行波参量放大器中的反射增强增益
Reflection-enhanced gain in traveling-wave parametric amplifiers
AI总结：
本文提出包含反射波相互作用的行波参量放大器增益解析解，揭示反射可增强增益并抑制非线性相位调制，并在两类非匹配超导TWPA上实验验证。
摘要：
行波参量放大器（TWPA）的工作原理通常基于标准耦合模理论来理解，该理论描述前向传播波的演化而不考虑任何反射，即假设理想阻抗匹配。然而，在实际中，超导微波放大器是非匹配的非线性有限长度器件，其中反射波经历复杂的参量过程，这些过程无法由标准耦合模理论描述。本文提出了一个包含反射波相互作用的TWPA增益解析解。这些反射导致对标准耦合模理论中众所周知结果的修正，该修正同时针对三波混频和四波混频过程获得。由于这些反射，增益得到增强，并且不需要的非线性相位调制被抑制。该模型的预测在两种非匹配TWPA上得到了实验验证，这两种TWPA基于共面波导，其中心导线分别由（i）高动感电感超导体和（ii）包含2000个约瑟夫森结的阵列构成。
英文摘要：
The operating principle of traveling-wave parametric amplifiers is typically understood in terms of the standard coupled mode theory, which describes the evolution of forward propagating waves without any reflections, i.e. for perfect impedance matching. However, in practice, superconducting microwave amplifiers are unmatched nonlinear finite-length devices, where the reflecting waves undergo complex parametric processes, not described by the standard coupled mode theory. Here, we present an analytical solution for the TWPA gain, which includes the interaction of reflected waves. These reflections result in corrections to the well-known results of the standard coupled mode theory, which are obtained for both 3-wave and 4-wave mixing processes. Due to these reflections, gain is enhanced and unwanted nonlinear phase modulations are suppressed. Predictions of the model are experimentally demonstrated on two types of unmatched TWPA, based on coplanar waveguides with a central wire consisting of i) a high kinetic inductance superconductor, and ii) an array of 2000 Josephson junctions.
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