In this letter, we report the near quantum-limited performance of a 230 GHz endfire superconductor-insulator-superconductor (SIS) mixer utilizing a Nb/Al-AlOx/Nb trilayer. An important feature of this mixer is its use of a unilateral finline for the waveguide-to-planar circuit transition, which allows for a wide radiofrequency (RF) bandwidth, a simple waveguide structure with easy alignment, and for the mixer chip to be aligned along the optical axis. Each of these factors is beneficial in the construction of large-format focal plane arrays. We tested the new finline mixer from 210 to 260 GHz in a liquid helium cryostat at ~4 K. The best recorded noise temperature was approximately twice the quantum limit, which is comparable to conventional radial probe mixers. This suggests that endfire SIS mixers can be used in large format arrays, comprising 100s or even 1000s of SIS mixing elements, while retaining state-of-the-art quantum mixing performance.

中文翻译：

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具有接近量子限制性能的 230 GHz Endfire SIS 混频器


在这封信中，我们报告了利用 Nb/Al-AlOx/Nb 三层的 230 GHz 端射超导体-绝缘体-超导体 (SIS) 混频器的近量子极限性能。该混频器的一个重要特点是它使用单边鳍线进行波导到平面电路的过渡，从而实现宽射频 (RF) 带宽、易于对准的简单波导结构以及混频器芯片的对准沿着光轴。这些因素中的每一个都有利于大尺寸焦平面阵列的构建。我们在约 4 K 的液氦低温恒温器中测试了 210 至 260 GHz 的新型鳍线混频器。记录的最佳噪声温度大约是量子极限的两倍，与传统的径向探针混频器相当。这表明 Endfire SIS 混合器可用于大型阵列，包括数百个甚至数千个 SIS 混合元件，同时保留最先进的量子混合性能。