82 results about "Nonlinear optics" patented technology

The invention provides a nonlinear data generation and processing method based on light quantum and a light quantum computer, and the method comprises the steps: obtaining a nonlinear function and attribute information of a nonlinear layer; according to the frequency spectrum number and the attribute information of the nonlinear function, constructing an initial light quantum circuit; measuring the initial light quantum circuit, and determining a target function corresponding to the initial light quantum circuit according to a measurement result; loss information of the target function is determined, whether the initial light quantum circuit is applied or not is determined according to the loss information, and if yes, the initial light quantum circuit serves as a target light quantum circuit; and performing operation on input data of the nonlinear layer based on the target light quantum circuit. According to the method, the low-energy-consumption characteristic of photon calculation, the nonlinear characteristic of light quantum calculation and the general programmable capability of electronic calculation can be fused, and high-energy-efficiency calculation can be carried out on input data of a nonlinear layer. In addition, the method also has the advantages that the complexity of a quantum circuit is smaller, and the participation of a nonlinear optical device is not needed.

The invention discloses a multi-mode nonlinear optical microscopic imaging device and system, and the device achieves the two-photon and three-photon excitation imaging of a sample through an integrated light source module, a dispersion compensation module, a scanning light path module, a fluorescence obtaining module, a synchronous control module and a signal processing module. Fluorescence intensity imaging and fluorescence lifetime imaging can be supported at the same time; wherein the scanning light path module is driven by the random mask to realize sparse scanning, so that scanning point locations are effectively reduced, and the exciting light dosage is reduced; the synchronous control module performs time window screening and processing on the fluorescence signal based on the pulse synchronous signal and the position code, so that the signal acquisition efficiency is improved; the signal processing module adopts an FPGA (Field Programmable Gate Array) to carry out real-time image reconstruction and life calculation, so that the imaging speed and quality are ensured; and the master control PC can also perform high-fidelity reconstruction on the sparse sampling image through a deep learning model, so that high-speed, low-light-dose and high-resolution nonlinear fluorescence intensity and life imaging is realized.

An optical parametric oscillator and method for generating coherent signal light involve a resonant optical cavity for coherent signal light, and in the cavity a non-parametric gain element for amplifying the coherent signal light to only partially compensate for passive optical roundtrip losses, thereby obtaining lower effective roundtrip losses. A parametric gain element is arranged in the cavity, for converting coherent pump light into coherent signal light through an instantaneous nonlinear optical interaction. The parametric oscillator has means for adjusting an intracavity optical power of the coherent pump light above a threshold value, where the parametric gain is balancing the effective roundtrip losses, thus inducing sustained oscillations of the signal light in the optical cavity. The non-parametric gain element is configured to have a limited non-parametric gain over a gain bandwidth of the parametric gain element, which is less than the passive optical roundtrip losses in the gain bandwidth.

The invention relates to a hundred-milliwatt high-power high-repetition-frequency terahertz strong source generating device at room temperature, belongs to the technical field of nonlinear optical frequency conversion, and solves the problems that the terahertz conversion rate is low and additional cooling equipment is needed in the prior art. The beam expanding lens group is used for carrying out light spot beam expanding on the femtosecond pumping laser until the diameter of a light spot is twice of the original diameter; the plane mirror group is used for guiding the pump laser after beam expansion; the first half-wave plate, the reflective diffraction grating, the gold reflector and the third ultrafast reflector are used for adjusting polarization and diffraction reflection; the 4-f telescope imaging lens group is used for reducing the spot diameter of the received pump laser and imaging the pump laser to the lithium niobate crystal; the lithium niobate crystal generates terahertz pulse radiation in the direction perpendicular to the wavefront; the terahertz collection module receives and focuses the terahertz pulse radiation; and the measuring device is used for receiving the focused terahertz pulse radiation for measurement.

The invention discloses a physical model discovery and reconstruction method for light beam transmission characteristics based on a sparse physical information neural network, and belongs to the technical field of nonlinear optics and deep learning intersection, and the method comprises the following steps: S1, making a sparse and low-fidelity data set; s2, establishing a candidate function library of items possibly existing in a data back model by using automatic differentiation; S3, constructing a physical information neural network model with sparse regression to discover a physical model structure; s4, coefficient fine tuning is carried out on the found physical model, and high-fidelity data is reconstructed.The method is suitable for model discovery of light beam transmission data supported by a constant coefficient or variable coefficient partial differential equation, scarce and noisy low-fidelity data can be utilized, and high-fidelity data can be obtained. A simple physical model is found according to a physical information neural network and sparse regression, and a light beam transmission dynamic process is reconstructed, so that subsequent theoretical analysis and research on light beam transmission characteristics are facilitated.

