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

Rotating mirror systems based on the Miller Principle are a mainstay modality for ultra-high speed imaging within the range 1-25 million frames per second. Importantly, the true temporal accuracy of observations recorded in such cameras is sensitive to the framing rate that the system directly associates with each individual data acquisition. The purpose for the present investigation was to examine the validity of such system-reported frame rates in a widely used commercial system (a Cordin 550-62 model) by independently measuring the framing rate at the instant of triggering. Here, we found a small but significant difference between such measurements: the average discrepancy (over the entire spectrum of frame rates used) was found to be 0.66 ± 0.48%, with a maximum difference of 2.33%. The principal reason for this discrepancy was traced to non-optimized sampling of the mirror rotation rate within the system protocol. This paper thus serves three purposes: (i) we highlight a straightforward diagnostic approach to facilitate scrutiny of rotating-mirror system integrity; (ii) we raise awareness of the intrinsic errors associated with data previously acquired with this particular system and model; and (iii), we recommend that future control routines address the sampling issue by implementing real-time measurement at the instant of triggering.

On the accuracy of framing-rate measurements in ultra-high speed rotating mirror cameras.

A low velocity intense source (LVIS) of cold rubidium atoms is guided along a co-propagating far-off resonance light guide. An 8% enhancement of the guided atomic flux is observed in the steady state. Data are presented for the transient response of the LVIS to the guide beam observing a non-adiabatic kick and a transient 25% enhancement of the guided flux. A characteristic decay time of 0.45 s is recorded for the return to the steady state flux.

Transient response of a cold atomic beam in the presence of a far-off resonance light guide

We investigated the occurrence of small but significant inaccuracies in the temporal integrity of a commercial high-speed [rotating mirror] imaging system (a Cordin 550-62 camera). Utilizing a relatively straightforward hardware addition, independent measurements of the actual frame rate at the point of camera triggering were conducted, and then compared to the Cordin system’s self-reported frame rate values for each recording. The present data thus represents a follow-up to our earlier preliminary report on this instrument’s performance, where we initially discovered that disparities between the true and reported values could arise 1 . Interestingly, the data trends observed in the present report suggest a disparity, the nature of which is consistent with the Cordin camera reporting a frame rate that arises a short time before the trigger event, i.e. that the system’s sampling algorithm senses the frame rate with a finite pre-trigger implemented, which runs counter to the procedure suggested by the manufacturer. As well as presenting the context, and supporting evidence for our own conclusions, we also developed an approach to reduce the error in the reported values by a factor of 7, from an average of 0.78% +/- 0.04% to 0.11% +/- 0.08% over the present data set.

Role of mirror dynamics in determining the accuracy of framing rate in an ultra high speed rotating mirror camera

Turning living cells into miniature lasers offers new opportunities for cell labelling, tracking and sensing on a grand scale.

Biophotonics: Cellular lasers

A method for sorting/separating at least two different particles in a fluid, the method comprising defining within the fluid a static optical landscape/pattern having one or more optical wells or troughs that are substantially the same size or slightly larger than at least one of the particles. By exploiting differing particle responses to the same light pattern, separation/sorting can be done. This type of sorting may potentially be performed to separate particles that are of different sizes, shapes or refractive indices.

David McGloin

Papers

On the accuracy of framing-rate measurements in ultra-high speed rotating mirror cameras.

Transient response of a cold atomic beam in the presence of a far-off resonance light guide

Role of mirror dynamics in determining the accuracy of framing rate in an ultra high speed rotating mirror camera

Biophotonics: Cellular lasers

Particle sorting in a tailored landscape