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Three-dimensional (3D) tracking of surface-tethered single particles reveals the dynamics of the molecular tether. However, most 3D tracking techniques lack precision, especially in the axial direction, for measuring the dynamics of biomolecules with a spatial scale of several nanometers. Here, we present a plasmonic imaging technique that can track the motion of ∼100 tethered particles in 3D simultaneously with sub-nanometer axial precision and single-digit nanometer lateral precision at millisecond time resolution. By tracking the 3D coordinates of a tethered particle with high spatial resolution, we are able to determine the dynamics of single short DNA and study its interaction with enzymes. We further show that the particle motion pattern can be used to identify specific and nonspecific interactions in immunoassays. We anticipate that our 3D tracking technique can contribute to the understanding of molecular dynamics and interactions at the single-molecule level.

Dynamic responses and vibration characteristics of a rotating functionally graded material (FGM) beam with a hollow circular cross-section in the temperature field are investigated in this paper. The material properties of the FGM beam are assumed to be temperature-dependent and vary along the thickness direction of the beam. By considering the rigid-flexible coupling effect, the geometrically nonlinear dynamic equations of a hub–FGM beam system are derived by employing the assumed modes method and Lagrange’s equations. With the high-order coupling dynamic model, the effect of temperature variations under two different laws of motion is discussed, and the free vibration of the system is studied based on the first-order approximate coupling model. This research can provide ideas for the design of space thermal protection mechanisms.

The effect of the optical feedback on the polarization flipping point and hysteresis loop was studied. The polarization flipping occurred at all angles between the polarizer axis and the laser polarization. The polarization flipping point changed by an optical feedback occurred at angles from 0° to 90°. Ability of choosing or controlling the laser polarization was determined by changing the direction of vertical and horizontal polarization by polarizer rotation in the external cavity from 0° to 90°.

In diffuse optics, quantitative assessment of the human brain is confounded by the skull and scalp. To better understand these superficial tissues, we advance interferometric near-infrared spectroscopy (iNIRS) to form images of the human superficial forehead blood flow index (BFI). We present a null source–collector (S-C) polarization splitting approach that enables galvanometer scanning and eliminates unwanted backscattered light. Images show an order-of-magnitude heterogeneity in superficial dynamics, implying an order-of-magnitude heterogeneity in brain specificity, depending on forehead location. Along the time-of-flight dimension, autocorrelation decay rates support a three-layer model with increasing BFI from the skull to the scalp to the brain. By accurately characterizing superficial tissues, this approach can help improve specificity for the human brain.

We propose a model of a bipolarised Nd : YAG laser with partially polarised pump radiation, providing competitive amplification of polarisation modes. A new type of instability is predicted, similar to the one that was first observed in [1]. The possibility of experimental verification of predictions is discussed.

The paper presents the investigation results of a metal plate re-melting process by a fiber laser beam using a high-speed video camera. The obtained video materials allow observing the transition process of molten metal to a solid state. The dependence of the molten metal transition to the solid state on the laser welding speed and on the focal distance (in the range of ± 20 mm) is analyzed. A quantitative analysis of the geometric dimensions of the microstructural components of the re-melted metal was carried out. When comparing the processed video material and microstructure elements of the molten pool, the similar trends are observed depending on the re-melting speed by a laser beam in a certain range of speeds from 20 to 45 mm/s. The obtained results can be used to develop a technique for estimating the presence of a key-hole depending on the laser focal distance.

We consider optical pulse propagation in cubic-quintic nonlinear media and analyze the dynamics of pulse compression within the framework of variational approach. Based on a potential model we find...

We study the propagation of ultrashort pulses of width around sub-10 femtosecond in an inhomogeneous highly nonlinear single-mode fibre within the framework of a generalized higher-order nonlinear ...

