Optical imaging techniques with mechanical contrast, including passive microrheology, optical coherence elastography and Brillouin microscopy, are critical for material and biological discovery owing to their less perturbative nature compared with traditional mechanical imaging methods. An emerging optical microscopy approach for mechanical imaging is stimulated Brillouin scattering microscopy, which has been shown to be useful for biomechanical imaging with high sensitivity and specificity. However, the excitation energy used is high and the temporal resolution remains limited by the need to acquire full spectra. Here we develop Brillouin gain microscopy that detects the Brillouin gain at a specific mechanically contrasting frequency corresponding to a Brillouin acoustic-vibrational mode of interest in the sample. Brillouin gain microscopy affords a 200-fold improvement in temporal resolution compared with stimulated Brillouin scattering microscopy, down to 100 μs at excitation energy as low as 23 μJ. Using Brillouin gain microscopy, we demonstrate cross-sectional, all-optical mechanical imaging of materials as well as of the structure and dynamics in living systems with low excitation energy and at high temporal resolution.

具有机械对比度的光学成像技术，包括被动微流变学、光学相干弹性成像和布里渊显微镜，由于与传统机械成像方法相比具有较少的扰动性质，因此对于材料和生物发现至关重要。受激布里渊散射显微镜是一种新兴的机械成像光学显微镜方法，它已被证明可用于具有高灵敏度和特异性的生物力学成像。然而，所使用的激发能量很高，并且时间分辨率仍然受到获取全光谱的需要的限制。在这里，我们开发了布里渊增益显微镜，可检测与样品中感兴趣的布里渊声振动模式相对应的特定机械对比频率下的布里渊增益。与受激布里渊散射显微镜相比，布里渊增益显微镜的时间分辨率提高了 200 倍，在激发能量低至 23 μJ 时可低至 100 μs。使用布里渊增益显微镜，我们以低激发能和高时间分辨率展示了材料以及生命系统中的结构和动力学的横截面全光学机械成像。