25 results about "Coherence length" patented technology

The invention relates to the field of optical measurement, in particular to a reflective interference film thickness measurement method and system for eliminating back scattering of a transparent substrate, and the method comprises the following steps: transmitting a light beam through a low-coherence-length broadband light source, and forming linearly polarized light through polarization modulation; focusing the light beam to the surface of the film through a confocal optical system; collecting reflection interference signals of the upper surface and the lower surface of the film; spatial filtering, low-coherence gating and polarization control are used for cooperatively inhibiting back scattering of the substrate. And processing the acquired interference signal, and calculating to obtain film thickness information. According to the invention, triple inhibition mechanisms are adopted for synergistic effect, and the method comprises the following steps: spatial filtering: shielding out-of-focus back reflected light through a confocal small hole; low-coherence gating: using a short coherence length to naturally suppress a reflected signal beyond a coherence range; and polarization control: further weakening stray light interference through polarization state matching, and effectively suppressing back scattering of the substrate.

The invention relates to the field of non-imaging optical design, and discloses a beam shaping reflector with a decoherence effect, the reflector comprises a plurality of first-level sub-surfaces, a plurality of beam propagation channels are formed, each first-level sub-surface is composed of a plurality of ellipsoid surface elements, and light distribution of light beams in a single channel is realized; the first-stage sub-surfaces are arranged in a preferable form, so that the optical path difference between light beams of each channel is greater than the coherence length of a light source, and a de-coherence function is realized; multi-channel light distribution is carried out on the light source, high-uniformity light spot shaping is achieved, meanwhile, the adaptability to the light source with energy distribution fluctuation is good, and high stability is provided for practical application of light beam shaping; besides, light beam shaping and de-coherence are completed only through one free-form surface, the size is small, the light path can be adjusted to the maximum extent according to actual requirements, and high practical value and application prospects are achieved.

This invention discloses a method for measuring the wavelength of low-coherence lasers using a synthetic Fizeau interferometer cavity. The method involves acquiring the interference fringes and extracting the initial phase of each actual Fizeau interferometer cavity with different free spectral ranges (FSRs) that meet the coherence length requirements of the low-coherence laser to be measured. Based on the FSRs and initial phases of each actual cavity, a synthetic Fizeau interferometer cavity with a FSR smaller than that of the physical cavities is constructed to obtain the synthetic free spectral range and synthetic initial phase. The interference order of the synthetic cavity is then determined by combining the input estimated wavelength or frequency, and wavelength refinement is performed to finally obtain the measurement wavelength. This invention does not limit the specific optical path structure or detector arrangement, and can effectively overcome the limitation of low-coherence laser coherence length on the accuracy of Fizeau wavelength measurement without increasing the optical path difference of the actual Fizeau interferometer cavity or reducing the fringe signal-to-noise ratio.

The application discloses a kind of based on the principle of OFDR's double-pulse long-distance distributed vibration detection device, including narrow linewidth laser light source and to-be-measured interferometer, and the application also includes auxiliary interferometer and phase noise demodulation and elimination mechanism, narrow linewidth laser light source includes NLL laser and first fiber coupler, the first output channel and the second output channel of first fiber coupler are connected with to-be-measured interferometer and auxiliary interferometer respectively, and to-be-measured interferometer and auxiliary interferometer are connected with phase noise demodulation and elimination mechanism.The application uses the above structure based on the principle of OFDR's double-pulse long-distance distributed vibration detection device, utilizes two homologous pulses to carry out Rayleigh scattering detection, mixes with auxiliary interferometer, realizes the elimination of phase noise, breaks through the limit of coherence length to range, realizes long range, frequency response high vibration signal detection, and only needs to mix in optical path twice, demodulation algorithm is simple, and phase correction speed is fast.

