39 results about "Quasi-phase-matching" patented technology

The invention discloses a compact monolithic dual-wavelength distributed feedback laser device and a manufacturing method thereof, and belongs to the technical field of laser, the laser device is composed of a front part, a middle part and a rear part, and the middle part comprises two equivalent Pi phase shift chirp sampling gratings. The laser is based on a reconstruction equivalent chirp technology and has a tunable wavelength interval. A chirp sampling grating with two equivalent phase shifts is arranged in the laser, and the grating is composed of a front part, a middle part and a rear part. Phase matching is achieved through the microstructure quasi-phase matching technology, it is ensured that a laser resonant cavity reaches the phase matching condition at the phase shift position, and wide-range adjustment expanded from 59.50 GHz to 116.25 GHz can be effectively achieved by changing injection current. The invention has the advantages of accurate wavelength control, simple structure, low power consumption, high integration level and the like.

The invention belongs to the technical field of nonlinear optics, and discloses a method and a structure for realizing nonlinear waveguide quasi-phase matching. A plurality of groups of micro-nano structures are formed on the nonlinear waveguide along the waveguide propagation direction, each group of micro-nano structures comprises one or more air holes, the micro-nano structures are utilized to cause relative phases between different wavelength modes to generate jump, phase differences caused by phase mismatch are compensated, and quasi-phase matching is realized. The phase matching scheme provided by the invention is applicable to all nonlinear materials and waveguides, and has the advantage of high universality.

The invention discloses a high-order frequency doubling orbital angular momentum mode generation device, which is characterized in that a laser direct writing technology is utilized to erase a second-order nonlinear coefficient in a lithium niobate crystal to form a three-dimensional fork-shaped grating array; each layer of fork-shaped grating is a pattern obtained by performing non-collinear interference on an OAM mode with topological charge of 10 and a Gaussian mode according to a holographic theory and then performing binarization processing; when each fork-shaped grating is processed, the central area of the fork-shaped grating is avoided; a fundamental frequency light beam meets a quasi-phase matching condition through the processed lithium niobate crystal, light field regulation and control are carried out while frequency multiplication conversion is carried out, and generation of a high-quality high-order nonlinear OAM mode is achieved.

A system for frequency conversion of laser pump radiation includes an optical element for frequency conversion of lasers or laser beams with power scalability. The element has a nonlinear birefringent, thin plate crystal. A pump beam generates frequency-shifted radiation. Phase or quasi-phase matching conditions are in the crystal between beams. Frontside and backside of the crystal have high-reflective and partially-reflective coatings, obtaining intensity enhancement of the pump and frequency-converted radiation, and maintaining relative phase delay between beams, maximizing conversion efficiency. The crystal contacts a heat sink through the high-reflective coating, minimizing temperature inhomogeneity in the crystal. Intrinsic longitudinal heat flow provides power scalability. The element, used intra-cavity, acts as a wavelength-selective component forcing laser operation on resonance of the element, maximizing frequency conversion. The wavelength selectivity allows single-frequency operation of high-power lasers with intra-cavity frequency conversion.

The application discloses a kind of multi-wavelength pumped mid-infrared upconversion spectral detection methods, its characteristics are that the method uses multi-wavelength narrowband laser as the pump source of nonlinear conversion, simultaneously adopt multi-period quasi-phase matching crystal as nonlinear upconversion medium, realize mid-infrared signal broadband and efficient conversion, and combine high-performance near-infrared spectral measurement and control element, finally obtain wide band, high resolution, ultra-sensitive mid-infrared spectral detection.The application has the characteristics of large bandwidth and high efficiency compared with existing upconversion spectral technology, simultaneously can high fidelity resolution mid-infrared spectral information, for realizing wide band, high resolution, ultra-sensitive mid-infrared spectral measurement provides effective means, is expected to be applied to molecular spectroscopy, trace substance detection, infrared remote sensing and atmospheric monitoring and other important fields.

