Optical tweezers use the forces exerted by a strongly focused beam of light to trap and move objects ranging in size from tens of nanometres to tens of micrometres. Since their introduction in 1986, the optical tweezer has become an important tool for research in the fields of biology, physical chemistry and soft condensed matter physics. Recent advances promise to take optical tweezers out of the laboratory and into the mainstream of manufacturing and diagnostics; they may even become consumer products. The next generation of single-beam optical traps offers revolutionary new opportunities for fundamental and applied research.

http://physics.nyu.edu/grierlab/nreview2c/nreview2c.pdf

A revolution in optical manipulation

Photonic crystal fibers guide light by corralling it within a periodic array of microscopic air holes that run along the entire fiber length Largely through their ability to overcome the limitations of conventional fiber optics—for example, by permitting low-loss guidance of light in a hollow core—these fibers are proving to have a multitude of important technological and scientific applications spanning many disciplines The result has been a renaissance of interest in optical fibers and their uses

https://science.sciencemag.org/content/sci/299/5605/358.full.pdf

Photonic crystal fibers

Bose-Einstein condensation (BEC) has been observed in a dilute gas of sodium atoms. A Bose-Einstein condensate consists of a macroscopic population of the ground state of the system, and is a coherent state of matter. In an ideal gas, this phase transition is purely quantum-statistical. The study of BEC in weakly interacting systems which can be controlled and observed with precision holds the promise of revealing new macroscopic quantum phenomena that can be understood from first principles.

Bose-Einstein condensation in a gas of sodium atoms

As they travel through space, some light beams rotate. Such light beams have angular momentum. There are two particularly important ways in which a light beam can rotate: if every polarization vector rotates, the light has spin; if the phase structure rotates, the light has orbital angular momentum (OAM), which can be many times greater than the spin. Only in the past 20 years has it been realized that beams carrying OAM, which have an optical vortex along the axis, can be easily made in the laboratory. These light beams are able to spin microscopic objects, give rise to rotational frequency shifts, create new forms of imaging systems, and behave within nonlinear material to give new insights into quantum optics.

/pdf/orbital-angular-momentum-origins-behavior-and-applications-1sv8qfuhrs.pdf

Orbital angular momentum: origins, behavior and applications

Internet data traffic capacity is rapidly reaching limits imposed by optical fiber nonlinear effects Having almost exhausted available degrees of freedom to orthogonally multiplex data, the possibility is now being explored of using spatial modes of fibers to enhance data capacity We demonstrate the viability of using the orbital angular momentum (OAM) of light to create orthogonal, spatially distinct streams of data-transmitting channels that are multiplexed in a single fiber Over 11 kilometers of a specially designed optical fiber that minimizes mode coupling, we achieved 400-gigabits-per-second data transmission using four angular momentum modes at a single wavelength, and 16 terabits per second using two OAM modes over 10 wavelengths These demonstrations suggest that OAM could provide an additional degree of freedom for data multiplexing in future fiber networks

http://science.sciencemag.org/content/sci/340/6140/1545.full.pdf

Terabit-Scale Orbital Angular Momentum Mode Division Multiplexing in Fibers

We demonstrate a single channel hydrodynamic stretching microfluidic device that relies
on high-speed imaging to allow repeated dynamic cell deformation measurements. Experiments on
prostate cancer cells suggest richer data than current approaches.

Microfluidics-based, time-resolved mechanical phenotyping of cells using high-speed imaging

This paper details progress towards the possibility of creating integrated optical devices capable of manipulating and analyzing airborne particles in the form of aerosols. We also describe work designed to look at the possibility of controlling optical cavities created using liquid aerosols using light.

Towards airborne optofluidics

We present a compact, diffuser-assisted, single-pixel computational camera. A rotating ground glass diffuser is adopted, in preference to a commonly used digital micro-mirror device (DMD), to encode a two-dimensional (2D) image into single-pixel signals. We retrieve images with an 8.8% sampling ratio after the calibration of the pseudo-random pattern of the diffuser under incoherent illumination. Furthermore, we demonstrate hyperspectral imaging with line array detection by adding a diffraction grating. The implementation results in a cost-effective single-pixel camera for high-dimensional imaging, with potential for imaging in non-visible wavebands.

Single-pixel diffuser camera

Bessel beams can be used as optical tweezers, to trap and manipulate small particles, including biological specimens. Here we demonstrate the use of such beams to trap and manipulate particles simultaneously that may reside in completely separate sample chambers, separated by distances that preclude trapping with a Gaussian beam. This also demonstrates another property of the Bessel beam, in that since it is a set of rings it can trap both low and high refractive index particles. The distance behind the particle that the Bessel beam reconstructs is dependent on the properties of the particle, and this may be useful in cell characterisation. We also demonstrate the generation of more complex patterns of nondiffracting light beams, by using interfering Bessel beams. We generate these by using a Mach-Zender interferometer in which each of the arms has a Laguerre-Gaussian beam of differing handedness.

Advanced micromanipulation using Bessel beams

Dual beam fiber traps are potentially useful for integrated trapping devices aimed at studying aerosols, and offer opportunities for cavity-enhanced traps. The alignment of such traps is typically seen to be critical. Here we explore the impact of the angular alignment of the optical fibers, and assess trapping viability as a function of misalignment and how particle dynamics change when interacting with displaced fibers. We find that good trapping capability for dual fibers tilted at the same angle, while more complex aerosol dynamics become apparent at higher single fiber tilt angles.

David McGloin

Papers

Microfluidics-based, time-resolved mechanical phenotyping of cells using high-speed imaging

Towards airborne optofluidics

Single-pixel diffuser camera

Advanced micromanipulation using Bessel beams

Dual beam optical fiber traps for aerosols with angular deviation