Dipartimento di Fisica-Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133, Milan, Italy.
Istituto di Fotonica e Nanotecnologie-CNR, Piazza Leonardo da Vinci 32, 20133, Milan, Italy.
Sci Rep. 2023 Feb 14;13(1):2634. doi: 10.1038/s41598-023-29589-7.
Vibrational spectroscopies offer great potential for standoff detection of chemical and biological warfare agents, avoiding contamination to the operator and equipment. Among them, particularly promising is Coherent anti-Stokes Raman scattering (CARS) spectroscopy, using synchronized pump/Stokes laser pulses to set up a vibrational coherence of target molecules at a laser focus, which is read by further interaction with a probe pulse, resulting in the emission of a coherent beam detectable at a distance. CARS has previously demonstrated the capability to detect bacterial spores based on the Raman spectrum of the characteristic molecule calcium dipicolinate (CaDPA); however, a complex and bulky laser technology, which is only suitable for a laboratory environment, was employed. Here we develop a broadband CARS setup based on a compact, industrial grade ytterbium laser system. We demonstrate high signal-to-noise ratio detection of Bacillus atrophaeus spores at a concentration of 10 cfu/mm, at a standoff distance of 1 m, and an acquisition time of 1 s. Our system, which combines chemical specificity and sensitivity along with improved ruggedness and portability, paves the way to a new generation of instruments for real-world standoff detection of chemical and biological threats.
振动光谱在化学和生物战剂的远程检测方面具有巨大的潜力，可以避免操作人员和设备受到污染。其中，相干反斯托克斯拉曼散射（CARS）光谱特别有前景，它使用同步的泵浦/斯托克斯激光脉冲在激光焦点处建立目标分子的振动相干性，然后通过与探测脉冲的进一步相互作用来读取，从而产生可在远处检测到的相干光束。CARS 先前已经证明了基于特征分子钙二吡咯酸酯（CaDPA）的拉曼光谱来检测细菌孢子的能力；然而，所采用的是一种复杂而庞大的激光技术，仅适用于实验室环境。在这里，我们基于紧凑的工业级掺镱激光系统开发了一种宽带 CARS 装置。我们在 1 m 的远程距离和 1 s 的采集时间下，以 10 cfu/mm 的浓度演示了对萎缩芽孢杆菌孢子的高信噪比检测。我们的系统结合了化学特异性和灵敏度，同时提高了坚固性和便携性，为新一代用于实际远程检测化学和生物威胁的仪器铺平了道路。
