We demonstrate a simple stacked scheme that enables absorption imaging through a hole in the surface of a grating magneto-optical trap (GMOT) chip, placed immediately below a micro-fabricated vacuum cell. The imaging scheme is capable of overcoming the reduced optical access and surface scatter that is associated with this chip-scale platform while further permitting both trapping and imaging of the atoms from a single incident laser beam. The through-hole imaging is used to characterize the impact of the reduced optical overlap volume of the GMOT in the chip-scale cell, with an outlook to an optimized atom number in low volume systems.

We present an additive-manufactured microwave cavity for a Ramsey-type, double resonance, compact cold-atom clock. Atoms can be laser cooled inside the cavity using a grating magneto-optic trap with the cavity providing an excellent TE011-like mode while maintaining sufficient optical access for atomic detection. The cavity features a low Q-factor of 360 which conveniently reduces the cavity pulling of the future clock. Despite the potential porosity of the additive-manufacturing process, we demonstrate that the cavity is well-suited for vacuum. A preliminary clock setup using cold atoms allows for measuring the Zeeman spectrum and Rabi oscillations in the cavity which enables us to infer excellent field uniformity and homogeneity, respectively, across the volume accessed by the cold atoms. Ramsey spectroscopy is demonstrated, indicating that the cavity is suitable for clock applications. Finally, we discuss the limitations of the future clock.

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A compact platform for cold atoms opens a range of exciting possibilities for portable, robust and accessible quantum sensors. In this work, we report on the development of a cold-atom microwave clock in a small package. Our work utilises the grating magneto-optical trap and high-contrast coherent population trapping in the lin$\perp $lin polarisation scheme. We optically probe the atomic ground-state splitting of cold 87Rb atoms using a Ramsey-like sequence whilst the atoms are in free-fall. We have measured a short-term fractional frequency stability of $5{\times}{10}^{-13}/\sqrt{\tau }$ with a projected quantum projection noise limit at the ${10}^{-13}/\sqrt{\tau }$ level.

We demonstrate a tunable, chip-scale wavelength reference to greatly reduce the complexity and volume of cold-atom sensors. A 1-mm optical path length microfabricated cell provides an atomic wavelength reference, with dynamic frequency control enabled by Zeeman-shifting the atomic transition through the magnetic field generated by the printed-circuit-board coils. The dynamic range of the laser frequency stabilization system is evaluated and used in conjunction with an improved generation of chip-scale coldatom platforms that traps 4 million 87 Rb atoms. The scalability and component consolidation provide a key step forward in the miniaturization of cold-atom sensors.