268 results about "Nonlinear crystals" patented technology

The invention discloses a walk-off compensation device for laser frequency tripling, and relates to the technical field of laser, and the device comprises a fundamental frequency light source which is used for generating fundamental frequency laser; the frequency doubling unit is used for converting the fundamental frequency laser into frequency doubling laser; the frequency tripling unit comprises a frequency tripling nonlinear crystal and is used for converting the frequency-doubled laser and the residual fundamental frequency laser into frequency tripled laser; the walk-off pre-compensation unit is arranged between the frequency doubling unit and the frequency tripling unit, the walk-off pre-compensation unit comprises a spherical lens which is eccentrically arranged, the spherical lens is used for enabling the frequency doubling laser and the residual fundamental frequency laser which is not completely converted to generate a preset included angle, and the preset included angle is matched with a walk-off angle generated in the frequency tripling nonlinear crystal; and the light beam shaping unit is used for outputting ultraviolet laser. According to the invention, a complex pre-compensation optical element does not need to be added in front of the frequency tripling unit, walk-off compensation can be realized only through the eccentrically placed spherical lens, and the structure of the optical system is greatly simplified.

The invention provides a cold atom gravity measurement method and device based on entangled state enhancement, and belongs to the technical field of cold atom gravity measurement, and the method comprises the steps: carrying out the excitation of a nonlinear crystal, obtaining an entangled photon pair, and enabling the entangled photon pair to comprise a first photon and a second photon in an entangled state; laser parameters of an area where a cold atomic group is located are controlled, the first photons are coupled into the cold atomic group, and a plurality of cold atoms in an entangled state are obtained; and placing the plurality of cold atoms in the entangled state in a gravity field, measuring the phase difference of the cold atoms under the action of the gravity field, and determining a gravity measurement result based on the phase difference. According to the invention, entangled photons are introduced to be coupled with cold atoms, so that the measurement limit is improved to the Heisenberg limit, and higher-precision gravity measurement is realized.

The invention discloses a device for realizing low-loss work of a long-wave infrared femtosecond optical parametric oscillator, which belongs to the field of optical parametric oscillators and comprises a pumping source, a pumping focusing lens, a long-wave infrared nonlinear crystal cut at a Brewster angle, a laser medium dichroscope and an output coupling mirror. Wherein the nonlinear crystal meets the I-type phase matching condition for the optical parameter process, and the front and rear surfaces of the crystal cut the central wavelength of the oscillated signal pulse at a Brewster angle so as to reduce the loss of the pulse in the resonant cavity. According to the long-wave infrared femtosecond optical parametric oscillator, the limitation of residual loss of a crystal antireflection film is broken through by adopting Brewster angle cutting on the crystal, so that the construction of the femtosecond optical parametric oscillator based on the long-wave infrared nonlinear crystal becomes possible, and the bottleneck of the existing long-wave infrared femtosecond optical parametric oscillator in the aspects of wavelength tuning range, output power and the like is expected to be broken through; and a practical low-cost technical scheme is provided for construction and application of the long-wave infrared femtosecond optical parametric oscillator.

The invention discloses an ultra-wideband femtosecond optical parametric oscillator capable of being quickly tuned, and relates to the technical field of optical parametric oscillators. The oscillator comprises a frequency doubling device, an optical parametric oscillator resonant cavity device and a dispersion compensation chirp mirror pair module. According to the invention, the original phase matching bandwidth is further broken through by adopting a non-collinear phase matching mode that the transmission included angle between the pump light and the signal light is 2.5 degrees, and rapid wavelength tuning can be realized only by finely tuning the cavity length under the condition that the angle of the nonlinear crystal is not adjusted; the broadband tunable optical parametric oscillator can break through the bottlenecks in the aspects of wavelength tuning range, wavelength tuning speed and the like of the existing near-infrared optical parametric oscillator, and provides a novel light source with larger wavelength tuning range and higher tuning speed for the fields needing broadband tunable light sources, such as spectroscopy, micro-nano processing, optical frequency combs and the like.

