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通过两块超导体之间,或者通过一块超导体和一块正常导体之间的绝缘势垒的隧道现象.已经被用作毫米波长上的极低噪声检测器和混频器。由两块超导体之间的隧道过程得到的 I—V 曲线性能够强烈到使经典理论失灵的地步。并且使得必须用光子参于隧道效应理论去理解器件的性能。量子理论预言,一个准粒子隧道结可以用作量子效率近于1的微波光子检测器,或者用作具有变频增益且噪声温度可与量子噪声极限 T_M=hω/k 相比较的外差混频器。在36GHz 上,用超导体—绝缘体—超导体结,这两个预言已经由实验所证实。看来,在毫米波段上,这些准粒子检测器和混频器可以胜过相应的约氏效应器件。
Tunneling through the two superconductors, or through the insulating barrier between a superconductor and a normal conductor, has been used as a very low noise detector and mixer at millimeter wavelengths. The I-V curve obtained by the tunneling process between two superconductors can be so strong that the classical theory fails. And make it necessary to understand the performance of the device using photon-induced tunneling theory. Quantum theory predicts that a quasi-particle tunnel junction can be used as a microwave photon detector with a quantum efficiency near 1 or as a heterodyne mixer with variable frequency gain and a noise temperature comparable to the quantum noise limit T_M = hω / k . At 36 GHz, using both superconductor-insulator-superconductor junctions, these two predictions have been experimentally demonstrated. It appears that these quasi-particle detectors and mixers outperform the corresponding Yosemite devices in the millimeter wave band.