61 results about "Modulation spectroscopy" patented technology

The invention provides a whispering gallery mode photonic device and a preparation method thereof. According to the preparation method of a micro ring array structure, solvent droplets are utilized to dissolve a polymer film, so that a "coffee ring effect" can be generated, and therefore, polymer can be accumulated at the periphery of liquid so as to form an annular structure of which the height is obviously different from the height of the film, and conduction and confinement of light in the polymer structure can be realized; and light signals are inputted to the micron ring structure through utilizing excitation, scattering or near field coupling modes, so that a resonance effect in a whispering gallery mode can be realized. The prepared micron ring structure can be adopted as a high-quality factor optical micro cavity, so that a modulation-mode spectrum can be obtained, the width of spectral lines of the spectrum being significantly narrowed; a whispering gallery-mode light amplification stimulated emission can be realized through optical gain; and in a multi-ring coupled array structure, light signal processing and high sensitive response to outside stimuli can be realized according to the wavelength change information of the modulated spectrum and laser modes.

The invention relates to a gas parameter online measurement method based on wavelength modulation spectroscopy and belongs to the field of tunable diode laser absorption spectroscopy. According to the method, a gas absorptivity function is fitted by using an odd number of harmonic signals of an X axis and a Y axis output by a phase-locked amplifier based on the wavelength modulation spectroscopy, normalization processing is carried out on the harmonic signals of the X axis and the Y axis by using first harmonic background signals so as to eliminate the influence of factors, such as background signal, laser intensity and modulation factor, and then, the temperature, concentration, pressure and spectroscopic constant of gas are directly measured by using the gas absorptivity function. The gas parameter online measurement method based on the wavelength modulation spectroscopy has the advantages that the problem that the wavelength modulation spectroscopy needs to calibrate experimental measuring temperature and concentration and cannot measure the pressure and spectroscopic constant of gas nowadays is solved, and the application range of the wavelength modulation spectroscopy is widened.

The invention relates to a method and a device for detecting gas, in particular to a modulation spectrum gas detection method based on quasi-continuous diode laser, and a device thereof. The invention adopts a technical proposal that a quasi-continuous diode laser spectrum modulation method for gas detection comprises the following steps: a modulation signal generator outputs a modulation signal and a reference signal; the modulation signal is supplied to a laser driver for controlling the injection current of a quasi-continuous diode laser; the reference signal is supplied to a lock-in amplifier and used as the reference signal; laser emitted by the quasi-continuous diode laser passes through to-be-detected gas and then is received by a photodetector; the output of the photodetector is transmitted to a preamplifier, amplified and then sent into the lock-in amplifier; and output signals of the lock-in amplifier are sent into a computer via an AD converter, processed and analyzed, so as to obtain the species and concentration data of the detected gas. The method is mainly applied to occasions needing trace gas detection with high sensitivity and high resolution.

A method for overcoming the drawback in a fiber CPA laser system that includes a process of generating a large negative TOD by implementing an AODS in a pulse shaper as a dispersive component. The AODS is implemented to arbitrarily modulate both the spectrum shape and phase to control with controllable amplitude to generate different orders of dispersions including a large negative TOD for compensating the positive TOD generated by the pulse stretching and amplification processes. The AODS, implemented as a dispersive component, can be an active and controllable dispersive component to generate adjustable levels of dispersions for flexibly compensating any order of dispersions generated in the amplifier chain including the nonlinear phase shift. The AODS implemented as a dispersive component can be an active and programmable dispersive component to interactively generate adjustable levels of dispersions in response to output laser amplitude and pulse shape measurements for flexibly compensating any order of dispersions generated in the amplifier chain including the nonlinear phase shift to achieve the shortest pulse duration.

