Phase-matching quantum key distribution is a promising scheme for remote quantum key distribution,breaking through the traditional linear key-rate bound.In practical applications,finite data size can cause significant...Phase-matching quantum key distribution is a promising scheme for remote quantum key distribution,breaking through the traditional linear key-rate bound.In practical applications,finite data size can cause significant system performance to deteriorate when data size is below 1010.In this work,an improved statistical fluctuation analysis method is applied for the first time to two decoy-states phase-matching quantum key distribution,offering a new insight and potential solutions for improving the key generation rate and the maximum transmission distance while maintaining security.Moreover,we also compare the influence of the proposed improved statistical fluctuation analysis method on system performance with those of the Gaussian approximation and Chernoff-Hoeffding boundary methods on system performance.The simulation results show that the proposed scheme significantly improves the key generation rate and maximum transmission distance in comparison with the Chernoff-Hoeffding approach,and approach the results obtained when the Gaussian approximation is employed.At the same time,the proposed scheme retains the same security level as the Chernoff-Hoeffding method,and is even more secure than the Gaussian approximation.展开更多
A novel method for designing chalcogenide long-period fiber grating(LPFG) sensors based on the dual-peak resonance effect of the LPFG near the phase matching turning point(PMTP) is presented. Refractive index sensing ...A novel method for designing chalcogenide long-period fiber grating(LPFG) sensors based on the dual-peak resonance effect of the LPFG near the phase matching turning point(PMTP) is presented. Refractive index sensing in a high-refractive-index chalcogenide fiber is achieved with a coated thinly clad film. The dual-peak resonant characteristics near the PMTP and the refractive index sensing properties of the LPFG are analyzed first by the phase-matching condition of the LPFG. The effects of film parameters and cladding radius on the sensitivity of refractive index sensing are further discussed. The sensor is optimized by selecting the appropriate film parameters and cladding radius. Simulation results show that the ambient refractive index sensitivity of a dual-peak coated thinly clad chalcogenide LPFG at the PMTP can be 2400 nm/RIU, which is significantly higher than that of non-optimized gratings. It has great application potential in the field of chemical sensing and biosensors.展开更多
Four-wave mixing induced by modulation instability in a single-mode fiber is analyzed from the phase-matching point of view. For the two-channel transmission, a method is proposed to select the four-wave-mixing-induce...Four-wave mixing induced by modulation instability in a single-mode fiber is analyzed from the phase-matching point of view. For the two-channel transmission, a method is proposed to select the four-wave-mixing-induced sidebands, which is based on the proper use of a continuous-wave and a pulse as light sources. We find that a mass of sidebands are generated in the modulation instability resonance region, and the power of the sideband increases with not only the peak power of the pump pulse but also the continuous-wave power which acts as a seed. The research will provide guidance for fiber communication and sensing systems using wavelength division multiplexing technology.展开更多
We theoretically investigate the frequency-nondegenerate and frequency degenerate squeezed lights with a four-wave mixing process(4WM)driven by two pump fields crossing at a small angle.Different from a 4WM process dr...We theoretically investigate the frequency-nondegenerate and frequency degenerate squeezed lights with a four-wave mixing process(4WM)driven by two pump fields crossing at a small angle.Different from a 4WM process driven by a single pump field,the refractive index of the corresponding probe field,np,can be converted to a value that is greater than 1 or less than 1 by an angle adjustment.In the new region with np<1,the bandwidth of the gain is relatively large due to the slow change in the refractive index with the two-photon detuning.In this region with an exchange of the roles of the pump and probe beams,the frequency degenerate and spatial nondegenerate twin beams can be generated,which has potential application in quantum information and quantum metrology.展开更多
In bistaic acoustic testing, there will be strong direct blast interference. An algorithm based on signal phase-matching array processing that rejects direct blast interference in bistatic acoustic testing has been st...In bistaic acoustic testing, there will be strong direct blast interference. An algorithm based on signal phase-matching array processing that rejects direct blast interference in bistatic acoustic testing has been studied, through which the object scattering signal is accurately extracted. Characteristics of bistatic acoustic testing and signal phase matching processing principle are fully integrated in this algorithm. Firstly, the direct blast interference is calculated from the receiving signal based on three subarrays signal phase matching processing. Secondly, the direct blast is rejected by subtraction from the receiving signal. In this way the limitations of the high signal to noise ratio that signal phase matching processing required for direct calculating the object scattering signal can be avoided. Simulation and sea trial results show that, when the ratio of signal to interference is greater than -20 dB, this algorithm of direct blast interference rejection based phase matching signal processing can accurately extract the object scattering signal.展开更多
