新型自由空间超长无衍射光束研究

Owing to the finite power in free space, the problem of diffraction is thought to be insurmountable. Thus, only light beam with finite anti-diffracting distance can be obtained in free space. For a long time, the problem of diffraction has not only confused optical scientists, but also restricted many applications, such as optical imaging, optical communication. Here, to solve this problem, we propose an approach to create a light beam with an ultralong anti-diffracting distance in free space. The anti-diffracting distance is no longer restricted by finite power in free space but instead depends on a new understanding of non-diffractive light beam, namely the inherent energy flux mechanism, which can be revealed by investigating the energy flux of non-diffractive light beam. In addition, a versatile wavefront modulation technique is developed to manipulate the position, number, amplitude and phase of non-diffractive light beam so that the inherent energy flux mechanism can be realized and a light beam with a tunable super-long anti-diffracting distance is eventually generated in free space. This work may not only facilitate the study of non-diffractive light beams to a new level, but also open up new avenues to the breakthrough of optical applications.

由于自由空间有限能量的限制，光波的衍射效应一直无法被克服，以至于无衍射光束只能在非常有限的距离内保持光束传播不变性。长期以来，这个问题不仅困扰了光学研究人员，也极大地阻碍了光学显微成像、光通信等领域的发展。本项目将针对光波衍射效应的问题开展研究工作，通过研究无衍射光束内部能量流动作用机制，提出光束在自由空间中传播的新机理，实现光束由能量依赖向非能量依赖的转化。此外，利用光程与光束相位的关系，开发基于光束传播机理的新型光场调控方法，实现对无衍射光束的光场位置、数量、振幅、相位的全方位调控，最终在自由空间中产生无衍射距离可控的超长无衍射光束。此项工作将推动无衍射光束基础研究的进一步发展，而且为光学相关应用领域的突破提供底层原理的支持。

项目主要围绕如何克服光波衍射效应开展研究工作。在项目执行期间，通过建立无衍射光束传播物理模型，我们揭示了无衍射光束在自由空间中保持无衍射特性的能量振荡机理。基于该机理，提出一种放能充能的方法，实现了光束由能量依赖向非能量依赖的转化。进一步地，我们利用光程补偿机制，开发出基于光束传播机理的新型光场调控方法，即光笔，实现了无衍射光束的光场位置、数量、振幅、相位的全方位调控。最后，结合能量机制及光笔，我们在自由空间中产生了无衍射距离可控的超长无衍射光束，在一定程度上克服了光波衍射效应，完成了项目预设目标。本项目所取得的成果不仅为光束传播行为提供新的认识，而且为为光学相关应用领域的突破提供底层原理的支持。