Fabrication and Modeling of a Cross‑Trap Atom Chip for Interferometric Applications

We present the design and fabrication of a novel cross-shaped atom-trapping chip, implemented on a direct-bond-copper (DBC) board featuring copper layers laminated onto an aluminum nitride substrate. This chip design addresses prevailing limitations in conventional chip-trap systems—particularly constraints on the location of the magnetic potential minimum and achievable trap tightness. For fabrication, the board was precision-cut using a WAZER water jet, and then the copper pattern was chemically etched using a mixture of hydrochloric acid (HCl) and hydrogen peroxide (H₂O₂). We achieve a trace width of about 1 mm with a copper thickness of 0.2 mm. Leads are attached with minimal resistance by soldering to 1.4-mm diameter rivets. We performed numerical modeling of the resulting devices, incorporating the thickness of the chip and fabrication imperfections. By analyzing how deviations from ideal geometry affect the magnetic field, we demonstrate that the trapping potential remains close to ideal. The improved trap configuration will be applied to Sagnac interferometry applications, where the tighter and more precisely controlled trap can enhance performance.