In high harmonic generation(HHG),Laguerre–Gaussian(LG) beams are used to generate extreme ultraviolet(XUV)vortices with well-defined orbital angular momentum(OAM),which have potential applications in fields such as m...In high harmonic generation(HHG),Laguerre–Gaussian(LG) beams are used to generate extreme ultraviolet(XUV)vortices with well-defined orbital angular momentum(OAM),which have potential applications in fields such as microscopy and spectroscopy.An experimental study on the HHG driven by vortex and Gaussian beams is conducted in this work.It is found that the intensity of vortex harmonics is positively correlated with the laser energy and gas pressure.The structure and intensity distribution of the vortex harmonics exhibit significant dependence on the relative position between the gas jet and the laser focus.The ring-like structures observed in the vortex harmonics,and the interference of quantum paths provide an explanation for the distinct structural characteristics.Moreover,by adjusting the relative position between the jet and laser focus,it is possible to discern the contributions from different quantum paths.The optimization of the HH vortex field is applicable to the XUV,which opens up a new way for exploiting the potential in optical spin or manipulating electrons by using the photon with tunable orbital angular momentum.展开更多
The angular spectrum gain characters and the power magnification characters of high gain non-walk-off colinear optical parametric oscillators have been studied using the non-colinear phase match method for the first t...The angular spectrum gain characters and the power magnification characters of high gain non-walk-off colinear optical parametric oscillators have been studied using the non-colinear phase match method for the first time. The experimental results of the KTiOAs04 and the KTiOP04 crystals are discussed in detail. At the high energy single resonant condition, low reflective ratio of the output mirror for the signal and long non-linear crystal are beneficial for small divergence angles. This method can also be used for other high gain non-walk-off phase match optical parametric orocesses.展开更多
Combined with the optical beam deflection,a novel approach of phase matched broadband scanning optical parametric chirped pulse amplification(OPCPA)was proposed.For this scheme,there was no superfluous operations to t...Combined with the optical beam deflection,a novel approach of phase matched broadband scanning optical parametric chirped pulse amplification(OPCPA)was proposed.For this scheme,there was no superfluous operations to the chirped signal pulse which propagated in a changeless direction straightforward,but the pump beam were deflected in space with time by passing through a KTN crystal,which was applied with varied driving voltage.The theories of phase matching of each chirped signal frequency based on pump beam deflection was analyzed detailedly.And the type-I amplification of chirped signal with 800 nm central wavelength and 20 nm bandwidth pumped by 532 nm in BBO crystal was simulated as a case in point.The simulation results showed that the spectral distribution of chirped signal pulse was almost the same as the initial form,i.e.,there was nearly no narrowing on the amplified spectrum by using of the scanning OPCPA based on pump beam deflection.In addition,the simulations demonstrated that it was worth minimizing the voltage deviation applied to KTN crystal as much as possible for the sake of better waveform,larger bandwidth and higher conversion efficiency of amplified signal pulse in the proposed scanning OPCPA.展开更多
Here we propose a hybrid polymer-LN waveguide for achieving phase-matched second-harmonic generation(SHG).From the aspect of super-mode theory,the geometric parameters of the hybrid semi-nonlinear waveguide were optim...Here we propose a hybrid polymer-LN waveguide for achieving phase-matched second-harmonic generation(SHG).From the aspect of super-mode theory,the geometric parameters of the hybrid semi-nonlinear waveguide were optimized to utilize both symmetric(even)and antisymmetric(odd)modes of the pump and SHG waves so as to facilitate phase matching with large modal overlap.Phase matching between a fundamental even(TE_(00)-like)mode at 1320 nm and a fundamental odd(TE_(01)-like)mode at 660 nm was found with a calculated modal overlap integral of 0.299,while utilizing the largest nonlinear coefficient d_(33),and achieving an efficient calculated normalized conversion efficiency of 148%W^(-1)·cm^(-2).Considering the fabrication feasibility of such hybrid waveguide with features including etchless,large dimension,and low structural sensitivity,we believe our findings would provide a useful reference for future on-chip efficient nonlinear conversion devices.展开更多
Red,blue and green visible lasers are more attractive with the development of the science and technology.Self frequency doubling is an important approach to realize visible lasers.For self frequency doubling,the basic...Red,blue and green visible lasers are more attractive with the development of the science and technology.Self frequency doubling is an important approach to realize visible lasers.For self frequency doubling,the basic requests are high figure of merit(FOM),high damage threshold,good chemical stability and mechanical properties.Perfection and growth characters are also important for a practical SFD crystal. In recent years,the discovery of rare earth calcium oxyborates has resulted in the renewal in the field of SFD crystal.ReCaO(BO 3) 3(ReCOB)is a new type of novel nonlinear optical crystals which is nearly congruently melt and can be grown with Czochralski method.ReCOB crystals possess high nonlinear coefficients and damage thresholds.They are non hydroscopic and easy cutting and polishing.They belong to monoclinic with point group m and space group cm.The strong anisotropy originated from the low symmetry makes the measurement and application of the crystal more complicated.More than half of naturally existed crystals belongs to low symmetry,consequently,the research on the nonlinear and anisotropic laser optical properties are not only important for ReCOB crystal,but also useful for the applications of other low symmetry crystals.展开更多
