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

The fabrication of a three-dimensional woodpile photonic-crystal is realised in a homogeneously doped PbSe polymer-nanocomposite-material. Infrared emission from the PbSe nanocrystals is overlapped with higher-order photonic-crystal pseudogaps and modification of spontaneous emission is observed.

https://researchbank.swinburne.edu.au/file/c7226fe5-e052-42d2-b185-3e5c93603713/1/PDF (Published version).pdf

Modified Spontaneous Emission Using Higher-Order Pseudogaps in 3D Polymer Photonic Crystal at Telecommunication Wavelengths

The key element in an optical microscope is an objective. As a result, an object embedded in a turbid medium is illuminated by a focused beam of angles of convergence determined by the numerical aperture of the objective. Consequently, scattered and unscattered photons are mixed in a range of angles when they leave a turbid medium. In this chapter, an angle-gating mechanism for separating scattered and unscattered photons, achieved by the utilization of polarized annular objectives in the illumination and collection beam paths of microscopic imaging systems, are presented. The principle of angle-gating together with the confirmation by Monte Carlo simulation is described in Sect. 5.1. The performance of annular objectives in transmission and reflection optical microscopes is presented in Sects. 5.2 and 5.3, respectively. In Sect. 5.4, a general issue regarding imaging resolution in turbid media is discussed.

Angle-Gating Mechanism

We present the theoretical study of achiral 2-srs-networks and we show that these structures possess the frequency-isolated linear point degeneracies in their three-dimensional dispersion relations that define the illusive Weyl points Our results are based on band structure calculations and can be realisable experimentally from microwave to optical frequencies via laser fabrication methods

Theoretical demonstration of Weyl points in 3D srs photonic crystals

We report on the investigation of optically detected magnetic resonance of nitrogen-vacancy centres in nanodiamonds exhibiting fluorescence intermittence through polarization microscopy. Applying this feature for super-resolution imaging of nanodiamond incorporated HeLa cells has been demonstrated.

Optically detected magnetic resonance of blinking nanodiamonds under a polarisation microscope

Photopolymerization assisted by up conversion nanoparticles (UCNPs) are reported to have promising potential in the biological field due to the unique fluorescent features of UCNPs. Here, we demonstrate a novel method in the fabrication of three-dimensional (3D) features at low power level with unique photo-luminescence property through the incorporation of UCNPs under a far-field direct laser writing (DLW) configuration. Equipped with long lifetime of excited energy levels, UCNPs were employed to function as the excitation light source for inducing controlled reversible deactivation radical polymerization through activating polymerization photo reagents via resonance energy transfer in the localized area surrounding the UCNPs, hence generating polymerized micro-scale features upon an incident near-infrared laser beam. UCNPs with unique emission qualities were custom-synthesized and dispersed in a monomer-based mixture containing polymerization photo-reagents to formulate a photo-sensitive nanocomposite. A thin film sample based off the nanocomposite was then placed under a DLW scheme for the fabrication of 3D micro-structures at low power level (100sW/cm2 for the writing laser beam intensity). Able to fabricate 3D micro-structures at very low power level with unique photo-luminescent properties compared to the traditional two-photon polymerization technique, this new method of laser fabrication method assisted by UCNPs has significant potential applications in research domains such as 3D low-power nanoscale optical memory, high-resolution imaging/display, functional micro-photonics devices and 3D micro-prototyping.

Min Gu

Papers

Modified Spontaneous Emission Using Higher-Order Pseudogaps in 3D Polymer Photonic Crystal at Telecommunication Wavelengths

Angle-Gating Mechanism

Theoretical demonstration of Weyl points in 3D srs photonic crystals

Optically detected magnetic resonance of blinking nanodiamonds under a polarisation microscope

Photopolymerization assisted by up-conversion nanoparticles for three-dimensional low-power photonics applications