184 results about "Nonlinear optics" patented technology

The invention relates to the technical field of laser control, in particular to a high-power fiber laser stable output control method and system. The method comprises the following steps: monitoring a multi-mode sensing signal of an optical fiber laser in real time based on an optical fiber sensor array; performing dynamic optical fiber sensing change analysis on the multi-mode sensing signal of the optical fiber laser to generate a dynamic optical fiber sensing change characteristic; laser output phase distribution analysis is carried out on the dynamic optical fiber sensing change characteristics, real-time power feedback adjustment is carried out, and a dynamic light beam power feedback adjustment strategy is constructed; overheat power unbalance analysis is carried out based on a fiber laser multi-mode sensing signal, and local temperature control power fine tuning is carried out, so that a local temperature control power fine tuning strategy is constructed; and performing sensor position calculation on the optical fiber sensor array one by one, and performing nonlinear optical effect analysis to generate nonlinear optical effect characteristics. According to the invention, efficient and stable laser output control is realized.

Described herein are methods and systems for measuring polarization states of nonlinearly generated light by a sample illuminated in response to receiving an incident beam having a known polarization state to determine a characteristic of the sample. The system includes an optical ellipsometer configured to be included in-line of a semiconductor fabrication line and generate measured signals proportional to different polarization parameters of second-harmonic light nonlinearly generated light by the sample, allowing determination of a complete polarization state of the second harmonic light using a characteristic of the sample is determined.

The invention discloses a method, a device and equipment for testing the uniformity of a light guide film, and the method comprises the steps: carrying out the dynamic temperature adjustment of the light guide film, and obtaining the multi-wavelength dynamic spectrum data of an edge region; nonlinear optical response characteristics are extracted; generating a dynamic optical characteristic diagram and performing three-dimensional structure analysis; calculating a thermo-optical coupling complexity index; generating dynamic change data of the optical performance of the edge region; and executing multi-dimensional evaluation index processing and time sequence analysis to obtain a dynamic accurate evaluation result. According to the technical scheme, the optical performance of the edge area of the light guide film can be accurately evaluated under the dynamic temperature condition, the influence of temperature change on the uniformity of the light guide film is effectively captured, the accuracy and practicability of a test result are improved, and a more reliable basis is provided for design optimization and quality control of the light guide film.

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.

A high-power narrow-pulse-width dual-wavelength laser based on LED pumping comprises a Porro prism, at least two groups of LED pumping modules, a passive Q-switch and an output mirror which are sequentially connected in series. And the Porro prism is used for adjusting and coupling an optical path so as to ensure that an incident light beam enters the system at a proper angle and direction. The main function of the LED array as a pumping source in the laser is to provide excitation energy and excite electrons in the gain medium to transition from a low energy state to a high energy state so as to generate stimulated radiation. When light emitted by the LED irradiates the gain medium, the medium absorbs light energy and enters an excited state, and then laser output is achieved in the resonant cavity through stimulated emission. The inner cavity seed light injection technology combines the advantages of high flexibility, high stability and easy regulation and control, greatly enhances the performance and application range of the dual-wavelength laser, and is particularly prominent in the fields of precision optical application, nonlinear optics and the like.

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.

The invention discloses a non-linear optical structure with perfect phase matching and high second harmonic generation efficiency. The non-linear optical structure comprises a fundamental frequency wave resonance structure, a non-linear optical layer, a second harmonic reflection structure and a substrate, the fundamental frequency wave resonance structure is used for generating electromagnetic field local enhancement at an incident fundamental frequency wavelength and realizing a phase matching condition by optimizing electric field phase distribution; the nonlinear optical layer is used for frequency conversion from fundamental frequency waves to second harmonics and regulating and controlling harmonic radiation capability and phase regulation and control; the second harmonic reflection structure is used for controlling coupling-out of second harmonics; the rotary nonlinear optical layer can adjust the phase characteristic of the radiated second harmonic so as to realize perfect phase matching of a harmonic field; according to the nonlinear optical structure with perfect phase matching and high-efficiency second harmonic generation efficiency, accurate control of phase matching conditions is realized through reasonable optical film stacking and phase matching technologies, and high-efficiency coupling-out and utilization of second harmonics are ensured.

