49 results about "Nonlinear spectroscopy" patented technology

An apparatus, method and system that uses a Q-switched laser or a Q-seed source for a seed pulse signal having a controlled high-dynamic-range amplitude that avoids and/or compensates for pulse steepening in high-gain optical-fiber and/or optical-rod amplification of optical pulses. Optionally, the optical output is used for LIDAR or illumination purposes (e.g., for image acquisition). In some embodiments, well-controlled pulse shapes are obtained having a wide dynamic range, long duration, and not-too-narrow linewidth. In some embodiments, upon the opening of a Q-switch in an optical cavity having a gain medium, the amplification builds relatively slowly, wherein each round trip through the gain medium increases the amplitude of the optical pulse. Other embodiments use quasi-Q-switch devices or a plurality of amplitude modulators to obtain Q-seed pulses. These configurations provide optical pulses having wide dynamic ranges that ameliorate problems of pulse steepening, non-linear spectral broadening and the like in very-high-power MOPA devices.

A self-similarity mode locking optical fiber femtosecond laser device based on spectrum compression and amplification is composed of an optical fiber coupling output laser diode, a wavelength division multiplexing coupler, a ytterbium-mixed monomode optical fiber, an optical fiber frequency spectrum filter, a monomode optical fiber, an optical fiber collimator, a quarter-wave plate, a half-wave plate, a polarization splitting prism, a 45-degree reflector, a grating and an optical fiber isolator. Spectrum is compressed by using the self-phase modulation generated when negative chirp pulses are amplified in the ytterbium-mixed monomode optical fiber, narrow-band chirp-free picosecond pulses are formed, the optical fiber frequency spectrum filter is used for eliminating residual side lobes in nonlinear spectrum compression, self-similarity evolution is completed in the monomode optical fiber, broadband linear chirp parabola pulses are output directly, and Fourier transformation extremity femtosecond lasers are output after chirps are eliminated. The self-similarity mode locking optical fiber femtosecond laser device is high in efficiency, large in self-similarity evolution spectrum widening amount, capable of obtaining Fourier transformation extremity femtosecond laser pulses high in energy and narrow in pulse width, compact in structure and easy to operate.

The invention discloses spectrum measuring device and method of a scattering substance of a sample cell with an isosceles triangle cross section. The measuring device comprises a sample cell, a light source and an emergent light detector, wherein the sample cell has a cross section of an isosceles triangle; both the incident position of the light source and the position of an emergent light detector are movable; and a light path formed by the sample cell, the light source and the light-emergent detector is changeable. Meanwhile, the invention also discloses a spectrum measuring method of the scattering substance of the sample cell with the isosceles triangle cross section which realizes the measurement on mutually-uncorrelated non-linear spectrums with multiple pathlength by horizontally and/or vertically moving the incident position of the light source and the position of the emergent light detector and changing the relative positions of the light source, the emergent light detector and the sample cell to form the change of the light path, thereby obtaining a distributed uncorrelated non-linear spectrum information of a substance to be measured. The invention can ensure that the analyzing precision of the component content of the substance to be measured is improved.

The invention discloses a broadband tunable optical fiber delay system of stimulated brillouin scattering. The SBS broadband tunable optical fiber delay system comprises a main laser, a first optical coupler, a first tunable optical attenuator, a first optical circulator, a slave laser, an optical amplifier, a second tunable optical attenuator, a second optical circulator, a Mach-Zehnder modulator, an optical fiber Bragg grating and a diffusion shifted fiber, wherein the first optical coupler is used for dividing the laser into first bean of laser and a second beam of laser; the first tunable optical attenuator is used for adjusting the laser power of the first beam of laser; the first optical circulator is used for injecting the first beam of laser into the slave laser; the slave laser is excited by the first beam of laser to produce nonlinear spectral light; the optical amplifier is used for amplifying the power of the pump light; the second optical circulator is used for injecting the pumping light into the diffusion shifted fiber; the Mach-Zehnder modulator, is used for modulating a microwave signal for the second beam of laser; the optical fiber Bragg grating is used for carrying out the phase position modulation for optical signal carrier; the diffusion shifted fiber is delayed under the effect of the stimulated brillouin scattering of the pump light in the propagation process of the diffusion shifted fiber.

