Li Zhili, Wang Zhen, Yang Fan, Jin Wei, Ren Wei
Opt Lett. 2017 Sep 15;42(18):3718-3721. doi: 10.1364/OL.42.003718.
We demonstrate mid-infrared photothermal interferometry (PTI) in a hollow-core fiber (HCF) for trace gas detection. Compared with free-space PTI, the optical intensity could be increased by orders of magnitude by confining the pump and probe lights in the hollow core. We coupled the pump light at 4.46 μm from a quantum cascade laser and the 1555.14 nm probe light into the HCF with a bore size of 200 μm. The HCF was filled with nitrous oxide (NO) which has strong absorption at the pump wavelength. The probe light detects the NO absorption-induced phase change in the HCF via a fiber-optic Mach-Zehnder interferometer. With a 25 cm fiber length and 6 mW of pump power, we have achieved a minimum detection limit of 0.8 ppm for NO, corresponding to a normalized noise equivalent absorption coefficient of 4.9×10 cm WHz.
我们展示了用于痕量气体检测的中空光纤（HCF）中的中红外光热干涉测量法（PTI）。与自由空间PTI相比，通过将泵浦光和探测光限制在中空芯中，光强度可以提高几个数量级。我们将来自量子级联激光器的4.46μm泵浦光和1555.14nm探测光耦合到内径为200μm的HCF中。HCF中填充有在泵浦波长处具有强吸收的一氧化二氮（NO）。探测光通过光纤马赫曾德尔干涉仪检测HCF中NO吸收引起的相位变化。在光纤长度为25cm且泵浦功率为6mW的情况下，我们实现了NO的最低检测限为0.8ppm，对应于归一化噪声等效吸收系数为4.9×10 cm WHz。
