We propose a novel wavelength modulation spectroscopy (WMS), which adds a triple frequency modulation current to the fundamental sinusoidal modulation current. By selecting theoretical optimum modulation indices, amplitude of the detected $2f$ improves 66% than that of the traditional wavelength modulation spectroscopy. Experimental results accord with theoretical expectation. Minimum detection limit obtained by the new modulation method develops 56.6% in open-path background. The transitions of ${\text{CH}}_4$ at = 1.654 μm are selected to verify this method. Our method presents good application prospects and can be applied to sense of other gas molecules.

中文翻译：

---

TDLAS中的新型波长调制光谱

我们提出了一种新颖的波长调制光谱（WMS），它将基本频率的正弦调制电流增加了三倍频调制电流。通过选择理论上最佳的调制指数，检测到的振幅$2F$比传统的波长调制光谱仪提高了66％。实验结果符合理论预期。通过新的调制方法获得的最小检测限在开放路径背景下发展为56.6％。的过渡${\text{CH}}_4$选择= 1.654μm的波长来验证该方法。我们的方法具有良好的应用前景，可应用于其他气体分子的检测。