The invention discloses a self-adaptive spatial transformation network for cross-medium optical distortion, and solves the problem that the existing spatial transformation network is difficult to consider both global transformation and local nonlinear optical distortion. The network is integrated in a target detection model, and the method comprises the steps that firstly, a parameter prediction network synchronously outputs affine transformation parameters and a water surface fluctuation physical parameter diagram; then, the local distortion grid generation network generates a distortion sampling grid based on the parameter diagram and a predefined water surface fluctuation physical model; meanwhile, the grid generator generates an affine sampling grid according to the affine transformation parameters; then, a grid fusion device fuses the two grids to generate a final sampling grid; and finally, the sampler samples the input image or the feature map according to the final sampling grid to obtain an output image or a feature map. Through a space transformation mechanism guided by physical prior, optical distortion caused by water surface fluctuation can be effectively relieved, and the accuracy and robustness of a target detection model in a cross-medium underwater scene are remarkably improved.

The invention discloses a reflective pumping detection nondestructive testing device and method capable of saturatively absorbing uniformity in a mirror surface. The device is based on a wavelength degeneracy pumping-detection principle, and comprises a femtosecond laser source, a beam splitter, an optical delay line, a double-frequency optical chopper, a two-dimensional precision translation stage, a coaxial focusing system, a spatial filtering diaphragm arranged in a reflection light path, a photoelectric detector, a lock-in amplifier and a signal processing unit. According to the method, different point positions of a sample are accurately positioned through a two-dimensional translation stage, a nonlinear differential reflectance dynamic curve of each point is measured under low power, the maximum differential reflectance and the carrier lifetime are extracted as characteristic parameters, the spatial relative standard deviation of the characteristic parameters is calculated, and lossless and quantitative in-plane uniformity evaluation is realized. According to the method, the interference of the pump light is effectively filtered through the space filtering diaphragm, the signal-to-noise ratio is remarkably improved in combination with the phase-locked amplification technology, and the problem that the nonlinear optical performance uniformity of the saturable absorber mirror cannot be quantitatively evaluated through a traditional method is solved.

The invention provides a method for realizing efficient frequency multiplication in a nonlinear scattering medium through wavefront shaping. The method for realizing efficient frequency multiplication in the nonlinear scattering medium through wavefront shaping comprises the following steps: S1, providing a beam of fundamental frequency light with the wavelength of 1064nm to form horizontal polarized light; s2, phase modulation is carried out on the adjusted light through a spatial light modulator, so that light field spatial distribution is optimized, and scattering interference is reduced; and S3, enabling the modulated light to enter a nonlinear scattering medium, and generating second harmonic light. According to the method for realizing high-efficiency frequency multiplication in the nonlinear scattering medium through wavefront shaping, light field propagation is optimized through a wavefront shaping technology, high-efficiency frequency multiplication in the nonlinear scattering medium is realized, and a higher-precision nonlinear optical application solution is provided.

The invention discloses a dual-wavelength frequency doubling regulation and control method based on a PPLN waveguide, and relates to the technical field of nonlinear optics. The method comprises the following steps: constructing a PPLN waveguide model, and determining a fundamental frequency light mode and a frequency doubling light mode; calculating effective refractive indexes of the fundamental frequency light and the frequency doubling light at respective wavelengths; the polarization period is calculated according to the effective refractive index, any target polarization period is fixed, the target polarization period is configured to correspond to two different working wavelengths at the same time, and therefore dual-wavelength frequency doubling light with a specific wave crest interval is generated at the output end of the waveguide; the wave crest interval is regulated and controlled by selecting different polarization periods; according to the invention, dynamic control of dual-wavelength frequency multiplication output is realized by changing the size of a polarization period; the single waveguide can complete various optical function design ideas, and has certain value for research in related fields such as multi-wavelength lasers and wavelength multiplexing communication.

