Català-Castro Frederic, Martín-Badosa Estela
Optical Trapping Lab, Grup de Biofotònica (BiOPT), Departament de Física Aplicada, Universitat de Barcelona, 08028 Barcelona, Spain.
Institut de Nanociència i Nanotecnologia (IN²UB), 08028 Barcelona, Spain.
Micromachines (Basel). 2021 May 15;12(5):559. doi: 10.3390/mi12050559.
Spatial light modulators (SLMs) have been widely used to achieve dynamic control of optical traps. Often, holographic optical tweezers have been presumed to provide nanometer or sub-nanometer positioning accuracy. It is known that some features concerning the digitalized structure of SLMs cause a loss in steering efficiency of the optical trap, but their effect on trap positioning accuracy has been scarcely analyzed. On the one hand, the SLM look-up-table, which we found to depend on laser power, produces positioning deviations when the trap is moved at the micron scale. On the other hand, phase quantization, which makes linear phase gratings become phase staircase profiles, leads to unexpected local errors in the steering angle. We have tracked optically trapped microspheres with sub-nanometer accuracy to study the effects on trap positioning, which can be as high as 2 nm in certain cases. We have also implemented a correction strategy that enabled the reduction of errors down to 0.3 nm.
空间光调制器（SLM）已被广泛用于实现对光阱的动态控制。通常，人们认为全息光镊能提供纳米或亚纳米级的定位精度。众所周知，一些与SLM数字化结构相关的特性会导致光阱转向效率的损失，但其对光阱定位精度的影响却鲜有分析。一方面，我们发现SLM查找表依赖于激光功率，当光阱在微米尺度上移动时会产生定位偏差。另一方面，相位量化使线性相位光栅变成相位阶梯轮廓，导致转向角出现意外的局部误差。我们以亚纳米精度跟踪了光阱捕获的微球，以研究其对光阱定位的影响，在某些情况下该影响高达2纳米。我们还实施了一种校正策略，能够将误差降低至0.3纳米。
