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

基于光片的显微术对现代显微术中新型智能照明方法的发展产生了巨大影响，显著提高了3D图像质量。这导致了发育生物学和3-D细胞生物学领域的进步，但也使激光束通过强散射介质传播的研究脱颖而出。最近可以表明，弱聚焦激光束的相位分布对光在非均匀弱吸收介质中的散射有很大的影响。特别是，贝塞尔光束揭示了一个惊人的能力，光束的自我重建和穿透深度增加了约50%，相对于传统的高斯光束。然而，贝塞尔光束携带一个同心环系统，这将导致在光片显微镜图像对比度的损失，在这个建议中，我们想使用线性和非线性光学方法来提高照明光束的数量在光片显微镜通过深入研究的依赖性的计算机全息产生的相位分布的光束传输特性。在线性光学领域，我们的目标是为不同平面中的散射光开发不同的读出程序。基于所提取的数据，然后我们想要通过反馈和迭代来测试和开发不同的波前校正程序。采用线共焦探测系统可以显著降低环形系统的对比度衰减影响，并采用非线性光学方法改善单光束质量，从而改善照明光片的质量，从而非线性地抑制贝塞尔光束环形系统的影响。一方面，我们将使用双光子荧光激发的原理，特别是全息成形相位对短激光脉冲通过散射介质的传播的影响将被研究。另一方面，我们计划应用STED原理，在该原理中，我们将使用第二个高阶自重构贝塞尔光束通过受激发射来耗尽环系统中的荧光。在这里，我们希望通过在第一步中通过时间选通提高耗尽效率来最大化光学分辨率。在第二步骤中，我们想要通过反馈全息控制来优化激发光束和STED光束的相位分布，使得在单个光束中产生的荧光将被显著改善，从而改善光片的质量。

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.