A spectrometer and spectrometry method comprising modulating a light source with a carrier waveform multiplied by an envelope function, directing light from the light source through a sample region and to a photodetector, and demodulating current from the photodetector at a reference frequency. Also a method for computing a modulation waveform comprising specifying a target detection efficiency in a Fourier space, computing a response of a waveform that comprises a carrier wave multiplied by an envelope function, and modifying the envelope function using nonlinear optimization means to minimize a difference between the computed response and a predetermined target gain spectrum.

Processing of information signals separated according to modulation and carrier components in a more controlled way is made possible by a device for processing an information signal including a unit for converting the information signal to a time / spectral representation by block-wise transforming of the information signal and a unit for converting the information signal from the time / spectral representation to a spectral / modulation spectral representation, wherein the unit for converting is designed such that the spectral / modulation spectral representation depends on both a magnitude component and a phase component of the time / spectral representation of the information signal. A unit then performs a manipulation and / or modification of the information signal in the spectral / modulation spectral representation to obtain a modified spectral / modulation spectral representation. A further unit finally forms a processed information signal representing a processed version of the information signal based on the modified spectral / modulation spectral representation.

The invention provides an image ratio constant flow source circuit driving a multipath light emitting diode, belonging to the electronic technical field. The circuit structure comprises a pedestal generation circuit (11), a low-pass filter circuit (12), a V / I0 conversion circuit (13), a multipath image ratio constant flow source circuit (14) and a switch control circuit (16), wherein the image ratio constant flow source circuit (14) comprises transistors (Q10, Q11, ... Q1n), Light Emitting Diode loads (D10, D11, ... D1n), ratio resistors (R10, R11, ... R1n) and a sampling resistor (R0); the switch control circuit (16) comprises a third resistor (R3) and a fourth transistor (Q4), and completes control action by a digital signal (Di). The circuit of the invention leads illumination intensity of the multipath light emitting diode to be stable, can obtain continuous spectrum or modulated spectrum, has convenient use, low cost and electricity conservation, and is convenient for portable instrument use.

The invention relates to a method and a device for detecting multi-component gas through a semiconductor laser modulated spectrum. A temperature controller and an adjustable constant flow source are adopted for driving a semiconductor laser, a scanning signal source generates a scanning control signal and injects the scanning control signal into the temperature controller to realize continuous change of temperature, so as to drive the semiconductor laser to output laser with continuous wavelength change, wherein the output laser is divided into two paths, one path of laser and the other path of laser passing through a gas absorption cell are received by a balanced detector commonly, and the scanning signal source synchronously triggers a data acquisition card to acquire a signal output by the balanced detector and input the signal to a computer for processing, so as to obtain the multi-component detection result. According to the method and the device for detecting the multi-component gas through the semiconductor laser modulated spectrum, the range of the continuous output wavelength of the semiconductor laser is expanded and the defects of narrow range of the continuous output wavelength and single detected gas type of a current driving laser are overcome, therefore, the method and the device for detecting multiple gases simultaneously by the single semiconductor laser are provided; the multi-component gas detection cost is reduced, the detection efficiency and the detection reliability are improved, and the method and the device are used for the monitoring and detecting industry of various gases.

An optical modulation spectroscopy system comprises a probe beam source and components for directing the probe beam at a sample. It also may comprise a modulated pump beam source and components for directing a modulated pump beam at the sample. A dispersive system may disperse the reflected probe beam into constituent wavelengths to provide dispersed beams. A detector array may detect multiple dispersed reflected probe beams and processes a signal corresponding to each. Thus, measurement may be multiplexed for very fast performance.

Several methods of calibrating a wavelength-modulation spectroscopy apparatus configured to measure a concentration of an analyte in a sample gas are disclosed. Each of the methods allows for calibration and recalibration using a relatively safe gas regardless of whether the sample gas for which the concentration of the analyte can be determined is a hazardous gas. In one embodiment of the invention, calibration that is sample-gas specific is accomplished by determining a first slope coefficient and calibration function for the sample gas, after which a scaling factor can be determined based on the first slope coefficient and a second slope coefficient for the same or a different sample gas and used in a subsequent calibration (or recalibration) to scale the calibration function. In other embodiments of the invention, calibration that is not sample-gas specific is accomplished to allow for the determination of the analyte concentration in variable gas compositions and constant gas compositions.

