Frozen Waves: Longitudinal Patterning of Twisted Light

公开发布的提案摘要：* 传统的光束遭受衍射，即，在横向于其传播方向的平面中测量的光束的空间尺寸随着传播距离而增加。它们在吸收介质中传播时也会受到衰减，并在其路径上被小物体散射（即改变其原始方向）。另一方面，冻结波（FW）和修改的冻结波（MFW）是一类光束，其不仅在预定义的有限距离上解决了上述缺点，而且可能更有趣的是将允许用户沿着其传播方向（即，沿着光束的光轴。）此外，MFW可以携带角动量（自旋或轨道），这意味着它们可以将扭矩和旋转传递给其路径上的小物体。在这个建议中，我们将进一步发展MFW的理论，并研究其在光学微操纵和传感中的应用。特别是，我们将研究观察光学扭转细胞的可能性，其中相反方向的扭矩施加到一个细胞的两端的运动类似于从湿毛巾挤水。从细胞的生物力学特性中收集的信息在确定细胞的健康和病理学方面非常重要。此外，我们将使用MFW的轨道角动量特性来感测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.