We investigate the transport of excitons and trions in monolayer semiconductor WS$_2$ subjected to controlled non-uniform mechanical strain. We actively control and tune the strain profiles with an AFM-based setup in which the monolayer is indented by an AFM tip. Optical spectroscopy is used to reveal the dynamics of the excited carriers. The non-uniform strain configuration locally changes the valence and conduction bands of WS$_2$, giving rise to effective forces attracting excitons and trions towards the point of maximum strain underneath the AFM tip. We observe large changes in the photoluminescence spectra of WS$_2$ under strain, which we interpret using a drift-diffusion model. We show that the transport of neutral excitons, a process that was previously thought to be efficient in non-uniformly strained 2D semiconductors and termed as "funneling", is negligible at room temperature in contrast to previous observations. Conversely, we discover that redistribution of free carriers under non-uniform strain profiles leads to highly efficient conversion of excitons to trions. Conversion efficiency reaches $\simeq 100\%$ even without electrical gating. Our results explain inconsistencies in previous experiments and pave the way towards new types of optoelectronic devices., 6 pages, 4 figures

ispartof: ADVANCED OPTICAL MATERIALS vol:9 issue:24 status: published

Understanding biological responses to directed energy (DE) is critical to ensure the safety of personnel within the Department of Defense. At the Air Force Research Laboratory, we have developed or adapted advanced optical imaging systems that quantify biophysical responses to DE. One notable cellular response to DE exposure is the formation of blebs, or semi-spherical protrusions of the plasma membrane in living cells. In this work, we demonstrate the capacity of quantitative phase imaging (QPI) to both visualize and quantify the formation of membrane blebs following DE exposure. QPI is an interferometric imaging tool that uses optical path length as a label-free contrast mechanism and is sensitive to the non-aqueous mass density, or dry mass, of living cells. Blebs from both CHO-K1 and U937 cells were generated after exposure to a series of 600 ns, 21.2 kV/cm electric pulses. These blebs were visualized in real time, and their dry mass relative to the rest of the cell body was quantified as a function of time. It is our hope that this system will lead to an improved understanding of both DE-induced and apoptotic blebbing.

This work is an experimental study of gravity-driven liquid film flowalong corrugated substrates. Thin liquid films appear in importantindustrial, environmental and biomedical flows. The modifications,resulting from the substitution of the flat substrate on which the filmflows by one with topography, are presently not well understood. Inparticular, there is little experimental evidence about the effect ofperiodic corrugations on the primary instability of the flow, and therelevant theoretical predictions appears contradictory. This problemis of significant interest, because of the potential for instability controlin such flows through the development of appropriately tailoredsubstrates.Systematic experiments were performed with water-glycerol solutions,in two flow facilities spanning a wide range of inclination angles. Substrateswith different shapes (sinusoidal and rectangular) and variouswavelengths and amplitudes were examined. The temporal variationof liquid film thickness was measured by conductance probes at multiplelocations along the flow. A photographic technique was developedto record the spatial variation of the free surface in the streamwisedirection. Using these techniques, the primary instability thresholdwas reliably determined, and the characteristics of traveling waves inthe unstable regime were recorded.A major finding of the thesis is that, for intermediate and high inclinations,steep enough corrugations trigger a new instability modeof finite wavelength, while they delay significantly the occurrence ofthe classical, convective, long-wave instability. The new mode is ashort, traveling wave, which is highly regular and persistently twodimensional,and appears to be a global mode. Transition from longtoshort-wave instability is observed to occur with increasing inclinationangle, and the exact location of the transition varies with thecorrugation shape. The parametric effects of liquid viscosity and ofcorrugation wavelength and amplitude are examined, and the importantspecial case of a vertical wall is investigated using a cylindricalflow geometry. Finally, an unexpected oscillatory instability is documented,specific to steep, rectangular substrates, which appears andintensifies when decreasing the liquid flow rate. It is speculated thatthis counter-intuitive behaviour is related to the specific separationcharacteristics of the rectangular substrate, and is triggered when thebackflow velocity exceeds a percentage of the forward stream.