A system configured to perform the DCS-type measurements with the use of low-coherence continuous-wave (CW) light source at levels of light intensities that are substantially lower and with pathlengths through the tissue that are substantially longer than those afforded by the use of conventional methods. The method includes utilizing the optical detection system to producing signals representing interference between the portion of CW light arriving through reference arm of interferometer and the sample CW light potion that has traversed the sample arm including different paths through the target tissue while switching between first and second of said different paths only by adjusting a delay in the delay line. The spatial resolution of different pathlengths of sample light through tissue is defined by coherence length of CW light.

The invention discloses a terahertz wave decoherence method, a terahertz wave decoherence system and an imaging system. The terahertz wave decoherence method comprises the following steps: carrying out active phase modulation on coherent terahertz waves by adopting a reconfigurable phased array comprising a plurality of array elements with independent terahertz wave phase regulation freedom degrees, and regulating and controlling the number of effective array elements of the reconfigurable phased array and / or the phase regulation and control change rate of the effective array elements, and the first-order coherence function modulus value of the terahertz wave is reduced, so that the terahertz wave decoherence is realized, and the intrinsic time coherence length of the terahertz source is not changed. The reconfigurable phased array is used for performing decoherence modulation, and the variable capacitance characteristic of the SBD is used, so that the phased array receives different voltages to cause the change of junction capacitance, thereby causing the change of the resonance mode of the terahertz antenna, realizing terahertz phase modulation, particularly realizing active and controllable terahertz decoherence operation, and further optimizing the terahertz imaging effect.

The application provides a full-field OCT system based on orthogonal double liquid crystal phase compensation, an imaging method, equipment and a medium, and comprises the following steps: a broadband light source module is used to provide broadband illumination light with a low coherence length; a light splitting module is used to make the broadband illumination light enter a reference arm and a sample arm according to a predetermined proportion; the reference arm is sequentially provided with a first liquid crystal phase modulation component, a first wave plate, a first microscope objective and a fixed reference mirror; the sample arm is sequentially provided with a second liquid crystal phase modulation component, a second wave plate, a second microscope objective and a sample to be measured; a detection module is used to receive an interference signal of the reference arm reflected light and the sample arm backscattered light and to perform photoelectric conversion; and a control module is used to apply a differential driving voltage to the first liquid crystal phase modulation component and the second liquid crystal phase modulation component and to synchronously control a face array camera to collect, so as to solve the problems of stability and defocusing caused by mechanical phase shifting in the FFOCT system and low light energy utilization and dispersion mismatch caused by liquid crystal polarization dependence.

The application discloses an interference distance measurement signal enhancement method and device based on reference optical path segmentation matching, and belongs to the technical field of weak coherent interference measurement. The method comprises the following steps: controlling a reference arm reflector to move, performing coarse positioning on a reflection characteristic peak of a front surface of a ball lens in a sample arm, and making the reflection characteristic peak enter a coherence length range; performing fine scanning near the coarse positioning position, extracting an interference envelope, and determining accurate coordinates of a zero optical path difference position; offsetting the reflector by a preset optical path amount according to a working distance of the ball lens, and making the zero optical path difference move to a focal point; in a probe moving process, A-scan signals are collected at preset time intervals, and an offset amount of an actual depth of the reflection characteristic peak relative to a reference depth is calculated; when the offset amount exceeds a tolerance threshold, the reflector is reversely driven to move by a compensation distance, and the zero optical path difference moves along with the focal point. The application does not need to reform the probe, adopts a translation type optical path adjustment to avoid optical path mismatch, realizes real-time following of the zero optical path difference position in a probe dynamic moving process, and enhances an interference signal.

