Opt Express. 2021 Aug 2;29(16):24723-24734. doi: 10.1364/OE.427105.
'Molecular fingerprinting' with Raman spectroscopy can address important problems-from ensuring our food safety, detecting dangerous substances, to supporting disease diagnosis and management. However, the broad adoption of Raman spectroscopy demands low-cost, portable instruments that are sensitive and use lasers that are safe for human eye and skin. This is currently not possible with existing Raman spectroscopy approaches. Portability has been achieved with dispersive Raman spectrometers, however, fundamental entropic limits to light collection both limits sensitivity and demands high-power lasers and cooled expensive detectors. Here, we demonstrate a swept-source Raman spectrometer that improves light collection efficiency by up to 1000× compared to portable dispersive spectrometers. We demonstrate high detection sensitivity with only 1.5 mW average excitation power and an uncooled amplified silicon photodiode. The low optical power requirement allowed us to utilize miniature chip-scale MEMS-tunable lasers with close to eye-safe optical powers for excitation. We characterize the dynamic range and spectral characteristics of this Raman spectrometer in detail, and use it for fingerprinting of different molecular species consumed everyday including analgesic tablets, nutrients in vegetables, and contaminated alcohol. By moving the complexity of Raman spectroscopy from bulky spectrometers to chip-scale light sources, and by replacing expensive cooled detectors with low-cost uncooled alternatives, this swept-source Raman spectroscopy technique could make molecular fingerprinting more accessible.
拉曼光谱的“分子指纹识别”可以解决一些重要的问题——从确保食品安全、检测危险物质，到支持疾病诊断和管理。然而，拉曼光谱技术的广泛应用需要低成本、便携式的仪器，这些仪器需要具有灵敏度，并使用对人眼和皮肤安全的激光。目前，现有的拉曼光谱方法无法做到这一点。虽然色散拉曼光谱仪已经实现了便携性，但由于光收集的熵限制，其灵敏度受到限制，并且需要高功率激光和冷却昂贵的探测器。在这里，我们展示了一种扫频源拉曼光谱仪，与便携式色散光谱仪相比，它的光收集效率提高了 1000 倍。我们仅用 1.5mW 的平均激发功率和一个未冷却的放大硅光电二极管实现了高检测灵敏度。低光功率要求允许我们利用接近人眼安全的微型片上微机电系统可调谐激光器进行激发，这些激光器的光功率很小。我们详细地描述了这种拉曼光谱仪的动态范围和光谱特性，并将其用于日常消费的不同分子种类的指纹识别，包括镇痛药片、蔬菜中的营养成分和受污染的酒精。通过将拉曼光谱技术的复杂性从笨重的光谱仪转移到片上光源，并使用低成本的非冷却替代品代替昂贵的冷却探测器，这种扫频源拉曼光谱技术可以使分子指纹识别更容易实现。
