激光功率对光镊光阱刚度标定的影响

光阱刚度是描述光镊对粒子进行操控的重要力学指标，实际使用过程中会受到激光功率的影响。采用均方位移法及玻尔兹曼统计法对搭建的光镊系统进行光阱刚度的标定，利用图像采集方法进行微粒位移的测量，并对两种方法的测量结果进行了比较。为了提高光阱刚度的标定结果的准确性，分析了光路放大倍数、温度变化对最后标定结果的精度影响。结果表明，两种方法进行标定的结果基本相同；光阱刚度在低激光功率（1 mW ~20 mW）范围时随功率近似线性增加，在高功率情况下（25 mW~60 mW）随功率增加不再线性增加，而是趋于一个饱和值。此外，光路放大倍数标定的精确性对标定的精度影响较大，10%的相对误差时，标定结果产生23%的变化，温度对标定的精度影响较小，0.1 ℃的温度变化导致标定结果0.034%的变化。

Influence of laser power on stiffness calibration of optical tweezers

The stiffness of optical trap has become an important parameter to describe the manipulation capacity of optical tweezers to particles, which can be affected by laser power. The equipartition theorem and Boltzmann statistic methods were used to calibrate the stiffness of the built optical tweezers, where an image acquisition method was used to measure the particles displacement, and the calibrated results based on these two methods were compared, which showed good agreement. Furthermore, the influences of sample cells laser power on the stiffness were studied. In order to increase the accuracy of stiffness, the amplification factor of light path and temperature should be considered. Seen from the results, the two calibration methods have similar results; the optical trap stiffness increases linearly with the laser power on the sample cell for lower power 1 mW~20 mW, but shows a tendency toward stabilization for higher power 25 mW~60 mW. Whats more, the calibrations accuracy of light path amplification brings a great impact, a 10% relative variation leads to a 23% offset of stiffness, and the temperature has a little influence, a variation of 0.1 ℃ results in 0.034% variation.