Some variations provide an atomic vapor-cell system comprising: a vapor-cell region configured with vapor-cell walls for containing an atomic vapor; and a coating disposed on at least some interior surfaces of the walls, wherein the coating comprises magnesium oxide, a rare earth metal oxide, or a combination thereof. The atomic vapor-cell system may be configured to allow at least one optical path through the vapor-cell region. In some embodiments, the coating comprises or consists essentially of magnesium oxide and/or a rare earth metal oxide. When the coating contains a rare earth metal oxide, it may be a lanthanoid oxide, such as lanthanum oxide. The atomic vapor-cell system preferably further comprises a device to adjust vapor pressure of the atomic vapor within the vapor-cell region. Preferably, the device is a solid-state electrochemical device configured to convey the atomic vapor into or out of the vapor-cell region.

An atomic clock employs alkali metal atoms such as cesium normally used for microwave atomic clocks but with optical stimulation. While alkali metals provide light emissions having a spectral width being as much as 10.sup.7 wider (and hence less precise) than alkali earth materials commonly targeted for optical atomic clocks, the present inventors have determined that this disadvantage is significantly reduced by improved signal-to-noise ratio in the obtained signal making practical an atomic clock with improved size, weight, and power consumption.

Vapor cells may include a body including a cavity within the body. A first substrate bonded to a second substrate at an interface within the body, at least one of the first substrate, the second substrate, or an interfacial material between the first and second substrates may define at least one recess or pore in a surface. A smallest dimension of the at least one recess or pore may be about 500 microns or less, as measured in a direction parallel to at least one surface of the first substrate partially defining the cavity.

Vapor cells may include a body including a cavity within the body. A first substrate bonded to a second substrate at an interface within the body, at least one of the first substrate, the second substrate, or an interfacial material between the first and second substrates may define at least one recess or pore in a surface. A smallest dimension of the at least one recess or pore may be about 500 microns or less, as measured in a direction parallel to at least one surface of the first substrate partially defining the cavity.

A clock generator includes a hermetically sealed cavity and clock generation circuitry. A dipolar molecule in the hermetically sealed cavity has a quantum rotational state transition at a fixed frequency. The clock generation circuitry generates an output clock signal based on the fixed frequency of the dipolar molecule. The clock generation circuitry includes a detection circuit, a reference oscillator, and control circuitry. The detection circuit generates a first detection signal and a second detection signal representative of amplitude of signal at an output of the hermetically sealed cavity responsive to a first sweep signal and a second sweep signal input to the hermetically sealed cavity. The control circuitry sets a frequency of the reference oscillator based on a difference in time of identification of the fixed frequency of the dipolar molecule in the first detection signal and the second detection signal.

In some embodiments, a molecular clock includes a waveguide gas cell containing gas molecules having a rotational spectral line with a first frequency a voltage-controlled oscillator (VCO) to generate a clock signal, a transmitter referenced to the clock signal to generate a probing signal for transmission through the waveguide gas cell, and a receiver to receive the probing signal transmitted through the waveguide gas cell and interacting with gas molecules. The receiver can include a filter circuit configured to filter out even harmonic components from the received signal and can further include a lock-in detector to generate an error signal indicating an offset between the first frequency and the second frequency. The error signal is fed back to control generation of the VCO clock signal.

In some embodiments, a molecular clock includes a waveguide gas cell containing gas molecules having a rotational spectral line with a first frequency a voltage-controlled oscillator (VCO) to generate a clock signal, a transmitter referenced to the clock signal to generate a probing signal for transmission through the waveguide gas cell, and a receiver to receive the probing signal transmitted through the waveguide gas cell and interacting with gas molecules. The receiver can include a filter circuit configured to filter out even harmonic components from the received signal and can further include a lock-in detector to generate an error signal indicating an offset between the first frequency and the second frequency. The error signal is fed back to control generation of the VCO clock signal.

Systems and methods for dynamic locking of optical path times using entangled photons are provided. A system includes an optical source for generating bi-photons; tracer laser beam sources for generating tracer laser beams; telescopes that emit the tracer laser beams and the bi-photons to remote reflectors, each bi-photon traveling along an optical path in a pair of optical paths toward a corresponding remote reflector, wherein the telescopes receive reflected bi-photons from the remote reflectors; and communication links, wherein the optical source respectively communicates with first and second remote reflectors through a first and second communication link. Also, the optical source uses the tracer laser beams and the communication links to respectively point the bi-photons towards the remote reflectors. Moreover, the system includes an interferometer that provides information regarding detection of the reflected bi-photons, wherein the optical source uses the information to adjust optical path lengths to be substantially equal.

A physics package for an atomic clock is provided herein. The atomic clock may include a resonance cell storing alkali vapor having first and second hyperfine ground states and an excited state, a light source to transmit light through the resonance cell at a frequency corresponding to electronic decay from the excited state to the first ground state, and a photodetector to receive light from the light source. The physics package may include a laser, and controller circuitry to, at a first time, allow light from the laser to optically pump the alkali vapor from the first hyperfine ground state to the excited state; and at a second time, allow the photodetector to receive light source light from the resonance cell while inhibiting light from the laser from optically pumping the alkali vapor in the resonance cell.

A physics package for an atomic clock is provided herein. The atomic clock may include a resonance cell storing alkali vapor having first and second hyperfine ground states and an excited state, a light source to transmit light through the resonance cell at a frequency corresponding to electronic decay from the excited state to the first ground state, and a photodetector to receive light from the light source. The physics package may include a laser, and controller circuitry to, at a first time, allow light from the laser to optically pump the alkali vapor from the first hyperfine ground state to the excited state; and at a second time, allow the photodetector to receive light source light from the resonance cell while inhibiting light from the laser from optically pumping the alkali vapor in the resonance cell.