Xiong Hanqing, Qian Naixin, Zhao Zhilun, Shi Lingyan, Miao Yupeng, Min Wei
Opt Express. 2020 May 11;28(10):15663-15677. doi: 10.1364/OE.391016.
Being able to image chemical bonds with high sensitivity and speed, stimulated Raman scattering (SRS) microscopy has made a major impact in biomedical optics. However, it is well known that the standard SRS microscopy suffers from various backgrounds, limiting the achievable contrast, quantification and sensitivity. While many frequency-modulation (FM) SRS schemes have been demonstrated to retrieve the sharp vibrational contrast, they often require customized laser systems and/or complicated laser pulse shaping or introduce additional noise, thereby hindering wide adoption. Herein we report a simple but robust strategy for FM-SRS microscopy based on a popular commercial laser system and regular optics. Harnessing self-phase modulation induced self-balanced spectral splitting of picosecond Stokes beam propagating in standard single-mode silica fibers, a high-performance FM-SRS system is constructed without introducing any additional signal noise. Our strategy enables adaptive spectral resolution for background-free SRS imaging of Raman modes with different linewidths. The generality of our method is demonstrated on a variety of Raman modes with effective suppressing of backgrounds including non-resonant cross phase modulation and electronic background from two-photon absorption or pump-probe process. As such, our method is promising to be adopted by the SRS microscopy community for background-free chemical imaging.
受激拉曼散射（SRS）显微镜能够以高灵敏度和速度对化学键进行成像，在生物医学光学领域产生了重大影响。然而，众所周知，标准的SRS显微镜存在各种背景干扰，限制了可实现的对比度、定量分析和灵敏度。虽然许多频率调制（FM）SRS方案已被证明能够获得清晰的振动对比度，但它们通常需要定制的激光系统和/或复杂的激光脉冲整形，或者会引入额外噪声，从而阻碍了其广泛应用。在此，我们报告了一种基于流行的商业激光系统和常规光学元件的简单而稳健的FM-SRS显微镜策略。利用皮秒斯托克斯光束在标准单模石英光纤中传播时自相位调制引起的自平衡光谱分裂，构建了一种高性能的FM-SRS系统，且不引入任何额外的信号噪声。我们的策略能够实现自适应光谱分辨率，用于对具有不同线宽的拉曼模式进行无背景SRS成像。我们的方法的通用性在多种拉曼模式上得到了证明，有效抑制了包括非共振交叉相位调制以及双光子吸收或泵浦-探测过程产生的电子背景等各种背景。因此，我们的方法有望被SRS显微镜领域采用，用于无背景化学成像。
