Frozen Waves: Longitudinal Patterning of Twisted Light

公开发布建议摘要：*传统光束受到衍射的影响--即光束的空间尺寸，在横跨其传播方向的平面上测量，随着传播距离的增加而增加。它们在吸收介质中传播时也会受到衰减，并受到路径上的小物体的散射(即改变它们的原始方向)。另一方面，冻结波(FWS)和修正冻结波(MFW)是一类光束，它不仅在预定的有限距离内解决了上述缺点，而且可能更有趣的是允许用户沿着其传播方向(即沿着光束的光轴)整形和修改光束的强度。此外，MFW可以携带角动量(自旋或轨道)，这意味着它们可以向其路径上的小物体施加扭矩和旋转。*在本方案中，我们进一步发展了MFW的理论，并将研究它们在光学微操作和传感方面的应用。特别是，我们将研究观察细胞中光学扭转的可能性；在细胞的两端施加相反方向的扭矩，其运动类似于从湿毛巾中挤压水。从细胞的生物力学属性中收集的信息在确定细胞的健康和病理方面极其重要。此外，我们将利用MFW的轨道角动量特性来感知和测量与各种液体和气体相关的折射率。

Summary of Proposal for Public Release:***Conventional optical beams suffer from diffraction – i.e., the spatial size of the beam, measured in a plane transverse to its direction of propagation, increases with the propagation distance. They also suffer from attenuation when traveling in an absorbing medium and scatter from small objects in their path (i.e. change their original direction). On the other hand, Frozen waves (FWs) and Modified Frozen Waves (MFWs) are a class of optical beams, which not only address the aforementioned shortcomings over a predefined finite distance, but perhaps more intriguing will allow the user to shape and modify the beam's intensity along its direction of propagation (i.e., along the beam's optical axis.) Moreover, MFW can carry angular momentum (spin or orbital) which means they can impart torque and rotation to small objects on their path.*** In this proposal, we further develop the theory of MFWs and we will investigate their applications in optical micromanipulation and sensing. In particular, we will examine the possibility of observing optical torsions in cells; in which oppositely directed torques are applied to the two-ends of a cell in a motion similar to squeezing water from a wet towel. Information gathered from biomechanical properties of cells is extremely important in determining cells' health and pathology. Moreover, we will use the orbital angular momentum properties of the MFWs to sense and measure the index of refraction associated with various liquids and gases.