We report a pulsed surface-emitted THz-wave parametric oscillator based on two MgO:LiNbO3 crystals pumped by a multi-longitudinal mode Q-switched Nd:YAG laser. Through varying the phase matching angle, the tunable T...We report a pulsed surface-emitted THz-wave parametric oscillator based on two MgO:LiNbO3 crystals pumped by a multi-longitudinal mode Q-switched Nd:YAG laser. Through varying the phase matching angle, the tunable THzwave output from 0.79 THz to 2.84 THz is realized. The maximum THz-wave output was 193.2 n J/pulse at 1.84 THz as the pump power density was 212.5 MW/cm2, corresponding to the energy conversion efficiency of 2.42Х10-6 and the photon conversion efficiency of about 0.037%. When the pump power density changed from 123 MW/cm^2 to 148 MW/cm^2 and 164 MW/cm^2, the maximum output of the THz-wave moved to the high frequency band. We give a reasonable explanation for this phenomenon.展开更多
Due to the fact that traditional ray field tracking approaches require a large number of geometrical optical(GO) ray tubes,they are very inefficient in many practical applications.An improved ray model scheme for a ...Due to the fact that traditional ray field tracking approaches require a large number of geometrical optical(GO) ray tubes,they are very inefficient in many practical applications.An improved ray model scheme for a complex source beam(CSB) tracking technique is proposed in this paper.The source field can be expressed by a superposition of CSBs,then every CSB basis function has a Gaussian-type amplitude distribution and is suitable for replacing a GO ray tube in the ray tracing approach.The complex phase matching technique is adopted to find the reflected beam in the reflection point where local approximation is used to represent the curved surface in its neighborhood.A new solution to multiple reflections using the conventional right-handed reflected system is used to track the field easily.Numerical results show the accuracy of the proposed method.展开更多
Within the second-order perturbation approximation, this paper investigates the physical process of generation of the time-domain second harmonic by a primary Lamb wave waveform in an elastic plate. The present work i...Within the second-order perturbation approximation, this paper investigates the physical process of generation of the time-domain second harmonic by a primary Lamb wave waveform in an elastic plate. The present work is performed based on the preconditions that the phase velocity matching is satisfied and that the transfer of energy from the primary Lamb wave to the double frequency Lamb wave is not zero. It investigates the influences of the difference between the group velocities of the primary Lamb wave and the double frequency Lamb wave, the propagation distance and the duration of the primary Lamb wave waveform on the envelope shape of the time-domain second harmonic. It finds that the maximum magnitude of the envelope of the second-harmonic waveform can grow within some propagation distance even if the condition of group velocity matching is not satisfied. Our analyses also indicate that the maximum magnitude of the envelope of the second-harmonic waveform is kept constant beyond a specific propagation distance. Furthermore, it concludes that the integration amplitude of the time-domain second-harmonic waveform always grows with propagation distance within the second-order perturbation. The present research yields new physical insight not previously available into the effect of generation of the time-domain second harmonic by propagation of a primary Lamb wave waveform.展开更多
Based on the second-order nonlinearity, we present a bidirectional tunable all-optical switch at C-band by introducing backward quasi-phase-matching technique in Mg-doped periodically poled lithium niobate (MgO:PPLN...Based on the second-order nonlinearity, we present a bidirectional tunable all-optical switch at C-band by introducing backward quasi-phase-matching technique in Mg-doped periodically poled lithium niobate (MgO:PPLN) waveguide with a nano-structure called multiple resonators. Two injecting forward lights and one backward propagating light interact with difference frequency generations. The transmission of forward signal and backward idler light can be modulated simultaneously with the variation of control light power based on the basic "phase shift" structure of a single resonator. In this scheme, all the results come from our simulation. The speed of this bidirectional optical switch can reach to femtosecond if a femtosecond laser is used as the control light.展开更多
An efficient widely tunable terahertz(THz)-wave parametric oscillator (TPO) has been designed based on the basic principle of optical parametric oscillator. The design of TPO comprises the theoretical calculations...An efficient widely tunable terahertz(THz)-wave parametric oscillator (TPO) has been designed based on the basic principle of optical parametric oscillator. The design of TPO comprises the theoretical calculations for wavelength dependent refractive index dependent wavelength when the frequency is in the far infrared region, the low-loss parametric gain has been discussed as a same form as the parametric gain in the optical region, realized the non-collinear phase-matching conditions of the terahertz optical parametric oscillator and structure of lithium niobate (LiNbO3) for TPO. The tunable spectrum range of terahertz-wave has been achieved. To increase THz output, a cut exit was made at the comer of the LiNbO3 crystal.展开更多
