5 results about "Coherence length" patented technology

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 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 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.

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.

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).