Directed propulsion of lightsails to relativistic speeds by laser radiation pressure demands for passive stabilization, which can be achieved with subwavelength metasurface elements. Our tailored nanophotonic design based on silicon nitride is predicted to give rise to restoring forces and torques upon small perturbations in its dynamics. By measuring the angles and intensities of the diffracted orders, we infer the light-induced pressures on our lightsail prototype. Using Michelson interferometry and laser deflection spectroscopy, we can directly observe the dynamical stability of spring-supported suspended membrane designs. Our results pave the way for lab-scale experiments on optical manipulation of microscopic lightsails.

Fiber-optic sensing (FOS) technology is gradually becoming a pervasive tool in the monitoring and surveillance toolkit for reservoir engineers. Traditionally, sensing with fiber optic technology in the form of distributed temperature sensing (DTS) or distributed acoustic sensing (DAS), and most recently distributed strain sensing (DSS), distributed flow sensing (DFS) and distributed pressure sensing (DPS) were done with the fiber being permanently clamped either behind the casing or production tubing. Distributed chemical sensing (DCS) is still in the development phase. The emergence of the composite carbon-rod (CCR) system that can be easily deployed in and out of a well, similar to wireline logging, has opened up a vista of possibilities to obtain many FOS measurements in any well without prior fiber-optic installation. Currently, combinations of distributed FOS data are being used for injection management, well integrity monitoring, well stimulation and production performance optimization, thermal recovery management, etc. Is it possible to integrate many of the distributed FOS measurements in the CCR or a hybrid combination with wireline to obtain multiple measurements with one FOS cable? Each one of FOS has its own use to get certain data, or combination of FOS can be used to make a further interpretation. This paper reviews the state of the art of the FOS technology and the gamut of current different applications of FOS data in the oil and gas (upstream) industry. We present some results of traditional FOS measurements for well integrity monitoring, assessing production and injection flow profile, cross flow behind casing, etc. We propose some nontraditional applications of the technology and suggest a few ways through. Which the technology can be deployed for obtaining some key reservoir description and dynamics data for reservoir performance optimization.

We experimentally investigate the complex dynamics of a multi-mode quantum-dot semiconductor laser with time-delayed optical feedback. We examine a two-dimensional bifurcation diagram of the quantum-dot laser as a comprehensive dynamical map by changing the injection current and feedback strength. We found that the bifurcation diagram contains two different parameter regions of low-frequency fluctuations. The power-dropout dynamics of the low-frequency fluctuations are observed in the sub-GHz region, which is considerably faster than the conventional low-frequency fluctuations in the MHz region. Comparing the dynamics of quantum-dot laser with those of single- and multi-mode quantum-well semiconductor lasers reveals that the fast low-frequency fluctuation dynamics are unique characteristics of quantum-dot lasers with time-delayed optical feedback.

High speed volumetric optical microscopy is an important tool for observing rapid processes in living cells or for real-time tracking of sub-cellular components. However, the 3D imaging capability often comes at the price of a high technical complexity of the imaging system and/or the requirement of demanding image analysis. Here, we propose a combination of conventional phase-contrast imaging with a customized multi-plane beam-splitter for enabling simultaneous acquisition of images in eight different focal planes. Our method is technically straightforward and does not require complex post-processing image analysis. We apply our multi-plane phase-contrast microscope to the real-time observation of the fast motion of reactivated Chlamydomonas axonemes with sub-µm spatial and 4 ms temporal resolution. Our system allows us to observe not only bending but also the three-dimensional torsional dynamics of these micro-swimmers.