An optical parametric device (OPD), which is selected from an optical parametric oscillator (OPO) or optical parametric generator (OPG), is configured with a nonlinear optical element (NOE) which converts an incoupled pump radiation at first frequency into output signal and idler radiations at one second frequency or different second frequencies, which is / are lower than the first frequency, by utilizing nonlinear interaction via a random quasi-phase matching process (RQPM-NOE). The NOE is made from a nonlinear optical material selected from optical ceramics, polycrystals, micro and nanocrystals, colloids of micro and nanocrystals, and composites of micro and nanocrystals in polymer or glassy matrices. The nonlinear optical material is prepared by modifying a microstructure of the initial sample of the NOE such that an average grain size is of the order of a coherence length of the three-wave interaction which enables the highest parametric gain achievable via the RQPM process.

The invention belongs to the technical field of laser technology and nonlinear optical frequency conversion, and discloses an intelligent control method for a PPLN frequency multiplication system, which comprises the following specific steps: step 1, initializing and self-checking the system, and completing initialization of hardware peripherals and a control program after the system is powered on; according to the method, a three-stage progressive optimal working point searching process is adopted, and the problem of optimal matching temperature drift caused by crystal heat absorption and photorefraction effects under high-power operation is effectively solved through the modes of low-power coarse scanning calibration of reference temperature, gradient power approximation real-time tracking of temperature drift and high-power dynamic locking closed-loop control; it is ensured that the system can work in the optimal state of quasi-phase matching under any input power; and meanwhile, through a power-temperature synchronous coordination feedforward + feedback control strategy, an efficient conversion interval is always maintained in a system output power adjustment process, and sudden efficiency drop caused by mismatch is avoided.

A fluid filled fiber for a quasi-phase matched generator and a laser incorporating such a fluid filled fiber. The liquid filled fiber has charge transfer molecules dissolved in a solvent. In another embodiment, the liquid of the LF fiber comprises or consists essentially of highly polar liquids and / or charge transfer molecules having relatively high molecular dipole values. The liquid filled fiber is usable with a laser for differential frequency generation.

A method for growing a periodically poled nonlinear crystal may comprise introducing a seed crystal into a melt to form a seed-melt mixture, wherein the seed crystal may comprise strontium tetraborate (SBO) and / or lithium triborate (LBO), and wherein the melt comprises a mixture of Sr, B, and O and / or a mixture of Li, B, and O. The method may further comprise heating the seed-melt mixture to a predetermined temperature until the periodically poled nonlinear crystal forms.

The invention discloses a device for realizing quasi-phase matching based on a pyroelectric field induced polarization ferroelectric domain, and the device is characterized in that the ferroelectric domain of a lithium niobate crystal is erased along an optical axis through employing a laser erasing technology, and a grating array structure is formed; then generating a pyroelectric field in the lithium niobate crystal by using a quenching process under vacuum to induce a ferroelectric domain to be polarized from the erasing position to the surface of the crystal along the optical axis, so that the polarized ferroelectric domain is also distributed in a grating array manner; the fundamental wave is subjected to frequency multiplication conversion through a ferroelectric domain polarization area, and the peak value of the frequency multiplication light spot power changing along with the wavelength of the fundamental wave is measured to be matched with the peak value calculated under the quasi-phase matching condition, so that quasi-phase matching is realized. Any external electric field is not needed, and a pyroelectric field opposite to the polarization direction can be generated in the crystal. The pyroelectric field can enable the ferroelectric domain to be reversed, and meanwhile the refractive index cannot be changed. According to the invention, the ferroelectric domain of the pyroelectric field polarized lithium niobate crystal is utilized, and frequency multiplication conversion meeting quasi-phase matching conditions is realized.

The invention discloses a thorium-doped strontium tetraborate crystal as well as a preparation method and application thereof, the chemical formula of the thorium-doped strontium tetraborate crystal is ThxSr1-xB4 + yO7 (Th SBO), and the thorium-doped strontium tetraborate crystal grows by adopting a solution method. The Th: SBO crystal disclosed by the invention is low in melting point, simple in component and beneficial to realizing high-quality crystal growth; the material has a wide band gap, has high transmittance in a vacuum ultraviolet band, is beneficial to reduction of absorption loss in a nuclear transition luminescence band, and is beneficial to excitation and detection of a nuclear transition signal; the SBO crystal is a random quasi-phase matching (RQPM) nonlinear optical crystal, 296.76 nm narrow linewidth laser 148.38 nm frequency doubling light can be used as an excitation source of the nuclear light clock through frequency doubling, and a Th host crystal and a frequency doubling crystal are combined, so that the complexity of a system is remarkably simplified, and a core material is provided for miniaturization of the nuclear light clock.

