A terahertz (THz) attenuation calibration system is developed using a photoacoustic (PA) detector for free-space beams. Based on the principle of the PA detector, the system measures the THz attenuation by substituting radio frequency (RF) attenuation with audio frequency (AF) attenuation. The AF attenuation at 1 kHz is directly calibrated using an inductive voltage divider (IVD) as the reference standard. The calibration is demonstrated for metalized film attenuators up to 20 dB at 0.11 THz. A Gunn oscillator with a corrugated horn antenna is used as the source, and its radiated beam is collimated using an off-axis parabolic mirror. Sources of uncertainties are also discussed in detail, and the expanded uncertainty is found to be 0.40–0.46 dB ( $k = 2$ ).

中文翻译：

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用于校准自由空间中太赫兹衰减的光声替代方法

使用用于自由空间光束的光声（PA）检测器开发了太赫兹（THz）衰减校准系统。根据PA检测器的原理，该系统通过将射频（RF）衰减替换为音频（AF）衰减来测量THz衰减。使用感应分压器（IVD）作为参考标准直接校准1 kHz时的AF衰减。演示了在0.11 THz时对高达20 dB的金属化薄膜衰减器的校准。使用带有波纹形喇叭天线的Gunn振荡器作为源，并使用离轴抛物面反射镜对它的辐射束进行准直。还详细讨论了不确定性的来源，发现扩展后的不确定性为0.40–0.46 dB（ $ k = 2 $ ）。