The invention establishes a calibration-free modulation spectrum measuring software system based on a tunable diode laser absorption spectrum by virtue of a wavelength modulation technique adapted to a severe environment. The system comprises a digital phase-locking signal demodulation module, a modulation spectrum simulation module and a measured parameter extraction module which comprise 14 sub-modules. The system has the specific functions that a photoelectric signal is demodulated by virtue of a digital phase-locking algorithm so as to obtain a harmonic signal; a simulation database of the harmonic signal can be obtained by carrying out accurate theoretical calculation; the speed, temperature and constituent concentration of a flow field can be extracted by combining the harmonic signal with the simulation database.

A microangiography method and system based on full-space modulation spectrum splitting and angle compounding is disclosed. Label-free three-dimensional optical coherence tomography angiography is realized by combining the three-dimensional space resolution capability of an optical coherence tomography and the motion recognition capability of a dynamic scattering technology. Probe light of different incident angles is encoded with a transverse scanning modulation spectrum in a spatial frequency domain, incident angle-resolved sub-angiograms which are independent of one another are obtained by splitting the modulation spectrum, and an angiogram with multiple space angles compounded is realized. Conjugate mirror images are removed from a depth (z) domain, a complex-valued OCT interference spectra are reconstructed, the full-space modulation spectrum is obtained in the spatial frequency domain, and the overlap of the modulation spectrum conjugate mirror images is avoided. And the absolute flow velocity of blood flow can be measured through a multi angle-resolved probing technology.

A polarization modulation photoreflectance technique has been developed for optical characterization of semiconductor quantum confined structures. By using a tunable laser source in conjunction with polarization state modulation, a single beam modulation spectroscopy technique may be used to characterize the optical response of semiconductor materials and structures. Disclosed methods and instruments are suitable for characterization of optical signatures of quantum electronic confinement, including resolution of excitonic states at the band edge or other direct or indirect critical points in the band structure. This allows for characterization of semiconductor quantum well structures, for characterization of strain in semiconductor films, and for characterization of electric fields at semiconductor interfaces.

The invention discloses a spectral reconstruction method based on frequency domain coding. The method comprises the following steps: firstly, a spectral imaging system collects spectral information ofa scene by using a mask, and the mask modulates the spectral dimension and the spatial dimension of the scene image; then the modulated image is obtained by projecting the spectral information onto abroadband substrate to modulate the spectral change, and the modulated image is mapped to a Fourier domain for multiplexing. Finally, the encoded images compressed in spectrum and space are collectedby the sensor, and the spectral information is reconstructed by decoding the spectral dimension. The method of the invention not only can improve the spatial resolution, but also simplifies the spectral encoding and decoding process in the process of collecting and reconstructing data, avoids the complex calculation load, and realizes the high-precision capture of the high-spectral data in a short time.

A polarization modulation photoreflectance technique has been developed for optical characterization of semiconductor electronic interfaces. By using a laser source in conjunction with polarization state modulation, a polarization modulation spectroscopy technique may be used to characterize the optical response of semiconductor materials and structures. Disclosed methods and instruments are suitable for characterization of optical signatures of electronic interfaces, including characterization of electric fields at semiconductor interfaces.

The invention discloses a spectral analysis type high-precision on-line detector for gas and liquid detection. The spectral analysis type high-precision on-line detector comprises a detection sensor probe, a detector host, and a laser device, a circuit board and a power supply battery which are mounted in a detector host shell, and a display screen, an alarm device and a communication interface which are arranged outside the shell. By the adoption of a light intensity modulation technology, and due to concentration calculation on a modulation spectrum subjected to wavelet analysis, the spectral analysis type high-precision on-line detector for gas and liquid detection has the characteristics of high detection sensitivity, high detection stability, short detection time, high detection precision and the like. According to the on-line detector, an optical fiber is connected with the detection sensor probe, so that the distance can be 4KM; the detector can be used in a fixed or portable state; when the detector is applied to gas detection, (a single or multiple serial connected) handheld, open and fixed gas probes can be adopted.

