Yang Mu-Han, Abashin Maxim, Saisan Payam A, Tian Peifang, Ferri Christopher G L, Devor Anna, Fainman Yeshaiahu
Opt Express. 2016 Dec 26;24(26):30173-30187. doi: 10.1364/OE.24.030173.
Non-degenerate 2-photon excitation (ND-2PE) of a fluorophore with two laser beams of different photon energies offers an independent degree of freedom in tuning of the photon flux for each beam. This feature takes advantage of the infrared wavelengths used in degenerate 3-photon excitation (D-3PE) microscopy to achieve increased penetration depths, while preserving a relatively high 2-photon excitation cross section in comparison to that of D-3PE. Here, using spatially and temporally aligned Ti:Sapphire laser and optical parametric oscillator beams operating at near infrared (NIR) and short-wavelength infrared (SWIR) optical frequencies, we employ ND-2PE and provide a practical demonstration that a constant fluorophore emission intensity is achievable deeper into a scattering medium using ND-2PE as compared to the commonly used degenerate 2-photon excitation (D-2PE).
使用具有不同光子能量的两束激光对荧光团进行非简并双光子激发（ND-2PE），可为每束光的光子通量调谐提供一个独立的自由度。此特性利用了简并三光子激发（D-3PE）显微镜中使用的红外波长，以实现更大的穿透深度，同时与D-3PE相比保持相对较高的双光子激发截面。在这里，我们使用在近红外（NIR）和短波红外（SWIR）光频率下运行的空间和时间对齐的钛宝石激光器和光学参量振荡器光束，采用ND-2PE，并提供了一个实际演示，即与常用的简并双光子激发（D-2PE）相比，使用ND-2PE可以在散射介质中更深的位置实现恒定的荧光团发射强度。
