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 laser system with optical feedback, includes an optical-feedback-sensitive laser which emits, via an output optical fibre, a continuous, frequency-adjustable, propagating, source optical wave, known as the source wave; a resonant optical cavity coupled by means of optical feedback to the laser and configured to generate an intra-cavity wave, one fraction of which returns to the laser in the form of a counter-propagating optical wave; an electro-optic fibre modulator placed on the optical path between the laser and the resonant optical cavity, the electro-optic modulator being configured to generate a phase-shifted source wave by phase-shifting the source wave and, by phase-shifting the counter-propagating optical wave, to generate a phase-shifted counter-propagating wave, known as the feedback wave, which reaches the laser; a phase-control device for generating a control signal for the electro-optic modulator from an error signal representative of the relative phase between the source wave and the feedback wave, such as to cancel the relative phase between the source wave and the feedback wave.

An optical and electronic feedback system can be used to significantly narrow the linewidth of distributed Bragg reflector lasers (DBRs) by reducing the high-frequency noise in the laser spectrum. An optical feedback path reduces the high-frequency noise of the laser. An electric-optic modulator placed inside of this feedback path applies electronic feedback with a very large bandwidth, allowing for robust and stable locking to a reference cavity. In addition, the servo-electronic component greatly increases the long-term stability of the laser locking to an external reference cavity, allowing for low noise, long-term operation of the laser. Specifically, it suppresses the frequency noise spectral density and narrows the total linewidth from a free-running value of 100 kHz to 30 Hz. The resulting modified DBR laser is both precise and stable and has applications in optical clocks, quantum information science, and precision metrology.

A tunable laser device includes a laser structure and a plurality of individually addressable, separated contact stripes disposed on the laser structure. The laser structure includes a substrate, an active portion disposed on the substrate, and a chirped distributed feedback (DFB) grating disposed on the active portion. The active portion includes at least top and bottom contact layers and a gain medium.

A laser light adjusting method includes detecting a pair of mode hops and a comparison saturated absorption line group of the pair of mode hops based on an intensity of a light output signal in response to a change applied to an actuator, comparing a mode center voltage value with a comparison voltage value which is the voltage value at which the comparison saturated absorption line group was generated; a control temperature adjustment process that increases a control temperature when the comparison voltage value is lower than the mode center voltage value, and that decreases the control temperature of the temperature adjuster when the comparison voltage value is greater than the mode center voltage value; and a laser light stabilization step that stabilizes an emission frequency of the laser light to a specific saturated absorption line after the control temperature adjustment process.

Aspects of the present disclosure are directed to methods and apparatuses for generating laser light. As may be implemented in accordance with one or more embodiments, laser light is generated at a laser light source and is modulated in response to a frequency modulation signal, to generate a plurality of different wavelengths of laser light. The frequency modulation signal is generated, for each particular one of the wavelengths of laser light, at a respective seeding frequency corresponding to the particular one of the wavelengths in which the seeding frequency is different for each of the different wavelengths. Such an approach may, for example, involve generating the frequency modulation signal with a frequency generator circuit and using the frequency modulation signal to control an electro-optical modulator for modulating the wavelength of the laser light.

An optical reference cavity includes: a cell that includes: a cylindrical body; end faces; an optical canal having an interior cylindrical geometry; and an exterior surface having an exterior cylindrical geometry; mirrors disposed on the end faces; an aspect ratio that is less than 1; a compression clamp that holds the cell through compression and includes compression platens disposed on the end faces so that the compression platens exert a compressive force to the end faces at a radius from a central axis of the cell so that the cell is compressed by the compression clamp, and a length of the optical canal is unperturbed to first order with a magnitude of the compressive force; and a compression intermediary interposed between the compression platens and end faces, wherein the length of the optical canal is insensitive to vibration coupled to the cell by the compression clamp and compression intermediaries.

A method and system for adjusting the profile of a laser wavefront formed by at least a laser beam to a desired laser wavefront profile, the laser beam or beams presenting random phases and intensities, comprises a mixing module, configured to generate, from interference phenomena among the laser beam or beams, a laser field, a second intensity measuring module configured to measure the mixed intensities of the laser field portions, a calculation unit configured to calculate one or several phase correction values of the phase of the laser beam or the phases of laser beams, from the intensities of the laser beams, the mixed intensities and one or several predetermined target phases, and a phase adjustment module configured to apply the phase correction value or values obtained from the calculation unit to the laser beam phases.

A system for generating an optical frequency standard is described. The system is based on a two-color approach and includes a first laser source that generates a first laser output at a first frequency and a second laser source that generates a second laser output at a second frequency corresponding. The first and second laser outputs are then respectively input into first and second harmonic generators to form frequency-doubled first and second laser outputs. The system also includes a two-color stabilization arrangement to stabilize the sum of the frequencies generated by first and second laser sources, including, for example, an interaction region incorporating a laser active material. The interaction region can be a gas reference cell and the laser active material can be Rubidium (in vapor form) having a two-photon transition.

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.