The invention relates to the technical field of laser, and provides a high-power pulse width repetition frequency tunable laser, which comprises an input and output light path configured to input seed light and output amplified laser; a regenerative amplifier optical path configured to amplify the input seed light; and the pulse width compression module is configured to perform pulse width compression on the amplified seed light and output high-power pulse laser with tunable pulse width, and the pulse width compression module comprises a third polarizing beam splitter, a third 1 / 2 wave plate, a first electric control transverse movement plane mirror, a second electric control transverse movement plane mirror, a nonlinear crystal and a fourth plane mirror. On the basis of a nonlinear crystal multi-pass compression method, a high-power disc laser is built, pulse width compression is carried out on an annular cavity which contains a nonlinear crystal and a 1 / 2 wave plate or is added into a Pockels cell, and a high-power pulse width repetition frequency tunable pulse string is finally obtained by transversely moving a plane mirror through electric control.

A nonlinear crystal flexible clamping and temperature control device comprises a clamping seat, a top face clamping block, a side face clamping block, a stud, a compression spring, a nut, a window mirror pressing ring, a wave spring, a window mirror gasket, a window mirror, a window mirror limiting block, a nonlinear crystal, silicon rubber, a thermistor and a ceramic heating piece. The flexible clamping device exerts pre-tightening force on the nonlinear crystal in the horizontal direction and the vertical direction through the compression spring, and meanwhile flexible clamping of the nonlinear crystal is achieved in a silicone rubber dispensing fixing mode. The temperature control device achieves accurate control over the temperature of the nonlinear crystal in the mode that a thermistor collects temperature signals and a ceramic heating piece heats a clamping base. The flexible clamping and temperature control device disclosed by the invention has the characteristics of performing thermal expansion compensation on the nonlinear crystal, being high in mechanical resistance and temperature control precision, uniform in crystal heat distribution and the like.

The invention relates to the technical field of light quantum metering, in particular to a multifunctional standard single photon source generation and calibration device and a use method, and the device comprises a pumping laser light source, a nonlinear crystal, a signal optical filter, a beam splitter, a temperature control module, an idler frequency optical filter, a control module, a single photon detector group, a beam splitter, a multi-channel coincidence counter, and an optical switch. The pumping laser light source pumps the nonlinear crystal to generate two paths of single photon output of signal light and idler frequency light, the two paths of single photon output are filtered by the filter and then divided into multiple paths by the beam splitter, and standard single photons are directly output or the paths of the signal light or the idler frequency light are controlled by the optical switch to enter the single photon detector group for detection. External input single photons are controlled by the optical switch to enter the single-photon detector group for detection, and a count value of the single-photon detector group is accessed to the multichannel coincidence counter to record data. A pump light stable power system and a multi-path beam splitting coincidence counting system are introduced into a light path, so that standard single photon output with known brightness and g (2) (0) value can be realized.

The invention provides an efficient OPO system with a bicrystal compensation and independent pumping regulation and control structure, and relates to the technical field of laser nonlinear frequency conversion. The device comprises a pump laser, a light source regulation and control unit, an incidence adjustment unit, an OPO resonant cavity and an output separation unit which are sequentially arranged, the OPO resonant cavity comprises a walk-off compensation and frequency conversion module and a tuning module, and the walk-off compensation and frequency conversion module comprises a nonlinear crystal I and a nonlinear crystal II which have opposite cutting angles. And a tuning module is arranged between the nonlinear crystal I and the nonlinear crystal II. The OPO system based on the bicrystal structure has space walk-off angle compensation and pump light independent regulation and control capabilities, and is suitable for constructing near-infrared and intermediate-infrared laser sources with high efficiency and high stability. According to the invention, the optical path structure is flexible, the multi-crystal and multi-band adaptation is supported, and the system compatibility is good; miniaturization and intelligent integration are easy, and industrial application and popularization are facilitated.

The waveguide carrying a nonlinear crystal with reflective interface, a pump photon source and a circulator define an optical parametric amplifier which uses optical power from the pump photons to boost incoming signal and idler photons which carry the encoded signal. The nonlinear crystal performs optical parametric amplification upon the incoming optical signal in a quantum photonic process that generates additional signal and idler photons to thereby boost the intensity of the incoming signal. A photodetector is coupled for communication with the third port and operative to convert the reflected optical signal into an electrical signal defining the output of the communications receiver.