The invention discloses a spherical optical lens three-dimensional contour detection method and system, and relates to the technical field of optical precision detection, and the method comprises the steps: transmitting a detection laser beam to a spherical optical lens, and collecting a non-linear optical characteristic signal penetrating through a coating layer and a polarized optical characteristic signal of a reflective coating layer through dynamically adjusting the incident angle of the detection laser beam; based on the nonlinear optical characteristic signals, generating substrate curvature space distribution data through a curvature inversion algorithm, and extracting thickness distribution characteristics of a coating layer and substrate surface optical response characteristics through a polarization characteristic analysis technology; correcting substrate curvature space distribution data through a refractive index compensation algorithm, and performing weighted fusion on thickness distribution characteristics of a coating layer and substrate surface optical response characteristics to generate a three-dimensional point cloud coordinate set; according to the method, the reconstruction precision of substrate curvature distribution is effectively improved; and analysis of real optical characteristics of the surface of the substrate 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.

A nonlinear optical device includes two coupling systems. A coupling coefficient between the two coupling systems is regulated and controlled. During operation, the pump light input from a straight waveguide is coupled into the second coupling system through the first coupling system and obtains great resonance enhancement in the second coupling system, so it is ensured that the second coupling system is in a high energy state. For signal light input from the same end of the straight waveguide, the signal light enters a resonator of the second coupling system through the coupling between the first and second coupling systems. A nonlinear effect of the system mainly occurs in the resonator of the second coupling system because in the resonator of the second coupling system, the pump light is in a great resonance enhancement. The entire resonator is in a high energy state.

The invention discloses a nonlinear chirped fiber grating preparation structure based on speed regulation and control, and belongs to the field of laser technology and nonlinear optics. Comprising a light source displacement control scheme, a phase mask plate displacement control scheme and a grating inscribing and monitoring scheme. The optical, electrical and mechanical devices comprise a laser light source, a diaphragm, a plano-concave mirror, a plano-convex mirror, a cylindrical lens, an electric control displacement platform, a control program, a signal generator, a function editor, a precise displacement platform, an optical isolator, an optical circulator, a photosensitive optical fiber and an optical fiber analyzer. According to the non-linear chirp fiber grating preparation scheme based on speed regulation and control, the adjustable displacement speed is introduced while the uniform phase mask plate is used, flexible chirp regulation and control are achieved while simple and stable preparation is guaranteed, the preparation scheme of the non-linear chirp tube fiber grating is widened, and the preparation cost is reduced.

A light source including: a pulse generator for providing an initial sequence of light pulses, the pulse generator including an optical source for producing optical pulses; a modulator in communication with the optical source for increasing or decreasing the selected number of pulses provided by the pulse generator in the selected time period; first and second optical arms, for propagating, respectively, first and second sequences 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 either the first sequence of light pulses or the second sequence of light pulses for reception by the nonlinear optical element.

The invention discloses a method for regulating and controlling the track of a self-acceleration circular Airy beam in a nonlinear Kerr medium. The method comprises the following steps: introducing a circular Airy beam into the nonlinear Kerr medium; a phase regulation function is deduced through analysis of the self-acceleration circular Airy beam trajectory declared by the method; the phase regulation and control function # imgabs0 # is combined with the circular Airy beam, and the circular Airy beam transmitted along a target track can be obtained by further adjusting related parameters. Besides, in numerous nonlinear optical effects, the Kerr effect is concerned due to the unique property of the Kerr effect, that is, the refractive index of the medium can change along with the change of the light intensity. The phenomenon not only has important significance in theory, but also shows wide potential value in practical application. By saving time and material cost, the working efficiency is improved, and the propagation track of the circular Airy beam in the nonlinear Kerr medium can be effectively controlled.

