A system for generating an optical frequency standard is described. The system comprises a first laser source for generating a first laser output at a first frequency, a first second harmonic generator receiving as an input the first laser output to generate a frequency-doubled first laser output at a doubled first frequency, a second laser source for generating a second laser output at a second frequency different from the first frequency and a second harmonic generator receiving as an input the second laser output to form a frequency-doubled second laser output at a doubled second frequency. The system further includes a two-colour stabilisation arrangement to stabilise a sum of the doubled first and the doubled second frequencies that includes an interaction region incorporating a laser active material having a two-photon transition from a first energy level to a second energy level which receives as an input the frequency-doubled first laser output and the frequency-doubled second laser output where these outputs are selected to together cause the two-photon transition from the first energy level to the second energy level using an intermediate energy level to enhance the two-photon transition rate. The system also includes a detector to detect an indicator of the two-photon transition occurring in the interaction region which generates a frequency stabilisation signal for modifying either the first laser output or the second laser output to stabilise the sum of the doubled first frequency and the doubled second frequency to the two-photon transition based on the indicator and a stabilised optical output generator that includes a sum frequency generator receiving as an input the first laser output and the second laser output to generate a stabilised optical output with a frequency corresponding to the optical frequency standard.

In some embodiments, a system includes a laser that generates an optical signal and a resonator that receives the optical signal. The resonator includes an optical resonator cavity comprising a first and second end, wherein the optical signal propagates at a resonant frequency; a first optical anti-resonator terminating the first end and having a first stopband; and a second optical anti-resonator terminating the second end and having a second stopband. The system includes a detector that generates an electrical signal from a modified resonator output of the resonator; and Pound-Drever-Hall servo circuitry configured to generate control signals for controlling a frequency of the optical signal generated by the laser or phase modulation devices attached to the optical resonator cavity or the first or second optical anti-resonator, wherein each phase modulation changes a length of at least one of the optical resonator cavity or the first or second optical anti-resonator.

Spectroscopic Laser Radar is a technique for the remote sensing of atmospheric composition. One of the technical challenges with this technique is the absolute stabilization of two or more laser wavelengths, generation of powerful laser pulses, and calibration of the acquired data. This invention describes the stabilization of one laser relative to an absolute optical frequency reference [claims 1, 2], and the beat-frequency stabilization of any number of additional lasers using passive beat frequency references [claims 1, 2, 5]. It describes control system and timing elements [claims 3, 4] to ensure accurate stabilization of all wavelengths [claim 6, 7, 8]. It describes a calibration technique, and a specific calibration technique for atmospheric water vapor [claim 9, 10]. This invention identifies specific novel optical frequency or optical wavelength bands for the spectroscopic detection of Methane and water vapor [claims 12, 13, 14].

Generally discussed herein are systems, devices, and methods for providing a frequency stabilized optical frequency comb, including frequency stabilizing the optical frequency comb to a laser that is frequency stabilized to an optical reference cavity, generating a low frequency electrical signal from the optical frequency comb, comparing the generated low frequency electrical signal to a reference low frequency electrical signal, determining an optical reference cavity drift based on the comparison, and then adjusting a frequency of the laser in response to the determined optical reference cavity drift.

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 two-stage laser stabilization method is described to simultaneously servo two coupled laser parameters that control the wavelength of a laser, such as the laser injection current and the laser temperature, in order to simultaneously stabilize the laser frequency and output power. Two error signals are generated by passing the laser light through a frequency discriminator, such as an atomic resonance, to generate two control loops for the two coupled laser parameters. A primary control loop servos the faster laser parameter, such as the laser injection current, by direct use of the error signal. A secondary slower control loop ensures that this said error signal will remain at zero, by controlling the second laser parameter, such as the laser temperature.

A light-emitting element module includes a light-emitting element that emits light, a base that has a depression portion in which the light-emitting element is accommodated, and a lid that covers an opening of the depression portion and is joined to the base. The lid includes a protrusion portion that protrudes on an opposite side to the base and has a hole through which the light passes and a window that is installed in the protrusion portion to block the hole and transmits the light. A surface of the window on a side of the light-emitting element is inclined with respect to a surface perpendicular to an optical axis of the light.

The present invention relates an apparatus and method for measuring range-resolved atmospheric sodium temperature profiles using a space-based Lidar instrument, including a diode-pumped Q-switched self-Raman c-cut Nd:YVO.sub.4 laser with intra-cavity frequency doubling that could produce multi-watt 589 nm wavelength output. The c-cut Nd:YVO.sub.4 laser has a fundamental wavelength that is tunable from 1063-1067 nm. A continuous wave narrow linewidth diode laser is used as an injection seeder to provide single-frequency grating tunable output around 1066 nm. The injection-seeded self-Raman shifted Nd:VO.sub.4 laser is tuned across the sodium vapor D.sub.2 line at 589 nm. In one embodiment, a space-qualified frequency-doubled 9 Watt at 532 nm wavelength Nd:YVO.sub.4 laser, is utilized with a tandem interference filter temperature-stabilized fused-silica-etalon receiver and high-bandwidth photon-counting detectors.

A frequency stabilization method and system for tunable light sources based on characteristic curve reconstruction are provided, which relate the field of frequency stabilization technologies of modulation absorption spectrum. A set of frequency stabilization control method and system based on internal modulation absorption spectroscopy of light source is constructed, and a high-precision laser frequency stabilization method under large-amplitude and high-bandwidth frequency modulation based on frequency discrimination curve reconstruction is proposed to solve a problem that it is difficult for micro-probe laser interferometry measurement benchmark to balance large-amplitude and high-bandwidth frequency modulation, and high-precision frequency stabilization, resulting in that it is difficult to obtain high relative accuracy measurement under large-range measurement. Under the large-amplitude and high-bandwidth frequency modulation, a distortion model of the frequency discrimination curve and a distortion correction model are constructed, which is used for feedback adjustment of phase compensation and reconstructing the frequency discrimination curve.

Systems and methods to stabilize a laser frequency include a birefringent resonator that introduces an arbitrary phase difference between two polarization components of the laser beam, a polarizing beam splitter to separate the two polarization components after the birefringent resonator, and a differential detector to monitor the separated two polarizations, based on which an error signal can be produced to control a servo to adjust the laser frequency or resonator resonance frequency accordingly. The birefringent resonator can comprise a fiber ring, a whispering gallery mode (WGM) resonator, or any other birefringent ring resonator. A servo can be included in the systems and methods to lock the laser frequency to the resonant frequency of the birefringent resonator or to lock the resonator resonant frequency to the laser frequency. One or more polarization controllers can also be employed to adjust the polarization state of the laser beam.