Polarization Decoupling Multi-Port Beam-Splitting Metasurface for Miniaturized Magneto-Optical Trap

In regular magneto-optical trap (MOT) systems, the delivery of six circularly polarized (CP) cooling beams requires complex and bulky optical arrangements including waveplates, mirrors, retroreflectors, etc. To address such technique challenges, a beam delivery system for miniaturized MOT is proposed entirely based on meta-devices. The key component is a novel polarization decoupling multi-port beam-splitting (PD-MPBS) metasurface that relies on both propagation phase and geometric phase. The fabricated samples exhibit high beam-splitting power uniformity (within 4.4%) and polarization purities (91.3-93.2%). By leveraging such a beam-splitting device as well as a reflective beam-expanding meta-device, an integrated six-beam delivery system for miniaturized MOT application is implemented. The experimental results indicate that six expanded beams have been successfully delivered with uniform power (within 9.5%), the desired CP configuration, and a large overlapping volume (76.2 mm³). It is believed that a miniaturized MOT with the proposed beam delivery system is very promising for portable application of cold atom technology in precision measurement, atomic clock, quantum simulation, and computing, etc.