent purity requirements.

Sources of error in determinations of carnitine and acylcarnitine in plasma.

PubMed

Fishlock, R C; Bieber, L L; Snoswell, A M

1984-02-01

Radioactive and nonradioactive L-carnitine and acyl-L-carnitine were used to evaluate the washing procedures used during the determination of free, total, short-chain, and long-chain acylcarnitine in human and sheep plasma. The volume of fluid trapped by the protein precipitated by perchloric acid is approximately 24% of the total fluid volume and thus contains 24% of free carnitine and short-chain acylcarnitine. Washing twice with distilled water removes about 25% of the long-chain acylcarnitine along with the trapped free carnitine and short-chain acylcarnitines. Washing the pellet twice with a 60 g/L solution of perchloric acid completely removes the trapped free carnitine and short-chain acylcarnitine but does not remove the bound long-chain acylcarnitines. Thus washing with perchloric acid is essential for accurate measurement of long-chain acylcarnitines in plasma samples.

Coupled microrings data buffer using fast light

NASA Astrophysics Data System (ADS)

Scheuer, Jacob; Shahriar, Selim

2013-03-01

We present a theoretical study of a trap-door optical buffer based on a coupled microrings add/drop filter (ADF) utilizing the white light cavity (WLC). The buffer "trap-door" can be opened and closed by tuning the resonances of the microrings comprising the ADF and trap/release optical pulses. We show that the WLC based ADF yields a maximally flat filter which exhibits superior performances in terms of bandwidth and flatness compared to previous design approaches. We also present a realistic, Silicon-over-Insulator based, design and performance analysis taking into consideration the realistic properties and limitations of the materials and the fabrication process, leading to delays exceeding 850ps for 80GHz bandwidth, and a corresponding delay-bandwidth product of approximately 70.

“Ultra-high resolution optical trap with single fluorophore sensitivity”

PubMed Central

Comstock, Matthew J; Ha, Taekjip; Chemla, Yann R

2013-01-01

We present a single-molecule instrument that combines a timeshared ultra-high resolution dual optical trap interlaced with a confocal fluorescence microscope. In a demonstration experiment, individual single-fluorophore labeled DNA oligonucleotides were observed to bind and unbind to complementary DNA suspended between two trapped beads. Simultaneous with the single-fluorophore detection, coincident angstrom-scale changes in tether extension could be clearly observed. Fluorescence readout allowed us to determine the duplex melting rate as a function of force. The new instrument will enable the simultaneous measurement of angstrom-scale mechanical motion of individual DNA-binding proteins (e.g., single base pair stepping of DNA translocases) along with the detection of fluorescently labeled protein properties (e.g., internal configuration). PMID:21336286

Coronagraphic and low-emissivity astronomical reflector (CLEAR): heat trap design

NASA Astrophysics Data System (ADS)

Siegmund, Walter A.

1998-08-01

The heat trap in a coronagraphic telescope is located at its prime focus and blocks the transmission of radiation from unwanted portions of the solar disk to subsequent optics in the telescope. This reduces light scattered and heat absorbed by these optics. For observations of the corona, the solar disk is completely blocked, whereas for observations of the disk, typically 90% or more of the disk is blocked. The proposed heat trap design is constructed largely of fused silica plates, partially coated with platinum, and cooled with air. It is robust and handles high irradiance, i.e., almost f megawatt/m(superscript 2) at f/3.75, without degrading the image quality of the telescope or contributing significant stray light to the focal surface.

Effect of sputtering power on MgF2 thin films deposited by sputtering technique under fluorine trapping

NASA Astrophysics Data System (ADS)

De, Rajnarayan; Haque, S. Maidul; Tripathi, S.; Prathap, C.; Rao, K. Divakar; Sahoo, N. K.

2016-05-01

A non-conventional magnetron sputtering technique was explored to deposit magnesium fluoride thin films using the concept of fluorine gas trapping without the introduction of additional fluorine gas flow inside the chamber. The effect of magnetron power from 50 W to 250 W has been explored on structural, optical and physical properties of the samples. Polycrystalline nature with tetragonal crystallinity of the films has been confirmed by GIXRD measurements along with thickness dependency. Monotonic increase of attenuation coefficient (k) with RF power has been explained in terms of target compound dissociation probability. In conclusion, with fluorine trapping method, the samples deposited at lower RF powers (<100 W) are found to be more suitable for optical applications.

