暗场共焦布里渊光谱探测系统

共焦布里渊光谱技术因其具有无创、无标记、高空间分辨等优点，被广泛应用在物理化学、材料科学、矿物学等领域。但自发布里渊散射强度弱，在探测系统消光比不足的情况下，布里渊信号光谱容易与弹性背景光发生交叠甚至是被湮没，因而无法实现对布里渊频移的精确测量。尤其在生物医学等前沿领域，浑浊介质粘弹性探测需求的日益增加对布里渊光谱探测系统的抗弹性背景光性能提出了更高的要求，解决共焦布里渊光谱探测系统消光比不足这一问题刻不容缓。为了提高共焦布里渊光谱探测系统的消光比，本文构建了一种暗场共焦布里渊光谱探测系统，将暗场照明应用于共焦布里渊探测中，利用光阑实现了中心遮挡的环形照明、中心通光的圆形收集的光路配置。照明光路与收集光路非交叉的特殊配置，保证了激发光强的同时避免了系统对镜面反射光的收集，因而使得弹性背景光被削弱，布里渊信号光谱显露，提高了系统的消光比。实验表明：相较于传统明场照明配置，暗场共焦布里渊探测系统的抗弹性背景光性能提升，消光比提高了20 dB；0.001%浓度的脂肪乳溶液在暗场配置下背景光得到明显压制，布里渊信号光谱显露，实现了对浑浊介质的布里渊频移数据的精确测量；选取蒸馏水、聚甲基丙烯酸甲酯、二氧化硅玻璃三个标准样品验证暗场配置下的非严格背向散射角，理论分析与实验相吻合，保证了后续轴向声速、纵向弹性模量等参数的计算结果的准确有效。暗场共焦布里渊光谱探测系统综合暗场照明与共焦探测的优点，既拥有共焦探测的高空间分辨率，又借助暗场光路配置提升了系统的抗弹性背景光性能，实现了高消光比、高空间分辨的布里渊光谱探测，为生物医学、材料科学等前沿领域实现对物质机械性能的实时无损探测提供了新的思路。

Dark-Field Confocal Brillouin Spectrum Detection System

Confocal Brillouin spectroscopy is widely used in physical chemistry, materials science, and mineralogy due to its advantages of non-invasive, label-free, high spatial resolution. Since the spontaneous Brillouin scattering intensity is weak, the signal spectrum easily overlaps with the elastic background or be obliterated when the extinction ratio of the system is insufficient, so accurately measuring the brillouin frequency shift is unachievable. The increasing demand for viscoelastic detection of turbid media in biomedicine also put forward higher requirements on the extinction ratio of the Brillouin detection system. In order to improve the extinction ratio of the confocal Brillouin system, a dark-field confocal Brillouin detection system is constructed in this paper. The non-intersecting optical path configuration avoids the collection of reflected light so it weakens the elastic background light to improve the extinction ratio while ensuring the excitation intensity. Experiments show that compared to the traditional bright field configuration, the extinction ratio of the dark field system is increased by 20 dB; The background light of an intralipid solution at a concentration of 0.001% is obviously suppressed in the dark illumination configuration, the signal spectrum is revealed, thereby attains the accurate measurement of the turbid medium’s Brillouin frequency shift data; Three standard samples of distilled water, PMMA, and SiO₂ glass were selected to verify the non-strict backscatter angle. The experimental result is consistent with the theoretical analysis, which ensures that subsequent calculations of axial sound velocity and longitudinal elastic modulus are accurate and effective. The dark field confocal Brillouin spectrum detection system combines the advantages of dark field illumination and confocal detection. It not only has a high resolution of confocal detection, but also improves the system’s anti-elastic background light performance and achieves high extinction detection. The dark field confocal Brillouin spectrum detection system provides a new idea for real-time non-destructive detection of the mechanical properties of substances in biomedicine and materials science.