Silica glasses doped with Bi2S3 microcystallite was prepared by the sol-gel process. Photoinduced second harmonic generation (SHG) was observed in the glass when it was irradiated with intense 1.06 μm and frequency d...Silica glasses doped with Bi2S3 microcystallite was prepared by the sol-gel process. Photoinduced second harmonic generation (SHG) was observed in the glass when it was irradiated with intense 1.06 μm and frequency doubled laser beams from a mode-locked Nd: YAG laser. It was found that the signal intensity increased with the irradiating time and approached a saturation gradually. The effect may be explained reasonably by the DC field model.展开更多
The emergence of two dimensional(2D)materials has opened new possibilities for exhibiting second harmonic genera-tion(SHG)at the nanoscale,due to their remarkable optical response related to stable excitons at room te...The emergence of two dimensional(2D)materials has opened new possibilities for exhibiting second harmonic genera-tion(SHG)at the nanoscale,due to their remarkable optical response related to stable excitons at room temperature.However,the ultimate atomic-scale interaction length with light makes the SHG of Transition Metal Dichalcogenides(TM-Ds)monolayers naturally weak.Here,we propose coupling a monolayer of TMDs with a photonic grating slab that works with doubly resonant bound states in the continuum(BIC).The BIC slabs are designed to exhibit a pair of BICs,reson-ant with both the fundamental wave(FW)and the second harmonic wave(SHW).Firstly,the spatial mode matching can be fulfilled by tilting FW's incident angle.We theoretically demonstrate that this strategy leads to more than four orders of magnitude enhancement of SHG efficiency than a sole monolayer of TMDs,under a pump light intensity of 0.1 GW/cm^(2).Moreover,we demonstrate that patterning the TMDs monolayer can further enhance the spatial overlap coefficient,which leads to an extra three orders of magnitude enhancement of SHG efficiency.These results demonstrate remarkable pos-sibilities for enhancing SHG with nonlinear 2D materials,opening many opportunities for chip-based light sources,nano-lasers,imaging,and biochemical sensing.展开更多
Carbon ion irradiation and precise diamond blade dicing are applied to fabricate Nd∶GdCOB ridge waveguides.The propagation properties of the fabricated Nd∶GdCOB waveguides are investigated through experiments and th...Carbon ion irradiation and precise diamond blade dicing are applied to fabricate Nd∶GdCOB ridge waveguides.The propagation properties of the fabricated Nd∶GdCOB waveguides are investigated through experiments and theoret-ical analysis.Micro-Raman analysis reveals that the Nd∶GdCOB crystal lattice expands during the irradiation process.Micro-second harmonic spectroscopic analysis suggests that the original nonlinear properties of the Nd∶GdCOB crystal are greatly enhanced within the waveguide volume.Under pulsed 1064 nm laser pumping,second harmonic generation(SHG)at 532 nm has been achieved in the fabricated waveguides.The maximum SHG conversion efficiencies are determined to be~8.32%·W^(-1) and~22.36%·W^(-1) for planar and ridge waveguides,respectively.展开更多
Broadband nonlinear frequency conversions of optical waves are widely employed in multiple areas of optics and photonics. However, the broadening of conversion bandwidth is often at a cost of reduction in efficiency, ...Broadband nonlinear frequency conversions of optical waves are widely employed in multiple areas of optics and photonics. However, the broadening of conversion bandwidth is often at a cost of reduction in efficiency, which may induce a limitation on practical applications. Here we theoretically propose a novel design of LiNbO_(3) ridge waveguides on LiTaO_(3) substrates which can be used for efficient and broadband second harmonic generation. Through group velocity engineering of the ridge waveguides, acceptance bandwidth over 20 nm with a high conversion efficiency of > 25%W^(-1)·cm^(-2) is achieved at telecom-band.展开更多
In attempts to fabricate thermally stable second-order nonlinear polymer thin films, we have investigated the second harmonic generation (SHG) from both nonlinear polymer and guest-host thin films. We have also invest...In attempts to fabricate thermally stable second-order nonlinear polymer thin films, we have investigated the second harmonic generation (SHG) from both nonlinear polymer and guest-host thin films. We have also investigated the role of capping on the SHG, temporal stability and relaxation of dipole alignment. Corona poling techniques were employed to orient the dopants into the noncentrosymmetric structure required to obtain the SHG. The effect of capping with a polymeric encapsulant below the glass transition temperature of the polymers on the unpoled and corona poled thin films was studied. Capping of the nonlinear polymer and guest host thin films have resulted in high SHG with good temporal stability. SHG signal falls drastically during the first 8 days after poling while no further significant decay in SHG signal was observed after about 33 days. Our investigations have identified the characteristics required for a good encapsulant on a non-con-ductive surface.展开更多
In this paper,we demonstrate efficient spontaneous quasi-phase matched(SQPM)second harmonic generation(SHG)in a microracetrack resonator on X-cut thin film lithium niobate.Our approach does not involve poling,but expl...In this paper,we demonstrate efficient spontaneous quasi-phase matched(SQPM)second harmonic generation(SHG)in a microracetrack resonator on X-cut thin film lithium niobate.Our approach does not involve poling,but exploits the anisotropy of the crystals to allow the phase-matching condition to be fulfilled spontaneously as the TE-polarized light circulates in a specifically designed racetrack resonator.In experiment,normalized on-chip conversion efficiencies of 1.01×10-4/W and 0.43×10-4/W are achieved by 37th-order and 111th-order SQPM,respectively.The configurable SQPM will benefit the application of nonlinear frequency conversion and quantum source generation in chip-scale integrated photonics compatible with standard CMOS fabrication processes.展开更多