A light source, including: a pulse generator for providing an initial sequence of light pulses, the initial sequence of light pulses including an initial number of light pulses within a predetermined time period, first and second optical arms, for propagating, respectively, first and second sequences of light pulses, each derived from the initial sequence of light pulses, wherein the first optical arm includes a first manipulator configured to generate the first sequence of light pulses from the initial sequence of light pulses, wherein the light source includes a nonlinear optical element arranged to receive the first sequence of light pulses or the second sequence of light pulses, and an optical switch arranged to switch that either the first sequence of light pulses or the second sequence of light pulses is received by the nonlinear optical element.

This invention relates to a high-power, high-repetition-rate terahertz source generating device at room temperature with a capacity of hundreds of milliwatts, belonging to the field of nonlinear optical frequency conversion technology. It solves the problems of low terahertz conversion efficiency and the need for additional cooling equipment in existing technologies. The device comprises, arranged sequentially along the optical path: a pump laser for providing femtosecond pump laser light; a beam-expanding lens group for expanding the femtosecond pump laser beam to twice its original diameter; a plane mirror group for guiding the expanded pump laser; a first half-wave plate, a reflective diffraction grating, a gold mirror, and a third ultrafast mirror for adjusting polarization and diffraction reflection; a 4-f telescope imaging lens group for reducing the diameter of the received pump laser beam and imaging it onto a lithium niobate crystal; a lithium niobate crystal for generating terahertz pulse radiation perpendicular to the wavefront; a terahertz collection module for receiving and focusing the terahertz pulse radiation; and a measurement device for receiving and measuring the focused terahertz pulse radiation.

The application discloses an SBS phase conjugation mirror capable of displaying a sound wave field in real time, and belongs to the technical field of nonlinear optics.The application comprises the following steps: pump light passes through a half-wave plate and a polarization beam splitter, passes through an optical isolator, changes a polarization state through a quarter-wave plate, is focused through a focusing lens, and then enters an SBS medium pool, stimulated Brillouin scattering occurs, a periodic density modulation is formed in the medium, and an equivalent acousto-optic grating structure is generated.Through introducing an independent probe light beam, the probe light enters the SBS medium pool at an incident angle satisfying the Bragg diffraction condition, and the probe light will be diffracted on the acousto-optic grating formed by the sound wave field.The intensity of the diffracted light changes with the intensity of the sound wave field, so that the real-time measurement of the sound wave field waveform and the life parameter in the SBS process can be realized by detecting the change of the diffracted light intensity with time.

The utility model discloses a metasurface unit structure and a metasurface formed by the metasurface unit structure, and belongs to the technical field of nonlinear optics. The metasurface unit structure comprises a substrate layer and a dielectric layer which are arranged from bottom to top, wherein a convex groove or a concave groove is formed in the dielectric layer. The sections of the substrate layer and the dielectric layer are square, and the sizes are nanoscale; the substrate layer is made of SiO2, and the dielectric layer is made of DAST crystals. The metasurface is formed by periodically arranging a plurality of metasurface unit structures. According to the utility model, the convex or concave grooved structure, the substrate layer with low refractive index, the DAST dielectric layer which has a higher damage threshold and is easy to process and the like are introduced, so that the loss can be reduced, the asymmetry degree can be conveniently adjusted by changing the grooved structure, the quality factor Q can be changed, the local electric field distribution can be optimized, and different application requirements can be met.

A length of optical fiber suppresses a nonlinear optical process so as to inhibit energy transfer away from a desired laser wavelength. The fiber has a core and a cladding designed to propagate a laser beam at the desired wavelength, alongside a nonlinear laser component having intensity that escalates as a function of distance due to the nonlinear optical process; a series of spaced-apart filters, each configured with a transmission level to redirect a proportion of the nonlinear laser component from the core into the cladding so as to collectively control exponential growth in the intensity of the nonlinear laser component by imparting resets in the intensity at predetermined intervals along the length; and an output configured to provide the laser beam following its suppressed escalation of the intensity and preservation of energy of the laser beam at the desired wavelength.

