scholarly journals Influence of Laser Intensity Fluctuation on Single-Cesium Atom Trapping Lifetime in a 1064-nm Microscopic Optical Tweezer

2020 ◽  
Vol 10 (2) ◽  
pp. 659
Author(s):  
Rui Sun ◽  
Xin Wang ◽  
Kong Zhang ◽  
Jun He ◽  
Junmin Wang
Keyword(s):  
Optical Tweezers ◽  
Intensity Fluctuation ◽  
Laser Intensity ◽  
Single Photon ◽  
Optical Tweezer ◽  
Optical Modulator ◽  
Quantum Bits ◽  
The Time Domain ◽  
The Impact ◽  
Coherent Manipulation

An optical tweezer composed of a strongly focused single-spatial-mode Gaussian beam of a red-detuned 1064-nm laser can confine a single-cesium (Cs) atom at the strongest point of the light intensity. We can use this for coherent manipulation of single-quantum bits and single-photon sources. The trapping lifetime of the atoms in the optical tweezers is very short due to the impact of the background atoms, the parametric heating of the optical tweezer and the residual thermal motion of the atoms. In this paper, we analyzed the influence of the background pressure, the trap frequency of optical tweezers and the laser intensity fluctuation of optical tweezers on the atomic trapping lifetime. Combined with the external feedback loop based on an acousto-optical modulator (AOM), the intensity fluctuation of the 1064-nm laser in the time domain was suppressed from ±3.360% to ±0.064%, and the suppression bandwidth in the frequency domain reached approximately 33 kHz. The trapping lifetime of a single-Cs atom in the microscopic optical tweezers was extended from 4.04 s to 6.34 s.

scholarly journals Nonlinear Double-arm Optical Tweezers for Controlling 3D Microspheres

2020 ◽  
Vol 30 (4) ◽  
pp. 355
Author(s):  
Nguyen Manh Thang
Keyword(s):  
Optical Tweezers ◽  
Intensity Distribution ◽  
Laser Power ◽  
Laser Intensity ◽  
Optical Trap ◽  
Optical Tweezer ◽  
Organic Dye ◽  
Objective Lens ◽  
Proposed Model ◽  
3D Microspheres

In this paper, a new nonlinear double-arm optical tweezer combining Mach-Zenhder interferometer, objective lens and organic dye layer is proposed. Based on the ray-optical and wave optical approximations, the expression describing the separation of two trap centers and laser intensity distribution is derived. The obtained results show that the separation between two trap centers, the laser intensity distribution, trap region's area and optical trap efficiency can be controlled by tuning laser power. The proposed model is seen to be a double-arm optical tweezer for controlling 3D microsphere by optical method.

scholarly journals Dynamic Stability Performance of Autonomous Microgrid Involving High Penetration Level of Constant Power Loads

Mathematics ◽  
2021 ◽  
Vol 9 (9) ◽  
pp. 922
Author(s):  
Mohamed Hassan ◽  
Muhammed Worku ◽  
Abdelfattah Eladl ◽  
Mohammed Abido
Keyword(s):  
Dynamic Stability ◽  
Power Sharing ◽  
Constant Power ◽  
Similar Frequency ◽  
Stability Performance ◽  
High Penetration ◽  
Constant Power Loads ◽  
The Time Domain ◽  
And Control ◽  
The Impact

Nowadays, behaving as constant power loads (CPLs), rectifiers and voltage regulators are extensively used in microgrids (MGs). The MG dynamic behavior challenges both stability and control effectiveness in the presence of CPLs. CPLs characteristics such as negative incremental resistance, synchronization, and control loop dynamic with similar frequency range of the inverter disturb severely the MG stability. Additionally, the MG stability problem will be more sophisticated with a high penetration level of CPLs in MGs. The stability analysis becomes more essential especially with high-penetrated CPLs. In this paper, the dynamic stability performance of an MG involving a high penetration level of CPLs is analyzed and investigated. An autonomous MG engaging a number of CPLs and inverter distributed generations (DGs) is modeled and designed using MATLAB. Voltage, current, and power controllers are optimally designed, controlling the inverter DGs output. A power droop controller is implemented to share the output DGs powers. Meanwhile, the current and voltage controllers are employed to control the output voltage and current of all DGs. A phase-locked loop (PLL) is essentially utilized to synchronize the CPLs with the MG. The controller gains of the inverters, CPLs, power sharing control, and PLL are optimally devised using particle swarm optimization (PSO). As a weighted objective function, the error in the DC voltage of the CPL and active power of the DG is minimized in the optimal problem based on the time-domain simulation. Under the presence of high penetrated CPLs, all controllers are coordinately tuned to ensure an enhanced dynamic stability of the MG. The impact of the highly penetrated CPLs on the MG dynamic stability is investigated. To confirm the effectiveness of the proposed technique, different disturbances are applied. The analysis shows that the MG system experiences the instability challenges due to the high penetrated CPLs. The simulation results confirm the effectiveness of the proposed method to improve the MG dynamic stability performance.

