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为了测试文中设计的太赫兹热释电探测器的性能,并验证太赫兹热释电探测器对自由空间与波导传输太赫兹辐射功率测试的兼容性,文中分别使用太赫兹激光器和太赫兹信号发生器对含有放大电路的太赫兹热释电探测器进行测试。
为了验证文中设计的太赫兹热释电探测器对自由空间传输太赫兹辐射功率的测试性能,文中使用太赫兹激光器测试太赫兹热释电探测器性能的实验装置如图7所示。实验使用的太赫兹激光器是FIRL 100激光器,它包含CO2泵浦激光器和结构紧凑的FIR激光室,通过改变选定气体分子的发射谱线,以及使用CO2泵浦激光激励气体分子,可以使太赫兹激光器发射的激光在0.25~7.5 THz范围内可调。FIRL 100激光器发出的太赫兹激光为连续激光,经太赫兹半透射反射镜之后分成两束,一束太赫兹激光进入功率控制系统,控制输出的太赫兹激光功率的稳定;另一束太赫兹激光经过斩波之后,入射到太赫兹辐射计或待测太赫兹热释电探测器。文中使用的太赫兹辐射计已经在中国计量科学研究院进行了校准,在0.3~10 THz的测量不确定度是5%(k=2)。
在实验过程中,设定FIRL 100激光器的参数,使其输出波长是2.52 THz的激光。首先使用太赫兹辐射计测试太赫兹激光的平均功率;其次把待测太赫兹热释电探测器移入光路,使太赫兹探热释电测器的光敏面与太赫兹辐射计的光敏面位置相同;最后记录示波器测试的太赫兹热释电探测器的输出电压。本次实验在10 Hz斩波频率时,太赫兹辐射计测试的太赫兹激光平均功率是3.90 mW,示波器测试的太赫兹热释电探测器输出电压如图8所示,上升时间(10%~90%)为30 ms,电压峰-峰值为1.30 V,则太赫兹热释电探测器的响应度是333.3 V/W。
为了进一步表征太赫兹热释电探测器的性能,文中开展了太赫兹热释电探测器的噪声等效功率测试。文中建立的太赫兹热释电探测器噪声电压测试装置如图9所示,前置放大器的放大倍数设置为1 000,频谱分析仪的中心频率、带宽均设置为10 Hz,太赫兹热释电探测器的噪声电压测试结果是156.2 μV/Hz1/2,主要表现为热噪声,则太赫兹热释电探测器的噪声等效功率是0.47 nW/Hz1/2。
为了验证文中设计的太赫兹热释电探测器对波导传输太赫兹辐射功率的测试性能,文中使用太赫兹信号发生器测试太赫兹热释电探测器性能的实验装置如图10所示。太赫兹信号发生器由1461微波合成信号发生器和82406A太赫兹倍频模块组成,82406A太赫兹倍频模块输出端口为WR10波导;太赫兹功率计由2434微波功率计和W8486A波导功率传感器组成,太赫兹功率计在75~110 GHz的测量不确定度是3.5%(k=2)。在实验过程中,设置太赫兹信号发生器的输出频率是0.1 THz、重复频率是10 Hz,太赫兹功率计测试的平均功率是12.38 mW,示波器测试的太赫兹热释电探测器输出电压如图11所示,上升时间(10%~90%)为30 ms,电压峰-峰值为720 mV,则太赫兹热释电探测器的响应度是58.2 V/W。
在波导传输太赫兹辐射功率测试实验中,太赫兹信号发生器的输出端口是WR10波导,太赫兹功率计的输入端口也是WR10端口,它们之间可以通过波导组成闭环连接,损耗小。然而,使用文中设计的太赫兹热释电探测器测试太赫兹信号发生器的输出功率时,太赫兹热释电探测器与太赫兹信号发生器之间增加了一个波导适配器,并且为了避免太赫兹热释电探测器与波导适配器之间发生机械磨损,太赫兹热释电探测器与波导适配器输出端口之间存在一定的空隙,对太赫兹辐射的传输损耗较大。因此,文中设计的太赫兹热释电探测器在0.1 THz的响应度比2.52 THz的响应度小,不能准确反映太赫兹热释电探测器响应度的性能。
为了进一步验证太赫兹热释电探测器的重复测试性能,文中使用太赫兹信号发生器对太赫兹热释电探测器的重复性进行测试,太赫兹热释电探测器测试的一组数据如表1所示,则太赫兹热释电探测器测试功率的重复性是0.12%。测试结果表明,文中设计的太赫兹热释电探测器能够实现太赫兹辐射功率的重复测试。
表 1 重复性测试数据
Table 1. Repeatability test data
Num Voltage/mV Power/mW Num Voltage/mV Power/mW 1 720.2 12.37 6 720.2 12.37 2 718.6 12.35 7 720.0 12.37 3 720.2 12.37 8 720.4 12.38 4 718.8 12.35 9 718.6 12.35 5 718.4 12.34 10 718.2 12.34
Large area terahertz pyroelectric detector
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摘要: 针对太赫兹光束的光斑直径较大和传输途径不同的现状,提出大面元太赫兹热释电探测器和多用途探测器结构研究,用于自由空间和波导传输太赫兹光束功率的测试。首先使用有限元分析软件建立太赫兹热释电探测器模型,开展热电耦合仿真设计;其次使用精密研磨抛光工艺、平面集成电路微纳米加工技术、匀胶与剥离工艺、砂轮划片技术等工艺技术,开展太赫兹热释电探测器研制;最后创新设计装配在探测器结构上的套筒与波导适配器。理论分析和实验结果表明:该方法设计的太赫兹热释电探测器具有噪声等效功率低、重复性高特点,并且解决了自由空间与波导传输太赫兹辐射功率兼容测试问题。Abstract: In view of the large diameter and different transmission channels of terahertz beam, the large area terahertz pyroelectric detector and the multi-purpose detector structure were proposed to measure the terahertz beam power, which was transmitted in free space and waveguide. Firstly, a terahertz pyroelectric detector model was established by using the finite element analysis software, and the thermoelectric coupling simulation design was carried out. Secondly, the terahertz pyroelectric detector was developed by using precision grinding and polishing process, micro-nano processing technology of planar integrated circuit, homogenized and peeling process, and grinding wheel slicing technology. Finally, the sleeve and waveguide adaptor mounted on the detector structure were innovatively designed. Theoretical analysis and experimental results show that the terahertz pyroelectric detector designed in this method has the characteristics of low noise equivalent power and high repeatability, and solves the compatibility test problem of terahertz radiation power transmitted in free space and waveguide.
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Key words:
- THz detector /
- finite element analysis /
- free space /
- waveguide
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表 1 重复性测试数据
Table 1. Repeatability test data
Num Voltage/mV Power/mW Num Voltage/mV Power/mW 1 720.2 12.37 6 720.2 12.37 2 718.6 12.35 7 720.0 12.37 3 720.2 12.37 8 720.4 12.38 4 718.8 12.35 9 718.6 12.35 5 718.4 12.34 10 718.2 12.34 -
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