The invention discloses a tunable narrow-band medium-wave infrared detection method based on up-conversion, and the method mainly comprises the steps: building a tunable narrow-band medium-wave infrared detection system, adjusting the power of signal light and pump light and the size of a beam waist, and controlling the temperature of a nonlinear crystal at a room temperature level to suppress the noise of a static system. A nonlinear crystal is designed through displacement of a multi-polarization period of a mechanical motion module, so that quasi-phase matching of signal light and pump light in a range of 3-5 microns is realized in different polarization period channels, sum frequency light of a visible wave band is generated, and flexible tuning of the signal light in a wide spectral range is realized; after stray light is filtered out, a sum frequency signal is received by a detector, a corresponding curve is obtained according to detected intensity information corresponding to each wavelength, and narrow-band response characteristics of different polarization periods are obtained.

The invention discloses a miniaturized high-efficiency frequency-stabilized 355nm ultraviolet pulse laser, and belongs to the technical field of lasers. Comprising a seed laser module, a laser frequency stabilization module, a laser amplification module, a beam shaping module and a frequency tripling module. After frequency stabilization control is carried out on seed laser, a large-energy pumping source is generated through laser amplification, flat-topped light beams are formed after the light beams pass through a light beam shaping module, and high-efficiency 355 nm ultraviolet pulse laser output is achieved in combination with a nonlinear crystal frequency conversion technology. The device has the advantages of miniaturization, high conversion efficiency, high frequency stability, strong anti-interference capability and the like, can be used for an atmospheric component detection laser radar light source, and can meet the application requirements of airborne, satellite-borne and other complex environments.

The invention relates to a high-order transverse mode compression state preparation device based on optical parameter resonant cavity mode selection, and belongs to the technical field of quantum state light field generation. Fundamental frequency light and pump light output by the laser source generate a high-order transverse mode light field through the mode conversion module, and then the high-order transverse mode light field enters the optical parametric resonant cavity to be subjected to parametric down-conversion with the nonlinear crystal. The cavity length of the optical parametric resonant cavity is locked at the optimal pumping mode position corresponding to the high-order transverse mode compression state, so that resonance of an impurity mode in the optical parametric resonant cavity can be avoided, and the compression level of a high-order transverse mode light field is improved. Under injection of high-order transverse mode pump light, the pump mode is purified through the optical parametric resonant cavity of the annular structure, the compression level of a high-order transverse mode light field is enhanced, adjustment is easy, practicability is high, productization is easy, and wide application prospects are achieved in the fields of quantum space measurement, biological measurement, atomic force microscope detection and the like.

The invention discloses a non-linear frequency conversion regenerative amplification device and a method thereof, and belongs to the technical field of laser non-linear frequency conversion. The device comprises a signal light injection unit, a regeneration amplification cavity unit and a pump light synchronization unit. The regenerative amplification cavity unit comprises an optical resonant cavity structure module, a polarization control module and a nonlinear action module. A time domain switch is formed through the polarization control module under the driving of the time schedule controller, and the preset number of times of circulation of signal light in the cavity is accurately controlled. And meanwhile, the pump light synchronization unit generates pump pulse string laser which is synchronous with the circulation process and has sub-pulse power increasing in sequence, so that the signal light and one corresponding pump sub-pulse are subjected to optical parametric amplification in the nonlinear crystal in each circulation. The space complexity of multi-stage amplification is converted into time domain controllability, high-efficiency and high-gain nonlinear frequency conversion is realized by using a single-stage compact structure, and the integration level and the stability of the system are remarkably improved.

The embodiment of the utility model provides a laser converter and a laser device. Wherein the laser converter comprises a shell, one side of the shell is provided with a laser input port, and the other side of the shell is provided with a laser output port; the nonlinear crystal is arranged in the shell and is used for converting the laser emitted from the laser input port into laser with a set wavelength; the first collecting lens is arranged in the shell and located on the side, away from the laser input port, of the nonlinear crystal, and the first collecting lens is used for focusing the laser with the set wavelength so that the laser output port can emit the focused laser. The laser converter can convert the laser, so that when the laser converter is applied to the laser device, the laser converter can be used for converting the laser originally emitted by the laser device, the laser originally emitted by the laser device is reserved, the laser device can emit the laser with the set wavelength by means of the laser converter, and the universality is good; and laser with set wavelength can be directly generated without adding a laser generator, so that the structure is simplified.