The invention belongs to the technical field of remote sensing image processing, in particular to a nonlinear de-mixing method for hyperspectral images considering spectral variability. At first, original data are mapped to a high-dimensional characteristic space by a kernel method, and the spectral variation coefficient is considered in the high-dimensional space to perform linear unmixing; at the same time, according to the spatial continuity of object distribution, local smoothing constraint is added to abundance and coefficient of variation, which makes them have spatial smoothness. This method can be used for unsupervised nonlinear spectral unmixing in the presence of spectral variability in Hapke and GBM nonlinear mixing models. The invention can overcome the problem of spectral variability existing in different nonlinear mixing scenes and improve the precision of spectral unmixing, and has important significance in practical application.

The invention relates to a nonlinear un-mixing method of hyperspectral images based on kernel sparse nonnegative matrix decomposition. The nonlinear un-mixing method comprises the following steps: estimating the number of end members for hyperspectral images by utilizing a dimension virtual method; then, popularizing the conventional un-mixing algorithm based on a linear mixing model to a nonlinear characteristic space by utilizing a kernel method, and solving a nonlinear spectrum un-mixing problem by using an alternative iterative optimization method. The nonlinear un-mixing method of hyperspectral images based on kernel sparse nonnegative matrix decomposition has the beneficial effects that from a mixing model of hyperspectral observation pixels, the sparsity of the hyperspectral abundance is added into a sparse model, and the linear mixing model is mapped into a nonlinear mixing model by virtue of the kernel method, so that the defects of linear un-mixing are effectively overcome, and good noise resistances are simultaneously achieved, and therefore, the nonlinear un-mixing method can be used as an effective means for solving the un-mixing of hyperspectral remote sensing images.

A fiber amplifier system including at least one seed source providing an optical seed beam and a harmonic driver providing a sinusoidal drive signal at a predetermined frequency. The system also includes a harmonic phase modulator that receives the seed beam and the drive signal, where the harmonic phase modulator frequency modulates the seed beam using the drive signal so as to remove optical power from a zeroth-order frequency of the seed beam and create sidebands separated by the frequency of the drive signal. A dispersion element receives the frequency modulated seed beam and provides temporal amplitude modulation to the seed beam and a nonlinear fiber amplifier receives the amplitude modulated seed beam from the dispersion element and amplifies the seed beam, where the dispersion element and the fiber amplifier combine to remove optical power from the sidebands and put optical power back into the zeroth-order frequency.

The application discloses a thin-layer electrochemical reaction cell for in-situ detection by a nonlinear spectrum during electrode interface kinetics in an electrochemical system, belongs to the technical field of spectroelectrochemical reaction, and solves the problem in the prior art that the incident light in the electrolytic cell is absorbed by the electrolyte to affect the second-order nonlinear signal strength and the problem of limitations of the electrolytic cell used only by the special shaped working electrode. The thin-layer electrochemical reaction cell provided by the applicationcomprises a working electrode, a counter electrode, a reference electrode, an electrolytic cell, a conductive base and a conductive column, wherein the reference electrode, the counter electrode andthe conductive column are arranged at the front end of the electrolytic cell, the working electrode is arranged on the conductive base and located in the electrolytic cell; one end of the conductive column is in contact with the conductive base, and the other end protrudes out of the electrolytic cell as a lead wire of the working electrode. The thin-layer electrochemical reaction cell provided bythe application can be used for the research of electrode interface dynamics in in-situ detection in an electrochemical system by nonlinear spectrometry.

The invention is a kind of nonlinear spectrum similarity measuring method, which belongs to information technology field. The invention uses kernel principal constituent analysis method to eliminate the strong correlation between spectrum wavebands: aiming at the strong correlation between spectrum wavebands, uses non-linear transformation to transform the original spectrum vectors into a new character space, in which the invention uses kernel function and principal analysis method to acquire the nonzero characteristic numbers and characteristic vectors of the covariance matrix, and arranges the characteristic numbers in descending order, selects the characteristic vectors correspondent to the front N characteristic numbers, forms a standard orthogonal basis, finally, the spectrum vectors in the characteristic space are projected onto the standard orthogonal basis; combines the spectrum reflection and absorption characters: multiplies the transferred reflecting rate vectors and the normalized absorption rate vector, forms a compound spectrum vector.