The embodiment of the invention provides a frequency conversion device based on a lithium niobate ridge waveguide on an insulator and a preparation method, and belongs to the field of integrated optical, nonlinear optical and optoelectronic devices. The device comprises a silicon substrate layer, a silicon dioxide buffer layer, an x-cut lithium niobate film layer and a silicon dioxide cladding from bottom to top, a ridge waveguide with width periodically changing is arranged on the x-cut lithium niobate layer, and light in the waveguide is propagated in the y-axis direction. The waveguide with the width periodically changing is prepared on the lithium niobate film, quasi-phase matching is achieved, and therefore the second harmonic conversion efficiency is greatly improved. By changing the period of the waveguide, second-order nonlinear phase matching conditions under different wavelengths, such as phase matching conditions of second harmonic generation, sum frequency generation and difference frequency generation, can be met. Correspondingly, according to the preparation method, the waveguide structure with the periodically changed width can be formed through a single etching process, and a complex ferroelectric domain inversion step is not needed. The preparation method has the advantages of simple process, controllable morphology and flexible design.

The invention belongs to the technical field of quantum optics and quantum information devices, and discloses a near-infrared-mid-infrared dual-wavelength quantum polarization entangled source generating device which comprises a mounting seat, and a near-infrared light source, a mid-infrared light source, a first entangled crystal, a second entangled crystal, a core crystal module, a polarization controller and a generator are mounted and connected above the mounting seat. High-coherence pump light is output through a near-infrared light source, and the high-coherence pump light is shaped into parallel light beams through an aspheric collimating lens group and then is coupled to a first entangled crystal; under a quasi-phase matching condition, the pump light is converted into a near-infrared entangled photon pair of a communication band of 1.5-1.7 [mu] m through a spontaneous parametric down-conversion process, and then the near-infrared entangled photon pair is input into the core crystal module along a preset optical axis; a mid-infrared light source outputs mid-infrared pump light, linear polarization direction locking and polarization state fine regulation and control are completed through a polarization controller, and interference of pump light polarization fluctuation on subsequent entanglement state generation is eliminated; the regulated and controlled mid-infrared pump light is coupled to the second entangled crystal, mid-infrared entangled photon pairs in the atmosphere window wave band of 3.5-4.0 microns are generated through spontaneous parametric down-conversion, the mid-infrared entangled photon pairs are synchronously input into the core crystal module along the optical axis, and actual application and operation are facilitated.

The present invention relates to the fields of laser technology, nonlinear optical physics technology, quantum optics and quantum communication technology, and in particular to a dual-color marking photon source generation module and a dual-compatible communication device including the module, wherein the dual-color marking photon source generation module includes an optical sheet component and a third quasi-phase matching crystal PPKTP3, which are sequentially arranged on an optical path and used to adjust the polarization state and focusing of input pulse light, and an input end of the optical sheet component inputs a third pump light of a set wavelength, and the third pump light is converted into a pair of signal photons and idler photons under the spontaneous output of the third quasi-phase matching crystal PPKTP3, and the wavelengths and bandwidths of the signal photons and the idler photons conform to the energy conservation and momentum conservation formulas and are converted into: ω p =ω s +ω i (1)Δk=k p ‑k s ‑k i +2π / Λ=0(2). The advantages of the invention are: the dual-color marking photon source generation module in the invention that meets formula (1) and formula (2) can simultaneously generate two pulse photon signals, and the wavelength can be compatible with both the underwater communication window and the optical fiber communication window.

The present invention relates to a method for preparing optical devices using LiNH4SO4 quasi-phase-matched crystals and their use. The LiNH4SO4 crystals are used in the preparation of deep-ultraviolet quasi-phase-matched optical devices. LiNH4SO4 quasi-phase-matched crystals have advantages such as a short UV absorption cutoff edge, moderate nonlinear optical effects, low refractive index dispersion, stable physical and chemical properties, and excellent mechanical properties, making them suitable for use in deep-ultraviolet quasi-phase-matched optical devices.