A modulation spectroscopy system (1) directs a probe beam (11) onto a sample (10), the reflected probe beam being collected by a collector (7) and processed by a detector (8). A pump beam generated by a source (4, 5) directs a pump beam (13) onto the sample at the same spot as the probe beam. However, it also switches the pump beam via a path (14) onto an adjacent location not overlapping the probe spot. This is referred to as spatial modulation. A cylindrical lens (16) in the collection subsystem (7) collects reflected light including luminescence from both pump beam spots simultaneously, so that the luminescence becomes a d.c. signal which can be easily eliminated, including means from the modulator for varying pump beam intensities and positions. This provides means to reject the unwanted background luminescence signal as well as improvement to the signal to noise ratio.

There is provided in one embodiment of the invention a method for analyzing a sample material using surface enhanced spectroscopy. The method comprises the steps of imaging the sample material with an atomic force microscope (AFM) to select an area of interest for analysis, depositing nanoparticles onto the area of interest with an AFM tip, illuminating the deposited nanoparticles with a spectrometer excitation beam, and disengaging the AFM tip and acquiring a localized surface enhanced spectrum. The method may further comprise the step of using the AFM tip to modulate the spectrometer excitation beam above the deposited nanoparticles to obtain improved sensitivity data and higher spatial resolution data from the sample material. The invention further comprises in one embodiment a system for analyzing a sample material using surface enhanced spectroscopy.

The invention discloses a harmonic wavelet analysis method for modulating spectral signals. The harmonic wavelet analysis method is based on the wavelength of a TDLAS, and includes the implementation steps of (1) building a harmonic wavelet equation of the modulated spectral signals of the TDLAS, (2) computing the harmonic wavelet expansion coefficients of the signals with a decomposition algorithm, (3) determining decomposition layer numbers required by signal analysis according to the corresponding relation between wavelet decomposition layer numbers and analysis frequency bands, (4) retaining the harmonic wavelet coefficients of the required frequency bands, and obtaining the signals of the frequency bands through Fourier transformation, (5) constructing an envelope function of the frequency bands, and (6) carrying out an envelope taking process on the signals of the frequency bands to obtain frequency doubling signals of the modulated signals of the TDLAS.

There is provided in one embodiment of the invention a method for analyzing a sample material using surface enhanced spectroscopy. The method comprises the steps of imaging the sample material with an atomic force microscope (AFM) to select an area of interest for analysis, depositing nanoparticles onto the area of interest with an AFM tip, illuminating the deposited nanoparticles with a spectrometer excitation beam, and disengaging the AFM tip and acquiring a localized surface enhanced spectrum. The method may further comprise the step of using the AFM tip to modulate the spectrometer excitation beam above the deposited nanoparticles to obtain improved sensitivity data and higher spatial resolution data from the sample material. The invention further comprises in one embodiment a system for analyzing a sample material using surface enhanced spectroscopy.

The invention provides an implementation method free of calibration of a modulated spectrum by adopting a wavelength modulation technology suitable for a severe environment based on a tunable diode laser absorption spectrum. The method comprises the following steps: demodulating digital phase locking signals, simulating the modulated spectrum and extracting measurement parameters. The concrete content of the method comprises the following steps: demodulating photoelectrical signals by utilizing a digital phase locking algorithm to obtain harmonic signals; obtaining a simulation database of the harmonic signals through accurate theoretical calculation; extracting the flow field speed, temperature and component concentrations by combining the harmonic signals with the simulation database.

