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

On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10(-21). It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410(-180)(+160)  Mpc corresponding to a redshift z=0.09(-0.04)(+0.03). In the source frame, the initial black hole masses are 36(-4)(+5)M⊙ and 29(-4)(+4)M⊙, and the final black hole mass is 62(-4)(+4)M⊙, with 3.0(-0.5)(+0.5)M⊙c(2) radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

/pdf/the-observation-of-gravitational-waves-from-a-binary-black-58srpupgg9.pdf

The Observation of Gravitational Waves from a Binary Black Hole Merger

With few exceptions biological tissues strongly scatter light, making high-resolution deep imaging impossible for traditional⎯including confocal⎯fluorescence microscopy. Nonlinear optical microscopy, in particular two photon–excited fluorescence microscopy, has overcome this limitation, providing large depth penetration mainly because even multiply scattered signal photons can be assigned to their origin as the result of localized nonlinear signal generation. Two-photon microscopy thus allows cellular imaging several hundred microns deep in various organs of living animals. Here we review fundamental concepts of nonlinear microscopy and discuss conditions relevant for achieving large imaging depths in intact tissue.

/pdf/deep-tissue-two-photon-microscopy-2aqu6d6n65.pdf

Deep tissue two-photon microscopy

Multiphoton microscopy (MPM) has found a niche in the world of biological imaging as the best noninvasive means of fluorescence microscopy in tissue explants and living animals. Coupled with transgenic mouse models of disease and 'smart' genetically encoded fluorescent indicators, its use is now increasing exponentially. Properly applied, it is capable of measuring calcium transients 500 microm deep in a mouse brain, or quantifying blood flow by imaging shadows of blood cells as they race through capillaries. With the multitude of possibilities afforded by variations of nonlinear optics and localized photochemistry, it is possible to image collagen fibrils directly within tissue through nonlinear scattering, or release caged compounds in sub-femtoliter volumes.

/pdf/nonlinear-magic-multiphoton-microscopy-in-the-biosciences-3fszv5aq8z.pdf

Nonlinear magic: multiphoton microscopy in the biosciences

Diarylethenes for Memories and Switches

In this paper, we report on near field optical tweezers using focused evanescent illumination. The intensity pattern of the focused evanescent field has been characterized using a SNOM. The near field trapping efficiency has been experimentally and theoretically investigated using both TEM 00 and TEM 01 beams. The trapping efficiency was found to be polarization dependent and also changed for the two modes of illumination used. By incorporating the near field and far field optical tweezers one could construct an optical micromanipulation setup with great flexibility and accuracy, which would find applications in optical nanometry. By coupling the techniques like morphology dependent resonance (MDR), one could employ near field tweezers for near field sensing and for characterization of microfluidic channels.

https://researchbank.swinburne.edu.au/file/57d9e8fc-97b8-4436-b689-4cfa1a7364a7/1/PDF (Published version).pdf

Near field optical tweezers

Observation of planar electromagnetic microcavity modes in woodpile-type void channel photonic crystal lattices

Optical pump-probe spectroscopy of single gold nanoparticles

The propagation of surface plasmon polaritons in graphene at a near infrared wavelength of 1.55 μm was demonstrated for the first time. Its application to nanofocusing has been studied numerically and experimentally.

Nanofocusing of the surface plasmon polaritons in graphene at near infrared frequencies

The effects of detector size and shape in the imaging properties of confocal microscopes are discussed The presence of stray light in the optical system, shot noise on the beam and detector performance limit the signal to noise ratio available The effects on the noise performance of the extended-focus (mean) and autofocus (peak) algorithms for forming image projections are presented Consideration of these various parameters allows the microscope user to obtain the best performance from his instrument for particular applications© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering Downloading of the abstract is permitted for personal use only

Min Gu

Papers

Near field optical tweezers

Observation of planar electromagnetic microcavity modes in woodpile-type void channel photonic crystal lattices

Optical pump-probe spectroscopy of single gold nanoparticles

Nanofocusing of the surface plasmon polaritons in graphene at near infrared frequencies

Signal strength and its effects on processing of confocal images