Large nonlinear optical(NLO)coefficient(d_(ij)),high laser damage threshold(LDT),and phase matching(PM)are crucial for the practical applications of IR NLO crystals.A great number of IR NLO materials with high dij hav...Large nonlinear optical(NLO)coefficient(d_(ij)),high laser damage threshold(LDT),and phase matching(PM)are crucial for the practical applications of IR NLO crystals.A great number of IR NLO materials with high dij have been explored,but many of them suffer from non-PM,which dramatically decreases their ultimate NLO output efficiencies.To settle this problem,we have developed a new strategy involving modulating normal dispersion via bandgap(E_(g))widening to achieve PM in this work.We synthesized successfully three new wide E_(g)(∼4.0 eV)IR NLO salt-inclusion sulfides[ABa_(3)Cl_(2)][Ga_(5)S_(10)](A=K,1;Rb,2;and Cs,3)with PM behaviors,mainly ascribed to the PM cut-off wavelength blue shift that originated from the wide Eg values,with less contribution from birefringence enhancement.All the compounds possessed large second-harmonic-generation(SHG)efficiency(∼1×AgGaS_(2))and hitherto the highest LDTs(188–200 MW/cm^(2),at 1.06μm,10 ns pulse width)for known chalcogenides with SHG efficiencies comparable to that of commercial silver gallium sulfide(AgGaS_(2))crystal.展开更多
Phase mismatching for third-harmonic generation(THG) in barium metaborate(BBO) crystal is investigated in detail.Upon using BBO crystal in the TypeⅠ(oo→e) scheme,in the two independent planes (principal secti...Phase mismatching for third-harmonic generation(THG) in barium metaborate(BBO) crystal is investigated in detail.Upon using BBO crystal in the TypeⅠ(oo→e) scheme,in the two independent planes (principal section of the crystal and the plane normal to principal section),when the input second-harmonic beam deviates from the expected direction,phase mismatching occurs and the angle deviation produces different effects on the conversion efficiency.We numerically simulate these two cases of phase mismatching and identify the relation between the conversion efficiency and the deviation angle in the air.The computational results indicate that the phase matching tolerance in the principal section is 0.2°(in the air),while the phase matching tolerance in the plane normal to principal section is 4.5°(in the air).After conducting a lab experiment,the results agree perfectly with the computational results,indicating that the deviation angle in the principal section has a greater effect on the conversion efficiency.展开更多
By optimizing the phase matching condition of high harmonic generation (HHG) from a supersonic neon gas jet, the enhanced HHG in the region of 60-70 eV has been selected. Three-dimensional numerical calculation show...By optimizing the phase matching condition of high harmonic generation (HHG) from a supersonic neon gas jet, the enhanced HHG in the region of 60-70 eV has been selected. Three-dimensional numerical calculation shows that plasma plays a significant role in the phase matching process of HHG in a supersonic gas jet with short medium length. Due to plasma formation, the harmonic emission decays as the laser intensity reaches over 3.5 ~ 1014 W/cm^2. The plasma induces the broadening and blue shift of the HHG spectra, which provides a method for fine-tuning the harmonic wavelength.展开更多
Refractive indices for crystals ammonium dihydrogen phosphate (ADP), 30% deuterated ADP (DADP), 50% DADP, and 70% DADP are measured from 253 to 1529 nm with 5 × 10^-6 accuracy. Numerical fits to modified doub...Refractive indices for crystals ammonium dihydrogen phosphate (ADP), 30% deuterated ADP (DADP), 50% DADP, and 70% DADP are measured from 253 to 1529 nm with 5 × 10^-6 accuracy. Numerical fits to modified double-pole Sellmeier equation are made. Second-harmonic generation, third-harmonic generation phase match- ing (PM) angles, and noncritical PM (NCPM) wavelengths are calculated using the Sellmeier parameters. The deuterated crystals show smaller PM angles than pure crystal. Fourth-harmonic generation process can be real- ized by DADP in smaller deuterium content than deuterated potassium dihydrogen phosphate (DKDP). The measured NCPM wavelengths are consistent with the calculated value. PM characteristics are compared between DADP and DKDP.展开更多
The noncollinear optical parametric amplification in BBO crystal is theoretically investigated. The phase matching angle, gain bandwidth, optimal noncollinear angle and conversion efficiency for both type-I and type-I...The noncollinear optical parametric amplification in BBO crystal is theoretically investigated. The phase matching angle, gain bandwidth, optimal noncollinear angle and conversion efficiency for both type-I and type-II BBO are simulated. The numerical simulation results are important to the practical optical parametric amplification experiments with BBO crystal.展开更多
文摘Phase-matching quantum key distribution is a promising scheme for remote quantum key distribution,breaking through the traditional linear key-rate bound.In practical applications,finite data size can cause significant system performance to deteriorate when data size is below 1010.In this work,an improved statistical fluctuation analysis method is applied for the first time to two decoy-states phase-matching quantum key distribution,offering a new insight and potential solutions for improving the key generation rate and the maximum transmission distance while maintaining security.Moreover,we also compare the influence of the proposed improved statistical fluctuation analysis method on system performance with those of the Gaussian approximation and Chernoff-Hoeffding boundary methods on system performance.The simulation results show that the proposed scheme significantly improves the key generation rate and maximum transmission distance in comparison with the Chernoff-Hoeffding approach,and approach the results obtained when the Gaussian approximation is employed.At the same time,the proposed scheme retains the same security level as the Chernoff-Hoeffding method,and is even more secure than the Gaussian approximation.