The present invention discloses a photoelectric gas monitoring device and method, which relates to the field of photoelectric detection technology, including ionizing a pre-treated target gas through a Tesla coil to generate a light signal; optically detecting the light signal through spectral separation and light signal detection; nonlinearly enhancing the light signal through a nonlinear optical effect and converting it into an electrical signal; calculating the actual concentration of the gas based on the electrical signal and generating a detection report. By performing ionization and nonlinear optical effect enhancement through a Tesla coil, a highly sensitive and highly adaptable photoelectric gas monitoring method is achieved. Among them, the Tesla coil ionization step solves the problems of insufficient light signal intensity and poor multi-gas adaptability, while the nonlinear optical effect enhancement step significantly improves detection sensitivity and signal quality. The present invention can achieve efficient monitoring of trace gases in complex environments, providing a new technical means for environmental protection, industrial safety and medical diagnosis.

The invention discloses a near-field terahertz nonlinear optical effect excitation detection method and system. A femtosecond laser space-time shaping technology is combined, a strong terahertz pulse is generated based on a femtosecond laser filament, the strong terahertz pulse is coupled with a tapping mode atomic force microscope, and space-time matching of probe vibration and the terahertz pulse is accurately controlled by using a synchronous sampling method, so that the time-space matching of the probe vibration and the terahertz pulse is realized. Mismatch between the low-repetition-frequency strong-field terahertz pulse and the vibration frequency of the near-field microscope probe is overcome, and strong-field terahertz near-field coupling and detection are achieved. The local field enhancement effect of the tip of the nanoprobe can realize nanoscale focusing (peak field intensity reaches MV / cm magnitude) of a terahertz field at a probe-sample gap, the near-field nonlinear interaction is remarkably enhanced, the diffraction limit is broken through, and the nanoscale spatial resolution is realized. According to the method, the excitation detection efficiency and the spatial resolution of the terahertz nonlinear effect are remarkably improved, and accurate excitation, characterization and regulation of the nonlinear optical effect of the sample can be realized.

The application discloses a kind of spherical optical lens three-dimensional profile detection method and system, it is related to optical precision detection technical field, including, towards spherical optical lens emission probe laser beam, by dynamic adjustment probe laser beam incidence angle, collect the nonlinear optical characteristic signal of penetration coating layer and the polarized optical characteristic signal of coating layer reflection;Based on nonlinear optical characteristic signal through curvature inversion algorithm generates substrate curvature spatial distribution data, extracts the thickness distribution characteristics of coating layer and substrate surface optical response characteristics by polarized feature analysis technique;Through refractive index compensation algorithm correction substrate curvature spatial distribution data, and weighted fusion thickness distribution characteristics of coating layer and substrate surface optical response characteristics, generate three-dimensional point cloud coordinate set;The application effectively improves the reconstruction accuracy of substrate curvature distribution;And realized the analysis of substrate surface real optical characteristics.

A terahertz wave generating device includes: a pump light source configured to generate pump light; a periodically poled element as a nonlinear optical element having a periodic structure in which a polarization or a crystal orientation is inverted at a certain inversion period; and a rotation stage configured to rotatably support the periodically poled element. The terahertz wave generating device causes the pump light to enter the periodically poled element to generate signal light that is a terahertz wave, and rotates the periodically poled element to change a wavelength of the signal light. The periodically poled element has an incident end face through which the pump light enters and an output end face through which the pump light exits. A rotation axis of the periodically poled element is closer to the incident end face than to the output end face.

The invention relates to a fluorescence microscopy system comprising a nonlinear optical medium (ML) and comprising: - a laser source (SL) suitable for delivering first laser pulses (IL1) having a first wavelength λ1; - a power optical modulator (MP) suitable for modulating a power of the first laser pulses (IL1) so as to form second laser pulses (IL2) having different optical powers; - said optical medium (MO) being suitable for the second pulses to propagate by undergoing self-focusing within the optical medium so as to define, for each second pulse, a focal point having a longitudinal position in the optical medium that is different from the other second pulses, laser radiation originating from the optical medium and having the second self-focused pulses, referred to as third pulses, being named the output beam (FS); - a microscope (M) suitable for: - collecting a first fluorescence radiation generated via the first wavelength λ1, by illuminating a sample (Ech) with the output beam; then - acquiring, from the first collected fluorescence radiation, at least one image of the sample for each of the third pulses illuminating the sample, each at least one image being associated with a transverse observation plane of the sample that is different from the other images.

