Widefield microwave imaging in alkali vapor cells with sub-100 μm resolution

Abstract

We report onwidefieldmicrowave vector field imagingwith sub-100 mmresolution using a microfabricated alkali vapor cell. The setup can additionally image dc magnetic fields, and can beconfigured to image microwave electric fields. Our camera-based widefield imaging system records 2D images with a 6×6mm2 field of viewat a rate of 10Hz. Itrovides up to 50 mmspatial resolution, and allows imaging of fields as close as 150 μmabove structures, through the use of thin external cell walls. This is crucial in allowing us to takeractical advantage of the high spatial resolution, as feature sizes in near-fields are on the order of the distance from their source, and represent an order of magnitude improvement in surface-feature resolution compared torevious vapor cell experiments. Wepresent microwave and dc magnetic field images above a selection of devices, demonstrating a microwave sensitivity of 1.4 μT Hz-1/2er 50 × 50 × 140 μm3 voxel, atresent limited by the speed of our camera system. Since we image 120120 voxels inarallel, a single scanned sensor would require a sensitivity of at least 12 nT Hz-1/2 toroduce imageswith the same sensitivity. Our technique couldrove transformative in the design, characterization, and debugging of microwave devices, as there are currently no satisfactory established microwave imaging techniques. Moreover, it could find applications in medical imaging.