Eriksson E, Keen S, Leach J, Goksör M, Padgett M J
Department of Physics, Göteborg University, SE-41296 Göteborg, Sweden.
Opt Express. 2007 Dec 24;15(26):18268-74. doi: 10.1364/oe.15.018268.
Holographic optical tweezers is a widely used technique to manipulate the individual positions of optically trapped micron-sized particles in a sample. The trap positions are changed by updating the holographic image displayed on a spatial light modulator. The updating process takes a finite time, resulting in a temporary decrease of the intensity, and thus the stiffness, of the optical trap. We have investigated this change in trap stiffness during the updating process by studying the motion of an optically trapped particle in a fluid flow. We found a highly nonlinear behavior of the change in trap stiffness vs. changes in step size. For step sizes up to approximately 300 nm the trap stiffness is decreasing. Above 300 nm the change in trap stiffness remains constant for all step sizes up to one particle radius. This information is crucial for optical force measurements using holographic optical tweezers.
全息光镊是一种广泛应用的技术，用于操纵样品中被光捕获的微米级粒子的个体位置。通过更新显示在空间光调制器上的全息图像来改变陷阱位置。更新过程需要有限的时间，导致光阱强度暂时降低，从而使光阱刚度降低。我们通过研究流体流动中被光捕获粒子的运动，研究了更新过程中陷阱刚度的这种变化。我们发现陷阱刚度变化与步长变化之间存在高度非线性行为。对于步长高达约300 nm的情况，陷阱刚度在降低。在300 nm以上，对于所有直至一个粒子半径的步长，陷阱刚度的变化保持恒定。此信息对于使用全息光镊进行光力测量至关重要。