We report an Aubrey-Andre-Harper (AAH) model based quasi-periodic lossless evanescently coupled waveguide lattice to study the unconventional physics of light localization. We find an exclusively new way to establish localization phase transition in a 1D-AAH lattice by observing the slope variation of the band and accordingly study the modal characteristics to reveal the fact that a higher value of quasi-periodic modulation strength is imperative for observing a signature of fully localized light states having higher eigenenergy. This analytical concept has numerically been implemented in the proposed quasi-periodic lattice to achieve light localization, where we have shown that the supported states not only depend on localization phase transition parameter, but also on the specific location of excitation which is due to quasi-periodic nature of lattice. Furthermore, we have investigated a unique effect of the presence of disorder on light localization phenomenon, where it has been reported that the presence of off-diagonal disorder, which is otherwise detrimental, favours light localization in the proposed structure due to its quasi-periodic nature. The findings indeed have the potential to open up a fertile platform to manipulate light in passive photonic devices.

Brightness of an object is determined by various factors including ambient illumination, surface reflectance of the object, and spatial and temporal relation between the object and its surrounding context. Recently, it has been demonstrated that the motion of an object alters its own and nearby object’s appearance such as brightness and color. This study aims to unveil mechanisms of the motion-induced brightness shift by measuring its temporal dynamics. We found that the motion-induced brightness shift occurred instantaneously with the motion onset when the motion was introduced abruptly. However, the brightness of a stationary object was altered gradually by a nearby moving object in about 2 s time window when the stationary dot was introduced abruptly. Two distinct temporal dynamics (slow vs. fast) of the motion-induced brightness shift demonstrate that both slow neural adaptation and fast neural normalization processes determine the brightness shift induced by the object’s motion.

We investigate the anomalous interactions of both in-phase and out-of-phase Airy beams in Kerr media with different intervals and initial launch angles (“velocity”) by means of direct numerical simulation. Interaction between double beams interference and initial launch angle leads to a host of new propagation dynamics of solitons shedding from Airy beams. Unlike the interaction between two Airy beams without initial velocity, where the two in-phase and out-of-phase Airy beams always attract and repel each other, here, both the in-phase and out-phase Airy beams can present attraction or repulsion under proper interval and initial angle condition. Their propagating dynamics depend in a sensitive way on the sign of the interval and initial launch angle.

We study the propagation of electromagnetic field through a two-waveguide coupler with saturable nonlinearity. We show that the model supports an analytical solution for the dynamics, by means of the linearization of the system around fixed points. Also we prove that this model is isomorphic to the semi-classical non-Hermitian Bose–Hubbard dimer.

Recent experiments demonstrating storage of optical pulses in acoustic phonons based on stimulated Brillouin scattering raise a number of questions about the spectral and temporal capacities of such protocols and the limitations of the theoretical frameworks routinely used to describe them. In this work, we consider the dynamics of photon-phonon scattering induced by optical pulses with temporal widths comparable to the period of acoustic oscillations. We revisit the widely adopted classical formalism of coupled modes and demonstrate its breakdown. We propose a simple extension to generalise the formulation and find potentially measurable consequences in the dynamics of Brillouin experiments involving ultra-short pulses., 5 pages, 3 figures

Scanning microscopy’s resolution of highly localized dynamics in awake animals is limited by bulk motion. We present a modular optical flow sensor based on spectral domain OCT which measures the specimen’s 3D displacement in real-time. A rose-function scan pattern rapidly acquires B-lines used to estimate displacements via an adaptive cross-correlation approach. Axial displacements are estimated from phase fluctuations apparent in the cross-correlation of the complex SD-OCT signal. The technique’s 3-dimensional readout rate and sensitivity to physiologically-relevant motion frequencies and magnitudes is evaluated.

Spectrally encoded interferometric microscopy (SEIM) is capable of detecting nanometer displacement at a frame rate in the kilohertz regime. By employing a wavelength-sweeping laser and a spectral disperser, SEIM can achieve en face imaging via one-axis scanning. In this study, we compared different processing algorithms for visualizing cilia-induced motion. Our Doppler-based method, combined with phase stabilization and bulk motion correction, provides the highest sensitivity for measuring ciliary beating frequency amongst the tested methods. Traveling waves induced by coordinated cilia motion were visualized. These results demonstrate the potential clinical utility of SEIM for monitoring respiratory function and therapeutic effects.

