1190 results about "Laser frequency" patented technology

The present invention includes novel techniques, apparatus, and systems for optical WDM communications. Various wavelocker apparatus and methods are disclosed that measure the frequency offsets between signal lasers and reference lasers. The measured offsets are used to adjust the signal laser frequencies to meet their target frequencies. The absolute accuracy of the reference laser frequency is improved by measuring the absorption of the reference laser by a gas cell with known fixed absorption lines versus the reference laser frequency. Apparatus and methods are disclosed to cover scenarios in which the reference laser polarization is aligned with the signal lasers, as well as those in which the reference laser polarization is not aligned with the signal lasers. The wavelocker apparatus may or may not be located at the same network site as the signal lasers.

A single-frequency Brillouin fiber ring laser with extremely narrow linewidth comprises a single-frequency narrow-linewidth rapid-tunable pump laser, a temperature-controlled acoustically-damped package for Brillouin fiber ring laser cavity, and an auto-tracking feedback electronic loop with novel configuration for active stabilization. The Pound-Drever-Hall frequency-locking technique is employed to keep pump laser frequency in resonance with one of the Brillouin fiber ring cavity modes. Instead of changing cavity length of Brillouin fiber ring laser, the pump laser frequency is rapidly tuned in the auto-tracking feedback electronic loop. This enables extremely narrow linewidth radiation emitted from a Brillouin fiber ring laser without stretching the fiber ring. Dual-wavelength actively stabilized Brillouin fiber ring laser may be generated from a single ring cavity by polarization-combining or wavelength-combining two pump laser beams and using two independent feedback loops to the two operation wavelengths.

A continuous wave Light Detection and Ranging (CW LiDAR) system utilizes two or more laser frequencies and time or range shifted pseudorandom noise (PN) codes to discriminate between the laser frequencies. The performance of these codes can be improved by subtracting out the bias before processing. The CW LiDAR system may be mounted to an artificial satellite orbiting the earth, and the relative strength of the return signal for each frequency can be utilized to determine the concentration of selected gases or other substances in the atmosphere.

Techniques for stabilizing a laser at a selectable frequency include splitting an output beam from an electrically adjustable laser into a first beam and a second beam. The second beam is transmitted through a modulator. Then the second beam is transmitted through a transient spectral hole burning material onto a detector. The laser is electronically adjusted in response to a detector output from the detector which senses the changes in the modulated second beam after it passes through the transient spectral hole burning material. Additions here to encompass the mode-locked case?

The invention relates to a device for measuring a frequency scanning absolute distance based on a femtosecond optical frequency comb and a method for measuring the absolute distance based on the device. The device comprises: a tunable laser (1), a polarization maintaining fiber system (2), a double-frequency heterodyne interferometer (3) and a system for measuring a laser frequency and an interferometric phase (4); the tunable laser (1) is used for generating single-frequency, single-line polarization laser, and an output laser frequency can be controlled by the working voltage and current ofthe tunable laser; the polarization maintaining fiber system (2) is used for coupling space laser with a polarization maintaining fiber in an unreflected way, and dividing the space laser into three paths of optical signals with equal optical intensity, and keeping an output laser polarization direction the same as an input laser polarization direction; the double-frequency heterodyne interferometer (3) is used for converting single-frequency laser into double-frequency orthogonal polarization laser, and converting distance information to be measured into phase information of a laser beat signal; and the system for measuring the laser frequency and the interferometric phase (4) is used for precisely measuring and locking and inputting the frequency of the laser, and measuring a phase different between the two paths of alternating current signals.

The invention discloses a fiber bragg grating array-based phase-sensitive optical time domain reflection device and method. The device includes a light source, a laser frequency adjustment module, a modulator, an optical fiber amplifier, a circulator, a sensing optical fiber, a light detector, a data acquisition module and a data processing module; the sensing optical fiber is provided with an optical fiber array formed by a plurality of FBGs (fiber bragg grating) which are arranged equidistantly; the laser frequency adjustment module is used for frequency adjustment of continuous light emitted by the light source; the continuous light is modulated by the modulator so as to form pulsed light; the optical fiber amplifier performs power amplification on the pulsed light; the sensing optical fiber is used for receiving and transmitting the pulsed light which has been subjected to power amplification; the light detector receives scattered light and reflected light; the scattered light and reflected light are acquired by the data acquisition module; and the data processing module generates interference signal frequency response spectrum and obtains the length variation quantity of the sensing optical fiber between two adjacent FBGs through processing. With the fiber bragg grating array-based phase-sensitive optical time domain reflection device and method of the invention adopted, strain quantitative detection can be realized, and high-spatial resolution measurement can be realized based on quantitative analysis.

