Zhao Pengcheng, Ho Hoi Lut, Jin Wei, Fan Shangchun, Gao Shoufei, Wang Yingying, Wang Pu
Opt Lett. 2020 Oct 15;45(20):5660-5663. doi: 10.1364/OL.404323.
We demonstrate sensitive gas detection with mode-phase-difference photothermal spectroscopy assisted by a long period grating (LPG) inscribed on a dual-mode negative-curvature hollow-core fiber (NC-HCF). The LPG is inscribed using a pulsed laser, which enables pump propagation in the fundamental mode to achieve maximum photothermal phase modulation while exciting both the and modes at the probe wavelength to form a dual-mode interferometer for detection of the phase difference. With a 1533 nm pump and a 1620 nm probe, a noise equivalent concentration of ∼2.2 ppb acetylene is achieved with an 85-cm-long NC-HCF gas cell and 1 s lock-in time constant.
我们展示了利用写入双模负曲率空心光纤（NC-HCF）的长周期光栅（LPG）辅助的模式相位差光热光谱技术进行灵敏的气体检测。该LPG通过脉冲激光写入，这使得泵浦光在基模中传播，以实现最大的光热相位调制，同时在探测波长处激发基模和高阶模，形成用于检测相位差的双模干涉仪。使用1533 nm的泵浦光和1620 nm的探测光，在一个85 cm长的NC-HCF气体池和1 s的锁定时间常数下，实现了乙炔的噪声等效浓度约为2.2 ppb。