A multi-wavelength entangled photon pair generation device includes: a multi-mode pump laser that radiates a broadband pump laser beam in an ultraviolet wavelength range including multiple Gaussian-distributed wavelengths; a nonlinear crystal that generates a multi-wavelength de-multiplexed entangled photon pair in a near-infrared wavelength range including multiple wavelength components corresponding to multiple Gaussian-distributed wavelengths of the broadband pump laser beam, respectively; a temperature controller that adjusts a temperature of the nonlinear crystal; and an output optical system that filters out the broadband pump laser beam from light output through the nonlinear crystal and passes the multi-wavelength de-multiplexed entangled photon pair.

A method and system for generating deep ultraviolet (DUV) laser light is disclosed, in one embodiment the DUV laser system includes a fiber laser source configured to emit a poised fundamental laser beam in the near-infrared with a pulse duration of less than 400 femtoseconds (fs), a nonlinear crystal assembly comprising first, second, and third nonlinear crystals that is configured to convert the fundamental laser beam to produce a fifth harmonic laser beam having a wavelength in a range from 200 nanometers (nm) to 230 nm, and at least one compensation plate disposed in at least one position preceding at least one of the first, second, and third nonlinear crystals and configured such that a pair of pulsed laser beams transmitted through the at least one compensation plate are spatially and temporally overlapped within the at least one of the first, second, and third nonlinear crystals.

The invention discloses a mid-infrared nonlinear crystal, a mid-infrared laser and a preparation method of the mid-infrared nonlinear crystal, a slice crystal is adopted, an included angle theta is formed between an optical axis Z axis of the slice crystal and the surface, the slice crystal is polarized into a periodic polarization structure with the period of lambda through a room temperature electric field polarization technology, and a large surface forms an optical plane through polishing. The problem of how to reduce the thermal lens effect of the intermediate infrared nonlinear crystal is solved, and the damage threshold of the intermediate infrared nonlinear crystal can be improved, so that the laser output power is improved.

An interferometric module, constructed in single pentagonal block to produce high quality, robust, low cost entangled-photon sources enabling polarization entanglement swapping. The compact block forms a generic platform that facilitates a comprehensive integration of optical components while allowing for quick optical alignments. Phase-stability of the self-balanced Sagnac interferometer is harnessed to offer a highly stable performance at room temperature and under sever operating conditions. High-quality entanglement is inherently achieved by equalizing two interferometric optical paths from counter-propagating photons. A periodically poled nonlinear crystal is placed between two half-wave plates, which also serve to correct the polarization states of the photons. The result is compensation-free and plug-and-play entangled-photon sources for quantum routers, distributed quantum sensing and quantum telecommunication. Wavelengths and generation rate of photon pairs are realized via the hosted crystal. Energy and polarization entanglement, and hyperentanglement can be remotely set by rotating the polarization state of the pump laser diode.

This application discloses an optical parametric oscillator and a laser generating device, relating to the field of laser technology. The optical parametric oscillator includes a first optical fiber, a mirror assembly, a nonlinear crystal, and a second optical fiber. The first optical fiber has a first receiving end and a first output end. The first receiving end is used to receive pump light. The second optical fiber has a second receiving end and a second output end. Light output from the first output end can be transmitted to the second receiving end via the mirror assembly and the nonlinear crystal. The second output end is used to output signal light. The mirror assembly includes multiple mirrors. The nonlinear crystal is located in the optical path between two mirrors. A first grating is disposed on the first optical fiber, and a second grating is disposed on the second optical fiber. Both the first and second gratings are fiber Bragg gratings. Because this application uses a first optical fiber and a second optical fiber to define the light transmission path, compared to a free-space optical path, the optical fiber can be coiled, which is beneficial for reducing the overall size and improving integration.

An assembly mobile device having a shape memory alloy actuator is disclosed. In one embodiment, the system may include a housing having a chamber formed therein, at least one nonlinear crystal disposed in the chamber, the nonlinear crystal configured to receive at least one incident signal and convert the wavelength of at least a portion of the incident signal, and at least one shape memory alloy element is configured such that thermal energy or electrical energy applied to the shape memory alloy causes linear translation of the nonlinear crystal.

An optical tomography device includes a sample optical path system for injecting light, scanned from a light source, into a sample corresponding to biological tissue; a reference optical path system for collecting the light scanned from the light source; and a detection unit for detecting a tomography image of the sample by interfering with sample light, transmitted from the sample optical path system and reflected from the sample, and reference light transmitted from the reference optical path system. The detection unit comprises: a nonlinear crystal which receives the sample light and the reference light and generates nonlinear light having a different wavelength than the sample light and the reference light; and an image sensor which detects a depth direction signal from the nonlinear light.

