Two-Photon Absorption Imaging by Laser Pulse Shaping

描述(由申请人提供)： 这项提案要求支持一项新的倡议，即使用由沃伦和普林斯顿大学的同事开发的飞秒激光脉冲整形技术，作为一种工具，在临床环境中允许增强多光子光学成像(在宾夕法尼亚大学)。沃伦在普林斯顿的团队开发了世界领先的技术，用于改变飞秒激光脉冲的形状(相位和幅度调制)，并在从高速光通信到原子和分子光谱分析的应用中，在广泛的波长范围内调谐这些激光脉冲。他的团队最近还证明，有可能使用特定的幅度和相位调制脉冲来检测双光子吸收，而激光功率非常有限。在宾夕法尼亚大学的初始设备和工作人员的支持下(宾夕法尼亚大学任命他为放射学兼职教授)，沃伦在医学院组建了一个飞秒激光实验室，将这些方法应用于临床环境，并聘请了拥有超快激光、共焦显微镜和组织光谱学专业知识的全职员工。这项提议包括一系列增强多光子成像的成形脉冲方法。例如，脉冲形状可以设计为使微弱的双光子吸收填充激光脉冲光谱中的“空洞”，从而允许低本底检测，这将允许直接观察在多光子显微镜下看不见的重要分子标记(如NAD+)。它还允许在长波长水窗口(约1.05和1.3微米)中激发，大大减少了光学散射，因此允许双光子吸收光谱，比传统的基于荧光的方法具有更大的穿透深度。普林斯顿大学对小的散射样本进行了初步研究；宾夕法尼亚大学的工作目标是在第一年在完整组织上展示双光子吸收光谱，在第二年在动物模型上展示双光子吸收光谱。

DESCRIPTION (provided by applicant): This proposal requests support for a novel initiative to use femtosecond laser pulse shaping technology, developed by Warren and coworkers at Princeton University, as a tool to permit enhanced multiphoton optical imaging in a clinical setting (at the University of Pennsylvania). Warren's group at Princeton has developed world-leading technologies for altering the shape (phase and amplitude modulation) of femtosecond laser pulses, and for tuning these laser pulses over a wide range of wavelengths, in applications ranging from high-speed optical communications to atomic and molecule spectroscopy. His group has recently also demonstrated that it is possible to use specific amplitude- and phase-modulated pulses to detect two-photon absorption with very modest laser powers. With initial equipment and staff support from the University of Pennsylvania (which has appointed him part-time as an Adjunct Professor in Radiology), Warren has assembled a femtosecond laser laboratory at the Medical School to adapt these methods to a clinical environment, and has hired full time staff with expertise in ultrafast lasers, confocal microscopy, and tissue spectroscopy. This proposal includes a range of shaped-pulse methods to enhance multiphoton imaging. For example, the pulse shape can be designed so that weak two-photon absorption refills "holes" in the spectrum of the laser pulse, permitting low-background detection, and this would permit direct observation of important molecular markers (such as NAD+) which are invisible in multiphoton microscopy. It also permits excitation in the long-wavelength water windows (around 1.05 and 1.3 microns) which have significantly reduced optical scattering, and hence permit two-photon absorption spectroscopy with greater penetration depth than conventional fluorescence-based methods. Initial studies have been conducted on small scattering samples at Princeton; the goal of the work at Penn is demonstration of two-photon absorption spectroscopy on intact tissue in the first year, and on animal models in the second year.