A Centimeter-Scale Dielectric Metasurface for the Generation of Cold Atoms.

The single-beam magneto-optical trap (MOT) based on the diffractive optical element offers a new route to develop compact cold atom sources. However, the optical efficiency in the previous single-beam MOT systems is usually low and unbalanced, which will affect the quality of the trapped atoms. To solve this issue, we developed a centimeter-scale dielectric metasurface optical chip with dynamic phase distributions, which was used to split a single incident laser beam into five separate ones with well-defined polarization states and uniform energy distributions. The measured diffraction efficiency of the metasurface is up to 47%. A single-beam MOT integrated with the metasurface optical chip was then used to trap the 87Rb atoms with numbers ∼1.4 × 108 and temperatures ∼7.0 µK. The proposed concept in this work may provide a promising solution for developing ultracompact cold atom sources.

Determining optical path difference with a frequency-modulated continuous-wave method.

A technique for determining the optical path difference (OPD) between two Raman beams using a frequency-modulated continuous-wave method is investigated. This approach greatly facilitates the measurement and adjustment of the OPD when tuning the OPD is essential to minimize the effects of the diode laser's phase noise on Raman lasers. As a demonstration, the frequencies of the beat note with different OPDs are characterized and analyzed. When the measured beat frequency is 0.367 Hz, the OPD between Raman beams is zero. The phase noise of the Raman laser system after implementation of zeroing of the OPD is also measured.

Vortex conveyor belt for matter-wave coherent splitting and interferometry.

We numerically study a matter wave interferometer realized by splitting a trapped Bose-Einstein condensate with phase imprinting. We show that a simple step-like imprinting pattern rapidly decays into a string of vortices that can generate opposite velocities on the two halves of the condensate. We first study in detail the splitting and launching effect of these vortex structures, whose functioning resembles the one of a conveyor belt, and we show that the initial exit velocity along the vortex conveyor belt can be controlled continuously by adjusting the vortex distance. We finally characterize the complete interferometric sequence, demonstrating how the phase of the resulting interference fringe can be used to measure an external acceleration. The proposed scheme has the potential to be developed into compact and high precision accelerometers.