The invention relates to a single-channel multi-entangled photon pair generation method, device and equipment and a medium, and belongs to the technical field of nonlinear optics. According to the method, an existing method for generating entangled light through spontaneous parametric down-conversion in a nonlinear crystal is improved, the quasi-phase matching period of the nonlinear crystal is designed in a targeted mode, based on the spontaneous parametric down-conversion process, high-dimensional polarization entangled photon pairs of two wavelengths are generated at the same time, conversion channels are reduced, and the conversion efficiency is improved. Compared with an existing spontaneous parametric down-conversion generation method, generated entangled photon pairs are doubled, and compared with an existing non-spontaneous parametric down-conversion generation method, a complex optical system is not needed, the multisource of experimental errors is reduced, and the experimental efficiency is improved. Therefore, compared with an existing entangled light generation method, the method has the advantages of being simple, efficient, reliable and flexible in design, the difficulty of preparing the high-dimensional entangled source is greatly reduced, and development of the quantum entangled source and the quantum information technology can be better promoted.

This invention provides a multi-channel three-dimensional quasi-phase matching method and apparatus. The method includes: focusing fundamental frequency light through a microscope objective to obtain fundamental frequency light with a modified focusing state; incident the modified fundamental frequency light onto a nonlinear photonic crystal via normal incidence, and obtaining an outgoing second harmonic through the nonlinear photonic crystal; and finally, outputting multi-channel frequency-doubled light waves based on the outgoing second harmonic. This invention focuses fundamental frequency light onto a nonlinear photonic crystal via a microscope objective, changing the direction range of the incident fundamental frequency wave vector simply by altering the numerical aperture of the focusing objective. Combined with the spatial reciprocal lattice vector combination of the three-dimensional nonlinear photonic crystal, the quasi-phase matching condition is satisfied, achieving variable multi-channel frequency doubling. This invention achieves controllable multi-channel second harmonic generation without structural changes.

A nonlinear crystal 300 comprising stacked strontium tetraborate SrB4O7 (SBO) crystal slabs 335-1, 335-2, 335-3, 335-4 cooperatively configured to produce a periodic structure for quasi-phase matching (QPM) is used in the final frequency doubling stage 230A, 230B of the laser assemblies 200A, 200B to produce laser output light 239A, 239B having a wavelength in the range of approximately 180 nm to 200 nm. One or more elementary laser beams 211A, 211B are frequency doubled, down-converted, and / or summed using one or more frequency conversion stages 220A, 220B-1, 221B, 222B to produce intermediate frequency light 212A, 214B having a corresponding wavelength in the range of about 360 nm to 400 nm, and then a final frequency conversion stage 130 utilizes the nonlinear crystal 300 to double the frequency of the intermediate frequency light 212A, 214B to produce the desired laser output light 239A, 239B at high power. Methods, inspection systems, lithography systems, and cutting systems incorporating the laser assembly are also described.

The present invention discloses a high-order frequency-doubled orbital angular momentum mode generating device. The device uses laser direct writing technology to erase the second-order nonlinear coefficient in a lithium niobate crystal to form a three-dimensional fork-shaped grating array. The fork-shaped grating of each layer is a pattern obtained by non-collinear interference of an OAM mode with a topological charge of l0 and a Gaussian mode according to holographic theory and then performing binarization processing. When processing each fork-shaped grating, its central region is avoided. The fundamental frequency beam passes through the processed lithium niobate crystal to satisfy the quasi-phase matching condition, and while performing frequency doubling conversion, the optical field is regulated to achieve the generation of a high-quality high-order nonlinear OAM mode.

Aiming at the defect that visible light output with customizable spectrum is difficult to realize by the existing tunable visible light source, the invention provides a multi-wavelength visible light source for improving spectrum performance by using a mixed nonlinear process, and the requirement of quasi-phase matching is greatly relaxed by using a chirp polarization period lithium niobate waveguide. Furthermore, in combination with a chirp polarization period lithium niobate waveguide and an acousto-optic adjustable filter, the defect that the number of filter channels is limited can be overcome by utilizing a mixed nonlinear process (including frequency multiplication and sum frequency), the number of output wavelengths is greatly expanded, and meanwhile, the output spectrum has the characteristics of adjustable wavelength number, intensity, interval and line width; and multi-wavelength visible light output with flexibly adjustable spectrum is realized.

