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.

Disclosed are a mold assembly for making alkali metal wax packets, a method for preparing same, and a method for using same. The mold assembly comprises a silicon substrate (10), the silicon substrate (10) comprising a mold isolator (11) at the edge of the silicon substrate (10) and a silicon substrate central portion (18). The upper surface of the silicon substrate central portion (18) is indented to form a plurality of wax packet receiving cavities (12). A cavity isolator (13) locates between adjacent wax packet receiving cavities (12). A release sacrificial layer (15) is formed on the upper surface of the silicon substrate (10), and a paraffin layer (16) is formed on the upper surface of the release sacrificial layer (15) away from the silicon substrate (10). Cavities (121) for containing alkali metal are formed on a side of the paraffin layer (16) away from the release sacrificial layer (15). The mold isolator (11) is provided with corrosion release holes (14). The mold assembly can reliably and controllably achieve batch production of uniform alkali metal wax packet arrays and is completely compatible with MEMS and microelectronic processes, with simple processes that can be easily implemented and high operability. The wax packet mold assembly can be reused, such that wasting of raw materials can be avoided, and the cost of batch production can be effectively reduced.

There is a need to maintain or enhance the magnetic field correction accuracy of a physics package while making the physics package more compact and portable. A triaxial magnetic field correction coil provided inside a vacuum chamber surrounding a clock transition space having atoms disposed therein. The triaxial magnetic field correction coil formed into a shape such that it is possible to correct, for magnetic field components of three axial directions passing through the clock transition space, a constant term, a first order spatial derivative term, a second order spatial derivative term, a third or higher order spatial derivative term, or some given combination of these terms. The triaxial magnetic field correction coil can be used in, for example, a physics package for an optical lattice clock.

There is a need to maintain or enhance the magnetic field correction accuracy of a physics package while making the physics package more compact and portable. A triaxial magnetic field correction coil provided inside a vacuum chamber surrounding a clock transition space having atoms disposed therein. The triaxial magnetic field correction coil formed into a shape such that it is possible to correct, for magnetic field components of three axial directions passing through the clock transition space, a constant term, a first order spatial derivative term, a second order spatial derivative term, a third or higher order spatial derivative term, or some given combination of these terms. The triaxial magnetic field correction coil can be used in, for example, a physics package for an optical lattice clock.

A grating emitter method and system for modulating the polarization of an optical beam, such as one for transmission through free-space or use in an atomic clock.

Methods and apparatus to monitor GPS/GNSS atomic clocks are disclosed. An example method includes establishing a measured difference between an atomic frequency standard (AFS) and a monitoring device. The method also includes modeling an estimated difference model between the AFS and the monitoring device, and computing a residual signal based on the measured difference and the estimated difference model. In addition, the method includes analyzing, by a first detector, the residual signal at multiple thresholds, each of the thresholds having a corresponding persistency defining the number of times a threshold is exceeded before one or more of a phase jump, a rate jump, or an acceleration error is indicated. Furthermore, the method includes analyzing, by a second detector, a parameter of the estimated difference model at multiple thresholds, each of the thresholds having a corresponding persistency defining the number of times a drift threshold is exceeded before a drift is indicated.

Methods and apparatus to monitor GPS/GNSS atomic clocks are disclosed. An example method includes establishing a measured difference between an atomic frequency standard (AFS) and a monitoring device. The method also includes modeling an estimated difference model between the AFS and the monitoring device, and computing a residual signal based on the measured difference and the estimated difference model. In addition, the method includes analyzing, by a first detector, the residual signal at multiple thresholds, each of the thresholds having a corresponding persistency defining the number of times a threshold is exceeded before one or more of a phase jump, a rate jump, or an acceleration error is indicated. Furthermore, the method includes analyzing, by a second detector, a parameter of the estimated difference model at multiple thresholds, each of the thresholds having a corresponding persistency defining the number of times a drift threshold is exceeded before a drift is indicated.

Coherent spectroscopic methods are described, to measure the total phase difference during an extended interrogation interval between the signal delivered by a local oscillator (10) and that given by a quantum system (QS). According to one or more embodiments, the method may comprise reading out at the end of successive interrogation sub-intervals (Ti) intermediate error signals corresponding to the approximate phase difference (φ) between the phase of the LO signal and that of the quantum system, using coherence preserving measurements; shifting at the end of each interrogation sub-intervals (Ti) the phase of the local oscillator signal, by a known correction value (.sub.φ(i).sub.FB) so as to avoid that the phase difference approaches the limit of the inversion region; reading out a final phase difference (φf) between the phase of the prestabilized oscillator signal and that of the quantum system using a precise measurement with no restriction on the destruction; reconstructing a total phase difference over the extended interrogation interval, as the sum of the final phase difference (φf) and the opposite of all the applied phase corrections figure (I).

Coherent spectroscopic methods are described, to measure the total phase difference during an extended interrogation interval between the signal delivered by a local oscillator (10) and that given by a quantum system (QS). According to one or more embodiments, the method may comprise reading out at the end of successive interrogation sub-intervals (Ti) intermediate error signals corresponding to the approximate phase difference (φ) between the phase of the LO signal and that of the quantum system, using coherence preserving measurements; shifting at the end of each interrogation sub-intervals (Ti) the phase of the local oscillator signal, by a known correction value (.sub.φ(i).sub.FB) so as to avoid that the phase difference approaches the limit of the inversion region; reading out a final phase difference (φf) between the phase of the prestabilized oscillator signal and that of the quantum system using a precise measurement with no restriction on the destruction; reconstructing a total phase difference over the extended interrogation interval, as the sum of the final phase difference (φf) and the opposite of all the applied phase corrections figure (I).

A reference time generator including a first clock source including a reference synthesizer and cesium atomic clock configured to produce a cesium reference signal and a cesium QOT metric, a second clock source including a reference synthesizer and rubidium atomic clock configured to produce a rubidium reference signal and a rubidium QOT metric, and a circuit for selecting from the clock sources one reference signal based on the best QOT metric.