A double-longitudinal-mode laser frequency-offset-lock method and a device based on cavity length thermal regulation belong to the application technical field; the invention takes the frequency of laser output by a power balanced type double-longitudinal-mode frequency stabilization laser A as a reference frequency, and simultaneously leads the frequency of laser output by the double-longitudinal-mode laser A with n being more than or equal to B1, B2,..., Bn to keep one fixed difference with the reference frequency, thus ensuring that the laser output by the double-longitudinal-mode laser B1, B2,..., Bn has uniform frequency value, the frequency stability and frequency consistency of the double-longitudinal-mode laser can reach 10<-8>, thereby overcoming the shortcoming that the frequency consistency between frequency stabilization lasers only reaches 10<-6>-10<-7> in the traditional frequency stabilization lasers.

For measuring a laser frequency electronic signals can be generated by means of optical interferometers, especially Michelson, Mach-Zehnder and Fabry-Perot interferometers. These signals present profiles with a variation of the laser frequency which are practically identical but shifted in phase by 90°. It is common to generate such phase-shifted signals for frequency measurement in various systems, e.g. by means of a sigmameter, which present, however, disadvantages on account of the great number of the necessary high-quality optical components. The inventive method is based on the analysis of transmission and reflection signals of a Fabry-Perot interferometer (FPI) wherein the signals are obtained from two component beams (PBA and PBB) which are passed through slightly different path lengths within the interferometer. These differences in the length of the optical paths are so selected by different angles of incidence of the component beams into the Fabry-Perot interferometer or by an appropriate shape of the interferometer that the required 90° phase shift is adjusted between the detected intensity signals. From these signals electronic signals can be obtained for detection and also for a rapid correction of the laser frequency.

An apparatus and method of controlling the frequency of laser outputs are provided. The apparatus includes an optical resonator having an optical length that supports a plurality of resonant modes dependent thereon. The optical resonator includes a modulation device for modulating the optical length in response to a modulation signal. A first and second laser having a respective first and second optical output at a respective first and second laser frequencies are independently locked to different resonant modes of the optical resonator using known locking mechanisms to produce first and second laser outputs having narrow linewidths. A beatnote generator generates a beatnote signal representative of the difference between the first and second frequencies of the first and second laser outputs. A negative feedback system having a reference signal and the beatnote signal as inputs generates the modulation signal representative of a difference between the reference and beatnote signals. The modulation signal so produced acts to correct for changes in the optical length of the optical resonator by actuating the modulation device so as to maintain a fixed optical length and thereby stabilize and control the first and second optical outputs.

Femtosecond pump / probe experiments using short X-Ray and optical pulses require precise synchronization between 100 meter-10 km separated lasers in a various experiments. For stabilization in the hundred femtosecond range a CW laser is amplitude modulated at 1-10 GHz, the signal retroreflected from the far end, and the relative phase used to correct the transit time with various implementations. For the sub-10 fsec range the laser frequency itself is upshifted 55 MHz with an acousto-optical modulator, retroreflected, upshifted again and phase compared at the sending end to a 110 MHz reference. Initial experiments indicate less than 1 fsec timing jitter. To lock lasers in the sub-10 fs range two single-frequency lasers separated by several teraHertz will be lock to a master modelocked fiber laser, transmit the two frequencies over fiber, and lock two comb lines of a slave laser to these frequencies, thus synchronizing the two modelocked laser envelopes.

