A clock generator includes a hermetically sealed cavity and clock generation circuitry. A dipolar molecule that exhibits a quantum rotational state transition at a fixed frequency is disposed in the cavity. The clock generation circuitry is configured to generate an output clock signal based on the fixed frequency of the dipolar molecule. The clock generation circuitry includes a detector circuit, a multiplier, and reference oscillator control circuitry. The detector circuit is coupled to the cavity, and is configured to generate a detection signal representative of an amplitude of a signal at an output of the cavity. The multiplier is coupled to the detector circuit, and is configured to multiply the detection signal with a mixing signal to produce a derivative of the detection signal. The reference oscillator control circuitry is configured to set a frequency of a reference oscillator based on the derivative of the detection signal.

A clock generator includes a hermetically sealed cavity and clock generation circuitry. A dipolar molecule that exhibits a quantum rotational state transition at a fixed frequency is disposed in the cavity. The clock generation circuitry is configured to generate an output clock signal based on the fixed frequency of the dipolar molecule. The clock generation circuitry includes a detector circuit, a multiplier, and reference oscillator control circuitry. The detector circuit is coupled to the cavity, and is configured to generate a detection signal representative of an amplitude of a signal at an output of the cavity. The multiplier is coupled to the detector circuit, and is configured to multiply the detection signal with a mixing signal to produce a derivative of the detection signal. The reference oscillator control circuitry is configured to set a frequency of a reference oscillator based on the derivative of the detection signal.

An atomic oscillator includes an atom cell that includes a first portion and a second portion at a position different from the first portion, and contains alkali metal atoms, a light emitting element that emits light for exciting the alkali metal atoms toward the atom cell, a first temperature measurement element that measures the temperature of the first portion, a first temperature control element that controls a temperature of the first portion based on the measurement result of the first temperature measurement element, a second temperature measurement element that is disposed in a portion having thermal resistance equal to or higher than thermal resistance between the first portion and the second portion, and measures a temperature of the portion, a second temperature control element that controls the temperature of the second portion to be higher than the temperature of the first portion based on the measurement result of the second temperature measurement element or information on temperature control performed by the first temperature control element, and a light receiving element that receives light transmitted through the atom cell.

An atomic oscillator includes an atom cell that includes a first portion and a second portion at a position different from the first portion, and contains alkali metal atoms, a light emitting element that emits light for exciting the alkali metal atoms toward the atom cell, a first temperature measurement element that measures the temperature of the first portion, a first temperature control element that controls a temperature of the first portion based on the measurement result of the first temperature measurement element, a second temperature measurement element that is disposed in a portion having thermal resistance equal to or higher than thermal resistance between the first portion and the second portion, and measures a temperature of the portion, a second temperature control element that controls the temperature of the second portion to be higher than the temperature of the first portion based on the measurement result of the second temperature measurement element or information on temperature control performed by the first temperature control element, and a light receiving element that receives light transmitted through the atom cell.

A tunable multi-mode laser is configured to generate a multi-mode optical signal at a tuned wavelength. The laser includes a semiconductor optical gain region, a feedback region, and a phase modulation region between the gain and feedback regions. Each of the regions may be monolithically integrated. A feedback loop is coupled to the tunable laser to receive the optical signal and includes at least one delay line. The delay line may also be monolithically integrated. An output of the delay line is fed back to the tunable multi-mode laser in order to provide at least one of self-injection locking and self-phase locked looping for the multi-mode tunable laser. Each of the optical gain region and phase modulation region of the laser is biased by the output of the delay line in order to reduce phase drift of the optical signal.

In described examples, a physics cell includes: a laser source configured to emit light towards an atomic chamber containing an atomic gas; a photodetector configured to receive emissions from the atomic chamber; and a field coil for generating a magnetic field in the atomic chamber. An electronics circuit includes: a controller circuit coupled to the photodetector output and having control outputs to a digital to analog converter circuit; the digital to analog converter circuit having a coil current output to adjust the magnetic field, a modulation control output to control a modulation of the light, and having an output to control a voltage controlled oscillator; and a radio-frequency output circuit having a voltage controlled oscillator coupled to the output of the digital to analog converter circuit outputting a radio frequency signal to the laser source in the physics cell.

In described examples, a physics cell includes: a laser source configured to emit light towards an atomic chamber containing an atomic gas; a photodetector configured to receive emissions from the atomic chamber; and a field coil for generating a magnetic field in the atomic chamber. An electronics circuit includes: a controller circuit coupled to the photodetector output and having control outputs to a digital to analog converter circuit; the digital to analog converter circuit having a coil current output to adjust the magnetic field, a modulation control output to control a modulation of the light, and having an output to control a voltage controlled oscillator; and a radio-frequency output circuit having a voltage controlled oscillator coupled to the output of the digital to analog converter circuit outputting a radio frequency signal to the laser source in the physics cell.

A frequency signal generation apparatus includes a light source, an atom cell with gaseous alkali metal atoms and a buffer gas enclosed therein, through which light output from the light source passes, and a container with a gas containing gas molecules in common with the buffer gas enclosed, housing the atom cell, wherein pressure of the common gas molecules is substantially the same within the atom cell and within the container.

A frequency signal generation apparatus includes a light source, an atom cell with gaseous alkali metal atoms and a buffer gas enclosed therein, through which light output from the light source passes, and a container with a gas containing gas molecules in common with the buffer gas enclosed, housing the atom cell, wherein pressure of the common gas molecules is substantially the same within the atom cell and within the container.

A clock apparatus includes: (a) a gas cell, including a continuous path cavity including a sealed interior for providing a signal waveguide; (b) an apparatus for providing an electromagnetic wave to travel along the continuous path cavity and for circulating around the continuous path cavity back toward and past a point of entry of the electromagnetic wave in the continuous path cavity; (c) a dipolar gas inside the sealed interior of the cavity; and (d) receiving apparatus for detecting an amount of energy in the electromagnetic wave, wherein the amount of energy is responsive to an amount of absorption of the electromagnetic wave as the electromagnetic wave passes through the dipolar gas.