The present invention discloses a non - linear optical coupling modulation method based on adiabatic shortcuts, which is used to achieve efficient conversion of signal light into output light. It includes: (1) calculation of the anti - diabatic term in frequency conversion based on the adiabatic shortcut theory; (2) design of the modulation function of the coupling parameters in the cascaded wavelength conversion process and the diabatic compensation method; (3) selection and modulation of the laser light source and the non - linear crystal; (4) process of realizing the conversion of signal light into output light. This method is based on the adiabatic shortcut theory and is a scheme for realizing efficient second - order cascaded non - linear optical frequency conversion by modulating the crystal parameters, so as to reduce the limitations on the modulation parameters and the pump light intensity in adiabatic conversion to meet the adiabatic condition. According to the designed coupling parameter modulation function, using the quasi - phase - matching technology, multi - process quasi - phase - matching is realized in the non - linear crystal, thereby obtaining efficient frequency conversion from signal light to output laser.

The present invention discloses a dual-polarization frequency-doubled orbital angular momentum mode generating device, which is processed in a lithium niobate crystal using laser processing technology. The processed lithium niobate crystal includes two regions; the first region is a non-processed region, which converts the fundamental frequency ordinary light into the frequency-doubled extraordinary light based on the principle of birefringence phase matching; the second region is a fork-shaped grating array, and due to the change in the refractive index of the region, the frequency-doubled extraordinary light is linearly holographically diffracted, and the orbital angular momentum is loaded at a high order; in addition, the change in the second-order nonlinear coefficient of the region also performs nonlinear holographic diffraction on the fundamental frequency extraordinary light based on the principle of quasi-phase matching, and generates the frequency-doubled extraordinary light with orbital angular momentum at a high order. The present invention is based on the principles of birefringence phase matching and quasi-phase matching, combined with linear holographic diffraction and nonlinear holographic diffraction, so that both polarizations of the fundamental frequency ordinary light and the extraordinary light can generate efficient frequency-doubled orbital angular momentum modes.

This invention provides a method, apparatus, device, and readable storage medium for generating a waveguide single-photon source, relating to the field of quantum optics. The method includes coupling a fundamental frequency light output from a laser into free space to form a spatial beam; adjusting the polarization state of the collimated spatial beam to match its polarization direction with the crystal axis of a fully encapsulated waveguide device; coupling the polarization-adjusted spatial beam into a polarization-maintaining transmission fiber to form fiber-optic transmission light; injecting the fiber-optic transmission light into the fully encapsulated waveguide device, and converting the fundamental frequency light into frequency-doubled light at a quasi-phase-matching operating temperature; outputting the frequency-doubled light from the fully encapsulated waveguide device and coupling it again into free space to form an output beam; and performing spatial spectral filtering and intensity attenuation on the output beam to reduce the average photon number per pulse to the single-photon level, obtaining a purified single-photon signal. This invention addresses the polarization matching problem between existing waveguide devices and fiber optic transmission links.

A single-pass compact vector light field frequency conversion device and method, comprising: a one-dimensional nonlinear photonic crystal with a dual-periodic structure, the nonlinear photonic crystal simultaneously having two quasi-phase matching modes: oo-o and ee-e quasi-phase matching modes, the dual-periodic structure comprising: a first and a second periodic polarization structure region and a relative spacing region between the two structures. The present invention achieves frequency conversion of two polarization states of a vector light field in a single crystal by designing a periodic nonlinear photonic crystal structure, does not require complex optical path design, has a simple, compact and stable structure, is less affected by the external environment, and can be further applied to integrated devices.

An optical parametric device (OPD), which is selected from an optical parametric oscillator (OPO) or optical parametric generator (OPG), is configured with a nonlinear optical element (NOE) which converts an incoupled pump radiation at first frequency into output signal and idler radiations at one second frequency or different second frequencies, which is / are lower than the first frequency, by utilizing nonlinear interaction via a random quasi-phase matching process (RQPM-NOE). The NOE is made from a nonlinear optical material selected from optical ceramics, polycrystals, micro and nanocrystals, colloids of micro and nanocrystals, and composites of micro and nanocrystals in polymer or glassy matrices. The nonlinear optical material is prepared by modifying a microstructure of the initial sample of the NOE such that an average grain size is of the order of a coherence length of the three-wave interaction which enables the highest parametric gain achievable via the RQPM process.