The application provides a backscattering measurement system and method based on low-coherence interference, wherein, during measurement, the system is first built, for backscattering light of each backscattering angle, a backscatterer is uniformly moved to provide a continuously changing optical path difference; two groups of interference lights are respectively subjected to real-time photoelectric conversion by using a balanced detector module, and an output voltage V is calculated by using a preset backscattering alternating current signal mathematical model to acquire an electric signal in real time; the electric signal is input into a central processing unit module in real time and is analyzed and processed to complete measurement of the backscattering light; the application uses the characteristics of a wide spectrum and a short coherence length of a low-coherence light source, controls the optical path difference, thereby filters out a concerned stray light source, removes the influence of other non-target stray lights, and can distinguish different stray light sources; in addition, the application uses an interference method to perform measurement, which is closer to the actual working condition of a telescope, and improves the sensitivity and accuracy of measurement.

This invention discloses a method for measuring the atmospheric coherence length of a free-space optical communication link. The method includes: firstly, within the framework of Kolmogorov's atmospheric turbulence theory, expressing the time average of the variance of the optical signal wavefront phase fluctuation caused by atmospheric turbulence in the free-space optical communication link using the time average of the phase structure function; then, establishing an analytical expression for the relationship between the time average of the variance of the optical signal wavefront phase fluctuation and the atmospheric coherence length based on the relationship between the phase structure function and the atmospheric coherence length, thereby indirectly measuring the atmospheric coherence length using the information on the optical signal wavefront phase fluctuation caused by atmospheric turbulence in the free-space optical communication link.

The invention provides a light beam shaping device and an optical system, the light beam shaping device comprises a first optical module, and the first optical module comprises a light splitting unit, a delay unit and an imaging unit; the light splitting unit is used for splitting the first light beam into N first split light beams in a first plane and emitting the first split light beams in parallel; the delay unit is arranged on the light emitting side of the light splitting unit and used for enabling the first split light beams to be emitted through different propagation lengths, and the minimum delay value between the emitted first split light beams is larger than or equal to the coherence length of the first light beams; the imaging unit is arranged on the light emitting side of the delay unit and used for imaging the first split light beams emitted through the different propagation lengths, the difference of the longitudinal positions of real images of the first split light beams is smaller than one time of the Rayleigh length, and the transverse positions of the real images of the first split light beams are overlapped. Through the light beam shaping device and the optical system provided by the invention, the problem that the existing Gaussian laser beam is not suitable for thin film processing is particularly solved.

The present disclosure provides a free space optical communication system comprising a superluminescent light emitting diode (SLED) with an ultrashort coherence length configured to generate a broadband beam of light, a modulator configured to modulate the broadband beam of light to encode data and generate a modulated beam of light, a semiconductor optical amplifier (SOA) configured to amplify the modulated beam of light to generate an amplified beam of light, wherein the SOA has a bandwidth of at least 25, 50, or 100 nanometers, and an output configured to transmit the amplified beam of light through a variably refractive medium. The system enables high-bandwidth optical communication with improved performance in atmospheric turbulence.

A method for producing a quantum device comprising forming a superconductive layer, forming a mask on the superconductive layer, the mask comprising masking patterns and at least two openings alternately in a direction, the at least two openings) being separated from one another by a separation distance, and further each having a width, such as the separation distance and the width are less than a coherence length of a Cooper pair in said superconductive material, and modifying, through the at least two openings, of the exposed portions of the superconductive layer, so as to form at least two barriers of width di separating the superconductive regions.

The invention provides a waveguide sheet, and relates to the technical field of optics, and the waveguide sheet comprises an optical region which is internally provided with a plurality of beam splitting surfaces; coupling-in light rays of the incident optical area are divided into turning light rays incident into a plurality of turning light paths after passing through the plurality of beam splitting surfaces. The multiple turning light paths comprise at least part of first turning light paths, the reflection times of turning light rays in the first turning light paths are smaller than a preset value, the different first turning light paths are not overlapped, and the optical path difference of the turning light rays in the different first turning light paths is larger than the coherence length. In the prior art, the turning light rays are reflected by different turning light paths and then are converged at one point on the same beam splitting surface, so that the illumination intensity of the point is too high, the optical path difference of the turning light rays in different first turning light paths is larger than the coherence length, the frequency of interference of different turning light rays is reduced, and the display effect is optimized.

