Liu Zhihai, Liang Peibo, Zhang Yu, Zhang Yaxun, Zhao Enming, Yang Jun, Yuan Libo
Opt Express. 2015 Apr 6;23(7):8650-8. doi: 10.1364/OE.23.008650.
Efficient and controllable launching function of an optical tweezers is a challenging task. We present and demonstrate a novel single fiber optical tweezers which can trap and launch (clean) a target polystyrene (PS) microsphere (diameter~10μm) with independent control by using two wavelengths beams: 980nm and 1480nm. We employ 980nm laser beam to trap the target PS microsphere by molding the fiber tip into a special tapered-shape; and we employ 1480nm laser beam to launch the trapped PS microsphere with a certain velocity by using the thermophoresis force generated from the thermal effect due to the high absorption of the 1480nm laser beams in water. When the launching force is smaller than the trapping force, the PS microsphere will be trapped near the fiber tip, and the launching force will blow away other PS microspheres in the workspace realizing the cleaning function; When the launching force is larger than the trapping force, the trapped PS microsphere will be launched away from the fiber tip with a certain velocity and towards a certain direction, realizing the launching function. The launching velocity, acceleration and the distance can be measured by detecting the interference signals generated from the PS microsphere surface and the fiber tip end-face. This PS microsphere launching and cleaning functions expanded new features of single fiber optical tweezers, providing for the possibility of more practical applications in the micro manipulation research fields.
光镊的高效且可控发射功能是一项具有挑战性的任务。我们提出并展示了一种新型单光纤光镊，它可以通过使用980nm和1480nm两种波长的光束，独立控制捕获并发射（清理）目标聚苯乙烯（PS）微球（直径约10μm）。我们利用980nm激光束通过将光纤尖端加工成特殊的锥形来捕获目标PS微球；并且利用由1480nm激光束在水中的高吸收产生的热效应所产生的热泳力，用1480nm激光束以一定速度发射被捕获的PS微球。当发射力小于捕获力时，PS微球将被捕获在光纤尖端附近，并且发射力会吹走工作空间中的其他PS微球，实现清理功能；当发射力大于捕获力时，被捕获的PS微球将以一定速度并朝着特定方向从光纤尖端发射出去，实现发射功能。发射速度、加速度和距离可以通过检测PS微球表面和光纤尖端端面产生的干涉信号来测量。这种PS微球的发射和清理功能扩展了单光纤光镊的新特性，为微操纵研究领域中更多实际应用提供了可能性。