Transition metal dichalcogenides(TMD)heterostructure is widely applied for second harmonic generation(SHG)and holds great promises for laser source,nonlinear switch,and optical logic gate.However,for atomically thin T...Transition metal dichalcogenides(TMD)heterostructure is widely applied for second harmonic generation(SHG)and holds great promises for laser source,nonlinear switch,and optical logic gate.However,for atomically thin TMD heterostructures,low SHG conversion efficiency would occur due to reduction of light-matter interaction length and lack of phase matching.Herein,we demonstrated a facile directional SHG amplifier formed by MoS2/WS2 monolayer heterostructures suspended on a holey SiO_(2)/Si substrate.The SHG enhancement factor reaches more than two orders of magnitude in a wide spectral range from 355 to 470 nm,and the radiation angle is reduced from 38°to 19°indicating higher coherence and better emission directionality.The giant SHG enhancement and directional emission are attributed to the great excitation and emission field concentration induced by a self-formed vertical Fabry-Pérot microcavity.Our discovery gives helpful insights for the development of two-dimensional(2D)nonlinear optical devices.展开更多
Two co-crystalline compounds containing telluric acid and iodate,namely AIO_(3)·H_(6)TeO_(6)(A=Rb^(+),NH_(4)^(+)),were investigated as potential nonlinear optical materials.They crystallize into isostructural and...Two co-crystalline compounds containing telluric acid and iodate,namely AIO_(3)·H_(6)TeO_(6)(A=Rb^(+),NH_(4)^(+)),were investigated as potential nonlinear optical materials.They crystallize into isostructural and consist of isolated[IO_(3)]group and[H_(6)TeO_(6)]molecule linked by hydrogen bonds and charge interactions of Rb^(+)/NH_(4)^(+).They show phase-matching second harmonic generation responses with moderate intensity of 1.2×KDP(Rb^(+))and 1.1×KDP(NH_(4)^(+)).They also possess large optical band gaps over 4.25 eV and can be easily grown from aqueous so-lutions.The local dipole moment calculations based on the structures of AIO_(3)·H_(6)TeO_(6)(A=K+,Rb^(+),NH_(4)^(+))series of compounds indicate that the change of A+cation in their structural frame causes a slight change in the arrangement directions of[IO_(3)]and[Te(OH)_(6)]groups,and further induces their SHG responses of different in-tensities at the macroscopic level.展开更多
Understanding the mechanisms and spatial correlations of crystallographic symmetry breaking in ferroelectric materials is essential to tuning their functional properties.While optical second harmonic generation(SHG)ha...Understanding the mechanisms and spatial correlations of crystallographic symmetry breaking in ferroelectric materials is essential to tuning their functional properties.While optical second harmonic generation(SHG)has long been utilized in ferroelectric studies,its capability for probing complex polar materials has yet to be fully realized.Here,we develop a SHG spectral imaging method implemented on a home-designed laser-scanning SHG microscope,and demonstrate its application for a model system of(K,Na)NbO3 single crystals.Supervised model fitting analysis produces comprehensive information about the polarization vector orientations and relative fractions of constituent domain variants as well as their thermal evolution across the polymorphic phase transitions.Multiple domains and phases are clearly delineated at different temperatures,suggesting the phase competitions in(K,Na)NbO3.Besides,we show that unsupervised matrix decomposition analysis can quickly and faithfully reveal domain configurations without a priori knowledge about specific material systems.The SHG spectral imaging method can be readily extended to other ferroelectric materials with potentials to be further enhanced.展开更多
This article proposed an angle measurement method based on second harmonic generation(SHG)using an artifcial neural network(ANN).The method comprises three sequential parts:SHG spectrum collection,data preprocessing,a...This article proposed an angle measurement method based on second harmonic generation(SHG)using an artifcial neural network(ANN).The method comprises three sequential parts:SHG spectrum collection,data preprocessing,and neural network training.First,the referenced angles and SHG spectrums are collected by the autocollimator and SHG-based angle sensor,respectively,for training.The mapping is learned by the trained ANN after completing the training process,which solves the inverse problem of obtaining the angle from the SHG spectrum.Then,the feasibility of the proposed method is verifed in multiple-peak Maker fringe and single-peak phase-matching areas,with an overall angle measurement range exceeding 20,000 arcseconds.The predicted angles by ANN are compared with the autocollimator to evaluate the measure-ment performance in all the angular ranges.Particularly,a sub-arcsecond level of accuracy and resolution is achieved in the phase-matching area.展开更多