The application provides a low noise fiber laser frequency combs device with controllable carrier envelope phase shift frequency. The low noise fiber laser frequency combs device with controllable carrier envelope phase shift frequency comprises an optical path structure and a circuit structure, wherein the optical path structure comprises an oscillator, an acousto-optic frequency shifter, an optical fiber amplifier, a pulse compressor, an optical fiber spread spectrum device and a coherent heterodyne beat device; and the circuit structure comprises a feed-forward circuit control phase device and a phase-locked loop circuit control repetition frequency device. The fiber laser oscillator can ensure long-time operation of a system, so that the stability of the system is superior to that of a system adopting a solid laser oscillator; through the technologies of optimizing intracavity net dispersion of the fiber oscillator, introducing an inner cavity modulator in the oscillator, adopting the feed-forward acousto-optic frequency shifter, and the like, the low noise fiber laser frequency combs device can be realized; and meanwhile, due to the application of the acousto-optic frequency shifter, the carrier envelope phase shift frequency of the optical frequency combs can be accurately regulated, so that the optical frequency combs device with precise phase position regulation and secular stability is provided for realizing applications such as optical frequency standard, attosecond science and non-linear optics.

An optical frequency comb calibration-based dual-color laser scanning absolute distance measuring device and a method are characterized in that the device comprises a laser light source system, a polarization-maintaining optical fiber system, a Michelson interference system and a laser frequency calibration system. The method comprises the steps of controlling two tunable lasers in the laser light source system to continuously simultaneously adjust the output light frequency without mode skips, wherein the laser frequency calibration system records the interference signal of the Michelson interference system and a beat frequency signal of the tunable lasers and the optical frequency comb; computing the scanning range of the lasers and the period integer and period decimal of the phase change of the interference signal in the scanning process according to the collected data; and finally computing to obtain the absolute distance of a to-be-measured light path refractive face. The optical frequency comb calibration-based dual-color laser scanning absolute distance measuring device and the method have the advantages of simple system structure, high measuring precision, compensating effect on air refractive index, and traceable measuring outcome, and are suitable for the measuring field of space absolute distance.

The invention relates to a double-femtosecond laser frequency comb ranging system. The double-femtosecond laser frequency comb ranging system is characterized in that a first femtosecond laser frequency comb transmits light pulses to a first frequency doubling crystal, the first frequency doubling crystal performs frequency doubling and transmits the two light pulses to a first light splitter, and the light pulses reflected by the first light splitter are transmitted to a light splitter through a first corner reflector and the first light splitter; the light pulses transmitted by the first light splitter are reflected to the light splitter through a second corner reflector and the first light splitter; a second femtosecond laser frequency comb transmits light pulses to a second frequency doubling crystal, and the second frequency doubling crystal performs frequency doubling and transmits the two light pulses to the light splitter simultaneously; the light pulses transmitted by the light splitter are mixed with light pulses emitted by a Michelson interference system, fundamental frequency light pulses of the mixed light pulses are transmitted to a first photoelectric detector through a color selective mirror, frequency doubling light pulses are reflected to a second photoelectric detector, the first photoelectric detector and the second photoelectric detector are connected to a central processing unit through an analog to digital (A / D) acquisition card, and the central processing unit processes signals to obtain a distance measuring value. The double-femtosecond laser frequency comb ranging system is widely applied to laser absolute distance measurement.

The invention discloses an all-fiber direct detection anemometric laser radar system and a closed-loop control method thereof. The system comprises an optical emission part, a frequency locking part, an emission part and a receiving part, wherein the optical emission part is used for emitting a modulated and amplified laser pulse; the frequency locking part is used for detecting the laser frequency variation, feeding back to the laser emission part, adjusting the laser wavelength and further realizing the function of locking the laser wavelength according to the deviation; the emission part is used for enabling the laser beam to point to the detection zone of the atmosphere, coupling the atmospheric back scattered light to a receiver through an optical telescope and modulating the near field signal strength; the receiving part is used for filtering out sun background from a signal and dividing the signal into two paths, one path of signal passes through a Fabry-Perot interferometer, the other path of signal is used as energy reference, the transmittance is obtained through the ratio of the signal intensities of the two paths of signal, and the wind velocity is obtained through inversion according to Doppler frequency shift. The laser radar adopts an all-fiber structure and has the advantages of small size and light weight, the manufacturing cost of the radar is low, the laser radar is controlled through a 3-level closed-loop, and the environmental adaptability and working stability of the laser radar are improved.