The application discloses a kind of based on non-interacting polarization multiplexing multi-path pulse compression device and method, it is related to ultrafast laser technology and nonlinear optics field, device includes: first polarization beam splitter, Faraday rotator, second polarization beam splitter and dispersion compensation module, dispersion compensation module is used to make pulse multiple pass through same dispersion compensation element and form return pulse, return pulse is converted into polarization state orthogonal with incident state by Faraday rotator after by first polarization beam splitter output. By Faraday non-interacting coaxial architecture, pulse keeps high-efficiency polarization matching, reduces astigmatism, spatial chirp and energy loss caused by off-axis folding, and when target dispersion amount is certain, optical envelope volume is reduced, and element light aperture requirement is reduced;While pulse compression and reverse light isolation are integrated in the same magneto-optical component, reduce the number of discrete components, improve system compactness and stability.

The present disclosure provides a light source for a coherent Raman scattering microscope at wavelengths of 1,000 nm or more with low scattering in a living body, said light source supporting measurements in both a Raman tag wavenumber range and a high wavenumber range.　Specifically, the present disclosure provides a light source (400) comprising: a mode-locked laser (1) having a function for outputting two different optical pulse trains with different center wavelengths λs; two steady-state oscillating solid-state lasers (3, 4) that output continuous light of two different oscillation wavelengths λp corresponding to the two different optical pulse trains with different center wavelengths λs; and two or one second-order nonlinear optical elements (8, 9) that convert combined light into a picosecond optical pulse train with a center wavelength λc, i.e., a difference-frequency generation conversion optical pulse train. The center wavelengths λs of the optical pulse trains, the oscillation wavelengths λp of the steady-state oscillating solid-state lasers, and the center wavelength λc of the difference-frequency generation conversion optical pulse train satisfy the relation 1 / λc = 1 / λp − 1 / λs.

To increase transmission capacity by suppressing deterioration in signal quality while suppressing nonlinear distortion in wavelength conversion from increasing.SOLUTION: A wavelength conversion device 100 includes: an optical power monitor 112 which monitors optical power variation of input signal light; an excitation light source 115; an optical amplifier 114 which performs intensity modulation on the output of excitation light of the excitation light source 115; a multiplexer 117 which multiplexes the intensity-modulated excitation light with the signal light; a nonlinear optical medium 118 which generates wavelength-converted light of the signal light that the multiplexer 117 outputs based upon nonlinear optical effect; and a control part. The control part performs control to vary the optical power of the excitation light source 115 based upon the optical power variation of the input signal light detected by the optical power monitor 112 and then output the resulting light to the optical modulator 114.SELECTED DRAWING: Figure 1

The present application belongs to the field of ultrafast laser and nonlinear optics, and particularly relates to a near-infrared few-cycle pulse generation system and method based on high-pressure nonlinear enhancement. The method fills inert gas into a hollow-core anti-resonant optical fiber and adjusts the gas pressure to the high-pressure interval of 20 bar-90 bar, enhances the nonlinear coefficient of the gas to realize the dispersion and nonlinear dynamic balance of the pulse in the waveguide, thereby compensating for the insufficient peak power of the low-energy pump pulse. The pulse feedback module collects the output time-domain intensity waveform and extracts the main peak energy proportion and the splitting factor as feedback indexes. The control module diagnoses the offset state of the self-compression focal point relative to the truncated end face according to the feedback indexes, controls the small-step pressure regulation of the gas pressure regulation module to anchor the focal point on the truncated end face, and directly outputs high-quality and high-coherence near-infrared few-cycle pulses without external dispersion compensation devices.

A kind of full-automatic intelligent, multi-functional high-order nonlinear fluorescence kinetics test method and device, it relates to nonlinear optics and nanophotonics field.The optical testing device consisting of excitation light generation module, automatic power regulation module, excitation light modulation module, sample scanning module, data acquisition and analysis module and intelligent control module is built, under the excitation of incident laser, based on the overall coordination of intelligent control module, drive the rest each module to complete the dynamic response test of nonlinear fluorescence sample, realize full-automatic intelligent, multi-functional, high-precision, simple, efficient, low cost, universal fluorescence kinetics test analysis.The problem of traditional manual time-consuming and low test accuracy is solved.In addition, the multi-functional integration of fluorescence response curve, fluorescence rise time, fluorescence lifetime and fluorescence imaging effectively improves the test efficiency and application scenario, greatly reduces the system cost.

