Mid-infrared upconversion spectroscopy based on a Yb:fiber femtosecond laser
Mid-infrared upconversion spectroscopy based on a Yb:fiber femtosecond laser
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DOI：
10.1007/s00340-011-4748-0
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发表时间：
2012-04-01
影响因子：
2.1
通讯作者：
Diddams, S. A.
中科院分区：
文献类型：
--
作者：
Johnson, T. A.;Diddams, S. A.
我们提出了一种利用宽带中红外激光器进行近红外探测的分子光谱系统。利用差频产生的Yb：光纤飞秒激光器产生了2100-3700 cm(-1)(2.7-4.7微米)可调的中红外(MIR)光源，平均功率可达40 mW。利用二维色散成像技术将MIR光谱上转换为近红外波长，以进行宽带探测。吸收测量带宽为240 cm(-1)(7.2THz)，分辨率为0.048 cm(-1)(1.4GHz)，绝对频率尺度不确定度优于0.005 cm(-1)(150 MHz)。通过在低压甲烷中的测量，每个光谱元素的最小可检测吸收系数被确定为4.4×10(-7)厘米(-1)，从而预测在纯氮气中的甲烷的检测下限为十亿分之二。在自然大气样本中，甲烷的检测下限被发现是十亿分之三十。该系统的光谱范围、分辨率和频率精度显示出在包含窄和宽重叠光谱特征的混合气体中测定痕量浓度的前景，我们在空气和溶剂样品的测量中证明了这一点。
We present a system for molecular spectroscopy using a broadband mid-infrared laser with near-infrared detection. Difference frequency generation of a Yb:fiber femtosecond laser produced a mid-infrared (MIR) source tunable from 2100-3700 cm(-1) (2.7-4.7 A mu m) with average power up to 40 mW. The MIR spectrum was upconverted to near-infrared wavelengths for broadband detection using a two-dimensional dispersion imaging technique. Absorption measurements were performed over bandwidths of 240 cm(-1) (7.2 THz) with 0.048 cm(-1) (1.4 GHz) resolution, and absolute frequency scale uncertainty was better than 0.005 cm(-1) (150 MHz). The minimum detectable absorption coefficient per spectral element was determined to be 4.4x10(-7) cm(-1) from measurements in low pressure CH4, leading to a projected detection limit of 2 parts-per-billion of methane in pure nitrogen. In a natural atmospheric sample, the methane detection limit was found to be 30 parts-per-billion. The spectral range, resolution, and frequency accuracy of this system show promise for determination of trace concentrations in gas mixtures containing both narrow and broad overlapping spectral features, and we demonstrate this in measurements of air and solvent samples.