Infrared photothermal heterodyne imaging: Contrast mechanism and detection limits
Infrared photothermal heterodyne imaging: Contrast mechanism and detection limits
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DOI：
10.1063/1.5142277
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发表时间：
2020-04-30
影响因子：
3.2
通讯作者：
Kuno, Masaru
中科院分区：
文献类型：
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作者：
Pavlovetc, Ilia M.;Podshivaylov, Eduard A.;Kuno, Masaru
红外光热外差成像(IR-PHI)是一种超灵敏技术，可实现超分辨率，在整个中红外“指纹”光谱区(2.5-10毫升：毫米波宽度=“0.1毫微米”毫米波：毫米波)进行红外成像。获得的空间分辨率类似于300mml：mspace Width=“.1em”mml：mspaceenm，比红外衍射极限小30倍。在这项研究中，我们建立了IR-PHI的信号对比机制，并利用单个聚苯乙烯(PS)和聚甲基丙烯酸甲酯(PMMA)微珠的特征红外振动跃迁对该技术的性能进行了基准测试。对所得结果的分析表明，IR-PHI对比度源于竞争的、光热诱导的样品尺寸和后向散射截面的折射率变化。对于PS和PMMA，热光折射率贡献是决定无介质IR-PHI信号对比度的主要因素。我们的分析同时建立了IR-PHI的当前的、无介质的峰吸收截面检测极限为Besigmaabs=3x10-18mml：mspace Width=“.1em”mml：mspaceem 2。这种对IR-PHI信号对比度的更好理解为超分辨率红外吸收显微镜和光谱学的未来发展提供了一个框架。
Infrared photothermal heterodyne imaging (IR-PHI) is an ultrasensitive technique for achieving super-resolution, infrared imaging throughout the mid-infrared "fingerprint" spectral region (2.5 - 10 mml:mspace width=".1em"mml:mspace mum). An achieved spatial resolution ofsimilar to 300 mml:mspace width=".1em"mml:mspacenm is up to 30-fold smaller than the infrared diffraction limit. In this study, we establish IR-PHI's signal contrast mechanism and benchmark the technique's capabilities using the characteristic infrared vibrational transitions of individual polystyrene (PS) and poly(methyl methacrylate) (PMMA) beads. The analysis of acquired results reveals that IR-PHI contrast originates from a competing, photothermally induced specimen size and refractive index changes to backscattering cross sections. For PS and PMMA, thermo-optic refractive index contributions dominate and are responsible for medium-free IR-PHI signal contrast. Our analysis simultaneously establishes IR-PHI's current, medium-free peak absorption cross-sectional limit-of-detection to besigmaabs = 3 x10- 18 mml:mspace width=".1em"mml:mspacem 2. This improved understanding of IR-PHI signal contrast provides a framework for future developments in super-resolution infrared absorption microscopy and spectroscopy.