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

We show that topological charge is not conserved in tightly focused beams. Conversion of spin angular momentum into orbital angular momentum occurs through a geometrical phase. We demonstrate a connection between the shape of the focal spot, and the recently discovered optical Hall effect.

https://researchbank.swinburne.edu.au/file/4fb2a4d4-7528-4143-a2f8-9124e0e39621/1/PDF (Published version).pdf

The optical Hall effect in tightly focused light beams

We reveal plasmonic nanoparticles are effective to enhance the light absorption in planar Si wafer cells, while the absorption enhancement can be significantly offset by the plasmonic induced losses in the textured cells

Surface Morphology Dependent Light Trapping of Plasmonic Nanoparticles on Silicon Wafer-based Solar Cells

The fabrication of high-resolution laser-scribed graphene devices is crucial to achieving large surface areas and thus performance breakthroughs. However, since the investigation mainly focuses on the laser-induced reduction of graphene oxide, the single-beam scribing provides a tremendous challenge to realizing subdiffraction features of graphene patterns. Here, we present an innovative 2-beam laser scribing pathway for the fabrication of subdiffraction graphene patterns. First, an oxidation reaction of highly reduced graphene oxide can be controllably driven by irradiation of a 532-nm femtosecond laser beam. Based on the oxidation mechanism, a 2-beam laser scribing was performed on graphene oxide thin films, in which a doughnut-shaped 375-nm beam reduces graphene oxide and a spherical 532-nm ultrafast beam induces the oxidation of laser-reduced graphene oxide. The spherical beam turns the highly reduced graphene oxide (reduced by the doughnut-shaped beam) to an oxidized state, splitting the laser-scribed graphene oxide line into 2 subdiffraction featured segments and thus forming a laser-scribed graphene/oxidized laser-scribed graphene/laser-scribed graphene line. Through the adjustment of the oxidation beam power, the minimum linewidth of laser-scribed graphene was measured to be 90 nm. Next, we fabricated patterned supercapacitor electrodes containing parallel laser-scribed graphene lines with subdiffraction widths and spacings. An outstanding gravimetric capacitance of 308 F/g, which is substantially higher than those of reported graphene-based supercapacitors, has been delivered. The results offer a broadly accessible strategy for the fabrication of high-performance graphene-based devices including high-capacity energy storage, high-resolution holograms, high-sensitivity sensors, triboelectric nanogenerators with high power densities, and artificial intelligence devices with high neuron densities.

Two-Beam Ultrafast Laser Scribing of Graphene Patterns with 90-nm Subdiffraction Feature Size

Spectral features of a photonic crystal fiber generated supercontinuum were used in the optical read out of nanoparticle fluorescence. Three nanoparticles, in this case colloidal semiconductor quantum dots, were synthesized to produce particles with different fluorescence spectra. The quantum dots were then randomly dispersed into a polymer matrix. It was observed that three color fluorescence signals can be measured by the excitation by supercontinuum.

https://researchbank.swinburne.edu.au/file/4cfbe27e-efae-4deb-b50a-a96000aa4cc7/1/PDF (Published version).pdf

Optical Read Out of Nanoparticle Fluorescence Using Supercontinuum Generation for Optical Data Storage

The development of communication technology is an important milestone in modern society. The safe transmission of information is particularly important in communication. Encryption technology has important uses in both military and commercial fields. Optical information encryption and decryption has the advantages of high speed, high efficiency and high security. Among them, digital holography technology can be regarded as an effective encryption method because it introduces Fourier transform in the calculation. At present, digital holography encryption has developed a variety of new methods such as OAM holography and meta-surface holography [1] , [2] . In daily life, decryption through a string of passwords is the most common used method. However, the security of this method is low. Take a string of 6-digit digital password as an example, the number of each digit can be selected is 0~9, so there are only about 10 6 kinds of passwords. It's easy for a computer to try all these numbers.

Min Gu

Papers

The optical Hall effect in tightly focused light beams

Surface Morphology Dependent Light Trapping of Plasmonic Nanoparticles on Silicon Wafer-based Solar Cells

Two-Beam Ultrafast Laser Scribing of Graphene Patterns with 90-nm Subdiffraction Feature Size

Optical Read Out of Nanoparticle Fluorescence Using Supercontinuum Generation for Optical Data Storage

All Optical Holographic Encryption in Reduced Graphene Oxide Based on Laser Direct Writing