Storing a very high frequency (VHF) band (30–300 MHz) electromagnetic wave has many potential applications, such as phase modulation, buffering, and radio frequency memory. It can be effectively achieved by applying coupled resonator-based electromagnetically induced transparency (EIT) due to its slow light effect. However, the wavelength in the VHF band is too long to design resonators, and the group delay is limited by the high resistive loss of metal. The practical application of EIT in the VHF band is still a big challenge. In this work, we propose and experimentally demonstrate EIT response in a high-temperature superconducting (HTS) microwave circuit with coupled-resonator-induced transparency. The chip size of the HTS circuit is only $34\mathrm{mm}\times 20\mathrm{mm}$ with a very low transparency frequency of 198.55 MHz. In addition, we implement very large group delay higher than 12.3 μs and 16.2 μs with working temperatures of 65 K and 50 K separately, which is much longer than the previous reported works on slow wave. The fabricated circuit is planar with working temperature about 65 K, and thus can be easily integrated into other microwave devices under the cryogenic conditions provided by a commercial portable Stirling cryocooler. Our proposed method paves a way for studying EIT in the microwave region due to the high quality factor of the HTS resonator, which has great potential use for radio-frequency memory in the future.

中文翻译：

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使用耦合高温超导谐振器的 VHF 频段中非常大的群延迟

存储甚高频 (VHF) 频带 (30–300 MHz) 电磁波具有许多潜在应用，例如相位调制、缓冲和射频存储器。由于其慢光效应，可以通过应用基于耦合谐振器的电磁感应透明 (EIT) 来有效实现。然而，VHF波段的波长太长，无法设计谐振器，并且群延迟受到金属高阻损耗的限制。EIT在VHF频段的实际应用仍然是一个很大的挑战。在这项工作中，我们提出并通过实验证明了具有耦合谐振器诱导透明性的高温超导 (HTS) 微波电路中的 EIT 响应。HTS电路的芯片尺寸仅为$34\mathrm{毫米}\times 20\mathrm{毫米}$具有 198.55 MHz 的非常低的透明度频率。此外，我们分别在 65 K 和 50 K 的工作温度下实现了高于 12.3 μs 和 16.2 μs 的非常大的群延迟，这比之前报道的慢波工作要长得多。制作的电路是平面的，工作温度约为 65 K，因此可以在商用便携式斯特林低温冷却器提供的低温条件下轻松集成到其他微波设备中。由于 HTS 谐振器的高品质因数，我们提出的方法为研究微波区域的 EIT 铺平了道路，这在未来在射频存储器中具有巨大的潜在用途。