This application provides a nonlinear optical device for generating an annular beam and a method for preparing the same. The method includes the following steps: designing a shaping structure for a hollow cylindrical quasi-phase-matching grating based on the distribution characteristics of a pump beam and the quasi-phase matching mechanism; modifying a ferroelectric crystal using a femtosecond laser to induce the spatial distribution of the ferroelectric crystal's second-order nonlinear coefficient to adopt the shaping structure, thereby preparing a nonlinear optical device; and generating an annular second harmonic beam when the pump beam is incident on the prepared nonlinear optical device. The nonlinear optical device prepared by the preparation method provided in this application can simultaneously generate an annular beam and double frequency. The preparation method provided in this application reduces processing difficulty and effectively controls the dark spot ratio at the center of the beam, providing a competitive nonlinear optical device product for generating annular beams.

A method for constructing a periodically-poled nonlinear crystal may include implanting ions in a bulk crystal of strontium tetraborate (SBO) or lithium triborate (LBO) to generate a damaged layer at a predetermined depth, attaching a handle material to the surface of the bulk crystal, cleaving the bulk crystal at the damaged layer to generate a thin plate, and polishing the thin plate to a thickness suitable for quasi-phase-matching (QPM) to generate laser output light having wavelengths in the range of about 120-200 nm. The surfaces of thin plates generated in this way are optically contacted, and resulting stacks are diced and arranged to generate many-layered QPM crystals. Methods, inspection systems, lithography systems and cutting systems incorporating the laser assembly are also described.

This invention discloses a broadband terahertz electro-optic sampling quasi-phase-matched structure, comprising at least two electro-optic crystals stacked sequentially, with a compensation crystal positioned between each pair of adjacent electro-optic crystals. The electro-optic crystals and the compensation crystals have opposite dispersion relations, facilitating the compensation crystals to compensate for the phase difference accumulated between the terahertz light and the probe light within the electro-optic crystals. This invention selects the type and thickness of the electro-optic crystals as needed, chooses a compensation crystal with an opposite dispersion relation to the electro-optic crystals, calculates its thickness based on the measurement bandwidth and phase-matching conditions, and then determines the number of electro-optic crystal layers according to the measurement bandwidth requirements. Compared with existing technologies, this invention can broaden the measurement bandwidth while maintaining signal strength. This invention does not involve precision micro / nano fabrication, is low-cost and easy to manufacture, does not involve destructive processing of the crystals, is reusable, and can be recombined and rearranged as needed, offering high flexibility.

The application relates to the technical field of strong laser nonlinear frequency conversion, in particular to a method for generating ultra-wideband mid-infrared laser in a single piece of polarized crystal. The method uses laser with a wavelength of 800 nm as pump light, laser with a wavelength of 0.95-1.6 microns as signal light, and a difference frequency conversion process occurs in the polarized crystal, thereby generating mid-infrared laser with a wavelength of 1.6-5 microns. In the method, a polarized crystal with a chirped period structure is used, that is, the polarization period of the crystal continuously changes with the position in the crystal. The polarized crystal is a 5% magnesium oxide doped chirped period lithium niobate crystal. The application utilizes quasi-phase matching technology, can use the maximum effective nonlinear coefficient of the chirped period lithium niobate crystal, and does not need to change the crystal angle or the polarization of the laser when the pump light is at different wavelengths. The application overcomes the shortcoming that the wavelength of the current mid-infrared band laser is difficult to expand due to the limitation of the gain medium.

The present application relates to a kind of single channel multi-entangled photon pair generation method, device, equipment and medium, belong to nonlinear optics technical field.The method improves the method for generating entangled light in existing nonlinear crystal spontaneous parametric down-conversion, by the quasi-phase matching period of nonlinear crystal is designed specifically, based on spontaneous parametric down-conversion process, simultaneously realize the generation of high-dimensional polarization entangled photon pair of two wavelengths, reduce conversion channel, compared with the existing spontaneous parametric down-conversion generation method, the generated entangled photon pair doubles, and compared with the existing non-spontaneous parametric down-conversion generation method, then no complex optical system, reduce the multi-source of experimental error, so comprehensive compared with the existing entangled light generation method has simple, efficient, reliable and flexible design characteristics, greatly reduce the difficulty of preparation high-dimensional entangled source, can better promote quantum entangled source and the development of quantum information technology.