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

C:WRPonbl\DCCOSPMM4747386_ LDOC-1511 /2012 A solar cell product including: a bulk semiconductor substrate having one or more solar cells formed therein; and nanoscale particles distributed over a surface of the solar cells to scatter sunlight forward into the solar cells and thereby enhance the efficiency of the solar cells. ~Cd C-o

Wafer-based solar cell

5. Summary Previous work on the generation of voids inside transparent material by ultrashort pulsed light has solely been from a data storage point of view, where only single void bits were generated. Here we have presented void channels inside a bulk polymer material and have used them in the application of two and three-dimensional photonic crystal structures. This work involved the characterisation of the response of a specific polymer material, NOA63 optical adhesive to a scanned femtosecond pulsed high repetition rate light beam. The size of individual void channels as well as the overall structure of woodpile type photonic crystals was controlled accurately. The high degree of perfection of these photonic crystals allowed for the observation of the fundamental as well as higher-order stop gaps. The benefits of fabricating photonic crystals based on void channels are numerous. Unlike other techniques the time to fabricate a structure is on the order of minutes. Polymer shrinkage has no effect and wash out or other chemical post etching is not required, unless higher dielectric contrasts for complete bandgaps are desired. In conclusion, this method is a fast, one step, and highly accurate technique suitable to fabricate a large variety of photonic crystals and micro-devices in polymers.

Chapter 18 Femtosecond fabrication of photonic crystals inside a bulk polymer material

We demonstrate a common UV photoinitiator with a two-photon absorption cross-section of 4.5 GM in the wavelength of 535 nm. Three-dimensional microstructured scaffolds could be achieved with two-photon polymerization of biocompatible hydrogels.

Two-Photon Polymerization of Biocompatible Hydrogels

Resolution in three-photon fluorescence scanning microscopy: errata.

For a confocal fluorescence microscope with annular pupils, the three-dimensional (3-D) image formation has been analyzed in terms of the three-dimensional optical transfer function (OTF). Based on the 3-D OTF, we have calculated the optical sectioning strength by considering the axial response. In addition, the effects of the size of the central obstruction of the lens and the detector have been investigated. In order to avoid the negative tail and the missing cone in the OTF, we have introduced optical fibers into the system. In this fiber- optical confocal scanning microscope, the illumination is from a fiber tip and the signal from the scan point is collected by another fiber and delivered to the detector. The optimum relationship of the central obstruction of the objective to the fiber spot size is presented.

Min Gu

Papers

Wafer-based solar cell

Chapter 18 Femtosecond fabrication of photonic crystals inside a bulk polymer material

Two-Photon Polymerization of Biocompatible Hydrogels

Resolution in three-photon fluorescence scanning microscopy: errata.

Three-dimensional image formation in confocal fluorescence microscopy