The invention discloses an information storage device and method based on a Rydberg atom antenna. Through superposition of two beams of coupled light, a vector interference field is generated in an atomic gas chamber of the Rydberg atomic antenna, detection light pulses are stored based on a nonlinear optical process, and an information storage function is realized on the basis of a quantum precision measurement function of the Rydberg atomic antenna. Compared with a traditional Rydberg atom antenna only having a detection function, the Rydberg atom antenna has the advantages that radio information can be stored while radio signals are detected by introducing a vector interference field; in addition, the information storage device based on the Rydberg atom antenna detects and stores radio information by using an all-optical means, and can realize rapid access of information.

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 an injection molding method and an injection molding device for a vehicle-mounted electronic structural member, and the method comprises the following steps: applying an excitation light source to obtain a polarization emission spectrum of engineering plastic, and forming a quantum optical fingerprint spectrum; carrying out polarization analysis on the spectral characteristic peak, and calculating a dichroic ratio to obtain molecular orientation three-dimensional distribution data; applying a laser pulse to acquire a coherent Raman scattering signal and a harmonic generation signal to obtain nonlinear optical response data; analyzing a molecular chain rearrangement characteristic and a stress relaxation characteristic based on the data to obtain kinetic parameters; and analyzing a molecular orientation evolution rule according to the kinetic parameters to obtain structure evolution prediction data. According to the technical scheme, the molecular orientation state of the engineering plastic can be monitored in real time in the injection molding process, and accurate characterization and prediction of the dynamic arrangement behavior of molecular chain segments are achieved through a method combining quantum spectrum analysis and nonlinear optical response characterization. And a scientific basis is provided for optimizing injection molding process parameters and controlling residual stress distribution in a product.

The invention discloses an ancient building brick wall reinforcing method based on three-dimensional scanning and data analysis, and particularly relates to the technical field of brick wall reinforcing. The internal structure of the brick wall is monitored through multi-frequency laser excitation, the interference degree of a heterogeneous repairing material on the integrity of a scanning signal is evaluated, and the influence of refraction and scattering of an optical signal on three-dimensional point cloud data is further analyzed. By constructing a local characteristic curve, the obstruction degree of the nonlinear optical effect on brick damage identification is evaluated. By analyzing the generalized spectral characteristics of the local characteristic curve and combining the refractive index of the repairing material and the energy conduction characteristics of the surface structure of the brick body, the error amplitude of the interface scattering anomaly on the measurement of the brick joint depth and the crack range is evaluated. And comprehensively analyzing the hindering degree of the nonlinear optical effect and the error amplitude of the interface scattering abnormity, evaluating the suitability of the brick body and the repairing material, and formulating a targeted reinforcing strategy to ensure the effectiveness and long-term stability of the reinforcing effect.

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 belongs to the technical field of photoelectric functional materials, and relates to a Dion-Jacobson type two-dimensional organic-inorganic hybrid chiral perovskite single crystal as well as a preparation method and application thereof. The chiral hybrid perovskite crystal is a non-centrosymmetric P212121 space group of an orthorhombic crystal system, and has the advantages of shortened inorganic interlayer spacing, eliminated interlayer Van der Waals gaps and excellent structural stability. The specific synthesis method comprises the following steps: completely dissolving the lead-based semiconductor in a haloid acid solution; adding chiral diamine organic molecules into the solution, and heating to completely dissolve the chiral diamine organic molecules; standing, and carrying out gradient cooling to room temperature to obtain millimeter-scale crystals; and after washing, putting into a vacuum drying oven for drying, so as to obtain the Dion-Jacobson type organic-inorganic hybrid chiral perovskite single crystal. The obtained single crystal has a non-centrosymmetric structure, shows strong chiral characteristics, and can be applied to the fields of circularly polarized photoelectric detectors, circularly polarized luminescence, light emitting diodes, displays, nonlinear optics and the like.

