Picotesla optically pumped magnetometer using a laser-written vapor cell with sub-mm cross section

We demonstrate a sensitive optically pumped magnetometer using rubidium vapor and 0.75 amg of nitrogen buffer gas in a sub-mm-width sensing channel excavated by femtosecond laser writing followed by chemical etching. The channel is buried less than 1 mm below the surface of its fused silica host material, which also includes reservoir chambers and micro-strainer connections, to preserve a clean optical environment. Using a zero-field-resonance magnetometry strategy and a sensing volume of 2.25 mm 3 , we demonstrate a sensitivity of ≈ 1 pT / Hz at 10 Hz. The device can be integrated with photonic structures and microfluidic channels with 3D versatility. Its sensitivity, bandwidth, and stand-off distance will enable detection of localized fields from magnetic nanoparticles and μ L NMR samples.