Measurement of Trap Stiffness of Holographic Optical Tweezers with Power Spectrum Method

2013 ◽  
Vol 787 ◽  
pp. 423-426
Author(s):  
Kai Xu ◽  
Jing Li ◽  
Gang Du ◽  
Chun Li Zhu ◽  
Peng Fei Li ◽  
...  
Keyword(s):  
Brownian Motion ◽  
Power Spectrum ◽  
Optical Tweezers ◽  
Laser Power ◽  
Optical Trap ◽  
Bottom Surface ◽  
Sample Cell ◽  
Spectrum Method ◽  
Holographic Optical Tweezers ◽  
Power Spectrum Method

A microsphere trapped by optical tweezers moves according to the Brownian motion law, which can be described by the Langevin equation. Based on it, a quadrant photodiode (QD) is used to track the displacement of the microsphere with a diameter of 2.5um trapped by holographic optical tweezers, and power spectrum method is adopted to obtain radial trap stiffness. Experiments show that the trap stiffness increases with the increase of the laser power, and decreases as the distance between the optical trap and the inside bottom surface of the sample cell increases.

scholarly journals Enhanced Signal-to-Noise and Fast Calibration of Optical Tweezers Using Single Trapping Events

Micromachines ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 570
Author(s):  
Alexander B. Stilgoe ◽  
Declan J. Armstrong ◽  
Halina Rubinsztein-Dunlop
Keyword(s):  
Brownian Motion ◽  
Optical Tweezers ◽  
Optical Trap ◽  
Force Transducer ◽  
Signal To Noise ◽  
Likelihood Estimator ◽  
Micro Fluidics ◽  
Large Numbers ◽  
Force Reconstruction ◽  
Micron Particle

The trap stiffness us the key property in using optical tweezers as a force transducer. Force reconstruction via maximum-likelihood-estimator analysis (FORMA) determines the optical trap stiffness based on estimation of the particle velocity from statistical trajectories. Using a modification of this technique, we determine the trap stiffness for a two micron particle within 2 ms to a precision of ∼10% using camera measurements at 10 kfps with the contribution of pixel noise to the signal being larger the level Brownian motion. This is done by observing a particle fall into an optical trap once at a high stiffness. This type of calibration is attractive, as it avoids the use of a nanopositioning stage, which makes it ideal for systems of large numbers of particles, e.g., micro-fluidics or active matter systems.

Constructing Von Karman Random Media Model with Power Spectrum Method

2014 ◽  
Vol 536-537 ◽  
pp. 911-914
Author(s):  
Ning Yang ◽  
Xu Qian
Keyword(s):  
Power Spectrum ◽  
Frequency Domain ◽  
Random Media ◽  
Correlation Lengths ◽  
Spectrum Method ◽  
Inverse Fourier Transformation ◽  
Von Karman ◽  
Auto Correlation Function ◽  
Power Spectrum Method ◽  
Von Kármán

In this paper, Von Karman random media is constructed with power spectrum method. The random media with Von Karman autocorrelation cannot be constructed in time domain but in frequency domain. So power spectrum method is utilized to solve the problem. The spectrum of random function is generated in frequency domain with random field and auto-correlation function. With inverse Fourier transformation, the Von Karman random media model is constructed. With different correlation lengths, six group of Von Karman random media are constructed.

scholarly journals Evaluation of Images Containing Scatter-rays Using the Power Spectrum Method

1998 ◽  
Vol 54 (8) ◽  
pp. 961-969
Author(s):  
TETSUO KIDA ◽  
HIDEO OONISHI ◽  
SATORU MATSUO ◽  
KAZUO NOMA ◽  
MASAHIRO YOSHIMURA ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Spectrum Method ◽  
Power Spectrum Method

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.

Atmospheric Phase Screen Simulation Using Zernike Polynomial

2012 ◽  
Vol 182-183 ◽  
pp. 1002-1006
Author(s):  
Wei Yan ◽  
Zhi Hua Chen ◽  
Tai Jiao Du ◽  
Jian Guo Wang
Keyword(s):  
Power Spectrum ◽  
Spatial Frequency ◽  
Structure Function ◽  
Atmospheric Turbulence ◽  
Phase Screen ◽  
Outer Scale ◽  
Spectrum Method ◽  
Theoretical Structure ◽  
Power Spectrum Method ◽  
Theoretical Results

An algorithm is described which simulates atmospheric phase screen (PS) distorted by von Karman atmospheric turbulence by using Zernike expansion of randomly weighted Karhunen-Loeve function. The statistics of the PS generated by using power spectrum method which is most commonly used for generating PS poorly match up with the theoretical structure function, especially at low spatial frequency, while the algorithm described in the this paper can compensate for this shortcoming. And the accuracy of the PS is verified by comparing with the theoretical results. Furthermore, comparing with the existed methods which also use the Zernike expansion to simulate PS, algorithm presented in this paper is more accurate because the effects of the finite outer scale L0.is included

Reconstructing the state space of chaotic BZ reaction system using power spectrum method

1998 ◽  
Vol 43 (17) ◽  
pp. 1447-1452
Author(s):  
Yongjun Li ◽  
Zunsheng Cai ◽  
Yanni Li ◽  
Dahai Song ◽  
Hao Song ◽  
...  
Keyword(s):  
Power Spectrum ◽  
State Space ◽  
Reaction System ◽  
The State ◽  
Bz Reaction ◽  
Spectrum Method ◽  
Power Spectrum Method

scholarly journals Anomalous Lehmann Rotation of Achiral Nematic Liquid Crystal Droplets Trapped under Linearly Polarized Optical Tweezers

Molecules ◽  
2021 ◽  
Vol 26 (14) ◽  
pp. 4108
Author(s):  
Jarinee Kiang-ia ◽  
Rahut Taeudomkul ◽  
Pongthep Prajongtat ◽  
Padetha Tin ◽  
Apichart Pattanaporkratana ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Optical Tweezers ◽  
Nematic Liquid Crystal ◽  
Laser Power ◽  
Optical Trap ◽  
Laser Trapping ◽  
Laser Trap ◽  
Continuous Rotation ◽  
Linearly Polarized ◽  
Optical Levitation

Continuous rotation of a cholesteric droplet under the heat gradient was observed by Lehmann in 1900. This phenomenon, the so-called Lehmann effect, consists of unidirectional rotation around the heat flux axis. We investigate this gradient heat effect using infrared laser optical tweezers. By applying single trap linearly polarized optical tweezers onto a radial achiral nematic liquid crystal droplet, trapping of the droplet was performed. However, under a linearly polarized optical trap, instead of stable trapping of the droplet with slightly deformed molecular directors along with a radial hedgehog defect, anomalous continuous rotation of the droplet was observed. Under low power laser trapping, the droplet appeared to rotate clockwise. By continuously increasing the laser power, a stable trap was observed, followed by reverse directional rotation in a higher intensity laser trap. Optical levitation of the droplet in the laser beam caused the heat gradient, and a breaking of the symmetry of the achiral nematic droplet. These two effects together led to the rotation of the droplet under linearly polarized laser trapping, with the sense of rotation depending on laser power.

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