Progress in light scattering engineering made it feasible to develop optical tweezers allowing capture, hold, and controllable displacement of submicrometer-size particles and biological structures. However, the momentum conservation law imposes a fundamental restriction on the optical pressure to be repulsive in paraxial fields, which severely limits the capabilities of optomechanical control, e.g., preventing attractive force acting on sufficiently subwavelength particles and molecules. Herein, we revisit the issue of optical forces by their analytic continuation to the complex frequency plane and considering their behavior in the transient regime. We show that the exponential excitation at the complex frequency offers an intriguing ability to achieve a pulling force for a passive resonant object of any shape and composition, even in the paraxial approximation. The approach is elucidated on a dielectric Fabry–Perot cavity and a high-refractive-index dielectric nanoparticle, a fruitful platform for intracellular spectroscopy and lab-on-a-chip technologies, where the proposed technique may find unprecedented capabilities.

中文翻译：

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虚拟光学拉力

光散射工程技术的进步使得开发光镊成为可能，该光镊可以捕获，保持和控制亚微米级颗粒和生物结构的位移。然而，动量守恒定律对在近轴场中排斥的光学压力施加了基本限制，这严重限制了光机械控制的能力，例如，防止吸引力作用在足够的亚波长粒子和分子上。在这里，我们通过对复数频率平面的解析连续性来重新考虑光学力的问题，并考虑它们在瞬态状态下的行为。我们证明了在复数频率下的指数激励提供了一种吸引人的能力，可以为任何形状和成分的无源谐振物体提供拉力，即使在近轴近似下也是如此。该方法在电介质Fabry-Perot腔体和高折射率电介质纳米颗粒上得到了阐明，这是一种用于细胞内光谱学和芯片实验室技术的卓有成效的平台，所提出的技术可能会找到前所未有的功能。