The generation of an optical supercontinuum with short (fs) input pulse duration is a highly complex process that exhibits rich nonlinear dynamics. Here, we show that one can teach a machine learning model to learn the nonlinear dynamics of ultrashort pulse propagation and predict the full-field propagation dynamics of supercontinuum based only on the input pulse characteristics (peak power, duration and chirp).

We demonstrate an interferometric method to provide direct, single-shot measurements of cavitation bubble dynamics with nanoscale spatial and temporal resolution with results that closely match theoretical predictions. Implementation of this method reduces the need for expensive and complex ultra-high speed camera systems for the measurement of single cavitation events. This method can capture dynamics over large time intervals with sub-nanosecond temporal resolution and spatial precision surpassing the optical diffraction limit. We expect this method to have broad utility for examination of cavitation bubble dynamics, as well as for metrology applications such as optorheological materials characterization. This method provides an accurate approach for precise measurement of cavitation bubble dynamics suitable for metrology applications such as optorheological materials characterization.

Differential dynamic microscopy (DDM) is increasingly used in the fields of soft matter physics and biophysics to extract the dynamics of microscopic objects across a range of wavevectors using optical microscopy. Standard DDM is limited to detecting dynamics no faster than the camera frame rate. We report on an extension to DDM where we sequentially illuminate the sample with spectrally-distinct light and image with a color camera. By pulsing blue and then red light separated by a lag time much smaller than the camera's exposure time we are able to use this two-color DDM method to measure dynamics occurring much faster than the camera frame rate., The following article has been accepted by Review of Scientific Instruments

Mode-locked lasers are the ideal source for precise measurements, from frequency combs to precise timing, which relies on the accurate control of the intracavity parameters in the lasers to stabilize the pulse. However, by the lack of accurate measurements, the interplays between intracavity parameters and the mode-locked pulse is still not real-time observable. Here, using the dispersive temporal interferometer, we report a method to single-shot probe the pulse evolution dynamics in time domain in the mode-locked laser. As a typical example, we demonstrate the first single-shot observation on the roundtrip time and phase evolutions of intracavity pulse during its buildup and relaxation. Three distinct evolution regimes for pulse buildup are unveiled for the first time. Moreover, the physical mechanism of the time-location and phase changes in these three regimes has also been analyzed, respectively. Our researches present a novel method to observe the intracavity-parameters-to-pulse interaction, which will improve laser design, ultrafast diagnostics, and nonlinear optics.

The temporal delayed orthogonal pulse pairs generated by the phase shaping technique are used to study the coherent control of the rotational wave packet dynamics in air. By continuously changing the intrapulse delay of the pump pulse, we measured the corresponding revival signals and obtained a two-dimensional rotational coherent spectrum (2D RCS). An additive property of the rotational dynamics is observed from the revival signals. Moreover, combining with the coherent control model, we find that the 2D RCS can be used to demonstrate the control over the underlying Raman rotational excitation. A beat frequency-dependent oscillation of each rotational transition is obtained. The transition process is revealed from the Fourier transformation about the pump delay. The scheme of this work can be used for further control and detection of the rotational wave packet and can be extended to other molecular dynamic researches.

We investigate time-resolved dynamics of single-shot laser damage on YAG for ∼9fs pulses near ∼760nm and compare to damage thresholds of 264fs pulses at 1025nm. Results are benchmarked against a modified Keldysh photoionization model.

The real-time buildup dynamics of multiple-soliton in spatiotemporal mode-locked fiber lasers are observed. The experimental results indicate that the dynamics vary for different transverse modes, and the multiple-soliton has spatiotemporal structure among the pulses.

Ultrafast dynamics of ultrafast single pulse induced micro-explosions in bulk fused silica was captured using.time resolved shadowgraphy. Experimental and theoretical considerations identify such micro-explosions creating warm dense matter (WDM) states.