scholarly journals A geometric based preprocessing for weighted ray transforms with applications in SPECT

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Fedor Goncharov
Keyword(s):  
Single Photon ◽  
Photon Emission ◽  
Reconstruction Algorithm ◽  
Emission Computed Tomography ◽  
Radon Transforms ◽  
Single Photon Emission Computed ◽  
Ray Transforms ◽  
Straight Lines ◽  
The Impact ◽  
Photon Emission Computed Tomography

AbstractIn this work we investigate numerically the reconstruction approach proposed in [F. O. Goncharov and R. G. Novikov, An analog of Chang inversion formula for weighted Radon transforms in multidimensions, Eurasian J. Math. Comput. Appl. 4 2016, 2, 23–32] for weighted ray transforms (weighted Radon transforms along oriented straight lines) in 3D. In particular, the approach is based on a geometric reduction of the data modeled by weighted ray transforms to new data modeled by weighted Radon transforms along two-dimensional planes in 3D. Such reduction could be seen as a preprocessing procedure which could be further completed by any preferred reconstruction algorithm. In a series of numerical tests on modelized and real SPECT (single photon emission computed tomography) data we demonstrate that such procedure can significantly reduce the impact of noise on reconstructions.

scholarly journals Assembly of multicomponent structures from hundreds of micron-scale building blocks using optical tweezers

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Jeffrey E. Melzer ◽  
Euan McLeod
Keyword(s):  
Optical Tweezers ◽  
Three Dimensional ◽  
Building Blocks ◽  
Optical Tweezer ◽  
Device Fabrication ◽  
Positional Accuracy ◽  
Component Structure ◽  
Material Development ◽  
Critical Process Parameters ◽  
Optical Positioning

AbstractThe fabrication of three-dimensional (3D) microscale structures is critical for many applications, including strong and lightweight material development, medical device fabrication, microrobotics, and photonic applications. While 3D microfabrication has seen progress over the past decades, complex multicomponent integration with small or hierarchical feature sizes is still a challenge. In this study, an optical positioning and linking (OPAL) platform based on optical tweezers is used to precisely fabricate 3D microstructures from two types of micron-scale building blocks linked by biochemical interactions. A computer-controlled interface with rapid on-the-fly automated recalibration routines maintains accuracy even after placing many building blocks. OPAL achieves a 60-nm positional accuracy by optimizing the molecular functionalization and laser power. A two-component structure consisting of 448 1-µm building blocks is assembled, representing the largest number of building blocks used to date in 3D optical tweezer microassembly. Although optical tweezers have previously been used for microfabrication, those results were generally restricted to single-material structures composed of a relatively small number of larger-sized building blocks, with little discussion of critical process parameters. It is anticipated that OPAL will enable the assembly, augmentation, and repair of microstructures composed of specialty micro/nanomaterial building blocks to be used in new photonic, microfluidic, and biomedical devices.