The invention discloses a device for detecting the ferroelectric direction of a thin film under the action of stress. The device is mainly composed of the following modules: an excitation light module which is used for polarization initialization and regulation of incident fundamental frequency light and stray light filtering; the excitation light source-femtosecond pulse laser is used for generating an incident excitation light beam with a proper frequency; the polarization module comprises a polaroid and is used for initializing polarization of incident light; the focusing module comprises a lens A and is used for focusing incident laser onto a to-be-detected sample; the half-wave plate comprises an electrically-controlled rotatable half-wave plate and is used for regulating and controlling polarization of incident light. The ferroelectric direction of the thin film under the stress is detected through nonlinear optics, the corresponding testing system and method are provided, the problems that in an existing measuring technology, sensitivity to the environment is high, and the sample preparation process is difficult are solved, and the problem that the sample is damaged in the measuring process and cannot be further researched is solved.

The invention discloses an ultrafast and high-sensitivity gas detection device and method based on gas nonlinear optics. The device comprises a high-power laser light source module, a light flux cell and a signal processing module. The light flux cell is of an integrated hollow structure, a high-reflectivity mirror face is arranged in the light flux cell to form a closed light path, laser enters the cell through an incidence hole at a certain incidence angle, 50-meter-level long-optical-path accumulation is achieved through multiple times of reflection, and the nonlinear effect excitation threshold value is effectively reduced. The light spot path is changed by adjusting the incident angle, the signal intensity is obviously enhanced by combining the nonlinear effect, and the detection limit reaches ppb level. The signal processing module extracts a target frequency component through phase-locked amplification, separates frequency domain aliasing signals in combination with wavelet transform, and reconstructs a complete nonlinear spectrum through Fourier transform. The device has the advantages of stable structure, high sensitivity, strong interference resistance and the like, and is suitable for environment trace gas monitoring and volatile organic compound early warning.

The invention discloses an alkali metal-rare earth carbonate functional material as well as a preparation method and application thereof. The inorganic rare earth carbonate functional material is prepared through a normal-temperature soaking method, hydrothermal conditions such as high temperature and high pressure are not needed, additives are not needed, the production cost is low, the number of preparation procedures is small, the production efficiency is greatly improved, and the purity of the prepared functional material is high. The inorganic rare earth carbonate functional material obtained by the invention has nonlinear optical performance and has a second harmonic effect with certain strength. The inorganic rare earth carbonate functional material obtained by the invention is a fibrous whisker, and has high length-diameter ratio and flexibility. The functional material can be used for fluorescence detection, anti-counterfeiting, phosphate adsorption removal, papermaking or filler for high polymer materials.

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 present disclosure provides a dual-path montmorillonite interlayer spacing control device and method. The present disclosure provides a device for controlling the interlayer spacing of montmorillonite by combining infrared continuous laser and infrared pulse laser. The experimental device includes an infrared nanosecond continuous laser and an infrared nanosecond pulse laser. The infrared nanosecond continuous laser is used to output continuous laser and provide stable radiation energy. The infrared nanosecond pulse laser is used to output high-energy pulse laser to achieve larger interlayer spacing control. The present invention uses a combination of continuous and pulse lasers to form a composite laser, utilizes photothermal effect and nonlinear optical effect, and combines operations to achieve interlayer spacing control of montmorillonite in a relatively large range, and can also achieve more accurate interlayer spacing adjustment in a local area.

A microscope according to the present invention is configured such that a phase difference observation optical system and a nonlinear optical observation optical system are provided opposite each other with an object to be provided therebetween. The microscope comprises: a ring diaphragm that functions as a diaphragm for primary light for phase difference observation and transmits secondary light that includes nonlinear optical effects from the object; and a phase ring that is provided at a location that is optically conjugate with the ring diaphragm.