Our planar platform provides a robust approach to beam generation on chip and represents a step towards realizing atomic technologies with manufacturable PICs. The combined lattice and clock beams are collinear to within 0.1° of one another and are vertically directed to within 1° from chip normal. In addition, we demonstrate the collinear combination of two separately waveguided beams to produce an optical lattice (at 813 nm) aligned with a probe beam at the clock transition (at 698 nm). We design this system to form both the 461 nm and 689 nm MOTs within a small (25 mm) 3 volume accommodating a vacuum chamber with strontium vapor. We demonstrate a compact photonic chip system generating twelve circularly polarized beams as large as 10 mm in diameter (461 nm). Our approach is based on a bonded planar platform that combines optical metasurfaces (MSs) with grating outcouplers 28 to produce beams with a high numerical aperture (NA), arbitrary tilt angles, prescribed polarizations, and collinear propagation. In this work, we design and fabricate an integrated photonics package for the miniaturization of a strontium atomic clock. Each MOT stage typically uses 3 pairs of counterpropagating beams to decrease the atomic momenta along all three spatial axes, with the lattice trap typically formed by a single beam and its retroreflection.
A commonly employed scheme 25 for lattice clocks based on strontium involves three physically overlapping optical cooling/trapping stages in sequence: a magneto-optical trap (MOT) at the wavelength of 461 nm for capture of thermal atoms, a smaller-volume MOT at 689 nm for further cooling, and an optical lattice trap at 813 nm for Doppler-free interrogation by a probe beam at the 698 nm clock transition 26, 27. Yet challenges remain for combining these various capabilities within a single platform for power-efficient arbitrary beam control within a single integrated technology.Īs an example, optical lattice clocks achieve state-of-the-art frequency instability and ultra-high timing accuracy 22, 23, 24, but require a complex combination of bulk optics to generate the numerous laser beams and wavelengths needed to prepare the atomic sample used for the clock reference. Grating technologies have advanced over the years to enable multi-wavelength control of light 8, 9, 10, surface-normal emission 11, 12, 13, 14, polarization control 15, 16, 17, and the generation of beams with large numerical apertures 18, 19 and large mode expansions 20, 21. Diffraction gratings can be integrated on chip to generate free-space beams from guided modes 6 and used to address atomic systems out of plane 7. PICs allow for foundry-scale integration of optical components that can range from laser sources and modulators all the way to on-chip detectors. Miniaturized optical systems can be constructed using a combination of compact bulk 1 or flat optics 2, 3, while photonic integrated circuits (PICs) may provide a scalable approach to manufacturing atomic technologies 4, 5. This control is readily achieved using laboratory-scale setups but becomes more challenging as optical systems are scaled down for commercialization. Precise control of the wavelength, power, and polarization of coherent free-space light is required for addressing the optical transitions in atomic systems. Optical systems form the backbone of atomic vapor, trapped ion, and neutral atom technologies. With these devices we demonstrate that our integrated photonic platform is scalable to an arbitrary number of beams, each with different wavelengths, geometries, and polarizations. These beams emit collinearly and vertically to probe the center of the magneto-optical trap, where they will have diameters of ≈100 µm. Our design also includes two co-propagating beams at lattice and clock wavelengths. These beams are directed above the chip to intersect at a central location with diameters as large as 1 cm.
Our planar design includes twelve beams in two co-aligned magneto-optical traps. In this work, we combine these two technologies using flip-chip bonding and demonstrate an integrated optical architecture for realizing a compact strontium atomic clock. Complex arrangements of free-space beams can be generated on chip through a combination of integrated photonics and metasurface optics. The commercialization of atomic technologies requires replacing laboratory-scale laser setups with compact and manufacturable optical platforms.
0 kommentar(er)
