14 results about "Coherence length" patented technology

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.

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.

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 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 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 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).

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.