A compact and tunable forward coupler based on high-impedance superconducting nanowires

Superconducting nanowire single-photon detector with integrated impedance-matching taper

Conventional readout of a superconducting nanowire single-photon detector (SNSPD) sets an upper bound on the output voltage to be the product of the bias current and the load impedance, $I_\mathrm{B}\times Z_\mathrm{load}$, where $Z_\mathrm{load}$ is limited to 50 $Ω$ in standard r.f. electronics. Here, we break this limit by interfacing the 50 $Ω$ load and the SNSPD using an integrated superconducting transmission line taper. The taper is a transformer that effectively loads the SNSPD with high impedance without latching. It increases the amplitude of the detector output while preserving the …

2微米波长下高性能、绝热纳米锥形光纤-芯片耦合器

High-performance, adiabatically nanotapered fibre-chip couplers in silicon at 2 microns wavelength

针对硅纳米线波导与光纤模式不匹配导致耦合效率低的问题，提出一种低损耗、宽带且平面的绝热纳米锥形光纤-芯片耦合方法，在2微米波长下实现高传输和宽带宽，并验证了优异的横向错位容忍度。

Impedance-matched differential superconducting nanowire detectors

Superconducting nanowire single-photon detectors (SNSPDs) are the highest performing photon-counting technology in the near-infrared (NIR). Due to delay-line effects, large area SNSPDs typically trade-off timing resolution and detection efficiency. Here, we introduce a detector design based on transmission line engineering and differential readout for device-level signal conditioning, enabling a high system detection efficiency and a low detector jitter, simultaneously. To make our differential detectors compatible with single-ended time taggers, we also engineer analog differential-to-single-…

50 Ohm Transmission Lines with Extreme Wavelength Compression Based on Superconducting Nanowires on High-Permittivity Substrates

We demonstrate impedance-matched low-loss transmission lines with a signal wavelength more than 150 times smaller than the free space wavelength using superconducting nanowires on high permittivity substrates. A niobium nitride thin film is patterned in a coplanar waveguide (CPW) transmission line geometry on a bilayer substrate consisting of 100 nm of epitaxial strontium titanate on high-resitivity silicon. The use of strontium titanate on silicon enables wafer-scale fabrication and maximizes process compatibility. It also makes it possible to realize a $50$ $Ω$ characteristic impedance acros…

Bridging the gap between nanowires and Josephson junctions: a superconducting device based on controlled fluxon transfer across nanowires

The basis for superconducting electronics can broadly be divided between two technologies: the Josephson junction and the superconducting nanowire. While the Josephson junction (JJ) remains the dominant technology due to its high speed and low power dissipation, recently proposed nanowire devices offer improvements such as gain, high fanout, and compatibility with CMOS circuits. Despite these benefits, nanowire-based electronics have largely been limited to binary operations, with devices switching between the superconducting state and a high-impedance resistive state dominated by uncontrolled…

超导纳米线单光子探测器的分布式电学模型

A distributed electrical model for superconducting nanowire single photon detectors

为了分析超导纳米线单光子探测器（SNSPD）的开关动力学和输出性能，通常将纳米线建模为电感器与由光子吸收引起的时变电阻器串联。我们最近的实验结果表明，由于动力学电感的影响，对于由足够长度的纳米线制成的SNSPD，其几何长度可以与输出脉冲中包含的频率的有效波长相当甚至更长。换句话说，超导纳米线可以表现为分布式传输线，使得读出脉冲取决于光子检测位置和纳米线的传输线特性。在这里，我们开发了一个分布式模型的超导纳米线和应用它来模拟的输出性能的长纳米线设计成共面波导。我们比较这种共面波导的几何形状，以传统的曲折纳米线的几何形状。模拟结果与我们的实验观察吻合得很好。在此基础上，讨论了纳米线微波设计的重要性以及阻抗匹配对输出脉冲波形的影响。我们还讨论了分布式模型如何影响光子触发的电阻热点的增长和衰减。