Embodiments herein describe spectroscopy systems that use an unmodulated reference optical signal to mitigate noise, or for other advantages. In one embodiment, the unmodulated reference optical signal is transmitted through the same vapor cell as a modulated pump optical signal. As such, the unmodulated reference optical signal experiences absorption by the vapor, which converts laser phase noise to amplitude noise like the other optical signals passing through the vapor cell. In one embodiment, the unmodulated reference optical signal has an optical path in the gas cell that is offset (or non-crossing) from the optical path of the modulated pump optical signal. The unmodulated reference optical signal allows removal or mitigation of the noise on the other optical signal.

A multi-quantum-reference (MQR) laser frequency stabilization system includes a laser system, an MQR system, and a controller. The laser system provides an output beam with an output frequency, and plural feedback beams with respective feedback frequencies. The feedback beams are directed to the MQR system which includes plural references, each including a respective population of quantum particles, e.g., rubidium 87 atoms, with respective resonant frequencies for respective quantum transitions. The degree to which the feedback frequencies match or deviate from the resonance frequencies can be tracked using fluorescence or other electro-magnetic radiation output from the references. The controller can stabilize the laser system output frequency based on plural reference outputs to achieve both short-term and long-term stability, e.g., in the context of an atomic clock.

Provided is a laser stabilization apparatus including an optical fiber resonator that is in the form of an optical fiber loop with an optical fiber delay-line, and is designed to resonate at a stabilized frequency of a laser, wherein when light emitted from the laser is input to the optical fiber resonator, a transmittance thereof changes according to a frequency of the input light, and a light measurer configured to measure light output from the optical fiber resonator and generate an error signal for stabilizing a frequency of the laser.

Optical pulse sources. In one example, the pulse source includes an optical fiber ring resonator with at least one normal dispersion fiber segment characterized by a positive group velocity dispersion (GVD) per unit length and at least one anomalous dispersion fiber segment characterized by a negative GVD per unit length. In another example, the pulse source includes an optical fiber ring resonator with one or more fiber segments having a positive net group velocity dispersion (GVD); and an intracavity spectral filter optically coupled to the one or more fiber segments. The pulse source is configured to generate one or more optical solitons in the optical fiber ring resonator.

Chip technology for fabricating ultra-low-noise, high-stability optical devices for use in an optical atomic clock system. The proposed chip technology uses diamond material to form stabilized lasers, frequency references, and passive laser cavity structures. By utilizing the exceptional thermal conductivity of diamond and other optical and dielectric properties, a specific temperature range of operation is proposed that allows significant reduction of the total energy required to generate and maintain an ultra-stable laser. In each configuration, the diamond-based chip is cooled by a cryogenic cooler containing liquid nitrogen.

A tunable laser system includes a tunable laser to be scanned over a range of frequencies and an interferometer having a plurality of interferometer outputs. At least two interferometer outputs of the plurality of interferometer outputs have a phase difference. A wavelength reference has a spectral feature within the range of frequencies, and the spectral feature does not change in an expected operating environment of the tunable laser. Processing circuitry uses the spectral feature and the plurality of interferometer outputs to produce an absolute measurement of a wavelength of the tunable laser and controls the tunable laser based on a comparison of the absolute measurement of the wavelength of the tunable laser with a setpoint wavelength.

A laser adjustment method includes a first adjustment step and a second adjustment step. In the first adjustment step, using a light detector detecting a second harmonic light, optical intensity and wavelength of the second harmonic light is detected and a first temperature adjuster is adjusted to adjust temperatures of a Nd:YVO.sub.4 crystal and a KTP crystal such that the detected wavelength of the second harmonic light approaches a desired wavelength and such that the optical intensity of the second harmonic light reaches at least a predetermined value. In the second adjustment step, after the first adjustment step, a temperature of an etalon is adjusted by a second temperature adjuster such that the detected wavelength of the second harmonic light approaches the desired wavelength and such that the optical intensity of the second harmonic light reaches at least a predetermined value.

A device may include a first photodetector to generate a first current based on an optical power of an optical beam. The device may include a beam splitter to split a portion of the optical beam into a first beam and a second beam. The device may include a wavelength filter to filter the first beam and the second beam. The wavelength filter may filter the second beam differently than the first beam based on a difference between an optical path length of the first beam and an optical path length of the second beam through the wavelength filter. The device may include second and third photodetectors to respectively receive, after the wavelength filter, the first beam and the second beam and to generate respective second currents.

A laser-source assembly that is configured to illuminate a vacuum chamber containing atoms in the gaseous state so as to implement a cold-atom inertial sensor, the atoms having at least two fundamental levels that are separated by a fundamental frequency difference comprised between 1 and a few gigahertz, the assembly comprises: a master laser that emits a beam having a master frequency; a first control loop that is configured to stabilize the master frequency of the master laser on a frequency corresponding to half a set frequency of an atomic transition between a fundamental level and an excited level of the atoms; a slave laser that has a slave frequency; and a second control loop that is configured to stabilize the slave frequency of the slave laser with respect to the master frequency, the slave frequency being offset with respect to the master frequency successively, over time, by a first preset offset value, a second preset offset value, and a third preset offset value, the offset values being comprised in an interval equal to half the fundamental frequency difference plus or minus a few hundred MHz.

A method for controlling the emission frequency of a laser comprises: recording a first spectrum by passing a laser light emitted by the laser through a sample onto a detector, the detector being connected to a multichannel analyzer which assigns pulses detected by the detector to a channel; determining a first channel to which the maximum of a first signal in the first spectrum has been assigned; determining a second channel to which the maximum of a second signal in the first spectrum has been assigned; recording a second spectrum in analog fashion like the first spectrum; determining whether the maximum of the first signal in the second spectrum has been assigned to the first channel and whether the maximum of the second signal in the second spectrum has been assigned to the second channel; adjusting the operating temperature of the laser in the event of deviations determined in the previous step.