An optical apparatus for rotation and trapping

PubMed Central

Gutiérrez-Medina, Braulio; Andreasson, Johan O. L.; Greenleaf, William J.; LaPorta, Arthur; Block, Steven M.

2010-01-01

We present details of the design, construction and testing of a single-beam optical tweezers apparatus capable of measuring and exerting torque, as well as force, on microfabricated, optically anisotropic particles (an ‘optical torque wrench’). The control of angular orientation is achieved by rotating the linear polarization of a trapping laser with an electro-optic modulator (EOM), which affords improved performance over previous designs. The torque imparted to the trapped particle is assessed by measuring the difference between left- and right-circular components of the transmitted light, and constant torque is maintained by feeding this difference signal back into a custom-designed electronic servo loop. The limited angular range of the EOM (±180°) is extended by rapidly reversing the polarization once a threshold angle is reached, enabling the torque clamp to function over unlimited, continuous rotations at high bandwidth. In addition, we developed particles suitable for rotation in this apparatus using microfabrication techniques. Altogether, the system allows for the simultaneous application of forces (~0.1–100 pN) and torques (~1–10,000 pN nm) in the study of biomolecules. As a proof of principle, we demonstrate how our instrument can be used to study the supercoiling of single DNA molecules. PMID:20627165

Single Particle Differentiation through 2D Optical Fiber Trapping and Back-Scattered Signal Statistical Analysis: An Exploratory Approach

PubMed Central

Ribeiro, Rita S. R.; Cunha, João P. S.; Rosa, Carla C.; Jorge, Pedro A. S.

2018-01-01

Recent trends on microbiology point out the urge to develop optical micro-tools with multifunctionalities such as simultaneous manipulation and sensing. Considering that miniaturization has been recognized as one of the most important paradigms of emerging sensing biotechnologies, optical fiber tools, including Optical Fiber Tweezers (OFTs), are suitable candidates for developing multifunctional small sensors for Medicine and Biology. OFTs are flexible and versatile optotools based on fibers with one extremity patterned to form a micro-lens. These are able to focus laser beams and exert forces onto microparticles strong enough (piconewtons) to trap and manipulate them. In this paper, through an exploratory analysis of a 45 features set, including time and frequency-domain parameters of the back-scattered signal of particles trapped by a polymeric lens, we created a novel single feature able to differentiate synthetic particles (PMMA and Polystyrene) from living yeasts cells. This single statistical feature can be useful for the development of label-free hybrid optical fiber sensors with applications in infectious diseases detection or cells sorting. It can also contribute, by revealing the most significant information that can be extracted from the scattered signal, to the development of a simpler method for particles characterization (in terms of composition, heterogeneity degree) than existent technologies. PMID:29495502

Single Particle Differentiation through 2D Optical Fiber Trapping and Back-Scattered Signal Statistical Analysis: An Exploratory Approach.

PubMed

Paiva, Joana S; Ribeiro, Rita S R; Cunha, João P S; Rosa, Carla C; Jorge, Pedro A S

2018-02-27

Recent trends on microbiology point out the urge to develop optical micro-tools with multifunctionalities such as simultaneous manipulation and sensing. Considering that miniaturization has been recognized as one of the most important paradigms of emerging sensing biotechnologies, optical fiber tools, including Optical Fiber Tweezers (OFTs), are suitable candidates for developing multifunctional small sensors for Medicine and Biology. OFTs are flexible and versatile optotools based on fibers with one extremity patterned to form a micro-lens. These are able to focus laser beams and exert forces onto microparticles strong enough (piconewtons) to trap and manipulate them. In this paper, through an exploratory analysis of a 45 features set, including time and frequency-domain parameters of the back-scattered signal of particles trapped by a polymeric lens, we created a novel single feature able to differentiate synthetic particles (PMMA and Polystyrene) from living yeasts cells. This single statistical feature can be useful for the development of label-free hybrid optical fiber sensors with applications in infectious diseases detection or cells sorting. It can also contribute, by revealing the most significant information that can be extracted from the scattered signal, to the development of a simpler method for particles characterization (in terms of composition, heterogeneity degree) than existent technologies.