Constricted junction based superconducting quantum interference devices via nano-laser direct writing

Thermal effects serve as universal stimuli for material transformation, capable of inducing processes, such as crystallization, evaporation, and melting in various materials. In this paper, we propose an efficient and cost-effective fabrication method based on nano-laser direct writing (NLDW) technology for the fabrication of Nb constricted junctions and superconducting quantum interference devices induced by thermal effects. By narrowing the spacing between laser paths step by step, the I–V characteristics of constricted junctions can be continuously adjusted from collective Cooper pair transport to Josephson junction behavior. Additionally, the heat-affected zones induced by laser irradiation were characterized by heat transfer simulations and electrical transport behavior. Furthermore, the flux noise spectral density of a patterned superconducting quantum interference device based on NLDW is 2.8μΦ0/Hz1/2 in the white noise range, which exhibits comparable performance to devices based on traditional ion beam or electron beam etching processes. In this case, this technique could provide a reliable and reproducible pathway for scaling up the fabrication of superconducting quantum circuits, as well as an avenue to conduct nanoscale thermal engineering in superconducting materials research for basic science.