The invention provides spectroscopy apparatuses and methods allowing precise overlapping between circularly polarized pump beam and a counter propagating linearly polarized probe beams in a sample which presents unique advantages for precision spectroscopy. In general, the apparatus comprises a phase retarding element with which by double pass by retro reflection of an incident beam turn linearly polarized light to circular and vice versa. This unique configuration enable to design a compact and miniature apparatus which may be applied for measuring polarization spectroscopy, nonlinear optical rotation and coherent population trapping phenomena with certain advantages resulting from the unique optical arrangement. The design of the apparatus further facilitates integration and scaling to produce arrays of units which may be particularly useful for magnetometry applications. Other important applications of the invention include laser frequency stabilization and atomic clocks.

The invention relates to a Fabry-Perot interference absolute distance measurement method based on a femtosecond optical frequency comb and a device thereof. Two tunable lasers with frequency capable of being tuned within a large range and free of mode skip are simultaneously adopted, the optical wavelengths of the two lasers are respectively locked on two transmission peaks at a distance of N free spectral ranges of a to-be-detected Fabry-Perot cavity with the cavity length located in a vacuum vibration isolation cavity by utilizing the Pound-Drever-Hall (PDH) method, a wavemeter and an optical frequency comb system are used to respectively measure absolute frequency of two beams of laser, and then the free spectral ranges of the to-be-detected Fabry-Perot cavity are obtained. The cavity length of the to-be-detected Fabry-Perot cavity is obtained by means of the relationship between the to-be-detected cavity length and the free spectral ranges, frequency of the two tunable lasers can be tuned within a large range and free of mode skip, and measurement range is increased. Meanwhile, frequency of the two lasers is locked, and measurement speed can be increased. The optical frequencycomb system for measuring the frequency of the two lasers enables recurrence frequency and off-set frequency to be traced to the source of microwave frequency standard so that measurement results canhave traceability.

The invention relates to a method for pumping a rubidium bubble for outputting standard frequency by a lamp pump rubidium gas laser and a rubidium atomic clock. The method comprises the following steps of: adopting a filtered rubidium gas electrodeless lamp as a pumping light source for pumping a rubidium gas atom in an atom steam chamber, realizing distribution quantity conversion and then forming a lamp pump rubidium gas laser under the action of a laser resonant cavity; carrying out laser pumping on the rubidium bubble arranged in a microwave cavity by utilizing the lamp pump rubidium gas laser and detecting the transition probability of the pumped rubidium atom for generating transition by generating interaction with a microwave field in the microwave cavity by utilizing the lamp pump rubidium gas laser; and locking microwave frequency fed in the microwave cavity according to the detected transition probability and locking the microwave frequency fed in the microwave cavity on clock transition frequency of the atom. In the embodiment of the invention, because the frequency of the lamp pump rubidium gas laser still operates on a rubidium transition spectral line broadening spectrum in an unlocking state, even if the frequency of the lamp pump rubidium gas laser is unlocked, the lamp pump rubidium gas laser can be rapidly locked on needed laser frequency.

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.

The invention discloses a method and a device for stabilizing laser frequency and power. The method comprises the following steps of: obtaining primary diffracted light, and radiating the primary diffracted light into a photoelectric detector; detecting the intensity of the primary diffracted light; processing a detected signal; sending the processed signal to a driving source; and enabling an output signal of the driving source to act on an acoustic optical modulator. The device comprises a laser, the acoustic optical modulator, an electrooptical modulator, a polarization splitting prism, a quarter-wave plate and a Fabry-Perot interferometer. The method and the device have the advantages that reference precision and stability are greatly improved, better power stabilizing effect is realized, and frequency stabilizing effect is improved.

A continuous wave Light Detection and Ranging (CW LiDAR) system utilizes two or more laser frequencies and time or range shifted pseudorandom noise (PN) codes to discriminate between the laser frequencies. The performance of these codes can be improved by subtracting out the bias before processing. The CW LiDAR system may be mounted to an artificial satellite orbiting the earth, and the relative strength of the return signal for each frequency can be utilized to determine the concentration of selected gases or other substances in the atmosphere.

