太赫兹时域光谱仪非线性度校准方法OA

With the development of terahertz time-domain spectrometers toward a large dynamic range,the system's nonlinear response has become a core bottleneck limiting the accuracy of quantitative analysis.However,traditional nonlinearity calibration methods generally suffer from issues such as optical path interference(e.g.,bulk material attenuators are prone to causing wavefront distortion),bandwidth limitations,and difficulty in metrological traceability.These problems severely restrict the standardized application of terahertz time-domain spectrometers.To address the above challenges,this study develops an attenuator with low wavelength selectivity based on the skin effect to achieve nonlinearity calibration of terahertz time-domain spectrometers.The attenuator is an Inconel 600 alloy film.By establishing a complete calibration sequence with 7 attenuation levels and constructing a three-level metrological traceability chain of"terahertz source-standard power meter-attenuator",the accuracy and traceability of the calibration results are ensured.Calibration experiments were conducted at three characteristic frequency points:0.3 THz,0.9 THz,and 1.6 THz.The results show that the system's nonlinearity exhibits a trend of"first decreasing and then increasing"with frequency.The system exhibits the best performance in the mid-frequency band(0.9 THz),with nonlinearity as low as 1.5%.The nonlinearity is 3.2%in the low-frequency band(0.3 THz)and increases to 7.7%in the high-frequency band(1.6 THz).Moreover,the calibration results at all frequency points comply with metrological specifications.This method effectively avoids the inherent defects of traditional attenuators,provides a high-precision and traceable technical solution for the nonlinearity calibration of terahertz time-domain spectrometers.