Galinskiy Ivan, Isaksson Oscar, Salgado Israel Rebolledo, Hautefeuille Mathieu, Mehlig Bernhard, Hanstorp Dag
Opt Express. 2015 Oct 19;23(21):27071-84. doi: 10.1364/OE.23.027071.
We have constructed a counterpropagating optical tweezers setup embedded in a Sagnac interferometer in order to increase the sensitivity of position tracking for particles in the geometrical optics regime. Enhanced position determination using a Sagnac interferometer has previously been described theoretically by Taylor et al. [Journal of Optics 13, 044014 (2011)] for Rayleigh-regime particles trapped in an antinode of a standing wave. We have extended their theory to a case of arbitrarily-sized particles trapped with orthogonally-polarized counter-propagating beams. The working distance of the setup was sufficiently long to optically induce particle oscillations orthogonally to the axis of the tweezers with an auxiliary laser beam. Using these oscillations as a reference, we have experimentally shown that Sagnac-enhanced back focal plane interferometry is capable of providing an improvement of more than 5 times in the signal-to-background ratio, corresponding to a more than 30-fold improvement of the signal-to-noise ratio. The experimental results obtained are consistent with our theoretical predictions. In the experimental setup, we used a method of optical levitator-assisted liquid droplet delivery in air based on commercial inkjet technology, with a novel method to precisely control the size of droplets.
我们构建了一种嵌入萨格纳克干涉仪的反向传播光镊装置，以提高几何光学 regime 中粒子位置跟踪的灵敏度。此前，泰勒等人 [《光学杂志》13, 044014 (2011)] 从理论上描述了使用萨格纳克干涉仪增强位置确定的方法，该方法针对被困在驻波波腹处的瑞利 regime 粒子。我们将他们的理论扩展到了用正交偏振反向传播光束捕获任意大小粒子的情况。该装置的工作距离足够长，可通过辅助激光束在与光镊轴线正交的方向上光学诱导粒子振荡。以这些振荡为参考，我们通过实验表明，萨格纳克增强背焦平面干涉测量法能够将信背比提高5倍以上，相当于将信噪比提高30倍以上。获得的实验结果与我们的理论预测一致。在实验装置中，我们基于商业喷墨技术采用了一种在空气中利用光悬浮辅助液滴输送的方法，并采用了一种精确控制液滴大小的新方法。
