高灵敏度干涉定量相位显微前沿进展与应用(封面文章·特邀)

Recent advances and applications of high-sensitivity interferometric quantitative phase microscopy(cover paper·invited)

在无标记原生状态下对活细胞进行精准观测具有重大挑战,因其结构变化引起的形变可小至亚纳米尺度。此外,针对下一代原子级尺度制造,缺乏高精度在线表征工具将导致大规模芯片生产中良品率偏低。干涉定量相位显微技术(Interferometric Quantitative Phase Microscopy,iQPM)作为一种无标记宽场显微技术,已被广泛应用于定量解析样本形貌及其动态变化,在晶圆缺陷检测与疾病诊断等应用上展现出巨大潜力。文中聚焦于高灵敏度iQPM技术的发展,首先介绍iQPM的工作原理、相位灵敏度理论和制约因素。针对细胞动态分析及原子材料计量需求,从干涉光路设计、探测和照明等方面进一步讨论了相位灵敏度极限拓展的策略,并梳理高灵敏度iQPM在前沿应用领域的进展。最后,分析并讨论了相位灵敏度提升的新思路。

Significance Live-cell imaging techniques offer an analytical platform for investigating cellular structures and functions,significantly advancing our understanding of disease mechanisms and drug development.The real-time observation of morphology and dynamics of cellular structures is crucial for studying cell activity and cell-materials interactions.Dynamic changes in living cells can occur even at the subnanometer level,such as the minute deformation of the cell membrane during neuronal action potentials.Additionally,to meet the trend of next-generation atomic manufacturing,nondestructive and accurate in-line characterization is crucial for ensuring high yields in large-scale manufacturing.However,the widely used metrology tools,such as scanning electron microscopy(SEM)and atomic force microscopy(AFM),suffer from extremely low measurement throughput and may introduce invasiveness to the samples.Interferometric Quantitative Phase Microscopy(iQPM),a label-free wide-field imaging technique,has been widely employed to obtain morphology distributions and dynamic changes of samples quantitatively.To satisfy the application demands,the development of high-sensitivity iQPM is of great significance and importance.Progress Firstly,the noise sources involved in the phase measurement process are introduced,such as camera noise(including photon shot noise,dark noise,readout noise),1/f noise,instability of light source,mechanical vibrations,and air disturbances.By analyzing these noise sources,the key limiting factors affecting the phase sensitivity of the iQPM system are discussed,which provides a solid theoretical basis for developing strategies to improve the phase sensitivity of iQPM.The sensitivity improvement strategies are introduced from the suppression of environmental noise,detection noise,and speckle noise,respectively.In terms of environmental noise,the common-path interferometry-based iQPM techniques can effectively alleviate the optical path difference changes between the sample beam and reference beam due to mechanical vibrations and air disturbances,thus improving the temporal phase sensitivity.Meanwhile,the noise caused by mechanical vibrations can be further reduced through the optimized spatiotemporal filtering method.To reduce the influence of camera noise on phase sensitivity,the methods of increasing the effective well capacity and expanding the dynamic range have been proposed,enabling the measurement of subtle phase changes.From the perspective of speckle noise,the proposed strategies aim to superpose images with uncorrelated speckle patterns,which can be achieved by reducing the illumination temporal coherence and modulating the spatial spectrum of the illumination light.The high-sensitivity iQPM techniques have been applied in cutting-edge fields such as neuroscience,atomic-scale material metrology,and wafer defect detection.Conclusions and Prospects This review summarizes critical strategies that have driven substantial advancements in the phase sensitivity of iQPM.By employing these methods,the temporal phase sensitivity of iQPM has been pushed to an impressive 2 pm level.The primary objective of this work is to provide an important reference for further improvement of phase sensitivity.Notably,current noise suppression-based sensitivity enhancement strategies are constrained by the inherent photon shot noise,sensitivity improvement methods based on signal amplification may offer a path to break through the current limitations and achieve higher phase sensitivity.