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中国物理学会期刊

基于超导Fano器件的低温射频开关和极低温区高灵敏温度传感

Low temperature RF switch with superconducting Fano device for high sensitive temperature sensing

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  • 开关是一种实现信号通断控制的器件,是保障电子系统高效、稳定运行的关键器件。近年来,室温工作的半导体开关、MHz频段功率开关及光学波段温控开关等已得到广泛应用,然而这类器件在极低温环境下往往因载流子冻析效应而发生功能失效,限制了在低温区的应用。针对这一问题,我们提出一种基于分布式半波长超导共面波导谐振器的低温射频开关,该器件利用超导薄膜动态电感的热敏感性,通过温度调制实现信号的开、关状态的切换。基于时域耦合模理论设计超导Fano器件,分析了器件物理参数对信号传输的调控机制,并在500-1150mK温区内测量了该器件Fano共振峰随温度而变化的特性,并表征了它对特定射频信号的开、关功能。结果发现,该器件对频率为5.87598GHz的射频信号可实现通断控制,消光比最高可达33.6dB。器件在接近超导转变温区时表现出较高的温度响应能力,在1150mK时噪声等效温差低至1.22mK,表明器件具备毫开尔文量级温度分辨能力,该研究为极低温环境下射频信号调控与片上高灵敏温度监测提供了一种新的实现思路。

     

    Low-temperature RF switches are key components in superconducting microwave circuits, quantum measurements, and cryogenic electronics systems. This is because that the traditional semiconductor RF switches usually fail at low temperatures, due to the carrier freeze-out effect, making them diffcult to be directly applied in superconducting microwave environments. In this work, we propose and experimentally demonstrate a low-temperature RF switch, based on a distributed half-wavelength superconducting coplanar waveguide resonator for generating a superconducting Fano device. By taking advantage of the temperature sensitivity of the resonant frequency of the Fano device, we implement the temperature-controlled resonant tuning, based on the temperature-sensitive superconducting aluminum film's dynamic inductance regulation, thereby converting the sensitive thermal-induced frequency shift of the asymmetric Fano line shape into the significant microwave transmission characteristics changes. Through the establishment of a time-domain coupled mode theory, considering the intrinsic loss of the resonator, we systematically analyze the working mechanism and tunability of the low-temperature RF switch and discuss the influence of the resonator's intrinsic quality factor, coupling quality factor, and through-path scattering parameters on the peak-to-valley separation of Fano scattering spectrum and peak-to-valley contrast of the Fano scattering spectrum. We measured the microwave transmission characteristics of the aluminum-film distributed superconducting resonator in a dilution refrigerator and then characterized its temperature-sensitive Fano effect in the temperature range of 500 to 1150 millikelvins. The experimental results show that the resonant frequency of the resonator redshifts significantly with the increase of temperature, confirming that the temperature sensitivity of the superconducting dynamic inductance can be used to achieve temperature-controlled tuning of the Fano scattering. By numerically fitting the temperature-dependent resonant frequency changes, the dynamic inductance ratio of the device was measured as approximately 1.94%; and the superconducting transition temperature of the device is about 1403.53 millikelvins. By testing the transmission characteristics of the device for a 5.87598 GHz RF signal, we demonstrated its temperature-controlled on/off state switching function, achieving the maximum extinction ratio of 33.6 dB. By taking advantage of the particularly sensitive temperature response of the device, near the superconducting transition temperature region, we demonstrated a noise equivalent temperature difference of 1.22 millikelvins at 1150 millikelvins, thereby achieving a temperature sensitivity of 0.2887 MHz/mK. This distributed superconducting resonator temperature-sensitive sensing with millikelvin-level temperature resolution does not require any additional active biasing or nonlinear component, thus can provide a feasible solution for high-precision temperature sensing measurements in the cryogenic region. In particular, it might provide a significant reference for the preparation of such highly temperature-sensitive Fano devices, using superconducting films with a transition temperature of around 50 mK, to achieve the desired real-time thermal condition monitoring on-chip for ultra-low-temperature superconducting quantum chips.

     

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