This application provides a semiconductor laser and a terahertz source for generating terahertz waves. The semiconductor laser includes: a substrate; a mesa located on the substrate; and a ridge waveguide and lateral coupling gratings located on the mesa, with the lateral coupling gratings located on both sides of the ridge waveguide. The lateral coupling gratings are configured such that the frequency difference between the fundamental transverse mode wavelength and the second-order transverse mode wavelength of the lasing light emitted by the semiconductor laser is 0.1 THz–10 THz. The semiconductor laser of this application, through the optimized configuration of the ridge waveguide and the lateral coupling gratings on both sides, precisely achieves simultaneous output of the fundamental and second-order transverse modes with a frequency difference on the order of terahertz. Combined with a polarization controller and a nonlinear crystal, it can stably output terahertz waves in the target frequency band. Compared with traditional solutions, the semiconductor laser of this application can simultaneously output the fundamental and second-order transverse modes with a frequency difference on the order of terahertz, offering advantages in miniaturization and low cost.

The invention discloses a single femtosecond laser pulse waveform measuring device. A measured vertically-polarized space-uniform measured femtosecond laser pulse is divided into transmission light and reflected light after passing through a spectroscope, the transmission light is divided into two beams, and the three beams are incident to a nonlinear crystal at the same angle and equal optical path along the edge of a regular triangular prism for third-order nonlinear harmonic conversion; the generated third harmonic light beam is a double-delay third-order intensity related signal of the measured pulse after space-time transformation, and pulse waveform information is obtained through image decoding. The measuring device improves time resolution, and is low in cost and convenient to adjust.

The invention discloses a high-efficiency optical parametric oscillator, and belongs to the technical field of lasers, the high-efficiency optical parametric oscillator comprises a pumping source output assembly, a coupling system, a first resonant cavity mirror and a nonlinear crystal which are sequentially arranged along the direction of an optical path, a dispersion prism is arranged at a light outlet of the nonlinear crystal, and the dispersion prism can divide light into signal light and idler frequency light; the dispersion prism and the light source are transmitted along a first light path and a second light path respectively, a second resonant cavity mirror is arranged on the first light path, an optical parameter adjusting assembly is arranged between the dispersion prism and the second resonant cavity mirror, and a third resonant cavity mirror is arranged on the second light path. According to the high-efficiency optical parametric oscillator provided by the invention, the light-light conversion efficiency and high light beam quality of parametric light can be simultaneously obtained under different power pumps under the conditions of not changing a cavity type structure and not needing to be reassembled and adjusted under the different power pumps.

The utility model discloses a femtosecond laser pulse width real -time monitoring device relates to optical instrument technical field, including main base plate, integral optical support module, integral optical support module is equipped with a plurality of, a plurality of integral optical support module is used for installing different optical elements, and optical elements include beam splitter, reflector, delay line and nonlinear crystal, and integral optical support module is vertically installed on main base plate through fixed peg, support stable clamping plate is formed with two clamping plates and is closed, and the round hole for clamping fixed peg is formed on support stable clamping plate, and both ends of support stable clamping plate are equipped with fixed hole, and the axial direction of fixed hole is perpendicular with the board face direction of support stable clamping plate, is used for further fixed integral optical support module group after clamping on main base plate. The utility model forms the door type frame structure through support stable clamping plate and makes a whole with a plurality of module, and the slight displacement and the shaking of each module top are restrained.

The application discloses a high-energy and few-cycle blue light laser generation method and device, and belongs to the technical field of ultrafast laser, wherein the method comprises the following steps: adopting a nonlinear crystal to double frequency of a base frequency pulse after compression, and performing at least twice pulse width compression on the obtained double frequency pulse to obtain high-energy and few-cycle blue light laser; wherein, the double frequency process and the pulse width compression process are both performed in a cavity filled with helium; the pulse width compression process is performed through spectral broadening of a solid sheet; since the helium has extremely low linear dispersion and nonlinear coefficient and extremely high ionization energy, not only the solid sheet damage can be avoided, and a part of spectral broadening is contributed, but also an environment close to vacuum can be provided in terms of dispersion and laser-induced ionization, so that the dispersion compensation of the double frequency pulse is easier, and the energy loss caused by gas ionization and the input energy limitation are avoided, and higher output energy is allowed; the problem that the high-energy and ultra-short pulse width blue light pulse is difficult to be realized simultaneously at present is effectively solved.