We simulate the linear and nonlinear propagation dynamics of multi-TW 10.6 μm square-frame wavepackets in the atmosphere. It is shown that the location of the obscuration is critical for multiple-filamentation and energy delivery downstream.

Polarization light microscopes are powerful tools for probing molecular order and orientation in birefringent materials. While a multitude of polarization light microscopy techniques are often used to access steady-state properties of birefringent samples, quantitative measurements of the molecular orientation dynamics on the millisecond time scale have remained a challenge. We propose polarized shearing interference microscopy (PSIM), a single-shot quantitative polarization imaging method, for extracting the retardance and orientation angle of the laser beam transmitting through optically anisotropic specimens with complex structures. The measurement accuracy and imaging performances of PSIM are validated by imaging a rotating wave plate and a bovine tendon specimen. We demonstrate that PSIM can quantify the dynamics of a flowing lyotropic chromonic liquid crystal in a microfluidic channel at an imaging speed of 506 frames per second (only limited by the camera frame rate), with a field-of-view of up to $350\times350 \mu m^2$ and a diffraction-limit spatial resolution of $\sim 2\mu m$. We envision that PSIM will find a broad range of applications in quantitative material characterization under dynamical conditions.

Multiple filamentation in air of high-power ultrashort laser radiation with transverse intensity profile resembling a "corona" composed by incoherent combining of several annularly distributed independent top-hat sub-beams is theoretically studied. Through the numerical solution of time-averaged nonlinear Schrodinger equation, we study the spatio-angular dynamics of synthesized near-infrared "corona-beam" (CB) along the optical path by varying the number and power of the beamlets (corona-spikes). For the first time to our knowledge, the evident advances in the multiple filamentation region manipulating of synthesized CB are demonstrated. Particularly, by adjusting the number and aperture of the constituting sub-beams it makes possible to significantly delay the CB filamentation onset distance and increase the filamentation length in air. In addition, at the post-filamentation stage of femtosecond pulse propagation under certain conditions the synthesized corona-beams exhibit significantly lower angular divergence of its most intense part (post-filamentation light channel) compared to the beams with regular uni-modal intensity profiles (Gaussian, plateau-like) that provides enhancing of laser power delivered to the receiver over the atmospheric links., 24 pages, 9 figures

Frequency comb generation by quantum-cascade lasers generating at 8 μm is demonstrated. Time resolved spectral measurements show generation of all modes of frequency comb during full length of flat section of pumping pulse.

In the paper, based on the linear Schrodinger equation, we analytically investigate the effect of initial chirp on the dynamics of the optical beam in a medium with the parabolic potential. For the linear chirp, the results show that the linear chirp of beam can induce a periodically oscillating behavior, where the oscillating amplitude is proportional to the linear chirp parameter, and the beam’s peak and width are related to the depth of parabolic potential. For the quadratic chirp, the results show that the quadratic chirp of beam can induce a periodically breathing behavior and affect the evolution of beam’s peak and width.

Sub-resonant tapping atomic force microscopy enables topography measurements with limited lateral tip-sample forces, while overcoming the limitations of excessive damage and measurement errors that occur during amplitude modulated operation on high aspect ratio samples. Therefore, it is a candidate to enable process quality monitoring in semiconductor device fabrication. However, at steep edges of such device geometries, the technique often results in stick-slip events for the probe, preventing the desired quasi-static motion of the cantilever and causing errors in the measured topography. To understand the stick-slip dynamics, a model is presented in this article that accurately predicts the consequences of stick-slip episodes. Employing this model, a time-domain based reconstruction technique is proposed to obtain an enhanced topography image. The proposed technique has been tested on a commercially available atomic force microscope with high aspect ratio tip probe and is shown to allow extraction of the topography of a grating sample with overhang features. Comparison of this technique with a conventional AFM method shows improved profile accuracy.