基于飞秒超连续白光的单光束宽带CARS光谱技术研究

Coherent anti-Stokes Raman scattering (CARS) spectroscopy can be employed to study molecular components and structures of materials. Because of its great advantages of high sensitivity against fluorescence background and high collection efficiency, it can be employed in studying material properties, optical bio-imaging, and et al. The applications of conventional CARS technique are greatly restricted as multi-beam is involved and wavelength scanning is needed to acquire the full vibrational spectrum. In this project, we propose a single-beam CARS spectroscopy based on femtosecond laser induced white-light supercontinuum. By modulating the excitation pulse with spectral notch filter, multi vibrational spectra of molecule can be achieved at the same time. This single-beam CARS shows great advantages with high spectral resolution, large dynamic spectral range and high signal-to-noise ratio. The study of the project includes:.(1) Investigating the key techniques in single-beam CARS measurements based on spectral notch filtered pulses, and realizing single-beam CARS detection with high spectral resolution. .(2) Enlarging the dynamic spectral range of the proposed single-beam CARS measurements, by developing supercontinuum white-light source induced by femtosecond laser pulses. .(3) The final goal of the project is to set up the single-beam broadband CARS spectrograph based on femtosecond white-light supercontinuum, and explore its application in bio-imaging and combustion flow imaging. The system is characterized by a spectral resolution less than 50 cm-1 and dynamic range higher than 3000 cm-1.

相干反斯托克斯拉曼散射(CARS)光谱技术可检测物质的分子组成和结构特征，具有信号强、灵敏度高、抗荧光干扰等优点，在材料检测、生物成像等领域具有重要应用价值。普通CARS测量需要多光束共同作用，且需波长扫描以获取完整的分子振动谱，限制了该技术的应用。本项目提出一种基于超连续白光的单光束CARS光谱技术，利用飞秒超连续白光作为激光光源，通过陷波调制产生具有窄带光谱特征的激发光脉冲，可同时完成分子多个振动模式的CARS测量，并具有光谱分辨率高、动态范围大、信噪比高的优点。项目拟研究基于光谱陷波调制的单光束CARS测量技术，实现光谱分辨率高的单光束CARS测量；利用飞秒激光在介质中诱导产生均匀稳定的超连续白光光源，扩展单光束CARS的动态测量范围；研制基于超连续白光的单光束宽带CARS测量系统，光谱分辨率优于50波数，测量动态范围高于3000波数。探索该技术在生物显微成像与燃烧场检测中的应用。

相干反斯托克斯拉曼散射（CARS）光谱技术在材料检测、生物成像以及燃烧场分析等多个领域具有重要应用。普通CARS测量需要多光束共同作用，且需通过波长扫描获取完整的分子振动谱，限制了该技术的应用。本项目提出了一种基于陷波调制技术的飞秒激光单光束CARS光谱技术，可同时完成分子中多个振动模式的测量；基于微透镜阵列光场调控技术，实现了高强度、稳定飞秒超连续白光光源；研制了高灵敏度飞秒时间分辨白光泵浦-探测光谱测量系统，并将其应用于材料光生载流子动力学研究。项目取得的主要研究成果如下：.（a）研究了基于飞秒脉冲激光的单光束CARS光谱测量技术，利用单光束飞秒脉冲激光实现了材料分子中多个振动能级的测量，克服了传统CARS光谱技术需要波长扫描的问题；通过陷波调制获得了2nm带宽的探测光谱，解决了飞秒脉冲谱线宽、CARS测量光谱分辨率低的难题，最终实现单光束CARS测量光谱分辨率优于40cm-1。.（b）为拓展飞秒脉冲激光单光束CARS光谱测量的光谱范围，提出基于微透镜阵列光场调控技术产生高强度、稳定飞秒超连续白光光源的新方法。利用微透镜阵列聚焦飞秒激光，并在透明介质中形成多重白光产生通道，经过光束整形后可产生高强度、稳定性好的超连续白光，解决了超连续白光探测光稳定性和强度无法兼顾的难题；在保证白光稳定的同时，使脉冲能量提升了2个量级。.（c）基于均匀稳定超连续白光产生方法，项目组自主搭建了飞秒时间分辨白光泵浦-探测光谱测量系统，系统时间分辨率、信噪比均达到国际先进水平。利用该系统，研究了石墨烯、过渡金属硫化物、钙钛矿材料等光电功能材料中的光生载流子动力学过程，为新型功能材料与器件的制备提供了重要参考依据。