Measurement and analysis of the diffuse reflectance of powdered samples at terahertz frequencies using a quantum cascade laser.
Measurement and analysis of the diffuse reflectance of powdered samples at terahertz frequencies using a quantum cascade laser.
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使用量子级联激光器测量和分析太赫兹频率下粉末样品的漫反射率。
DOI：
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发表时间：
2011
影响因子：
4.4
通讯作者：
A. Davies
中科院分区：
文献类型：
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作者：
P. Dean;A. Burnett;K. Tych;S. Khanna;M. Lachab;John E. Cunningham;E. Linfield;A. Davies
报道了用窄带量子级联激光器在2.83THz频率下测量块状粉末样品的太赫兹(THz)漫反射。所研究的样品包括多分散粉末，其吸收系数从∼3 cm(-1)到>；200 cm(-1)超过两个数量级。漫反射测量用于从后向散射截面获得这些样品的有效吸收系数，该散射截面是在T矩阵公式中的准晶近似(QCA)下预测的，并与Percus-Yevick对分布函数相结合。将计算结果与THz时域谱测量得到的压片样品的有效吸收系数进行了比较，结果表明在所研究的有效吸收系数范围内符合得很好。我们观察到，在QCA下预测的后向散射截面强烈依赖于样品复介电常数的实部和虚部，并且我们表明，从漫反射测量中可靠地确定吸收系数需要知道样品的折射率。这项工作证明了使用太赫兹频率量子级联激光器的漫反射测量在太赫兹频率下对块状粉末样品的高分辨率光谱分析的适用性。
We report terahertz (THz) diffuse reflectance measurements of bulk powdered samples at a frequency of 2.83 THz using a narrowband quantum cascade laser. Samples studied comprise polydisperse powders with absorption coefficients extending over two orders of magnitude from ∼3 cm(-1) to >200 cm(-1). Diffuse reflectance measurements are used to obtain the effective absorption coefficient of these samples from the backscattering cross-section, predicted under the quasi-crystalline approximation (QCA) in the T-matrix formulation and in conjunction with the Percus-Yevick pair distribution function. Results are compared with effective absorption coefficients obtained from THz time-domain spectroscopy measurements on pressed pellet samples, and show good agreement over the range of effective absorption coefficients studied. We observe that the backscattering cross-section predicted under the QCA is strongly dependent on both the real and imaginary components of the complex permittivity of the sample, and we show that reliable determination of the absorption coefficient from diffuse reflectance measurements therefore requires knowledge of the sample's refractive index. This work demonstrates the applicability of diffuse reflectance measurements, using a THz frequency quantum cascade laser, to the high-resolution spectroscopic analysis of bulk powdered samples at THz frequencies.