A rubidium optical atomic clock uses a modulated 778 nanometer (nm) probe beam and its reflection to excite rubidium 87 atoms, some of which emit 758.8 nm fluorescence as they decay back to the ground state. A spectral filter rejects scatter of the 778 nm probe beams while transmitting the 775.8 nm fluorescence so that the latter can be detected with a high signal-to-noise ratio. Since the spectral filter is only acceptably effective at angles of incidence less than 8° from the perpendicular, the atoms are localized by a magneto-optical trap so that most of the atoms lie within a conical volume defined by the 8° angle so that the resulting fluorescence detection signal has a high signal-to-noise ratio. The fluorescence detection signal can be demodulated to provide an error signal from which desired adjustments to the oscillator frequency can be calculated.

A magneto-optical trap apparatus includes a vacuum vessel for encapsulating an atom to be trapped, an anti-Helmholtz coil for applying a magnetic field to an inside of the vacuum vessel, a laser device for generating a laser beam, and an irradiation device for irradiating the generated laser beam from a plurality of directions. The laser beam includes a first laser beam detuned from a first resonance frequency when the atom transits from a total angular momentum quantum number F in a ground state to a total angular momentum quantum number F′=F+1 in an excited state, and a second laser beam detuned from a second resonance frequency when the atom transits from the total angular momentum quantum number F in the ground state to a total angular momentum quantum number F′=F−1 in the excited state, among transitions from J=0 in a ground state to J′=1 in an excited state.

According to some aspects of the present disclosure, an atomic clock and methods of forming and/or using an atomic clock are disclosed. In one embodiment, an atomic clock includes: a light source configured to illuminate a resonance vapor cell; a narrowband optical filter disposed between the light source and the resonance vapor cell and arranged such that light emitted from the light source passes through the narrowband optical filter and illuminates the resonance vapor cell. The resonance vapor cell is configured to emit a signal corresponding to a hyperfine transition frequency in response to illumination from the light source, and a filter cell is disposed between the light source and the resonance vapor cell and configured to generate optical pumping. An optical detector is configured to detect the emitted signal corresponding to the hyperfine transition frequency.

A fluorescence detection process begins by localizing rubidium 87 atoms within an optical (all-optical or magneto-optical) trap so that at least most of the atoms in the trap are within a cone defined by an effective angle, e.g., 8°, of a spectral filter. Within the effective angle of incidence, the filter effectively rejects (reflects or absorbs) 778 nanometer (nm) fluorescence and effectively transmits 775.8 nm fluorescence. Any 775.8 nm fluorescence arrive outside the effective angle of incidence. Thus, using an optical trap to localize the atoms within the cone enhances the signal-to-noise ratio of the fluorescence transmitted through the spectral filter and arriving a photomultiplier or other photodetector, resulting fluorescence detection signal with an enhanced S/N.

A rubidium optical atomic clock uses a modulated 778 nanometer (nm) probe beam and its reflection to excite rubidium 87 atoms, some of which emit 758.8 nm fluorescence as they decay back to the ground state. A spectral filter rejects scatter of the 778 nm probe beams while transmitting the 775.8 nm fluorescence so that the latter can be detected with a high signal-to-noise ratio. Since the spectral filter is only acceptably effective at angles of incidence less than 8° from the perpendicular, the atoms are localized by a magneto-optical trap so that most of the atoms lie within a conical volume defined by the 8° angle so that the resulting fluorescence detection signal has a high signal-to-noise ratio. The fluorescence detection signal can be demodulated to provide an error signal from which desired adjustments to the oscillator frequency can be calculated.

The invention relates to a coherent population trapping (CPT) phase modulation and demodulation method and a system for implementing the method of this invention. The method comprises the following steps: Generating a coherent bichromatic light, in which the relative phase between the two frequency components is modulated with proper modulation depth. The phase modulated coherent bichromatic light interacts with a quantum resonance system, and prepares it alternately into two inverted CPT states. Detecting the transmitted light with a photodetector, two inverted dispersive CPT signals in two detection windows are observed. With synchronous phase demodulation, a CPT error signal is obtained, which is used for locking the local oscillator to implement a CPT atomic clock.

An atomic oscillator including an oscillator that outputs an oscillation signal, a light emitter to which a signal based on the oscillation signal is inputted, an atomic cell, a light receiver that detects the light passing through the atomic cell and outputs a detection signal, a first temperature controller, and a control circuit, and the control circuit has a first mode including the process of operating the light emitter and the first temperature controller and the process of causing the oscillator to output the oscillation signal, a second mode including the process of causing the light emitter and the first temperature controller to stop operating and the process of causing the oscillator to stop outputting the oscillation signal, and a third mode including the process of causing the light emitter to stop operating, the process of operating the first temperature controller, and the process of causing the oscillator to stop outputting the oscillation signal.

A semiconductor laser including: a first mirror layer; a second mirror layer; an active layer, a current confinement layer, a first region, and a second region, in which the first mirror layer, the second mirror layer, the active layer, the current confinement layer, the first region, and the second region constitute a laminated body, the first region and the second region constitute an oxidized region of the laminated body, in a plan view, the laminated body includes a first part, a second part, and a third part disposed between the first part and the second part and resonating light generated in the active layer, and in a plan view, at least at a part of the third part, W1>W3 and W2>W3, W1 is a width of the oxidized region of the first part, W2 is a width of the oxidized region of the second part, and W.sub.3 is a width of the oxidized region of the third part.

A physics cell includes a sealed glass vial that contains a high-purity dipolar gas (e.g., OCS) at a low pressure (e.g., between about 0.01 millibar and 0.2 millibar). The vial can be sealed using a laser cutting process that involves only local heating of the vial that does not denature the bulk of the contained gas. One or more electromagnetically translucent windows or vial-end access points provide access to electromagnetic waves launched or received by one or more electromagnetic antennas at a frequency that is adjusted to match the quantum transition frequency of the gas based on a detected maximum absorption frequency. The glass-vial physics cell can be fabricated at lower cost than physics cells fabricated from bonded wafers. Multiple vials can be joined by a waveguide in an enclosure so that launch and receive antennas can be provided at a single end of the vials.

In a resonance generation method, a Ramsey resonance is generated by repeating a first period and a second period. In the first period, an atomic cell, in which an alkali metal atom is accommodated and a hydrocarbon film is disposed on an inner wall, is irradiated with light having a first intensity while sweeping a center frequency within a sweep range, and a center frequency of light with which the atomic cell is to be irradiated in a next first period is determined based on a light intensity signal obtained by detecting light transmitted through the atomic cell. In the second period, an intensity of light incident on the atomic cell is reduced as compared with the first intensity.