A modulation spectroscopy system (1) has an acousto-optic modulator (5) providing a pump beam onto a sample. The modulator receives a light beam from a source (4) and diffracts it to provide an output which is the first order beam, the zeroth order or undeflected beam being terminated and the 2nd and higher orders being negligible and terminated also. The modulator is driven alternately by two drive frequencies at a modulation or toggle frequency. The first order output is at one angle for a first drive frequency and at another angle for the other drive frequency. The duty cycle of alternating between the different drive frequencies sets the output beam position duty cycle for incidence at two different spots on the sample. Also, either or both beams may be position and / or intensity varied by control of the modulator drive frequencies and their amplitudes.

Disclosed are a method and an apparatus for measuring terahertz time-domain spectrum, which relate to the field of terahertz time-domain spectrum. The method comprises the steps of: generating a first pulse laser beam from a first femtosecond laser device at a preset repetition frequency to generate THz pulses; generating a second pulse laser beam from a second femtosecond laser device at the repetition frequency; measuring electric field intensities of the THz pulses at respective phase differences between the first pulse laser beam and the second pulse laser beam; and obtaining a THz time-domain spectroscopy by performing Fourier transformation of data representative of the electric field intensities. Compared with prior art, THz spectrum measured according to the method and apparatus of present invention has higher spectroscopy resolution and broader detection range, which makes the technology of present invention have stronger capability for discriminating substances.

The invention provides a method for achieving nonuniform combustion field gas parameter quantitative measurement based on the modulated spectrum technology. The method comprises a wavelength modulated spectrum measurement step, a wavelength modulated spectrum fitting step and a step of calculating gas parameters in a nonuniform flow field. According to the specific content of the method, an absorption spectral line with the line strength linearly changing along with temperature within the measured temperature range is selected; transmission light intensity signals are measured through tests, and harmonic signals measured through the tests are obtained; the integral optical density, Gaussion line width and Lorentz line width are adopted as free variables, and the harmonic signals of the spectral line are fit based on the least square method; the gas parameters in the nonuniform combustion field are calculated.

The invention discloses an optical fiber laser amplifying system and a dynamic amplitude and spectrum modulating method thereof,and relates to the field of optical fiber laser devices. The optical fiber laser amplifying system comprises a laser pump,a stretcher,a pulse reshaper,an amplifier and a compressor; the laser pump generates pump light,the pump light is emitted into the stretcher,and the stretcher stretches the pump light to generate a laser pulse with a stretched pulse width; the laser pulse is projected into the pulse reshaper,and the pulse reshaper reshapes the laser pulse through dynamic amplitude and spectrum modulating and projects the laser pulse into the amplifier; the amplifier amplifies the power of the reshaped laser pulse,and projects the laser pulse into the compressor,so that the pulse width of the laser is compressed to output laser with an original pulse width. By means of the optical fiber laser amplifying system and the dynamic amplitude and spectrum modulating method thereof,through the acousto-optic dispersion reshaper,the shape and phase of the spectrum are randomly modulated,and different dispersion levels are controlled to be generated with the controllable amplitude. The stretcher achieves pulse broadening and the amplifier amplifies the laser power so that a high-quality,compact and reliable optical fiber laser system can be implemented.

Processing of information signals separated according to modulation and carrier components in a more controlled way is made possible by a device for processing an information signal including a unit for converting the information signal to a time / spectral representation by block-wise transforming of the information signal and a unit for converting the information signal from the time / spectral representation to a spectral / modulation spectral representation, wherein the unit for converting is designed such that the spectral / modulation spectral representation depends on both a magnitude component and a phase component of the time / spectral representation of the information signal. A unit then performs a manipulation and / or modification of the information signal in the spectral / modulation spectral representation to obtain a modified spectral / modulation spectral representation. A further unit finally forms a processed information signal representing a processed version of the information signal based on the modified spectral / modulation spectral representation.