The invention discloses an external cavity type annular human eye safety optical parametric oscillator, and relates to the technical field of laser. The oscillator sequentially comprises a first cavity mirror, a first nonlinear crystal, a second cavity mirror, a second nonlinear crystal, a third cavity mirror and a third nonlinear crystal, the pump light is converted into human eye safety laser through optical parameters to be output, and the remaining pump light is transmitted and output from the first cavity mirror. An external cavity type OPO technology and a three-mirror annular cavity structure are adopted, a plurality of nonlinear crystals are placed in an annular cavity to fully absorb pump light, high conversion efficiency can be obtained under low pump power density, the problem that optical devices are damaged due to the fact that the power density in an internal cavity type OPO cavity is too high is solved, pump light pumping is an annular route, and the pumping efficiency is greatly improved. And the residual pump light cannot return to the pump light resonant cavity, so that the reliability of the laser is improved.

The invention provides a wide-band fast wavelength tuning light source device and method, and belongs to the field of laser technologies and precise spectrums.The wide-band fast wavelength tuning light source device comprises a first laser source and a second laser source, the first laser source generates first coherent light, the first coherent light is coupled into an annular resonant cavity, and the second laser source generates second coherent light; the first laser source generates first coherent light, optical parametric conversion is achieved at the first nonlinear crystal, idle light and signal light are output, the second laser source generates second coherent light, and the second coherent light is coupled into the annular resonant cavity from the other port. First coherent light and second coherent light which are left after optical parametric conversion at the first nonlinear crystal are coaxially injected into a second nonlinear medium, so that stimulated Raman intensity amplification and phase change of the first coherent light are realized; the intensity of the second coherent light injected into the second nonlinear medium is regulated and controlled, so that the three-wave phase matching condition in the resonant cavity can be quickly regulated and controlled, rapid and broadband wavelength tuning of signal light and idle light is realized, and the technical blank of broadband rapid wavelength tuning is filled.

The application relates to the field of laser technology, in particular to a device and a method for generating wide-tuning narrow-line-width mid-infrared laser, wherein the pump light emitted by a nanosecond pulse OPO base frequency pump source is reflected to a beam splitter by a full reflection mirror after passing through a first adjuster; the pump light emitted by a continuous wave OPO base frequency pump source is irradiated to the beam splitter after passing through a second adjuster; the two beams of pump light are combined after passing through the beam splitter, are focused after passing through a plano-convex lens, are irradiated to a first plano-concave full reflection mirror, and then are transmitted to a nonlinear crystal to generate signal light and idler mid-infrared laser through nonlinear frequency conversion; the idler mid-infrared laser and the residual pump light are transmitted to a doublet mirror and are separated by the doublet mirror; the signal light is reflected to the nonlinear crystal in sequence through a second plano-concave full reflection mirror, a first plane full reflection mirror, a second plane full reflection mirror and the first plano-concave full reflection mirror, and an oscillation closed loop is formed. The application realizes that the pulse OPO outputs a pulse with a line width less than 90 MHz in the tuning range, and the extraction efficiency of the idler light is as high as 9.3%.

The application relates to the technical field of solid laser emitters, in particular to a device for the thermal management of a nonlinear crystal in a laser. The device comprises a base, a fixing member, a pressing member and a pressing device, the pressing member is located between the base and the vertical plate part, a through V-shaped groove is formed on the side of the pressing member facing the base, the V-shaped groove and the mounting plate of the electric push rod arranged on the base and perpendicular to each other form a containing cavity for containing the nonlinear crystal, the mounting surface of the mounting plate and the V-shaped surface of the V-shaped groove are both provided with a temperature control assembly for adjusting the temperature of the nonlinear crystal, the temperature control assembly comprises a heating plate and a heat dissipation plate; and the pressing device is used for pressing the nonlinear crystal. The device can quickly adjust the temperature of the nonlinear crystal material, realizes the efficient thermal management of the amorphous material, and improves the stability of the nonlinear crystal material.