Plasmonic nanoantennas provide unprecedented opportunities to concentrate light fields in subwavelength-sized volumes.By placing a nonlinear dielectric nanoparticle in such a hot spot,one can hope to take advantage of...Plasmonic nanoantennas provide unprecedented opportunities to concentrate light fields in subwavelength-sized volumes.By placing a nonlinear dielectric nanoparticle in such a hot spot,one can hope to take advantage of both the field enhancement provided by nanoantennas and the large,nonlinear optical susceptibility of dielectric nanoparticles.To test this concept,we combine gold gap nanoantennas with second-order,nonlinear zinc sulfide nanoparticles,and performsecond harmonic generation(SHG)spectroscopy on the combined hybrid dielectric/plasmonic nanoantennas as well as on the individual constituents.We find that SHG from the bare gold nanoantennas,even though it should be forbidden due tosymmetry reasons,is several orders ofmagnitude larger than that of the bare zinc sulfide nanoparticles.Even stronger second harmonic signals are generated by the hybrid dielectric/plasmonic nanoantennas.Control experiments with nanoantennas containing linear lanthanumfluoride nanoparticles reveal;however,that the increasedSHG efficiency of the hybrid dielectric/plasmonic nanoantennas does not depend on the nonlinear optical susceptibility of the dielectric nanoparticles but is an effect of the modification of the dielectric environment.The combination of a hybrid dielectric/plasmonic nanoantenna,which is only resonant for the incoming pump light field,with a second nanoantenna,which is resonant for the generated second harmonic light,allows for a further increase in the efficiency of SHG.As the second nanoantenna mediates the coupling of the second harmonic light to the far field,this double-resonant approach also provides us with control over the polarization of the generated light.展开更多
We report a method to tune the second harmonic generation(SHG) frequency of a metallic octamer by employing cylindrical vector beams as the excitation. Our method exploits the ability to spatially match the polarizati...We report a method to tune the second harmonic generation(SHG) frequency of a metallic octamer by employing cylindrical vector beams as the excitation. Our method exploits the ability to spatially match the polarization state of excitations with the fundamental target plasmonic modes, enabling flexible control of the SHG resonant frequency.It is found that SHG of the octamer is enhanced over a broad band(400 nm) by changing the excitation from the linearly polarized Gaussian beam to radially and azimuthally polarized beams. More strikingly, when subjected to an azimuthally polarized beam, the SHG intensity of the octamer becomes 30 times stronger than that for the linearly polarized beam even in the presence of Fano resonance.展开更多
Deep-ultraviolet(UV)nonlinear optical(NLO)crystals with excellent performances are of great importance in laser science and technology.However,to design and synthesize an ideal deep-UV NLO material with a balance betw...Deep-ultraviolet(UV)nonlinear optical(NLO)crystals with excellent performances are of great importance in laser science and technology.However,to design and synthesize an ideal deep-UV NLO material with a balance between second harmonic generation(SHG)response and UV cut-off edge is still a huge challenge.Herein,a new oxy-borate BaYOBO_(3)(BaYBO)was designed and synthesized by substituting Be^(2+)with Y^(3+)from Sr_(2)Be_(2)B_(2(O_(7).The BaYBO features a stable three-dimensional framework and satisfies the property balance between a large SHG response(~2.6×KH_(2)PO_(4)KDP))and a short UV cut-off edge(<190 nm)as a promising deep-UV NLO candidate.The study of structure-property relationship indicates that the large SHG response of BaYBO is mainly attributed to the coplanar arrangement and large number density of BO_(3 )triangles.These results demonstrate that substituting Be^(2+)with Y^(3+)cations is also a feasible strategy for developing new deep-UV NLO crystals.展开更多
Lithium niobate has received interest in nonlinear frequency conversion due to its wide transparency window,from ultraviolet to mid-infrared spectral regions,and large second-order nonlinear susceptibility.However,its...Lithium niobate has received interest in nonlinear frequency conversion due to its wide transparency window,from ultraviolet to mid-infrared spectral regions,and large second-order nonlinear susceptibility.However,its nanostructure is generally difficult to etch,resulting in low-Q resonance and lossy nanostructures for second harmonic generation.By applying the concept of bound states in the continuum,we performed theoretical and experimental investigations on high-Q resonant etchless thin-film lithium niobate with Si O_(2) nanostructures on top for highly efficient second harmonic generation.In the fabricated nanostructured devices,a resonance with a Q factor of 980 leads to the strong enhancement of second harmonic generation by over 1500 times compared with that in unpatterned lithium niobate thin film.Although the pump slightly deviates from central resonance,an absolute conversion efficiency of 6.87×10^(-7) can be achieved with the fundamental pump peak intensity of 44.65 MW/cm^(2),thus contributing to the normalized conversion efficiency of 1.54×10^(-5)cm^(2)/GW.Our work establishes an etchless lithium niobate device for various applications,such as integrated nonlinear nanophotonics,terahertz frequency generation,and quantum information processing.展开更多