A frequency swept laser source that generates an optical signal that is tuned over a spectral scan band at single discrete wavelengths associated with longitudinal modes of the swept laser source. Laser hopping over discrete single cavity modes allows long laser coherence length even under dynamic very high speed tuning conditions. A ramp drive to the laser is used to linearize laser frequency tuning. A beam splitter is used to divide the optical signal between a reference arm leading to a reference reflector and a sample arm leading to a sample. A detector system detects the optical signal from the reference arm and the sample arm for generating depth profiles and images of the sample.

The invention discloses a frequency drift compensation-based phase sensitive optical time domain reflectometer and a measuring method thereof. According to the system, a Mach-Zehnder interferometer (MZI) with fixed arm length difference is formed and a laser frequency drift detection module is formed by introducing time delay optical fiber and connecting optical fiber with specific optical path difference on the basis of the traditional phi-OTDR. The frequency drift of the layer is obtained according to the signal intensity of the MZI in the system and the phase position of a phi-OTDR sensingsystem is compensated through a phase compensation algorithm, so that the influence on the sensing property of the phi-OTDR by the frequency drift of the laser is eliminated. The influence on the sensing property by the frequency drift of the laser is eliminated by constructing a novel phi-OTDR system, the influence of noise can be reduced by processing methods such as phase compensation, and theaccuracy of quantitatively measuring a vibration event by the system is improved.

The invention relates to a ranging method and a ranging system of femtosecond laser frequency comb synthesis wave interference. The ranging method and the ranging system of the femtosecond laser frequency comb synthesis wave interference comprises a femtosecond laser frequency comb, a Michelson interference system and the like. The light emitted by the femtosecond laser frequency comb enters a first spectroscope, transmission light through the first spectroscope is emitted to a first reflecting mirror, and reflected light returns to the first spectroscope through the first reflecting mirror. The emitted light is emitted to a second spectroscope through the first spectroscope, reflected light through the second spectroscope is emitted to a second reflecting mirror through a first single wavelength generating and frequency shifting light path, and the reflected light through the second reflecting mirror and the first single wavelength generating and frequency shifting light path returns to the second spectroscope. The emitted light through the second reflecting mirror is emitted to a third reflecting mirror through a second single wavelength generating and frequency shifting light path, and reflected light through the third reflecting mirror returns to the second spectroscope through the second single wavelength generating and frequency shifting light path. The reflected light through the second reflecting mirror and the reflected light through the third reflecting mirror are combined on the position of the second spectroscope, and are combined with light pulses of a gage beam, the interference signals of two wavelengths are divided through a diffraction grating and are respectively detected and received by two photoelectric detectors, and range measurement is completed.

This invention is an unconcerned laser anemometric method and the laser radar to realize mentioned method. Firstly it produces the pulse laser with narrow line width, and locks the pulse laser frequency to form the laser radar emitting unit, then makes the laser pulse sequence emit into the atmosphere. Using the telescope to receive the atmosphere molecules and the aerosol backward dispersion lights, the received light signals are divided into two ways. The light signals in one way are directly transformed into electric signals I, and the light signals through the iodine absorbing filter in the other way are transformed into electric signals II. We can obtain the radial wind speed by the data processing of the two way computer collected electric signals. The key point of data processing is to obtain the response curve of the laser radar wind speed. By tuning the seminal laser frequency, scan the laser frequency of the frequency chart width covered by the absorbing line around 532 nm in the iodine absorbed filter. The changing of the rate of the laser echo signals in the two way (I / II) which is received in the covered frequency chart width with the changing of the laser frequency is just the measured real-time wind speed response curve. Emendate the radial wind speed according to the wind speed response curve, then obtained the aclinic wind speed section plane orderly through the triangle geometrical relation of the radial wind speed in two directions and the aclinic wind speed.

