Lamard Laurent, Balslev-Harder David, Peremans Andre, Petersen Jan C, Lassen Mikael
Appl Opt. 2019 Jan 10;58(2):250-256. doi: 10.1364/AO.58.000250.
We demonstrate the usefulness of a nanosecond-pulsed single-mode mid-infrared (MIR) optical parametric oscillator (OPO) for photoacoustic (PA) spectroscopic measurements. The maximum wavelength ranges for the signal and idler are 1.4 μm to 1.7 μm and 2.8 μm to 4.6 μm, respectively, with a MIR output power of up to 500 mW, making the OPO useful for different spectroscopic PA trace-gas measurements targeting the major market opportunity of environmental monitoring and breath gas analysis. We perform spectroscopic measurements of methane (CH), nitrogen dioxide (NO), and ammonia (NH) in the 2.8 μm to 3.7 μm wavelength region. The measurements were conducted with a constant flow rate of 300 mL/min, thus demonstrating the suitability of the gas sensor for real-time trace-gas measurements. The acquired spectra are compared with data from the HITRAN database, and good agreement is found, demonstrating a resolution bandwidth of 1.5 cm. An Allan deviation analysis shows that the detection limit for methane at optimum integration time for the PA sensor is 8 ppbV (nmol/mol) at 105 s of integration time, corresponding to a normalized noise equivalent absorption coefficient of 2.9×10 W cm Hz.
我们展示了纳秒脉冲单模中红外（MIR）光学参量振荡器（OPO）在光声（PA）光谱测量中的实用性。信号光和闲频光的最大波长范围分别为1.4μm至1.7μm和2.8μm至4.6μm，MIR输出功率高达500mW，这使得该OPO可用于针对环境监测和呼吸气体分析这一主要市场机遇的不同光谱PA痕量气体测量。我们在2.8μm至3.7μm波长区域对甲烷（CH）、二氧化氮（NO）和氨（NH）进行了光谱测量。测量以300mL/min的恒定流速进行，从而证明了该气体传感器适用于实时痕量气体测量。将采集到的光谱与HITRAN数据库的数据进行比较，发现吻合良好，显示出1.5cm的分辨率带宽。阿伦偏差分析表明，在105s积分时间下，PA传感器在最佳积分时间时甲烷的检测限为8ppbV（nmol/mol），对应归一化噪声等效吸收系数为2.9×10⁻⁹W⁻¹cm⁻²Hz。