Recently, nonlinear photonics has attracted considerable interest. Among the nonlinear effects, second harmonic generation(SHG) remains a hot research topic. The recent development of thin film lithium niobate(TFLN) t...Recently, nonlinear photonics has attracted considerable interest. Among the nonlinear effects, second harmonic generation(SHG) remains a hot research topic. The recent development of thin film lithium niobate(TFLN) technology has superior performances to the conventional counterparts. Herein, this review article reveals the recent progress of SHG based on TFLN and its integrated photonics. We mainly discuss and compare the different techniques of TFLN-based structures to boost the nonlinear performances assisted by localizing light in nanostructures and structured waveguides.Moreover, our conclusions and perspectives indicate that more efficient methods need to be further explored for higher SHG conversion efficiency on the TFLN platform.展开更多
We theoretically propose a hybrid lithium niobate(LN) thin-film waveguide that consists of an amorphous silicon stripe and etch-free z-cut LN for highly efficient wavelength conversion, circumventing the challenging e...We theoretically propose a hybrid lithium niobate(LN) thin-film waveguide that consists of an amorphous silicon stripe and etch-free z-cut LN for highly efficient wavelength conversion, circumventing the challenging etching on LN material.Profiting from the spatial symmetry breaking of the waveguide, the asymmetric hybrid modes can spontaneously achieve phase matching with small modal area and large spatial mode overlap, enabling enhanced second harmonic generation with a normalized conversion efficiency over 3900% W^(-1)· cm^(-2)(0.5-mm-long propagation distance). The choice of integrating silicon with LN alleviates the fabrication challenge, making the platform potentially compatible with silicon photonics.展开更多
The purpose of this study is to explore the second harmonic generation(SHG)of a high power Cosh-Gaussian beam in cold collisionless plasma.The ponderomotive force causes carrier redistribution from high field to low f...The purpose of this study is to explore the second harmonic generation(SHG)of a high power Cosh-Gaussian beam in cold collisionless plasma.The ponderomotive force causes carrier redistribution from high field to low field region in presence of a Cosh-Gaussian beam thereby producing density gradients in the transverse direction.The density gradients so produced the results in electron plasma wave(EPW)generation at the frequency of the input beam.The EPW interacts with the input beam resulting in the production of 2nd harmonics.WKB and paraxial approximations are employed for obtaining the 2nd order differential equation describing the behavior of the beam’s spot size against normalized distance.The impact of well-established laser-plasma parameters on the behavior of the beam’s spot size and SHG yield are also analyzed.The focusing behavior of the beam and SHG yield is enhanced with an increase in the density of plasma,the radius of the beam and the decentred parameter,and with a decrease in the intensity of the beam.The results of the current problem are really helpful for complete information of laser-plasma interaction physics.展开更多
Stimulus re s ponsive materials can provide a variety of desirable properties in one equipment unit,such as optoelectronic devices,data communications,actuators,memories,sensors and capacitors.However,it remains a lar...Stimulus re s ponsive materials can provide a variety of desirable properties in one equipment unit,such as optoelectronic devices,data communications,actuators,memories,sensors and capacitors.However,it remains a large challenge to design such stimulus responsive materials,especially functional materials having both dielectric switch and second harmonic generation(SHG).Here,a new stimuli-responsive switchable material [(CH_(3))_(3)N(CH_(2))_(2)Cl]_(2)]Mn(SCN)_(4)(H_(2)O)_(2)] was discovered as a potential secondharmonic generation(SHG) dielectric switch.It is worth noting that it has SHG characteristics before and after undergoing reversible high-temperature phase transitions.In this work,we successfully refined the tetramethylammonium cation to obtain a quasi-spherical cation,which is tetramethylchloroethylamine(TMCEM) cation.By substituting H with a halogen,the increased steric hindrance of the molecular makes energy barrier increased,resulting in the reversible high-temperature phase transition.At the same time,the interactions of quasi-spherical cations and [Mn(SCN)_(4)(H_(2)O)_(2)]^(2-) anions affect a noncentrosymmetric structure to induce the SHG effect.These findings provide a new approach to design novel functional switch materials.展开更多
We examine the profile of second harmonic generation(SHG)for GaAs/GaAlAs spherical quantum dots(QDs)of Woods-Saxon(WS)plus attractive inversely quadratic(AIQ)potential under the joint influence of additional factors(p...We examine the profile of second harmonic generation(SHG)for GaAs/GaAlAs spherical quantum dots(QDs)of Woods-Saxon(WS)plus attractive inversely quadratic(AIQ)potential under the joint influence of additional factors(pressure and temperature)and structural parameters(strengths and radius).The energies and wave functions in GaAs/GaAlAs spherical QDs under WS-AIQ limiting potential are calculated using the parametric Nikiforov-Uvarov(NU)method.Depending on the calculated energies and corresponding wave functions,the SHG coefficient is examined by the iterative procedure in the density matrix method for this system.Finally,the calculated results display that a strong SHG coefficient response,and red shift or blue shift energy can be acquired by adjusting parameters.展开更多
文摘Silica glasses doped with Bi2S3 microcystallite was prepared by the sol-gel process. Photoinduced second harmonic generation (SHG) was observed in the glass when it was irradiated with intense 1.06 μm and frequency doubled laser beams from a mode-locked Nd: YAG laser. It was found that the signal intensity increased with the irradiating time and approached a saturation gradually. The effect may be explained reasonably by the DC field model.
