Waclawek Johannes P, Moser Harald, Lendl Bernhard
Opt Express. 2021 Mar 1;29(5):7794-7808. doi: 10.1364/OE.416536.
The interferometric cavity-assisted photothermal spectroscopy (ICAPS) method has been proven highly suitable for sensitive and compact gas detection by application of an optical cavity as transducer for photothermal spectroscopy. This work reports on the implementation of an overall fiber-coupled probe laser configuration detecting the reflectance of the individual interferometers in a balanced-detection ICAPS system. The layout greatly improves the overall sensor system robustness. Two identical 1 mm path length cavities were used for balanced detection, enabling sensor operation close to the fundamental limit of shot noise by efficiently cancelling excess noise. A quantum cascade laser served as a mid-infrared excitation source to induce refractive index changes in the sample, and a near-infrared fiber laser served as probe source to monitor the photo-induced refractive index variations. The metrological figures of merit for the sensor were investigated by SO detection. For the targeted absorption band centered at 1380.93 cm, a 3 ppbv minimum detection limit was achieved with a 1 s integration time, corresponding to a normalized noise equivalent absorption of 4.5 × 10 cm W Hz.
干涉腔辅助光热光谱法（ICAPS）已被证明非常适合用于灵敏且紧凑的气体检测，它通过应用光学腔作为光热光谱的换能器来实现。这项工作报道了一种全光纤耦合探测激光配置的实现，该配置用于检测平衡检测ICAPS系统中各个干涉仪的反射率。这种布局极大地提高了整个传感器系统的稳健性。两个相同的1毫米光程腔用于平衡检测，通过有效消除多余噪声，使传感器能够在接近散粒噪声基本极限的条件下运行。一个量子级联激光器用作中红外激发源，以在样品中诱导折射率变化，一个近红外光纤激光器用作探测源，以监测光致折射率变化。通过SO检测研究了该传感器的计量品质因数。对于以1380.93厘米为中心的目标吸收带，在1秒积分时间内实现了3 ppbv的最低检测限，对应于4.5×10厘米瓦特赫兹的归一化噪声等效吸收。
