Abstract: A low-power, chip-scale atomic beam clock is provided that maintains high precision for at least one week at any practical temperature. In some variations, the invention provides a chip-scale atomic beam clock comprising: a micro-optical bench; an atom collimator configured to generate a collimated atomic beam via differential pumping through microchannels; a VCSEL configured to emit laser photons horizontally in the plane of the micro-optical bench; an in-plane lithographically defined diffraction grating configured to split the laser photons into a first photon beam and a second photon beam; in-plane lithographically defined mirrors configured to retroflect the photon beams; in-plane photodetectors configured to detect the photon beams after being retroflected, wherein the first photon beam and the second photon beam interrogate the collimated atomic beam in-plane with the micro-optical bench.

Abstract: In some variations, an interferometric frequency-reference apparatus comprises: an atom source configured to supply neutral atoms; a collimator configured to form a collimated beam of the neutral atoms; one or more probe lasers; and a Doppler laser configured to determine a ground-state population of the neutral atoms. Other variations provide a method of creating a stable frequency reference, comprising: forming a collimated beam of neutral atoms; illuminating the neutral atoms with first and second probe lasers; adjusting the frequencies of the first probe laser and second probe laser using Ramsey spectroscopy to an S?D transition of the neutral atoms; and determining a ground-state population of the neutral atoms with another laser. The interferometric frequency-reference apparatus may provide an optical frequency reference or a microwave frequency reference.

Abstract: In some variations, an interferometric frequency-reference apparatus comprises: an atom source configured to supply neutral atoms to be ionized; an ionizer configured to excite the neutral atoms to form ionized atoms; an ion collimator configured to form a collimated beam of the ionized atoms; probe lasers; and a Doppler laser configured to determine a ground-state population of the ionized atoms, wherein the atom source, the ionizer, and the ion collimator are disposed within a vacuum chamber. Other variations provide a method of creating a stable frequency reference, comprising: forming ionized atoms from an atomic vapor; forming a collimated beam of ionized atoms; illuminating ionized atoms with first and second probe lasers; adjusting the frequencies of the first probe and second probe lasers using Ramsey spectroscopy to an S?D transition of ionized atoms; and determining a ground-state population of the ionized atoms with another laser.

Abstract: In some variations, an interferometric frequency-reference apparatus comprises: an atom source configured to supply neutral atoms; a collimator configured to form a collimated beam of the neutral atoms; one or more probe lasers; and a Doppler laser configured to determine a ground-state population of the neutral atoms. Other variations provide a method of creating a stable frequency reference, comprising: forming a collimated beam of neutral atoms; illuminating the neutral atoms with first and second probe lasers; adjusting the frequencies of the first probe laser and second probe laser using Ramsey spectroscopy to an S?D transition of the neutral atoms; and determining a ground-state population of the neutral atoms with another laser. The interferometric frequency-reference apparatus may provide an optical frequency reference or a microwave frequency reference.

Abstract: In some variations, an interferometric frequency-reference apparatus comprises: an atom source configured to supply neutral atoms to be ionized; an ionizer configured to excite the neutral atoms to form ionized atoms; an ion collimator configured to form a collimated beam of the ionized atoms; probe lasers; and a Doppler laser configured to determine a ground-state population of the ionized atoms, wherein the atom source, the ionizer, and the ion collimator are disposed within a vacuum chamber. Other variations provide a method of creating a stable frequency reference, comprising: forming ionized atoms from an atomic vapor; forming a collimated beam of ionized atoms; illuminating ionized atoms with first and second probe lasers; adjusting the frequencies of the first probe and second probe lasers using Ramsey spectroscopy to an S?D transition of ionized atoms; and determining a ground-state population of the ionized atoms with another laser.