The invention relates to the technical field of semiconductor measurement, in particular to a film layer measuring device and method.The film layer measuring method comprises the steps that a to-be-measured position on the upper surface of a to-be-measured film layer is irradiated with pump light, and the pump light initiates second-order nonlinear optical coefficient change of the to-be-measured film layer and forms local disturbance; the local disturbance is propagated back and forth between the upper surface and the lower surface of the to-be-detected film layer; probe light is adopted to irradiate the to-be-detected position, the probe light generates frequency multiplication signal light based on the second-order nonlinear optical effect, and when the local disturbance is transmitted to the upper surface, the light intensity of the frequency multiplication signal light reaches a peak value; and receiving the frequency-doubled signal light, and obtaining the thickness of the to-be-measured film layer based on a time interval between two adjacent light intensity peak values of the frequency-doubled signal light. The invention is at least beneficial to improving the film thickness measurement precision.

The invention provides a nonlinear optical neural network system and a nonlinear optical calculation method, and the system comprises an optical feedback structure which is used for forming a circulating light path so as to enable a light beam to be circularly transmitted in the system; the input coupling assembly and the output coupling assembly are respectively used for coupling an input light beam to the circulating light path and coupling a part of light beam from the circulating light path as an output light beam; the spatial light modulation device is used for regulating and controlling at least one of the amplitude and the phase of the light beam input by the spatial light modulation device; the diffraction regulation and control assembly is used for executing multi-layer diffraction operation and regulation and control on the light beams input by the diffraction regulation and control assembly; wherein the spatial light modulation device and the diffraction regulation and control assembly are both arranged in the circulation light path, and the configuration mode of the spatial light modulation device and the diffraction regulation and control assembly enables a light beam to sequentially pass through the spatial light modulation device and the diffraction regulation and control assembly in each circulation, and the light beam reaches the output coupling assembly after passing through the diffraction regulation and control assembly.

The present invention generally relates to improved methods for characterizing the cell wall complex composition of a bacterial specimen via differential transport kinetics of a small molecule. The present invention also relates to improved and automated methods for Gram differentiation of a bacterial specimen using nonlinear optical techniques.

A wavelength converting device includes: an optical power monitor that monitors fluctuation of optical power of signal light input to the wavelength converting device; a pump light source that outputs pump light; an optical modulator that performs intensity modulation which includes modulating an intensity of the pump light output by the pump light source; a multiplexer that multiplexes the intensity-modulated pump light and the signal light; a nonlinear optical medium that, using a nonlinear optical effect, generates wavelength converted light of the signal light output by the multiplexer; and a controller configured to vary and output to the optical modulator, optical power of the pump light of the pump light source, the controller varying the optical power of the pump light based on the fluctuation detected by the optical power monitor.

The invention provides a nonlinear data generation and processing method based on light quantum and a light quantum computer, and the method comprises the steps: obtaining a nonlinear function and attribute information of a nonlinear layer; according to the frequency spectrum number and the attribute information of the nonlinear function, constructing an initial light quantum circuit; measuring the initial light quantum circuit, and determining a target function corresponding to the initial light quantum circuit according to a measurement result; loss information of the target function is determined, whether the initial light quantum circuit is applied or not is determined according to the loss information, and if yes, the initial light quantum circuit serves as a target light quantum circuit; and performing operation on input data of the nonlinear layer based on the target light quantum circuit. According to the method, the low-energy-consumption characteristic of photon calculation, the nonlinear characteristic of light quantum calculation and the general programmable capability of electronic calculation can be fused, and high-energy-efficiency calculation can be carried out on input data of a nonlinear layer. In addition, the method also has the advantages that the complexity of a quantum circuit is smaller, and the participation of a nonlinear optical device is not needed.

The invention discloses a cylindrical light-transmitting frequency doubling device for generating tunable yellow light and a laser device, and belongs to the nonlinear optical technology, the cylindrical light-transmitting frequency doubling device comprises a rubidium titanyl phosphate crystal, the rubidium titanyl phosphate crystal is processed into a cylinder along the Y-axis direction, and the cylindrical surface of the cylinder is plated with a dual-waveband antireflection film of 1140-1180 nm and a dual-waveband antireflection film of 570-590 nm. By means of the cylindrical surface light-passing frequency doubling device, the comprehensive performance of the yellow light frequency doubling device can be improved.