A method for spectral interpretation in absorption spectroscopy uses a nonlinear spectral fitting algorithm for interpretation of spectral features in complex absorption spectra. The algorithm combines two spectral modeling techniques for generating spectral models to be used in the curve fitting process: a line-shape model and a basis-set model. The selected models for all gas components are additively combined using a least squares minimization, allowing for quantification of multiple species simultaneously.

The invention discloses a nonlinear spectral phase measuring method and relates to the technical field of nonlinear spectral detection. The nonlinear spectral phase measuring method is applicable to the measurement of all nonlinear optical spectra, such as doubled-frequency spectrum, sum-frequency spectrum and four-wave mixing spectrum; different pumped sources are selected for collinear input according to different nonlinearity conditions. Two CCD (charge coupled device) spectrographs are used respectively to detect a sum of nonlinear signals from sample under test and reference crystal, and a sum of a nonlinear signal of a sample under test, having half-wave loss, and a nonlinear signal of the reference crystal; the acquired spectral signals are subjected to simple data processing to obtain amplitude and phase information of the nonlinear spectrum of the sample under test; the nonlinear spectral phase measuring method is an efficient accurate nonlinear spectral information acquisition means, having a promising prospect in nonlinear spectrum studies.

The invention relates to a photonic crystal all-optical diode, which is formed by an asymmetrical one-dimensional photonic crystal containing a single-layer Kerr nonlinear medium. Two sides of the nonlinear medium are a regular film medium with periodic alternation and a magneto-optical medium sensitive to an external magnetic field. Based on the multivalued bistable state characteristics of a nonlinear spectral response and spatial asymmetry of the structure in the case of being larger than threshold light strength, photodiode characteristics of one-way transmission with positive incident high transmission and reverse incident cutoff can be realized. Through adjusting the size of the input light strength and/or the external magnetic field, flexible tuning of a wavelength range of an all-optical diode one-way transmission area can be realized. The all-optical diode has the protruding advantages of simple structure, easy realization, high transmission, large wavelength range, flexible tuning and the like.

A method and system for delivering laser pulses achieves the delivery of high quality laser pulses at the location of an application. The method includes the steps of: generating laser pulses, amplifying the laser pulses, temporally stretching the amplified laser pulses, and propagating the amplified laser pulses through an optical delivery fiber of desired length, wherein the laser pulses are temporally compressed in the optical delivery fiber and wherein the laser pulses undergo nonlinear spectral broadening in the optical delivery fiber.

The invention provides a high-spatial resolution photofilament fluorescence spectrum imaging and positioning method and a system and relates to the field of ultrafast laser and laser spectrum measurement, in particular to ultrafast femtosecond optics, light-matter interaction physics and nonlinear spectroscopy. According to the high-spatial resolution photofilament fluorescence spectrum imaging and positioning method, opposite filamentation is carried out in a to-be-measured sample medium by using two-color laser field asynchronous femtosecond pulses; molecular fluorescence capable of being measured by a spectrometer is excited in common through nonlinear interaction of the two-color laser field asynchronous femtosecond pulses; and positioning and fixed-point analysis of a fluorescence spectrum are achieved through the self-scanning effect of the asynchronous pulses at the overlapping position along the light propagation axis. The method is a multidimensional spectrum measurement method, and high-precision spatial position information of ionized/dissociated molecules in a photofilament can be obtained while a femtosecond photofilament spectrum is measured.

Apparatus and methods for generating mid-IR frequency combs using intra-pulse DFG. A mode-locked pulse generation laser generates near-IR pulses which are amplified. The amplified pulses are spectrally broadened by a nonlinear element, for example a normal dispersion highly nonlinear fiber (ND-HNLF) to generate broadened pulses. The nonlinear spectral broadening element is a transparent dielectric material having a cubic nonlinear response. Broadened pulses are temporally compressed to generate short, high-power pulses which few-cycle conditioned pulses which are ready for the intrapulse DFG process. The DFG block generates a mid-IR comb by difference frequency generation. It might comprise an orientation patterned GaP (OP-GaP) crystal or a poled lithium niobate (PPLN) crystal.