基金financial supports from the National Natural Science Foundation of China(Grant No.11604150)Fundamental Research Funds for the Central Universities of China(Grant No.ZYGX2020J010)M.Rahmani.acknowledges support from the UK Research and Innovation Future Leaders Fellowship(MR/T040513/1)。
文摘The emergence of two dimensional(2D)materials has opened new possibilities for exhibiting second harmonic genera-tion(SHG)at the nanoscale,due to their remarkable optical response related to stable excitons at room temperature.However,the ultimate atomic-scale interaction length with light makes the SHG of Transition Metal Dichalcogenides(TM-Ds)monolayers naturally weak.Here,we propose coupling a monolayer of TMDs with a photonic grating slab that works with doubly resonant bound states in the continuum(BIC).The BIC slabs are designed to exhibit a pair of BICs,reson-ant with both the fundamental wave(FW)and the second harmonic wave(SHW).Firstly,the spatial mode matching can be fulfilled by tilting FW's incident angle.We theoretically demonstrate that this strategy leads to more than four orders of magnitude enhancement of SHG efficiency than a sole monolayer of TMDs,under a pump light intensity of 0.1 GW/cm^(2).Moreover,we demonstrate that patterning the TMDs monolayer can further enhance the spatial overlap coefficient,which leads to an extra three orders of magnitude enhancement of SHG efficiency.These results demonstrate remarkable pos-sibilities for enhancing SHG with nonlinear 2D materials,opening many opportunities for chip-based light sources,nano-lasers,imaging,and biochemical sensing.
基金Project supported by the Taishan Scholars Youth Expert Program of Shandong Provincethe Qilu Young Scholar Program of Shandong University, China
文摘Carbon ion irradiation and precise diamond blade dicing are applied to fabricate Nd∶GdCOB ridge waveguides.The propagation properties of the fabricated Nd∶GdCOB waveguides are investigated through experiments and theoret-ical analysis.Micro-Raman analysis reveals that the Nd∶GdCOB crystal lattice expands during the irradiation process.Micro-second harmonic spectroscopic analysis suggests that the original nonlinear properties of the Nd∶GdCOB crystal are greatly enhanced within the waveguide volume.Under pulsed 1064 nm laser pumping,second harmonic generation(SHG)at 532 nm has been achieved in the fabricated waveguides.The maximum SHG conversion efficiencies are determined to be~8.32%·W^(-1) and~22.36%·W^(-1) for planar and ridge waveguides,respectively.
文摘Broadband nonlinear frequency conversions of optical waves are widely employed in multiple areas of optics and photonics. However, the broadening of conversion bandwidth is often at a cost of reduction in efficiency, which may induce a limitation on practical applications. Here we theoretically propose a novel design of LiNbO_(3) ridge waveguides on LiTaO_(3) substrates which can be used for efficient and broadband second harmonic generation. Through group velocity engineering of the ridge waveguides, acceptance bandwidth over 20 nm with a high conversion efficiency of > 25%W^(-1)·cm^(-2) is achieved at telecom-band.
文摘In attempts to fabricate thermally stable second-order nonlinear polymer thin films, we have investigated the second harmonic generation (SHG) from both nonlinear polymer and guest-host thin films. We have also investigated the role of capping on the SHG, temporal stability and relaxation of dipole alignment. Corona poling techniques were employed to orient the dopants into the noncentrosymmetric structure required to obtain the SHG. The effect of capping with a polymeric encapsulant below the glass transition temperature of the polymers on the unpoled and corona poled thin films was studied. Capping of the nonlinear polymer and guest host thin films have resulted in high SHG with good temporal stability. SHG signal falls drastically during the first 8 days after poling while no further significant decay in SHG signal was observed after about 33 days. Our investigations have identified the characteristics required for a good encapsulant on a non-con-ductive surface.
基金supported by the National Key R&D Program of China(Grant No.2019YFB2203501)National Natural Science Foundation of China(Grant Nos.12134009,and 91950107)+1 种基金Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01-ZX06)Shanghai Jiao Tong University(SJTU)(Grant No.21X010200828)。
文摘In this paper,we demonstrate efficient spontaneous quasi-phase matched(SQPM)second harmonic generation(SHG)in a microracetrack resonator on X-cut thin film lithium niobate.Our approach does not involve poling,but exploits the anisotropy of the crystals to allow the phase-matching condition to be fulfilled spontaneously as the TE-polarized light circulates in a specifically designed racetrack resonator.In experiment,normalized on-chip conversion efficiencies of 1.01×10-4/W and 0.43×10-4/W are achieved by 37th-order and 111th-order SQPM,respectively.The configurable SQPM will benefit the application of nonlinear frequency conversion and quantum source generation in chip-scale integrated photonics compatible with standard CMOS fabrication processes.
基金the National Natural Science Foundation of China(Nos.51991340,51991344,52072006,62022089,and 11874405)the Natural Science Foundation of Beijing Municipality(No.JQ21004)+2 种基金the National Key Research and Development Program of China(No.2019YFA0308000)Chongqing Outstanding Youth Fund(No.2021ZX0400005)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(No.XDB33000000).