Selection of random vibration theory procedures for the NGA-East project and ground-motion modeling

2021 ◽  
Vol 37 (1_suppl) ◽  
pp. 1420-1439
Author(s):  
Albert R Kottke ◽  
Norman A Abrahamson ◽  
David M Boore ◽  
Yousef Bozorgnia ◽  
Christine A Goulet ◽  
...  
Keyword(s):  
Ground Motion ◽  
Time Domain ◽  
Random Vibration ◽  
Amplitude Spectrum ◽  
Motion Modeling ◽  
Peak Response ◽  
Vibration Theory ◽  
Random Vibration Theory ◽  
The Time Domain ◽  
The Impact

Traditional ground-motion models (GMMs) are used to compute pseudo-spectral acceleration (PSA) from future earthquakes and are generally developed by regression of PSA using a physics-based functional form. PSA is a relatively simple metric that correlates well with the response of several engineering systems and is a metric commonly used in engineering evaluations; however, characteristics of the PSA calculation make application of scaling factors dependent on the frequency content of the input motion, complicating the development and adaptability of GMMs. By comparison, Fourier amplitude spectrum (FAS) represents ground-motion amplitudes that are completely independent from the amplitudes at other frequencies, making them an attractive alternative for GMM development. Random vibration theory (RVT) predicts the peak response of motion in the time domain based on the FAS and a duration, and thus can be used to relate FAS to PSA. Using RVT to compute the expected peak response in the time domain for given FAS therefore presents a significant advantage that is gaining traction in the GMM field. This article provides recommended RVT procedures relevant to GMM development, which were developed for the Next Generation Attenuation (NGA)-East project. In addition, an orientation-independent FAS metric—called the effective amplitude spectrum (EAS)—is developed for use in conjunction with RVT to preserve the mean power of the corresponding two horizontal components considered in traditional PSA-based modeling (i.e., RotD50). The EAS uses a standardized smoothing approach to provide a practical representation of the FAS for ground-motion modeling, while minimizing the impact on the four RVT properties ( zeroth moment, [Formula: see text]; bandwidth parameter, [Formula: see text]; frequency of zero crossings, [Formula: see text]; and frequency of extrema, [Formula: see text]). Although the recommendations were originally developed for NGA-East, they and the methodology they are based on can be adapted to become portable to other GMM and engineering problems requiring the computation of PSA from FAS.

scholarly journals Feedback Control for Optical Tweezers Instruments: Position Clamping and Detection Laser Intensity Stabilization

2009 ◽  
Vol 96 (3) ◽  
pp. 290a
Author(s):  
Heikki Ojala ◽  
Anders Korsbäck ◽  
Anders E. Wallin ◽  
Edward Haeggström
Keyword(s):  
Feedback Control ◽  
Optical Tweezers ◽  
Laser Intensity ◽  
Intensity Stabilization

scholarly journals Temporal resolution of single-photon responses in primate rod photoreceptors and limits imposed by cellular noise

2019 ◽  
Vol 121 (1) ◽  
pp. 255-268 ◽  
Author(s):  
Greg D. Field ◽  
Valerie Uzzell ◽  
E. J. Chichilnisky ◽  
Fred Rieke
Keyword(s):  
Temporal Resolution ◽  
Moving Objects ◽  
Single Photon ◽  
Night Vision ◽  
Detection Sensitivity ◽  
Sensory Receptor ◽  
Rod Photoreceptor ◽  
Scotopic Vision ◽  
Central Processing ◽  
The Impact

Sensory receptor noise corrupts sensory signals, contributing to imperfect perception and dictating central processing strategies. For example, noise in rod phototransduction limits our ability to detect light, and minimizing the impact of this noise requires precisely tuned nonlinear processing by the retina. But detection sensitivity is only one aspect of night vision: prompt and accurate behavior also requires that rods reliably encode the timing of photon arrivals. We show here that the temporal resolution of responses of primate rods is much finer than the duration of the light response and identify the key limiting sources of transduction noise. We also find that the thermal activation rate of rhodopsin is lower than previous estimates, implying that other noise sources are more important than previously appreciated. A model of rod single-photon responses reveals that the limiting noise relevant for behavior depends critically on how rod signals are pooled by downstream neurons. NEW & NOTEWORTHY Many studies have focused on the visual system’s ability to detect photons, but not on its ability to encode the relative timing of detected photons. Timing is essential for computations such as determining the velocity of moving objects. Here we examine the timing precision of primate rod photoreceptor responses and show that it is more precise than previously appreciated. This motivates an evaluation of whether scotopic vision approaches limits imposed by rod temporal resolution.

scholarly journals Calibration of ultrasonic hardware for enhanced total focusing method imaging

