Hayden Torrey R S, Rieker Gregory B
Opt Express. 2016 Nov 28;24(24):27910-27921. doi: 10.1364/OE.24.027910.
We demonstrate large amplitude wavelength modulation spectroscopy (WMS) with a MEMS-tunable vertical cavity surface-emitting laser (MEMS-VCSEL) to measure high-density gases. WMS enables sensitive measurements of gas phase thermodynamic properties in harsh environments, but has been limited to moderate pressure and density conditions because of the narrow tuning range of traditional DFB lasers. The MEMS-tunable laser is able to rapidly modulate across the broadened features of high-density gas mixtures to produce the harmonic signals in the detected light intensity typical of WMS. We illustrate the technique on high-pressure mixtures of CO in air that are 2.5 times higher density than previously published WMS measurements (equivalent to greater than 255 atm at 1500 K). We develop a WMS model that accounts for nonlinear tuning of the laser to enable extraction of thermodynamic properties from measured data. The agreement of the measured data and model suggests that this technique could be used now for calibrated measurements of gas concentration, and in the future for calibration-free operation with further high-pressure absorption model development and laser tuning characterization.
我们展示了利用微机电系统可调谐垂直腔面发射激光器（MEMS-VCSEL）进行的大振幅波长调制光谱（WMS）技术，用于测量高密度气体。WMS能够在恶劣环境中灵敏地测量气相热力学性质，但由于传统分布反馈（DFB）激光器的调谐范围较窄，其应用一直局限于中等压力和密度条件。MEMS可调谐激光器能够快速调制高密度气体混合物的展宽谱线特征，从而在检测到的光强中产生WMS典型的谐波信号。我们在空气中CO的高压混合物上展示了该技术，其密度比之前发表的WMS测量结果高2.5倍（相当于在1500K时大于255个大气压）。我们开发了一个WMS模型，该模型考虑了激光器的非线性调谐，以便能够从测量数据中提取热力学性质。测量数据与模型的一致性表明，该技术目前可用于气体浓度的校准测量，未来随着进一步的高压吸收模型开发和激光调谐特性研究，有望实现免校准操作。