The invention discloses an ultraviolet double-optical-comb absorption spectrum measurement device and method based on heterodyne detection. The device comprises two femtosecond mode-locked pulse lasers, two femtosecond laser pulse amplifiers, two femtosecond laser pulse time-frequency domain control systems, two nonlinear spectrum conversion systems and a sample measurement and analysis system. Femtosecond lasers outputted by the two femtosecond mode-locked pulse lasers are amplified by the two femtosecond laser pulse amplifiers and inputted into the two femtosecond laser pulse time-frequencydomain control systems. Two paths of optical combs with the same wave band and coherent phases are outputted, the two paths of optical combs are respectively inputted into the two nonlinear spectrum conversion systems so as to expand the wave bands of the two paths of optical combs to ultraviolet light, the two paths of output ultraviolet light combs are inputted into the sample measurement and analysis system, and a double-optical-comb absorption spectrum of sample molecules in the ultraviolet wave band is generated. The device has the advantages of being simple in structure, good in stability, extremely high in resolution ratio, high in precision, high in measurement speed, capable of achieving real-time monitoring and high in sensitivity.

The invention provides a device and a method for measuring non-linear refractive index coefficients of inert gasses, wherein the principle is to obtain the non-linear refractive index coefficients of the inert gas to be measured at a specific centre frequency through data analysis by measuring the change of the non-liner spectrum widening, accumulated when femtosecond laser pulses at the specific centre frequency are spread in a hollow waveguide filled with the inert gas, along with the pressure of the inert gas. The device comprises a focusing lens, an inert gas tube internally provided with a hollow optical fiber, a diffuser screen and a spectrograph, which are respectively located on an optical path where the femtosecond laser pulses travel, and a gas pressure gauge, an inert gas bottle and a vacuum pump all connected to the inert gas tube.

The invention provides a nonlinear hyperspectral image mixed pixel decomposition method and device. The mixed pixel decomposition precision can be improved. The method comprises the following steps: taking end-member spectral information in a mixed pixel as a non-perturbation item, taking interaction among different spectrums as a perturbation item, carrying out nonlinear mathematical descriptionon the mixed pixel, and constructing a nonlinear spectral correlation mixing model meeting self-consistency; By taking the spectral cluster as an impurity, mapping the nonlinear spectral correlation mixing model to an impurity model, and constructing a superlattice local Green function of the impurity model for solving to obtain an end member component and an end member abundance estimation result; And according to the obtained end member components and the end member abundance estimation result, clustering the estimation end members by using a density peak clustering method, and merging the same kind of estimation end members. The invention relates to the technical field of remote sensing image processing.

A method and system for delivering laser pulses achieves the delivery of high quality laser pulses at the location of an application. The method includes the steps of: generating laser pulses, amplifying the laser pulses, temporally stretching the amplified laser pulses, and propagating the amplified laser pulses through an optical delivery fiber of desired length, wherein the laser pulses are temporally compressed in the optical delivery fiber and wherein the laser pulses undergo nonlinear spectral broadening in the optical delivery fiber.

The invention provides a second harmonic characterization method, a characterization optical system based on the second harmonic characterization method and a detection device.The second harmonic characterization method comprises the steps that after a scanning point location is selected on the surface of a sample to be detected, the wavelength of fundamental frequency light is continuously tuned from a first set wavelength to a second set wavelength through tuning, and after the wavelength of the fundamental frequency light is tuned each time, the second set wavelength of the fundamental frequency light is tuned; the fundamental frequency light with the tuned wavelength is incident to the scanning point position, and a second harmonic signal generated according to the fundamental frequency light with the tuned wavelength is collected; and drawing a nonlinear spectrum of the second harmonic signal according to the collected second harmonic signal. Different defect types, defect levels of the different defect types and fundamental frequency light wavelengths corresponding to the different defect types of the scanning point position in the scanning process can be obtained through the second harmonic signal nonlinear spectrum. Second harmonics are utilized to effectively characterize low defect density, relevant parameters of the sample to be detected can be extracted in a targeted mode, and time consumed for extracting the relevant parameters of the device is shortened.