文摘Transition metal dichalcogenides(TMD)heterostructure is widely applied for second harmonic generation(SHG)and holds great promises for laser source,nonlinear switch,and optical logic gate.However,for atomically thin TMD heterostructures,low SHG conversion efficiency would occur due to reduction of light-matter interaction length and lack of phase matching.Herein,we demonstrated a facile directional SHG amplifier formed by MoS2/WS2 monolayer heterostructures suspended on a holey SiO_(2)/Si substrate.The SHG enhancement factor reaches more than two orders of magnitude in a wide spectral range from 355 to 470 nm,and the radiation angle is reduced from 38°to 19°indicating higher coherence and better emission directionality.The giant SHG enhancement and directional emission are attributed to the great excitation and emission field concentration induced by a self-formed vertical Fabry-Pérot microcavity.Our discovery gives helpful insights for the development of two-dimensional(2D)nonlinear optical devices.
基金support from the National Natural Science Foundation of China(Grant No.22105046)the Natural Science Foundation of Guangxi Province(No.2022GXNSFBA035484)the Shanghai Pujiang Program(20PJ1412900).
文摘Two co-crystalline compounds containing telluric acid and iodate,namely AIO_(3)·H_(6)TeO_(6)(A=Rb^(+),NH_(4)^(+)),were investigated as potential nonlinear optical materials.They crystallize into isostructural and consist of isolated[IO_(3)]group and[H_(6)TeO_(6)]molecule linked by hydrogen bonds and charge interactions of Rb^(+)/NH_(4)^(+).They show phase-matching second harmonic generation responses with moderate intensity of 1.2×KDP(Rb^(+))and 1.1×KDP(NH_(4)^(+)).They also possess large optical band gaps over 4.25 eV and can be easily grown from aqueous so-lutions.The local dipole moment calculations based on the structures of AIO_(3)·H_(6)TeO_(6)(A=K+,Rb^(+),NH_(4)^(+))series of compounds indicate that the change of A+cation in their structural frame causes a slight change in the arrangement directions of[IO_(3)]and[Te(OH)_(6)]groups,and further induces their SHG responses of different in-tensities at the macroscopic level.
基金supported by National Natural Science Foundation of China(NSFC)under Grants No.52073155 and No.52150092the National Key Basic Research Program of China under Grant No.2020YFA0309100,and by the Project for Introduced Innovation Team in Jinan(2020GXRC037).
文摘Understanding the mechanisms and spatial correlations of crystallographic symmetry breaking in ferroelectric materials is essential to tuning their functional properties.While optical second harmonic generation(SHG)has long been utilized in ferroelectric studies,its capability for probing complex polar materials has yet to be fully realized.Here,we develop a SHG spectral imaging method implemented on a home-designed laser-scanning SHG microscope,and demonstrate its application for a model system of(K,Na)NbO3 single crystals.Supervised model fitting analysis produces comprehensive information about the polarization vector orientations and relative fractions of constituent domain variants as well as their thermal evolution across the polymorphic phase transitions.Multiple domains and phases are clearly delineated at different temperatures,suggesting the phase competitions in(K,Na)NbO3.Besides,we show that unsupervised matrix decomposition analysis can quickly and faithfully reveal domain configurations without a priori knowledge about specific material systems.The SHG spectral imaging method can be readily extended to other ferroelectric materials with potentials to be further enhanced.
基金supported by the Japan Society for the Promo-tion of Science(20H00211).
文摘This article proposed an angle measurement method based on second harmonic generation(SHG)using an artifcial neural network(ANN).The method comprises three sequential parts:SHG spectrum collection,data preprocessing,and neural network training.First,the referenced angles and SHG spectrums are collected by the autocollimator and SHG-based angle sensor,respectively,for training.The mapping is learned by the trained ANN after completing the training process,which solves the inverse problem of obtaining the angle from the SHG spectrum.Then,the feasibility of the proposed method is verifed in multiple-peak Maker fringe and single-peak phase-matching areas,with an overall angle measurement range exceeding 20,000 arcseconds.The predicted angles by ANN are compared with the autocollimator to evaluate the measure-ment performance in all the angular ranges.Particularly,a sub-arcsecond level of accuracy and resolution is achieved in the phase-matching area.
基金support from the Deutsche Forschungsgemeinschaft(SPP1391 and SFB TRR 142)。
文摘Plasmonic nanoantennas provide unprecedented opportunities to concentrate light fields in subwavelength-sized volumes.By placing a nonlinear dielectric nanoparticle in such a hot spot,one can hope to take advantage of both the field enhancement provided by nanoantennas and the large,nonlinear optical susceptibility of dielectric nanoparticles.To test this concept,we combine gold gap nanoantennas with second-order,nonlinear zinc sulfide nanoparticles,and performsecond harmonic generation(SHG)spectroscopy on the combined hybrid dielectric/plasmonic nanoantennas as well as on the individual constituents.We find that SHG from the bare gold nanoantennas,even though it should be forbidden due tosymmetry reasons,is several orders ofmagnitude larger than that of the bare zinc sulfide nanoparticles.Even stronger second harmonic signals are generated by the hybrid dielectric/plasmonic nanoantennas.Control experiments with nanoantennas containing linear lanthanumfluoride nanoparticles reveal;however,that the increasedSHG efficiency of the hybrid dielectric/plasmonic nanoantennas does not depend on the nonlinear optical susceptibility of the dielectric nanoparticles but is an effect of the modification of the dielectric environment.The combination of a hybrid dielectric/plasmonic nanoantenna,which is only resonant for the incoming pump light field,with a second nanoantenna,which is resonant for the generated second harmonic light,allows for a further increase in the efficiency of SHG.As the second nanoantenna mediates the coupling of the second harmonic light to the far field,this double-resonant approach also provides us with control over the polarization of the generated light.