The invention provides a method for establishing an amount of displacement between a first and a second object, in particular a displacement in the order of tens of nanometres, more in particular in the order of nanometres, comprising generating a phase-synchronised radio-frequency signal which is phase-synchronised using a clock signal having an accuracy of at least 10-10-th of a second, in particular at least 10-11-th of a second, more in particular at least 10-12-th of a second, providing an optical laser beam having a coherence length of less than 100 mm, in particular less than 10 mm, more in particular less than 1 mm, adding said phase-synchronised radio-frequency signal to said optical laser beam, transmitting said optical laser beam into an optical resonance cavity which has one end fixed to the first object and another end to the second object, extracting said optical laser beam from said optical resonance cavity, extracting a resonated radio-frequency signal from said resonated laser beam, determining a cavity length change from the resonated radio-frequency signal, and determining from said resonance cavity length change said amount of displacement.

The application relates to a transformer rapid explosion suppression and fire prevention method, and belongs to the technical field of power equipment safety, which specifically comprises the following steps: S1, collecting multi-physical field data in real time through a sensor network arranged in the transformer; S2, determining an electric-thermal instability index, a fractal dimension of a fire core growth, a maximum eigenvalue of an irradiance Hessian matrix, and a spectral coherence length decay rate based on the multi-physical field data; S3, combining the electric-thermal instability index, the fractal dimension of the fire core growth, the maximum eigenvalue, and the spectral coherence length decay rate to construct a feature vector; and S4, identifying a preliminary fault state based on the feature vector, correcting the preliminary fault state by using a preset physical model to obtain a final fault state, and triggering a hierarchical response strategy according to the final fault state. The application solves the problem that a single signal source is prone to failure under the interference of a complex electromagnetic and thermal environment, and provides a solid data foundation for subsequent accurate diagnosis.

The application discloses a time delay interference laser phase noise compensation method and device for optical frequency domain reflection, and comprises the following steps: obtaining a linear sweep signal light based on a signal source; obtaining a first heterodyne signal through a measurement interferometer, and obtaining a second heterodyne signal through a reference interferometer; and processing the first heterodyne signal and the second heterodyne signal by using a time delay interference algorithm, so that direct compensation of laser phase noise is realized; and obtaining a strain signal based on the direct compensation of the laser phase noise. Through compensation of the laser phase noise, high-precision measurement of the strain signal can be realized at a distance far beyond the coherence length of the light source.

The present application relates to the field of laser, especially to the field of high-power single-frequency laser design. First, high-power single-frequency laser is generated by using high-power multi-end pump unidirectional circulation cavity, second, high-power single-frequency laser is used to generate single-frequency second and third harmonic laser output by intracavity frequency doubling, and finally, high-power single-frequency light and frequency is realized by designing coupling light path outside the circulation cavity, so as to generate high-power single-frequency five times frequency laser. The structure of the present application can easily obtain 1um laser band single-frequency five times frequency laser, and is widely used in the scene application requiring coherence length.

The application discloses a low-coherence laser wavelength measurement method using a synthetic Fizeau interference cavity. The method is aimed at at least two actual Fizeau interference cavities with different free spectral ranges (FSRs) and meeting the coherence length requirements of a low-coherence laser to be measured, interference fringes of the actual Fizeau interference cavities are acquired respectively and fringe initial phases are extracted; based on the free spectral ranges and the fringe initial phases of the actual cavities, a synthetic Fizeau interference cavity with a free spectral range smaller than that of the actual cavities is constructed, a synthetic free spectral range and a synthetic initial phase are obtained; then the synthetic cavity interference order is determined in combination with an input estimated wavelength or frequency, and wavelength refinement is performed, and finally the measurement wavelength is obtained. The application does not limit specific optical path structures and detector arrangement modes, can effectively break through the limitation of the coherence length of a low-coherence laser on the Fizeau wavelength measurement precision without increasing the optical path difference of the actual Fizeau interference cavities and without reducing the signal-to-noise ratio of the fringes.