基金Project supported by the Natural Science Foundation of China (Grant Nos.62075107,61935006,62090064,and62090065)K.C.Wong Magna Fund in Ningbo University。
文摘A novel method for designing chalcogenide long-period fiber grating(LPFG) sensors based on the dual-peak resonance effect of the LPFG near the phase matching turning point(PMTP) is presented. Refractive index sensing in a high-refractive-index chalcogenide fiber is achieved with a coated thinly clad film. The dual-peak resonant characteristics near the PMTP and the refractive index sensing properties of the LPFG are analyzed first by the phase-matching condition of the LPFG. The effects of film parameters and cladding radius on the sensitivity of refractive index sensing are further discussed. The sensor is optimized by selecting the appropriate film parameters and cladding radius. Simulation results show that the ambient refractive index sensitivity of a dual-peak coated thinly clad chalcogenide LPFG at the PMTP can be 2400 nm/RIU, which is significantly higher than that of non-optimized gratings. It has great application potential in the field of chemical sensing and biosensors.
基金Project supported by the National Natural Science Foundation of China (Grant No. 61177073)the Specialized Research Fundfor the Doctoral Program of Higher Education of China (Grant No.20104307110020)+1 种基金the Fund of Innovation of Graduate School of National University of Defense Technology, China (Grant No.B110703)the Hunan Provincial Innovation Foundation for Postgraduate, China (Grant No. CX2011B033)
文摘Four-wave mixing induced by modulation instability in a single-mode fiber is analyzed from the phase-matching point of view. For the two-channel transmission, a method is proposed to select the four-wave-mixing-induced sidebands, which is based on the proper use of a continuous-wave and a pulse as light sources. We find that a mass of sidebands are generated in the modulation instability resonance region, and the power of the sideband increases with not only the peak power of the pump pulse but also the continuous-wave power which acts as a seed. The research will provide guidance for fiber communication and sensing systems using wavelength division multiplexing technology.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11974111,11474095,11874152,11604069,91536114,11654005,and 11234003)the Fundamental Research Funds for the Central Universities,China,the Science Foundation of Shanghai,China(Grant No.17ZR1442800)the National Key Research and Development Program of China(Grant No.2016YFA0302001).
文摘We theoretically investigate the frequency-nondegenerate and frequency degenerate squeezed lights with a four-wave mixing process(4WM)driven by two pump fields crossing at a small angle.Different from a 4WM process driven by a single pump field,the refractive index of the corresponding probe field,np,can be converted to a value that is greater than 1 or less than 1 by an angle adjustment.In the new region with np<1,the bandwidth of the gain is relatively large due to the slow change in the refractive index with the two-photon detuning.In this region with an exchange of the roles of the pump and probe beams,the frequency degenerate and spatial nondegenerate twin beams can be generated,which has potential application in quantum information and quantum metrology.
