Jun Chang Su, Kim Byoung Yoon, Park Ju Hyun, Lee Jae Yong, Lee Eun Seong, Yeom Dong-Il
Fiber Optics Laboratory, Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, South Korea.
Appl Opt. 2010 Jul 10;49(20):3916-21. doi: 10.1364/AO.49.003916.
We studied the nonlinear signal generated in the fiber at an anti-Stokes wavelength during the delivery of the picosecond (ps) pump and Stokes beams in coherent anti-Stokes Raman scattering (CARS) microscopy. A small non-phase-matched four-wave mixing (FWM) signal was prevalently observed in the fiber at the power level where other nonlinear processes, including self-phase modulation and cross-phase modulation, were well suppressed. We analyzed the features of the FWM signal generation by varying the location of temporal overlap between two input pulses in the fiber to compare this to the CARS signal generated in the sample. Numerical modeling based on the nonlinear Schrödinger equation was also conducted and clearly explains the results in the experiment. In addition, we experimentally verified the interferometric feature of this FWM signal with the CARS signal by employing a phase-shifting unit, which potentially suggests the use of the FWM signal as a local oscillator for the interferometric CARS system.
我们研究了在皮秒（ps）泵浦光和斯托克斯光束传输过程中，相干反斯托克斯拉曼散射（CARS）显微镜中光纤在反斯托克斯波长处产生的非线性信号。在光纤中，当包括自相位调制和交叉相位调制在内的其他非线性过程得到很好抑制的功率水平下，普遍观察到一个小的非相位匹配四波混频（FWM）信号。我们通过改变光纤中两个输入脉冲的时间重叠位置来分析FWM信号产生的特征，并将其与样品中产生的CARS信号进行比较。还基于非线性薛定谔方程进行了数值建模，清楚地解释了实验结果。此外，我们通过采用相移单元，实验验证了该FWM信号与CARS信号的干涉特性，这可能意味着FWM信号可作为干涉式CARS系统的本地振荡器。
