Laser Direct Writing-Assisted Fabrication and Characterization of High- T c Superconducting Quantum Magnetometers

This paper presents a comprehensive systematic approach methodology for the development of high-temperature superconducting (HTS) magnetometers based on YBa₂Cu₃O₇₋δ (YBCO), encompassing material synthesis, device design, nanofabrication, characterization and their mutual interdependencies and closed-loop feedback dynamics. The approach integrates the optimization of YBCO thin-film growth, the design of low-noise superconducting quantum interference device (SQUID) magnetometer circuits, and advanced micro/nanofabrication processes respectively. Besides that, we introduce and implement a novel nano-laser direct writing (NLDW) technique for precise alignment of grain-boundary on bi-crystal substrates, achieving high-yield, well-defined Josephson junctions and circuit interconnects. Through iterative optimization across all stages – from the initial material properties through circuit layout to the final fabrication steps – we demonstrate integrated YBCO magnetometers exhibiting low magnetic field white noise levels of approximately 100 fT/Hz1/2at 77 K. The established systematic approach, assisted by the NLDW alignment capability, paves the way for practical high-Tcmagnetometers application.