基金National Key R&D Program of China(2017YFA0303800)National Natural Science Foundation of China(NSFC)(11634010,51777168,61377035,61675170,61675171,61701303)+4 种基金Australian Research Council(ARC)(DP140100883)Natural Science Basic Research Plan in Shaanxi Province,China(2017JM6022)Fundamental Research Funds for the Central Universities,China(3102017zy017)Natural Science Foundation of Shanghai,China(17ZR1414300)Shanghai Pujiang Program,China(17PJ1404100)
文摘We report a method to tune the second harmonic generation(SHG) frequency of a metallic octamer by employing cylindrical vector beams as the excitation. Our method exploits the ability to spatially match the polarization state of excitations with the fundamental target plasmonic modes, enabling flexible control of the SHG resonant frequency.It is found that SHG of the octamer is enhanced over a broad band(400 nm) by changing the excitation from the linearly polarized Gaussian beam to radially and azimuthally polarized beams. More strikingly, when subjected to an azimuthally polarized beam, the SHG intensity of the octamer becomes 30 times stronger than that for the linearly polarized beam even in the presence of Fano resonance.
基金supported by the National Natural Science Foundation of China(51972230,22071179,51890864,61835014,51802217,51890865)the Natural Science Foundation of Tianjin(20JCJQJC00060,19JCZDJC38200)+1 种基金Tianjin Science and Technology Plan Program(19ZYPTJC00070)the National Key R&D Program of China(2016YFB0402103)。
文摘Deep-ultraviolet(UV)nonlinear optical(NLO)crystals with excellent performances are of great importance in laser science and technology.However,to design and synthesize an ideal deep-UV NLO material with a balance between second harmonic generation(SHG)response and UV cut-off edge is still a huge challenge.Herein,a new oxy-borate BaYOBO_(3)(BaYBO)was designed and synthesized by substituting Be^(2+)with Y^(3+)from Sr_(2)Be_(2)B_(2(O_(7).The BaYBO features a stable three-dimensional framework and satisfies the property balance between a large SHG response(~2.6×KH_(2)PO_(4)KDP))and a short UV cut-off edge(<190 nm)as a promising deep-UV NLO candidate.The study of structure-property relationship indicates that the large SHG response of BaYBO is mainly attributed to the coplanar arrangement and large number density of BO_(3 )triangles.These results demonstrate that substituting Be^(2+)with Y^(3+)cations is also a feasible strategy for developing new deep-UV NLO crystals.
基金supported by the National Natural Science Foundation of China (Grant Nos. 61775084, and 62075088)the National Safety Academic Fund (Grant No. U2030103)+2 种基金the Natural Science Foundation of Guangdong Province (Grant Nos. 2020A1515010791, and 2021A0505030036)the Open Fund of Guangdong Provincial Key Laboratory of Information Photonics Technology of Guangdong University of Technology (Grant No. GKPT20-03)the Fundamental Research Funds for the Central Universities (Grant Nos. 21622107, and 21622403)。
文摘Lithium niobate has received interest in nonlinear frequency conversion due to its wide transparency window,from ultraviolet to mid-infrared spectral regions,and large second-order nonlinear susceptibility.However,its nanostructure is generally difficult to etch,resulting in low-Q resonance and lossy nanostructures for second harmonic generation.By applying the concept of bound states in the continuum,we performed theoretical and experimental investigations on high-Q resonant etchless thin-film lithium niobate with Si O_(2) nanostructures on top for highly efficient second harmonic generation.In the fabricated nanostructured devices,a resonance with a Q factor of 980 leads to the strong enhancement of second harmonic generation by over 1500 times compared with that in unpatterned lithium niobate thin film.Although the pump slightly deviates from central resonance,an absolute conversion efficiency of 6.87×10^(-7) can be achieved with the fundamental pump peak intensity of 44.65 MW/cm^(2),thus contributing to the normalized conversion efficiency of 1.54×10^(-5)cm^(2)/GW.Our work establishes an etchless lithium niobate device for various applications,such as integrated nonlinear nanophotonics,terahertz frequency generation,and quantum information processing.
