Feedback holographic control of self-reconstructing laser beams in strongly scattering media.

基于光片的显微镜对现代显微镜中新型智能照明方法的发展产生了强烈的影响，它显著提高了三维图像质量。这导致了发育生物学和三维细胞生物学领域的进步，但也使激光束在强散射介质中的传播研究脱颖而出。最近研究表明，每周聚焦激光束的相位分布对非均匀每周吸收介质中的光散射有很大的影响。特别是贝塞尔光束显示出惊人的光束自重建能力和穿透深度，比传统的高斯光束增加了约50%。然而，贝塞尔光束携带一个同心环系统，这导致在光片显微镜图像对比度的损失。在这个建议中，我们想通过深入研究计算机全息生成的相位分布对光束传播特性的依赖，利用线性和非线性光学方法来提高光片显微镜中照明光束的数量。在线性光学领域，我们的目标是开发不同平面散射光的不同读出程序。基于提取的数据，我们希望通过反馈和迭代来测试和开发不同的波前校正方法。通过使用线共聚焦检测系统，环形系统的对比度衰减影响将显著降低。此外，我们的目标是通过非线性光学方法提高单束激光的质量，从而提高照明光片的质量，从而非线性地抑制贝塞尔光束环系统的影响。一方面，我们将利用双光子荧光激发原理，特别是全息形相位对短激光脉冲在散射介质中传播的影响进行研究。另一方面，我们计划应用sted原理，我们将使用第二次高阶自重构贝塞尔光束通过受激发射耗尽环系统中的荧光。在这里，我们希望在第一步通过时间门控提高耗尽效率来最大化光学分辨率。在第二步中，我们希望通过反馈全息控制来优化激发光束和STED-光束的相位分布，从而显著提高单光束产生的荧光，从而提高光片的质量。

Light sheet based microscopy has had a strong impact on the development of novel intelligent illumination methods in modern microscopy, which improved 3D image quality significantly. This led to an advance in the areas of developmental biology and 3-D cell biology, but also made the investigation of laser beam propagation through strongly scattering media come to the fore. Recently it could be shown, that the phase profile of a weekly focused laser beam had a strong influence on light scattering in inhomogeneous, weekly absorbing media. In particular, Bessel beams revealed an amazing capability of beam self-reconstruction and a penetration depth which was increased by about 50% relative to conventional Gaussian beams. However, Bessel beams carry a concentric ring system, which results in a loss of image contrast in light sheet microscopy.In this proposal we want to use linear and nonlinear optical methods to improve the quantity of illumination beams in light sheet microscopy by investigating intensively the dependency of computer- holographically generated phase profiles on the beam propagation properties. In the area of linear optics, we aim to develop different read-out procedures for scattered light in different planes. Based on the extracted data, we then want to test and develop different wavefront correction procedures by feedback and iteration. The contrast diminishing influence of the ring system shall be reduced significantly by using a line-confocal detection system.In addition we aim to improve the quality of single laser beams and thereby of the illuminating light sheet by using nonlinear optical approaches, such that the influence of the Bessel beams ring system is nonlinearly suppressed. On the one hand we will use the principle of two-photon fluorescence excitation, where especially the influence of the holographically shaped phase on the propagation of short laser pulses through the scattering medium is to be investigated. On the other hand, we plan to apply the STED-principle, where we will use a second self-reconstructing Bessel beam of higher order to deplete the fluorescence in the ring system by stimulated emission. Here, we want to maximize the optical resolution by improving the depletion efficiency through time-gating in a first step. In a second step, we want to optimize the phase profiles of the excitation beam and the STED- beam by a feedback holographic control, such that fluorescence generated in the single beams will be improved significantly and thereby the quality of the light sheet.