2020 ◽  
Vol 62 (7) ◽  
pp. 408-415
Author(s):  
M Ingram ◽  
A Gachagan ◽  
A Nordon ◽  
A J Mulholland ◽  
M Hegarty
Keyword(s):  
Time Domain ◽  
Pressure Profile ◽  
Side Lobe ◽  
Destructive Testing ◽  
Experimental Variation ◽  
Focal Position ◽  
Measured Time ◽  
The Time Domain ◽  
Ray Path ◽  
The Impact

Experimental variation from ultrasonic hardware is one source of uncertainty in measured ultrasonic data. This uncertainty leads to a reduction in the accuracy of images generated from these data. In this paper, a quick, easy-to-use and robust methodology is proposed to reduce this uncertainty in images generated using the total focusing method (TFM). Using a 128-element linear phased array, multiple full matrix capture (FMC) datasets of a planar reflection are used to characterise the experimental variation associated with each element index in the aperture. Following this, a methodology to decouple the time-domain error associated with transmission and reception at each element index is presented. These time-domain errors are then introduced into a simulated array model used to generate the two-way pressure profile from the array. The side-lobe-to-main-lobe energy ratio (SMER) and beam offset are used to quantify the impact of these measured time-domain errors on the pressure profile. This analysis shows that the SMER is raised by more than 6 dB and the beam is offset by more than 1 mm from its programmed focal position. This calibration methodology is then demonstrated using a steel non-destructive testing (NDT) sample with three side-drilled holes (SDHs). The time delay errors from transmission and reception are introduced into the time-of-flight (TOF) calculation for each ray path in the TFM. This results in an enhancement in the accuracy of defect localisation in the TFM image.

scholarly journals Investigation of the impact of SBS-parameters and loss modulation on the mode locking of an SBS-laser oscillator

2007 ◽  
Vol 25 (1) ◽  
pp. 107-116 ◽  
Author(s):  
PHILIP KAPPE ◽  
ALEXANDER STRÄßER ◽  
MARTIN OSTERMEYER
Keyword(s):  
Brillouin Scattering ◽  
Longitudinal Mode ◽  
Mode Locking ◽  
Equation Model ◽  
Optical Modulator ◽  
Round Trip ◽  
Laser Oscillator ◽  
Parameter Variations ◽  
Stimulated Brillouin ◽  
The Impact

A Nd:YAG laser oscillator Q-switched and mode locked via a nonlinear mirror based on stimulated Brillouin scattering (SBS) and aided by an acousto optical modulator (AOM) has been realised. A rate equation model and a round trip model are used to describe the longitudinal mode dynamics. Parameter variations of the nonlinear SBS mirror and the loss modulating AOM in the resonator are investigated with regard to their effect on the pulse duration and spectra of the pulses.

The Effects of Flare and Overhangs on the Motions of a Yacht in Head Seas

1993 ◽  
Author(s):  
John C. Kuhn ◽  
Eric C. Schlageter
Keyword(s):  
Nonlinear Differential Equations ◽  
Equations Of Motion ◽  
Linear Equations ◽  
Order Effects ◽  
Third Order ◽  
Numerical Work ◽  
Strip Theory ◽  
Hull Forms ◽  
The Time Domain ◽  
The Impact

The coupled heave and pitch motions of hull forms with flare and overhangs are examined numerically. The presence of flare and overhangs is numerically modelled with nonlinear hydrostatic and Froude-Krylov forces based on integrals over the instantaneous wetted surface. Forces due to radiation and diffraction are computed with a linear strip-theory. These forces are combined in two coupled nonlinear differential equations of motion that are solved in the time domain with a fourth-order Runge-Kutta integration method. An assessment of the impact of flare and overhangs on motions is obtained by comparing these nonlinear solutions with solutions of the traditional linear equations of motion, which do not contain forces due to flare and overhangs. For an example based on an International America's Cup Class yacht design, it is found that the nonlinear heave and pitch motions are smaller than the linear motions. This is primarily due to reduced first-order response components, which are coupled with nonlinear response components. Comparisons of these results with towing tank data demonstrate that the nonlinear procedure improves prediction quality relative to linear results. In support of this numerical work, the hydrostatic and Froude­Krylov force integrals are expanded in Taylor series with respect to wave elevation. These results indicate how hydrostatic and Froude-Krylov forces change with changing flare and overhang angles, revealing that sectional slope has second and third-order effects on forces while sectional curvature and overhang angles produce third-order effects.

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