A method including generating a first laser beam pulse having a first wavelength and a first pulse length, and generating a second laser beam pulse having a second wavelength and a second pulse length, wherein the first wavelength and the second wavelength are selected to have a wavelength separation. The wavelength separation is more than a gain bandwidth of stimulated Brillouin scattering for an optical fiber into which the first and second laser beam pulses are delivered. The first and second laser beam pulses are sequential such that, together, the first laser beam pulse and the second laser beam pulse form an overall laser beam pulse having an overall length being at least a combination of the first pulse length and the second pulse length. First and second coherence lengths of the first and second laser beam pulses are longer than the first and second laser beam pulses.

Disclosed are a system and method for detecting a workpiece surface. The workpiece can be a packaged die, a processed wafer, or other types of workpieces. The present disclosure has an adaptive Michelson structure that illuminates the workpiece surface with long coherence length illumination light, such as infrared (IR) illumination light, to generate a fringe pattern. The Michelson structure includes a first path of reflected light reflected by a reference mirror and a second path of reflected light reflected by the workpiece surface. The two paths of reflected light are directed to an image acquisition module by a main beam splitter. The reference mirror, the workpiece surface, and the main beam splitter are configured to maintain a constant phase difference between the two paths of reflected light to achieve constructive interference and thereby generate the fringe pattern. The Michelson structure can enable detection of sub-micron cracks as small as 0.2-0.25 µm. The Michelson structure can be integrated into a standalone system or into an integrated detection system for detecting a variety of defects from micron-scale defects or larger defects to sub-micron defects (e.g., as small as 0.2-0.25 µm).

The invention provides a method and a system for realizing variable wavelength correlated imaging based on a thermal light source. The method comprises the following steps: firstly, generating a first light beam and a second light beam which are orthogonal in polarization, and combining the first light beam and the second light beam; then, the combined light is subjected to a second harmonic generation effect under the II-type phase matching condition, and part of infrared photons are coherently converted into visible photons, so that cross-wavelength intensity correlation between infrared and visible wavebands is established; separating infrared fundamental frequency light and visible frequency doubling light, and respectively detecting the infrared fundamental frequency light and the visible frequency doubling light; and finally, carrying out intensity correlation calculation on the two paths of signals, and inverting and reconstructing an infrared image of a target. According to the method, coherent transfer of intensity correlation is realized through a physical nonlinear process, and the problem of mismatching of double-color speckles is fundamentally solved; based on a classic thermal light source, quantum entanglement is not needed, and the system is stable and simple; the imaging quality can be optimized by regulating and controlling the coherence length of the light source, the flexibility is high, and the method has wide application prospects in the fields of infrared remote sensing, biological imaging, safety monitoring and the like.

An interferometric measurement system for evaluating a sample having a region of interest of a given depth, the interferometric measurement system comprising a memory configured to store interference pattern measurements indicative of interference patterns associated with different measurement conditions and different positions of the sample and an analysis unit; the interference pattern measurements are associated with a coherence length less than a given depth; the analysis unit includes processing circuitry configured to: extract coherent interference data from the interference pattern measurements while operating in a first mode; and when operating in the first mode, determining one or more attributes of the region of interest based on the coherent interference data.

Various implementations of the invention compensate for “phase wandering” in tunable laser sources. Phase wandering may negatively impact a performance of a lidar system that employ such laser sources, typically by reducing a coherence length / range of the lidar system, an effective bandwidth of the lidar system, a sensitivity of the lidar system, etc. Some implementations of the invention compensate for phase wandering near the laser source and before the output of the laser is directed toward a target. Some implementations of the invention compensate for phase wandering in the target signal (i.e., the output of the laser that is incident on and reflected back from the target). Some implementations of the invention compensate for phase wandering at the laser source and in the target signal.