The proper functioning of living systems and physiological phenotypes depends on molecular composition. Yet simultaneous quantitative detection of a wide variety of molecules remains a challenge^{1,2,3,4,5,6,7,8}. Here we show how broadband optical coherence opens up opportunities for fingerprinting complex molecular ensembles in their natural environment. Vibrationally excited molecules emit a coherent electric field following few-cycle infrared laser excitation^9,10,11,12, and this field is specific to the sample’s molecular composition. Employing electro-optic sampling^{10,12,13,14,15}, we directly measure this global molecular fingerprint down to field strengths 10⁷ times weaker than that of the excitation. This enables transillumination of intact living systems with thicknesses of the order of 0.1 millimetres, permitting broadband infrared spectroscopic probing of human cells and plant leaves. In a proof-of-concept analysis of human blood serum, temporal isolation of the infrared electric-field fingerprint from its excitation along with its sampling with attosecond timing precision results in detection sensitivity of submicrograms per millilitre of blood serum and a detectable dynamic range of molecular concentration exceeding 10⁵. This technique promises improved molecular sensitivity and molecular coverage for probing complex, real-world biological and medical settings.

生命系统和生理表型的正常运作取决于分子组成。然而，多种分子的同时定量检测仍然是一个挑战^{1,2,3,4,5,6,7,8}。在这里，我们展示了宽带光学相干性如何为在自然环境中对复杂分子集合进行指纹识别提供机会。^{振动激发的分子在几个周期的红外激光激发9,10,11,12}后会发出相干电场，该电场特定于样品的分子组成。采用电光采样^{10,12,13,14,15}，我们直接测量这个全局分子指纹到场强 10 ⁷比激励弱几倍。这使得能够透照厚度约为 0.1 毫米的完整生命系统，从而允许对人体细胞和植物叶子进行宽带红外光谱探测。在人体血清的概念验证分析中，红外电场指纹与其激发的时间隔离以及阿秒定时精度的采样导致每毫升血清亚微克的检测灵敏度和可检测的动态范围分子浓度超过10 ⁵。该技术有望提高分子灵敏度和分子覆盖率，以探测复杂的现实世界生物和医学环境。