基金supported by the Foundation of Key Laboratory for Underwater Test & Control Technology under Grant No.9140C260201110C26
文摘In bistaic acoustic testing, there will be strong direct blast interference. An algorithm based on signal phase-matching array processing that rejects direct blast interference in bistatic acoustic testing has been studied, through which the object scattering signal is accurately extracted. Characteristics of bistatic acoustic testing and signal phase matching processing principle are fully integrated in this algorithm. Firstly, the direct blast interference is calculated from the receiving signal based on three subarrays signal phase matching processing. Secondly, the direct blast is rejected by subtraction from the receiving signal. In this way the limitations of the high signal to noise ratio that signal phase matching processing required for direct calculating the object scattering signal can be avoided. Simulation and sea trial results show that, when the ratio of signal to interference is greater than -20 dB, this algorithm of direct blast interference rejection based phase matching signal processing can accurately extract the object scattering signal.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11974137,92250306,and 12304302)the National Key Program for Science and Technology Research and Development(Grant No.2019YFA0307700)+1 种基金the Natural Science Foundation of Jilin Province,China(Grant Nos.YDZJ202101ZYTS157 and YDZJ202201ZYTS314)the Scientific Research Foundation of Jilin Provincial Education Department,China(Grant No.JJKH20230283KJ)。
文摘In high harmonic generation(HHG),Laguerre–Gaussian(LG) beams are used to generate extreme ultraviolet(XUV)vortices with well-defined orbital angular momentum(OAM),which have potential applications in fields such as microscopy and spectroscopy.An experimental study on the HHG driven by vortex and Gaussian beams is conducted in this work.It is found that the intensity of vortex harmonics is positively correlated with the laser energy and gas pressure.The structure and intensity distribution of the vortex harmonics exhibit significant dependence on the relative position between the gas jet and the laser focus.The ring-like structures observed in the vortex harmonics,and the interference of quantum paths provide an explanation for the distinct structural characteristics.Moreover,by adjusting the relative position between the jet and laser focus,it is possible to discern the contributions from different quantum paths.The optimization of the HH vortex field is applicable to the XUV,which opens up a new way for exploiting the potential in optical spin or manipulating electrons by using the photon with tunable orbital angular momentum.
文摘The angular spectrum gain characters and the power magnification characters of high gain non-walk-off colinear optical parametric oscillators have been studied using the non-colinear phase match method for the first time. The experimental results of the KTiOAs04 and the KTiOP04 crystals are discussed in detail. At the high energy single resonant condition, low reflective ratio of the output mirror for the signal and long non-linear crystal are beneficial for small divergence angles. This method can also be used for other high gain non-walk-off phase match optical parametric orocesses.
基金supported by Science and Technology Innovation Seedling Project of Sichuan Province,China(Grant No.2018100)Major Project of CDNU(Grant No.CS18ZDZ0511).
文摘Combined with the optical beam deflection,a novel approach of phase matched broadband scanning optical parametric chirped pulse amplification(OPCPA)was proposed.For this scheme,there was no superfluous operations to the chirped signal pulse which propagated in a changeless direction straightforward,but the pump beam were deflected in space with time by passing through a KTN crystal,which was applied with varied driving voltage.The theories of phase matching of each chirped signal frequency based on pump beam deflection was analyzed detailedly.And the type-I amplification of chirped signal with 800 nm central wavelength and 20 nm bandwidth pumped by 532 nm in BBO crystal was simulated as a case in point.The simulation results showed that the spectral distribution of chirped signal pulse was almost the same as the initial form,i.e.,there was nearly no narrowing on the amplified spectrum by using of the scanning OPCPA based on pump beam deflection.In addition,the simulations demonstrated that it was worth minimizing the voltage deviation applied to KTN crystal as much as possible for the sake of better waveform,larger bandwidth and higher conversion efficiency of amplified signal pulse in the proposed scanning OPCPA.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.91850107 and 12174116)the National Key Research and Development Program of China(Grant No.2018YFA0306200)+3 种基金Guangdong Innovative and Entrepreneurial Research Team Program(Grant No.2016ZT06C594)the Key Program of Guangzhou Scientific Research Special Project(Grant No.201904020013)the Science and Technology Project of Guangdong Province,China(Grant No.2020B010190001)the Fundamental Research Funds for the Central Universities。
文摘Here we propose a hybrid polymer-LN waveguide for achieving phase-matched second-harmonic generation(SHG).From the aspect of super-mode theory,the geometric parameters of the hybrid semi-nonlinear waveguide were optimized to utilize both symmetric(even)and antisymmetric(odd)modes of the pump and SHG waves so as to facilitate phase matching with large modal overlap.Phase matching between a fundamental even(TE_(00)-like)mode at 1320 nm and a fundamental odd(TE_(01)-like)mode at 660 nm was found with a calculated modal overlap integral of 0.299,while utilizing the largest nonlinear coefficient d_(33),and achieving an efficient calculated normalized conversion efficiency of 148%W^(-1)·cm^(-2).Considering the fabrication feasibility of such hybrid waveguide with features including etchless,large dimension,and low structural sensitivity,we believe our findings would provide a useful reference for future on-chip efficient nonlinear conversion devices.
