基于光纤飞秒激光器及PPLN的宽带CARS显微成像系统

本项提出基于光纤飞秒激光器及PPLN晶体的宽带CARS显微成像方案。该方案只需一台价格相对低廉的光纤飞秒激光器作为光源，就能够搭建宽带CARS显微成像系统，实现分子中多个化学键的同时成像。光纤飞秒激光器输出脉冲一分为二，一束泵浦全正色散光子晶体光纤产生时谱结构良好的超连续谱作为斯托克斯光；另一束经透镜聚焦至一片特殊设计的PPLN晶体，通过光学参量产生过程，将光源输出的单一波长的脉冲光转换为红外波段的可调谐光，调谐范围约为1400nm~1600nm，另外选择一片PPLN晶体对红外可调谐脉冲倍频，得到光束质量良好且波长范围在700nm~800nm内可调谐的光脉冲作为探测光。两束激光脉冲作为激发光，同步后共线输入显微物镜，为获取分子完整谱信息的CARS显微图像奠定基础。

The project is a broadband CARS microscopy solutions based on optical fiber laser and the PPLN crystal. The output pulse of the fiber laser is split in two beams, one is used to pump the all-normal dispersion photonic crystal fiber and produce supercontinuum as Stokes beam; another path will focus on a piece of special designed PPLN crystal, and wavelength of the beam can be converted to an infrared tuning pulse, and the tuning range from 1400 nm to 1600 nm range, immediately after the pulse will pass through another PPLN to acquire a tuning beam from 700 nm to 800 nm, which will play as the probe beam. The combined two beams focus on the specimen via an objective to acquire the broadband CARS signal.