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 Letter reports the generation of a high-quality longitudinally polarized photonic nanojet by illuminating a dielectric microdisk with a focused radially polarized light. High-quality longitudinally polarized beams can be generated using a microdisk with a wide range of refractive indices. By optimizing the shape and refractive index of the microdisk, the radial component can be effectively suppressed, and a maximum beam quality of 90% and a field enhancement factor of up to two orders can be achieved with a sub-diffraction-limited spot size. Moreover, the focusing performance of the microdisk is observed to be stable within a wide range of focusing numerical aperture values of the incident light.

High-quality longitudinally polarized photonic nanojet created by a microdisk.

We numerically and theoretically investigate the plasmonic Schottky photodetection in a novel hybrid silicon-on-insulator waveguide system, which consists of the silicon waveguides and detection area with the metal stripes and doped silicon film on the silicon dioxide substrate. The results illustrate that the fundamental TE mode in the silicon waveguide can be effectively coupled into the metal/silicon waveguide with the excitation of surface plasmon polaritons (SPPs). The coupling is suppressed for the TM mode due to the mismatch between the electric field distributions of the TM and SPP modes. It is found that the coupling efficiency from the TE to SPP mode is dependent on the width and height of the silicon waveguide and can significantly approach ~36.1%. The ultracompact configuration yields a high responsivity of ~21.7 mA/W and low dark current of ~0.45 μA for the photodetection at the communication wavelength. The plasmonic Schottky photodetector could find favorable applications in the chip-integrated optical interconnects and signal processing.

Chip-integrated plasmonic Schottky photodetection based on hybrid silicon waveguides

In this paper, image enhancement and reconstruction through a turbid medium by utilizing polarization gating and math- ematical image reconstruction methods in a microscopic imaging sys- tem are investigated. A Monte Carlo simulation model based on Mie theory and the concept of the effective point spread function (EPSF) is adopted to study image formation under a transmission-mode micro- scope. The results show that polarization gating methods, and particu- larly the differential polarization gating method, can be efficient in suppressing highly scattered light, which leads to a significant en- hancement of image quality. An image reconstruction method based on the concept of the EPSF is demonstrated to be efficient in further

https://researchbank.swinburne.edu.au/file/f0a2aa0c-fc29-40a1-a1e3-b977caa84ddf/1/PDF (Published version).pdf

Image reconstruction through turbid media under a transmission-mode microscope

Optical data storage is an important and critical part of optical information technology in which case photons rather than electrons are used for information generation, processing, transmission and storage. We have witnessed the revolution of photonics in optical communications. The advance in photonic chips will allow for the development of ultrafast optical signal generation and processing. While optical data storage such as the optical compact (CD) disk, digital video (DVD) disk and Blue-ray disk technologies has transformed our society in the last two decades, the development in this area has been slow down and seemingly become less active due to the fast development of flush memory and hard disks. However, the optical data storage technology has held its distinctive advantages of long lifetime, low-energy consumption, and ultra-secure encryption [1-3]. Nanophotonics that is the integration of photonics and nano-materials has extended optical data storage from three-dimensions to five dimensions or more [1, 2]. If combined with supresolution optics that allows for the break of the diffraction limit, nanophotonics-enabled optical data storage will make it possible to develop Petabype optical disks, forming a green-technology platform for future data centres.

Min Gu

Papers

High-quality longitudinally polarized photonic nanojet created by a microdisk.

Chip-integrated plasmonic Schottky photodetection based on hybrid silicon waveguides

Image reconstruction through turbid media under a transmission-mode microscope

Optical data storage with diffraction-unlimited resolution

Non-Hermitian Eigenvalue Problems.