发表机构
Department of Physics and Astronomy, Vrije Universiteit Amsterdam（阿姆斯特丹自由大学物理与天文学系）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
研究中红外光热显微镜中前向散射（FWS）与后向散射（BWS）检测几何的权衡问题，通过双向飞秒中红外泵浦-探测全息显微镜及新成像模态内部前向散射（IFS）解决，实现兼顾二者优势的成像。
AI 中文摘要
中红外光热显微镜结合红外吸收化学特异性与可见光检测空间分辨率，但FWS和BWS检测几何存在权衡。本文提出能在单仪器内切换FWS和BWS几何的双向飞秒中红外泵浦-探测全息显微镜，并引入验证新成像模态IFS，展示其优势，使其成为光热成像实用定量方法。
英文摘要
Mid-infrared photothermal microscopy combines the chemical specificity of infrared absorption with the spatial resolution of visible-light detection, but practical implementations face a persistent trade-off between forward-scattering (FWS) and backward-scattering (BWS) detection geometries. FWS provides quantitative, shape-independent phase contrast but requires two-sided optical access that is difficult to achieve in aqueous or thick samples. BWS offers convenient single-sided access, but its signals are strongly distorted by depth-dependent interference for micron-scale objects. Here we present a bidirectional femtosecond mid-infrared pump-probe holographic microscope capable of switching between FWS and BWS geometries within a single instrument, and use it to introduce and validate a new imaging modality, internal forward scattering (IFS). IFS exploits the back-reflection generated at the top surface of the mid-infrared-transparent sample substrate as an internally generated forward-scattering illumination wave, isolated from the directly backscattered field via temporal coherence gating. Using polystyrene beads on CaF2 substrates in air, water, and a refractive-index-matched glycerol-water mixture, we show that IFS reproduces the signal magnitudes and temporal dynamics of true FWS measurements while retaining the mechanical simplicity and single-sided accessibility of BWS. These results establish IFS as a practical, quantitative alternative to conventional FWS and BWS geometries for photothermal, and more broadly quantitative phase, imaging, with direct relevance to single-sided imaging of biological or solvent-contained specimens.
