太赫兹谐波混频检测器变频效率测量

Measurement of Terahertz Harmonic Mixing Detector’s Conversion Efficiency

太赫兹波是电磁波谱中最后一个未被全面研究开发的频段,它的开发和利用具有重大的科学价值。利用高温超导双晶结制备的太赫兹谐波混频探测器,具有灵敏度高、变频效率高、谐波次数高、工作频带宽、噪声系数低等优点。基于GM制冷机搭建了高温超导双晶结太赫兹混频系统,并采用了准光学系统增强结与太赫兹波的耦合。在2.7 K的温度下对结进行了测量,获得了结对623 GHz太赫兹波的响应,并且成功进行了254次谐波混频实验,中频输出信噪比达10 dB。对高温超导约瑟夫森双晶结的变频效率进行了计算,并且测量和分析了变频效率与本振功率、谐波混频次数的关系。

Terahertz(THz) wave is the last one which is not a comprehensive study of the development of the frequency bandof the electromagnetic spectrum.Due to its excellent performance in high frequency band and good nonlinear properties,high temperature superconducting(HTS) Josephson junction can be used in HTS frequency mixer to detect THz signal.Mixer with HTS bi-crystal Josephson junction has many unique advantages,including low local oscillator frequency and microwave power,high sensitivity and conversion efficiency,high harmonic number,wide frequency band,low noise factor and so on.A HTS THz harmonic mixing system is constructed based on the GM refrigerator.And quasi-optical coupling system is applied in harmonic mixing system to further improve microwave’s coupling to Josephson junction.The Josephson junction is measured under the temperature of 2.7 K.And response is got when the frequency of the electromagnetic irradiation is 623 GHz.The harmonic number of the intermediate frequency(IF) is up to 254,whose signal to noise ratio(SNR) is up to 10 dB.Finally,the parameter conversion efficiency of the junction and its relationship with other parameters are tested and analyzed.