Proposal of on-chip manipulation of cold atoms with superimposed holographic gratings

An integrated platform, consisting of two superimposed holographic gratings (SHGs) on the cross-section of waveguides, has been proposed to facilitate atom trapping, excitation, and fluorescence collection on a chip. Two blue-detuned vortex beams diffracted from the SHGs can create an optical dipole trap, enabling the trapping of atoms without interference from the trapping optical field. A Gaussian beam is diffracted to interact with the trapped atoms, and their fluorescence is collected by the SHGs for detection. For the 87 Rb atom, the numerical results show that a trap depth of 0.435 mK can be achieved with an incident power of 100 mW at wavelengths of 760 and 765 nm, respectively. The calculated collection efficiency of the SHGs at 780 nm can reach 1.03% from atoms positioned 5 μm above the surface of the chip. This setup presents a promising method for integrating atoms and photons on a chip.