基金supported by the National Natural Science Foundation of China(Nos.61775084,61705089,61705087,62075088,and 61505069)NSAF(No.U2030103)+3 种基金Guangdong Special Support Program(No.2016TQ03X962)Natural Science Foundation of Guangdong Province(Nos.2021A0505030036,2020A151501791,and 2021A1515011875)Open Fund of Guangdong Provincial Key Laboratory of Information PhotonicsTechnologyofGuangdongUniversityof Technology(No.GKPT20-03)Fundamental Research Funds for the Central Universities(No.11620444)。
文摘Recently, nonlinear photonics has attracted considerable interest. Among the nonlinear effects, second harmonic generation(SHG) remains a hot research topic. The recent development of thin film lithium niobate(TFLN) technology has superior performances to the conventional counterparts. Herein, this review article reveals the recent progress of SHG based on TFLN and its integrated photonics. We mainly discuss and compare the different techniques of TFLN-based structures to boost the nonlinear performances assisted by localizing light in nanostructures and structured waveguides.Moreover, our conclusions and perspectives indicate that more efficient methods need to be further explored for higher SHG conversion efficiency on the TFLN platform.
基金supported by the National Key R&D Program of China(No.2017YFA0303701)the National Natural Science Foundation of China(Nos.11674167,91850204,and 11621091)Dengfeng Project B of Nanjing University for the support。
文摘We theoretically propose a hybrid lithium niobate(LN) thin-film waveguide that consists of an amorphous silicon stripe and etch-free z-cut LN for highly efficient wavelength conversion, circumventing the challenging etching on LN material.Profiting from the spatial symmetry breaking of the waveguide, the asymmetric hybrid modes can spontaneously achieve phase matching with small modal area and large spatial mode overlap, enabling enhanced second harmonic generation with a normalized conversion efficiency over 3900% W^(-1)· cm^(-2)(0.5-mm-long propagation distance). The choice of integrating silicon with LN alleviates the fabrication challenge, making the platform potentially compatible with silicon photonics.
文摘The purpose of this study is to explore the second harmonic generation(SHG)of a high power Cosh-Gaussian beam in cold collisionless plasma.The ponderomotive force causes carrier redistribution from high field to low field region in presence of a Cosh-Gaussian beam thereby producing density gradients in the transverse direction.The density gradients so produced the results in electron plasma wave(EPW)generation at the frequency of the input beam.The EPW interacts with the input beam resulting in the production of 2nd harmonics.WKB and paraxial approximations are employed for obtaining the 2nd order differential equation describing the behavior of the beam’s spot size against normalized distance.The impact of well-established laser-plasma parameters on the behavior of the beam’s spot size and SHG yield are also analyzed.The focusing behavior of the beam and SHG yield is enhanced with an increase in the density of plasma,the radius of the beam and the decentred parameter,and with a decrease in the intensity of the beam.The results of the current problem are really helpful for complete information of laser-plasma interaction physics.
基金supported by the National Natural Science Foundation of China(Nos.21673038,21771037,21805033)Natural Science Foundation of Jiangsu Province(JSNSF,No.BK20170659)。
文摘Stimulus re s ponsive materials can provide a variety of desirable properties in one equipment unit,such as optoelectronic devices,data communications,actuators,memories,sensors and capacitors.However,it remains a large challenge to design such stimulus responsive materials,especially functional materials having both dielectric switch and second harmonic generation(SHG).Here,a new stimuli-responsive switchable material [(CH_(3))_(3)N(CH_(2))_(2)Cl]_(2)]Mn(SCN)_(4)(H_(2)O)_(2)] was discovered as a potential secondharmonic generation(SHG) dielectric switch.It is worth noting that it has SHG characteristics before and after undergoing reversible high-temperature phase transitions.In this work,we successfully refined the tetramethylammonium cation to obtain a quasi-spherical cation,which is tetramethylchloroethylamine(TMCEM) cation.By substituting H with a halogen,the increased steric hindrance of the molecular makes energy barrier increased,resulting in the reversible high-temperature phase transition.At the same time,the interactions of quasi-spherical cations and [Mn(SCN)_(4)(H_(2)O)_(2)]^(2-) anions affect a noncentrosymmetric structure to induce the SHG effect.These findings provide a new approach to design novel functional switch materials.
基金the National Natural Science Foundation of China(Grant Nos.51702003,61775087,11674312,52174161 and 12174161)the Provincial Foundation for Excellent Top Talents of Colleges and Universities of Anhui Province of China(Grant No.gxgwfx2019016)+1 种基金the Anhui Provincial Natural Science Foundation,China(Grant Nos.1808085ME130 and 1508085QF140)University Outstanding Young Talents Support Program Fund(Grant No.gxyqZ D2018039)。
文摘We examine the profile of second harmonic generation(SHG)for GaAs/GaAlAs spherical quantum dots(QDs)of Woods-Saxon(WS)plus attractive inversely quadratic(AIQ)potential under the joint influence of additional factors(pressure and temperature)and structural parameters(strengths and radius).The energies and wave functions in GaAs/GaAlAs spherical QDs under WS-AIQ limiting potential are calculated using the parametric Nikiforov-Uvarov(NU)method.Depending on the calculated energies and corresponding wave functions,the SHG coefficient is examined by the iterative procedure in the density matrix method for this system.Finally,the calculated results display that a strong SHG coefficient response,and red shift or blue shift energy can be acquired by adjusting parameters.
