CN112067574A - 不等光程法太赫兹光谱测量方法及其系统 - Google Patents
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Abstract
本发明公开了一种提高太赫兹光谱测量精度的新方案。利用飞秒激光器和太赫兹时域光谱系统，对不同厚度的待测样品进行时域太赫兹信号扫描，得到样品材料在两种不同厚度下的透射信号。通过样品厚度为
的信号为参考信号，通过样品厚度为
Description
技术领域
本发明基于不等光程法提高太赫兹光谱测量的精度，为太赫兹波段精确测量材料光学参数提供了新的方法，属于太赫兹技术领域。
背景技术
太赫兹时域光谱技术是继紫外光谱、红外光谱、圆二色谱、X射线等传统光谱技术之后又一种新的测量技术，该技术可以弥补传统测量技术低频部分的空白，成为研究材料在太赫兹波段吸收率、折射率等光学参数的新的方法。从太赫兹光谱的应用上来看，渗透到生物分子、化学反应、医学、通信和安全检查等领域，目前利用太赫兹时域光谱仪对样品的测量模式有3种，分别为透射式、反射式和衰减全反射式。传统的太赫兹时域光谱系统是由飞秒激光器、太赫兹脉冲发射器、信号接收器、时间延迟控制系统和信号处理系统组合。在THz-TDS 中，利用光电导天线产生并探测太赫兹脉冲。一束激光脉冲被分束器分为两束激光，分别被用作产生太赫兹脉冲的泵浦光和用来探测太赫兹信号的探测光。太赫兹脉冲穿过空气和样品，分别记录下通过空气的参考信号和通过样品的太赫兹时域电场波形，对时域波形进行傅立叶变换得到参考和样品的频域波形，进一步处理提取出样品的折射率、吸收系数、消光系数等材料参数。
传统的太赫兹时域光谱测量方法是把通过空气的太赫兹信号作为参考信号，将通过待测样品的太赫兹信号与参考信号进行比较，经过傅里叶变换等手段获得待测样品不同频率的折射率、消光系数、吸收系数以及介电常数，这会导致材料折射率和吸收系数的提取存在明显误差。
发明内容
本发明基于不等光程法实现对太赫兹光谱测量精度的增强。精确计算材料折射率和吸收系数等材料参数。
本发明为实现上述目的，采用如下的技术解决方案：第一步，获取参考信号和样品信号。取两种不同厚度的同种材料，将其放置在透射式太赫兹时域光谱系统上进行测量，从而获取参考信号和样品信号，通过样品厚度为d1的信号为参考信号，通过样品厚度为d2的信号为样品信号。
第二步，不等光程法提取样品参数。将带有样品信息的太赫兹脉冲所形成的时域信号经过傅里叶变换转换成频域谱，提取振幅和相位信息，利用不等光程法计算样品的吸收系数和折射率等参数。
本发明的优势在于：(1)不等光程测量法可以有效的消除由于两层介质之间信号反射引起的测量误差。(2)不等光程法测量不需要做近似处理，且光学常数计算独立，能够更加精确计算材料折射率和吸收系数等材料参数。不等光程法较常规法比可以揭示常规方法无法测得的材料特征吸收峰，与常规法相比测量精度更加精确，更具有优势。
附图说明
图1为太赫兹时域光谱原理示意图。
图2为太赫兹透射式测量示意图。
具体实施方式
实施例1
获取参考信号和样品信号实验方案：利用透射式太赫兹时域光谱获得参考信号和样品信号的实验方案如图1所示。飞秒激光器中发射出激光通过分光镜后被分成泵浦脉冲和和探测脉冲两部分。泵浦脉冲通过时间延迟装置平移台后入射到太赫兹辐射产生装置上，从而产生太赫兹脉冲。然后，从太赫兹福射产生装置中发射出的太赫兹脉冲透过固定好的待测实验样品，此时太赫兹脉冲中就含有了实验样品的信息。最后，太赫兹脉冲与探测脉冲一起共线入射到透射探测装置上。通过对泵浦脉冲和探测脉冲的时间延迟进行调节，就能够获得在整个实验时域内带有样品信息的太赫兹脉冲的完整波形。
实施例2
不等光程法样品参数提取方案：利用不等光程法太赫兹时域光谱技术，提取出样品在太赫兹波段的光学参量原理如图2所示。左图是常规法透射式太赫兹时域光谱测量原理，发射器与探测器之间的距离为L，以通过空气Air的太赫兹信号为参考信号Eref，通过厚度为d的样品 Sample信号为样品信号Esam；右图是透射式不等光程法太赫兹时域光谱测量原理图，取两种不同厚度同种材料进行测量，通过样品厚度为d1的信号为参考信号Eref'，通过样品厚度为d2的信号为样品信号Esam'。
取同种材料但厚度不同的两个样品先后进行测量。设厚度分别为d1、d2(d2＞d1)，若只考虑垂直入射并忽略反射信号，参考信号和样品信号强度分别表示为：