文摘Red,blue and green visible lasers are more attractive with the development of the science and technology.Self frequency doubling is an important approach to realize visible lasers.For self frequency doubling,the basic requests are high figure of merit(FOM),high damage threshold,good chemical stability and mechanical properties.Perfection and growth characters are also important for a practical SFD crystal. In recent years,the discovery of rare earth calcium oxyborates has resulted in the renewal in the field of SFD crystal.ReCaO(BO 3) 3(ReCOB)is a new type of novel nonlinear optical crystals which is nearly congruently melt and can be grown with Czochralski method.ReCOB crystals possess high nonlinear coefficients and damage thresholds.They are non hydroscopic and easy cutting and polishing.They belong to monoclinic with point group m and space group cm.The strong anisotropy originated from the low symmetry makes the measurement and application of the crystal more complicated.More than half of naturally existed crystals belongs to low symmetry,consequently,the research on the nonlinear and anisotropic laser optical properties are not only important for ReCOB crystal,but also useful for the applications of other low symmetry crystals.
基金Project supported by the National Basic Research Program of China (Grant No. 2007CB310403)the National Natural Science Foundation of China (Grant No. 60801017)the Research Fund for the Doctoral Program of Higher Education of China(Grant No. 20070420118)
文摘We report a pulsed surface-emitted THz-wave parametric oscillator based on two MgO:LiNbO3 crystals pumped by a multi-longitudinal mode Q-switched Nd:YAG laser. Through varying the phase matching angle, the tunable THzwave output from 0.79 THz to 2.84 THz is realized. The maximum THz-wave output was 193.2 n J/pulse at 1.84 THz as the pump power density was 212.5 MW/cm2, corresponding to the energy conversion efficiency of 2.42Х10-6 and the photon conversion efficiency of about 0.037%. When the pump power density changed from 123 MW/cm^2 to 148 MW/cm^2 and 164 MW/cm^2, the maximum output of the THz-wave moved to the high frequency band. We give a reasonable explanation for this phenomenon.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61301056 and 61231001)the Fundamental Research Funds for the Central Universities,China(Grant No.ZYGX2014J012)+2 种基金the Fok Ying Tung Education Foundation,China(Grant No.141062)the Aero-Science Fund,China(Grant No.20142580012)the"111"Project(Grant No.B07046)
文摘Due to the fact that traditional ray field tracking approaches require a large number of geometrical optical(GO) ray tubes,they are very inefficient in many practical applications.An improved ray model scheme for a complex source beam(CSB) tracking technique is proposed in this paper.The source field can be expressed by a superposition of CSBs,then every CSB basis function has a Gaussian-type amplitude distribution and is suitable for replacing a GO ray tube in the ray tracing approach.The complex phase matching technique is adopted to find the reflected beam in the reflection point where local approximation is used to represent the curved surface in its neighborhood.A new solution to multiple reflections using the conventional right-handed reflected system is used to track the field easily.Numerical results show the accuracy of the proposed method.
基金Project supported by the National Natural Science Foundation of China (Grant No 10974256)
文摘Within the second-order perturbation approximation, this paper investigates the physical process of generation of the time-domain second harmonic by a primary Lamb wave waveform in an elastic plate. The present work is performed based on the preconditions that the phase velocity matching is satisfied and that the transfer of energy from the primary Lamb wave to the double frequency Lamb wave is not zero. It investigates the influences of the difference between the group velocities of the primary Lamb wave and the double frequency Lamb wave, the propagation distance and the duration of the primary Lamb wave waveform on the envelope shape of the time-domain second harmonic. It finds that the maximum magnitude of the envelope of the second-harmonic waveform can grow within some propagation distance even if the condition of group velocity matching is not satisfied. Our analyses also indicate that the maximum magnitude of the envelope of the second-harmonic waveform is kept constant beyond a specific propagation distance. Furthermore, it concludes that the integration amplitude of the time-domain second-harmonic waveform always grows with propagation distance within the second-order perturbation. The present research yields new physical insight not previously available into the effect of generation of the time-domain second harmonic by propagation of a primary Lamb wave waveform.
基金supported by the National "863" Program of China (No. 2007AA01Z273)the National Natural Science Fundation of China (No. 10874120)the Scientific Research Foundation for the Returned Overseas Chinese Scholars, Ministry of Education of China
文摘Based on the second-order nonlinearity, we present a bidirectional tunable all-optical switch at C-band by introducing backward quasi-phase-matching technique in Mg-doped periodically poled lithium niobate (MgO:PPLN) waveguide with a nano-structure called multiple resonators. Two injecting forward lights and one backward propagating light interact with difference frequency generations. The transmission of forward signal and backward idler light can be modulated simultaneously with the variation of control light power based on the basic "phase shift" structure of a single resonator. In this scheme, all the results come from our simulation. The speed of this bidirectional optical switch can reach to femtosecond if a femtosecond laser is used as the control light.