The invention discloses a device for achieving a minitype CPT atomic clock physical system. The device comprises a Bias-Tee, a VCSEL, a first quarter wave plate, an atomic gas chamber, a second quarter wave plate, a polarization beam splitter, a first photoelectric detector and a second photoelectric detector. The invention further discloses a method for achieving the minitype CPT atomic clock physical system. Elliptically-polarized light is adopted for resonance with atom CPT, and difference detection is conducted on the optical rotation effect generated by the resonance. According to the device and method for achieving the minitype CPT atomic clock physical system, background noise generated by optical frequency components which do not interact with atoms in multi-color light output by the VCSEL and conversion noise generated by light interacting with the atoms due to light frequency jitter which is converted into signal amplitude jitter through action with the atoms are eliminated, and the signal to noise ratio of CPT resonance signals is greatly increased; in addition, the device and the method further have the advantages that the influence on the obtained CPT resonance signals by environment magnetic field intensity fluctuation is small, and laser frequency stabilization can be easily achieved through an achieved atomic clock.

The invention relates to a composite wave interferometry ranging distance system with two femtosecond laser frequency combs. The composite wave interferometry ranging distance system is characterized in that a first femtosecond laser frequency comb emits an optical pulse to a first spectroscope, the optical pulse reflected by the first spectroscope is transmitted to a first corner reflector, and the optical pulse reflected by the first corner reflector is transmitted to a second spectroscope through the first spectroscope. The optical pulse transmitted by the first spectroscope is transmitted to a second corner reflector, and the optical pulse reflected by the second corner reflector is reflected to the second spectroscope through the first spectroscope. A second femtosecond laser frequency comb emits an optical pulse to the second spectroscope, the optical pulse transmitted by the second spectroscope and an optical pulse emitted by a Michelson interference system are mixed and transmitted to a third spectroscope, the optical pulse transmitted by the third spectroscope is received by a first photoelectric detector in a detection mode through a first narrow-band band-pass filter, and the optical pulse reflected by the third spectroscope is received by a second photoelectric detector in a detection mode through a second narrow-band band-pass filter. The first photoelectric detector and the second photoelectric detector are connected with an A / D converter connected with a signal processing unit through a corresponding data interface to process the received signal to obtain the required distance measuring value.

The invention provides a device and a method for generating an active laser frequency standard based on a four-energy-level quantum system. An air chamber in which a gain medium is filled is formed in a Fabry-Perot cavity, wherein the gain medium is the atomic gas of the four-energy-level quantum system. Pumping laser is emitted into one end of the Fabry-Perot cavity, and the atomic gas is excited from a ground-state energy level to a fourth energy level. Atoms in the fourth energy level are transited to a low energy level through spontaneous radiation, and atom population inversion is realized between a third energy level and a second energy level. The atoms in the third energy level are transited to the second energy level through spontaneous radiation or stimulated radiation photons, stimulated radiation is generated under the action of the Fabry-Perot cavity, and laser is output from the other end of the Fabry-Perot cavity. The active laser frequency standard is high in frequency stability and accuracy.

The invented Rayleigh windfinding laser radar calibration method uses acoustooptic frequency shift and laser spectrum Doppler broadening principle as basis, and utilizes two acoustooptic frequency shifters whose frequency can be regulated, and makes them be series-connected to implement laser frequency zero-crossed wideband continuous regulation, and utilizes Doppler stretcher to stretch spectrum so as to make accurate and quick calibration of Rayleigh windfinding radar.

The invention discloses a small ultraviolet frequency sweeping laser-based resonance Raman spectrum detection system method. The small ultraviolet frequency sweeping laser based resonance Raman spectrum detection system comprises a small ultraviolet frequency sweeping laser, a main controller and a data analysis system, wherein the small ultraviolet frequency sweeping laser is composed of a pulse semiconductor laser assembly, an optical fiber laser assembly and an ultraviolet frequency sweeping optical assembly; the testing point of a detected object is located in a molecular composition of a material, has the intensity of a stokes Raman line of molecules with the ultraviolet frequency sweeping wavelength corresponding to the resonance Raman excitation wavelength is enhanced by tens of thousands to millions of times, and thus, multiple molecules of a sample, having extremely low concentration, can be detected. The system has the beneficial effects that an electronic-optical fiber integrated structure is adopted, so that an ultraviolet frequency sweeping laser source is miniaturized; an acousto-optic tunable filter is adopted, and thus, the ultraviolet laser frequency can be rapidly adjusted; and according to the ultraviolet frequency sweeping resonance Raman method, fluorescence interference is eliminated, the high-sensitivity resonance Raman detection of the multiple molecules of the sample can be achieved through fast frequency sweeping.