记△d＝d2-d1,利用公式(1)、(2)，可得到通过厚度为d1、d2材料的传递函数：
时域信号经过傅里叶变换后得到包含相位的频谱，比值写成指数形式：
通过公式(3)、(4)可以得到样品的折射率消光系数和吸收系数分别为：
Claims (3)
1.一种提高太赫兹光谱测量精度的方法，其特征在于：能够更加精确计算材料折射率和吸收系数等材料参数，并可以揭示常规方法无法测得的材料特征吸收峰。
2.根据权利要求1所述的提高太赫兹光谱测量精度的方法，其特征在于：对不同厚度的
待测样品进行时域太赫兹信号扫描，通过样品厚度为
的信号为参考信号，通过样品厚度
为
的信号为样品信号。
3.根据权利要求1、2所述的提高太赫兹光谱测量精度的方法，其特征在于：垂直入射不同厚度的样品信号会产生光程差，时域信号经过傅里叶变换后得到包含相位的频谱，通过光程差和所提取的包含相位的频谱信息，获取更高精度的材料参数。
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|---|---|---|---|---|
| CN112763452A (zh) * | 2020-12-29 | 2021-05-07 | 西北工业大学 | 一种复合材料分层损伤的检测方法及系统 |
| CN113038678A (zh) * | 2021-03-09 | 2021-06-25 | 北京环境特性研究所 | 基于太赫兹时域光谱的等离子体密度测量方法 |
| CN114152588A (zh) * | 2021-08-27 | 2022-03-08 | 北京工业大学 | 反射式太赫兹时域光谱复合材料自参考光学参量测量方法 |
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| CN115435696A (zh) * | 2022-07-12 | 2022-12-06 | 福州大学 | 一种基于太赫兹时域光谱的轴套自润滑涂层厚度检测方法 |
| CN117195734B (zh) * | 2023-09-18 | 2024-04-16 | 安徽工程大学 | 融合时间序列与太赫兹特征的热生长氧化层演变预测方法 |
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| JP6517202B2 (ja) * | 2013-11-15 | 2019-05-22 | ピコメトリクス、エルエルシー | テラヘルツ放射線を使用してシート誘電体サンプルの少なくとも１つの特性を判定するためのシステム |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112763452A (zh) * | 2020-12-29 | 2021-05-07 | 西北工业大学 | 一种复合材料分层损伤的检测方法及系统 |
| CN113038678A (zh) * | 2021-03-09 | 2021-06-25 | 北京环境特性研究所 | 基于太赫兹时域光谱的等离子体密度测量方法 |
| CN114152588A (zh) * | 2021-08-27 | 2022-03-08 | 北京工业大学 | 反射式太赫兹时域光谱复合材料自参考光学参量测量方法 |
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Inventor after: Li Dehua Inventor after: Ji Beibei Inventor after: Zhou Wei Inventor after: Li Zhaoxin Inventor after: Song Binbin Inventor after: Cao Qiuhong Inventor before: Li Dehua Inventor before: Ji Beibei Inventor before: Li Zhaoxin Inventor before: Zhou Wei Inventor before: Song Binbin Inventor before: Cao Qiuhong |
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