文摘An efficient widely tunable terahertz(THz)-wave parametric oscillator (TPO) has been designed based on the basic principle of optical parametric oscillator. The design of TPO comprises the theoretical calculations for wavelength dependent refractive index dependent wavelength when the frequency is in the far infrared region, the low-loss parametric gain has been discussed as a same form as the parametric gain in the optical region, realized the non-collinear phase-matching conditions of the terahertz optical parametric oscillator and structure of lithium niobate (LiNbO3) for TPO. The tunable spectrum range of terahertz-wave has been achieved. To increase THz output, a cut exit was made at the comer of the LiNbO3 crystal.
基金supported by the NSF of China(21921001,21827813,and 21701176)the Strategic Priority Research Program of the CAS(XDB20010100 and YJKYYQ20180006)the NSF of Fujian Province(2018J05034).
文摘Large nonlinear optical(NLO)coefficient(d_(ij)),high laser damage threshold(LDT),and phase matching(PM)are crucial for the practical applications of IR NLO crystals.A great number of IR NLO materials with high dij have been explored,but many of them suffer from non-PM,which dramatically decreases their ultimate NLO output efficiencies.To settle this problem,we have developed a new strategy involving modulating normal dispersion via bandgap(E_(g))widening to achieve PM in this work.We synthesized successfully three new wide E_(g)(∼4.0 eV)IR NLO salt-inclusion sulfides[ABa_(3)Cl_(2)][Ga_(5)S_(10)](A=K,1;Rb,2;and Cs,3)with PM behaviors,mainly ascribed to the PM cut-off wavelength blue shift that originated from the wide Eg values,with less contribution from birefringence enhancement.All the compounds possessed large second-harmonic-generation(SHG)efficiency(∼1×AgGaS_(2))and hitherto the highest LDTs(188–200 MW/cm^(2),at 1.06μm,10 ns pulse width)for known chalcogenides with SHG efficiencies comparable to that of commercial silver gallium sulfide(AgGaS_(2))crystal.
文摘Phase mismatching for third-harmonic generation(THG) in barium metaborate(BBO) crystal is investigated in detail.Upon using BBO crystal in the TypeⅠ(oo→e) scheme,in the two independent planes (principal section of the crystal and the plane normal to principal section),when the input second-harmonic beam deviates from the expected direction,phase mismatching occurs and the angle deviation produces different effects on the conversion efficiency.We numerically simulate these two cases of phase mismatching and identify the relation between the conversion efficiency and the deviation angle in the air.The computational results indicate that the phase matching tolerance in the principal section is 0.2°(in the air),while the phase matching tolerance in the plane normal to principal section is 4.5°(in the air).After conducting a lab experiment,the results agree perfectly with the computational results,indicating that the deviation angle in the principal section has a greater effect on the conversion efficiency.
基金supported by the Chinese Academy of Sciences,the Chinese Ministry of Science and Technology,the National Natural Science Foundation of China(Nos.10734080,10523003,60921004,and 60978012)the National "973" Program of China (No.2006CB806000)the Shanghai Commission of Science and Technology(Nos.06DZ22015 and 07pj14091)
文摘By optimizing the phase matching condition of high harmonic generation (HHG) from a supersonic neon gas jet, the enhanced HHG in the region of 60-70 eV has been selected. Three-dimensional numerical calculation shows that plasma plays a significant role in the phase matching process of HHG in a supersonic gas jet with short medium length. Due to plasma formation, the harmonic emission decays as the laser intensity reaches over 3.5 ~ 1014 W/cm^2. The plasma induces the broadening and blue shift of the HHG spectra, which provides a method for fine-tuning the harmonic wavelength.
基金supported by the National Natural Science Foundation of China(Nos.51323002 and 51402173)the Independent Innovation Foundation of Shandong University(No.2012JC016)+1 种基金the Natural Science Foundation for Distinguished Young Scholar of Shandong Province(No.JQ201218)the Project supported by NPL and CAEP(No.2014BB07)
文摘Refractive indices for crystals ammonium dihydrogen phosphate (ADP), 30% deuterated ADP (DADP), 50% DADP, and 70% DADP are measured from 253 to 1529 nm with 5 × 10^-6 accuracy. Numerical fits to modified double-pole Sellmeier equation are made. Second-harmonic generation, third-harmonic generation phase match- ing (PM) angles, and noncritical PM (NCPM) wavelengths are calculated using the Sellmeier parameters. The deuterated crystals show smaller PM angles than pure crystal. Fourth-harmonic generation process can be real- ized by DADP in smaller deuterium content than deuterated potassium dihydrogen phosphate (DKDP). The measured NCPM wavelengths are consistent with the calculated value. PM characteristics are compared between DADP and DKDP.
文摘The noncollinear optical parametric amplification in BBO crystal is theoretically investigated. The phase matching angle, gain bandwidth, optimal noncollinear angle and conversion efficiency for both type-I and type-II BBO are simulated. The numerical simulation results are important to the practical optical parametric amplification experiments with BBO crystal.