By observing two-photon response and anisotropy of the light-induced voltage in Al-Si Schottky barrier potential,it is certified from the experimental and theoretical analysis that the built-in electric field generate...By observing two-photon response and anisotropy of the light-induced voltage in Al-Si Schottky barrier potential,it is certified from the experimental and theoretical analysis that the built-in electric field generated by the Schottky barrier potential will induce the phenomena of optical rectification in Si photodiode.Thus,it is deduced that there must be double-frequency absorption caused by phase-mismatch in the mechanism of two-photon response of Si photodiode.If the intensity of the built-in electric field is strong enough,the double-frequency absorption will be the main factor of the two-photon response,which is different from the conventional opinion that the two-photon response is just the two-photon absorption.展开更多
The polaron effect on the optical rectification in spherical quantum dots with a shallow hydrogenic impurity in the presence of electric field is theoretically investigated by taking into account the interactions of t...The polaron effect on the optical rectification in spherical quantum dots with a shallow hydrogenic impurity in the presence of electric field is theoretically investigated by taking into account the interactions of the electrons with both confined and surface optical phonons. Besides, the interaction between impurity and phonons is also considered. Numerical calculations are presented for typical Zn1-xCdxSe/ZnSe material. It is found that the polaronic effect or electric field leads to the redshifted resonant peaks of the optical rectification coefficients. It is also found that the peak values of the optical rectification coefficients with the polaronic effect are larger than without the polaronic effect, especially for smaller Cd concentrations or stronger electric field.展开更多
We consider the effects of quantum dot radius,confinement potential depth and controllable effective mass on the optical rectification coefficient(ORC)in spherical quantum dots,which is confined with Modified Kratzer-...We consider the effects of quantum dot radius,confinement potential depth and controllable effective mass on the optical rectification coefficient(ORC)in spherical quantum dots,which is confined with Modified Kratzer-Coulomb Potential(MKCP).Using the Nikiforov-Uvarov method and compact density matrix theory,the ground state energy,ORC and wave function of electrons under the combined action of many factors are calculated.The results show that they affect the optical rectification response from different angles,including the position of peak and formant.展开更多
We investigate the nonlinear optical rectification(NOR) of spherical quantum dots(QDs) under Hulthén plus Hellmann confining potential with the external tuning elements. Energy and wavefunction are determined by ...We investigate the nonlinear optical rectification(NOR) of spherical quantum dots(QDs) under Hulthén plus Hellmann confining potential with the external tuning elements. Energy and wavefunction are determined by using the Nikiforov–Uvarov method. Expression for the NOR coefficient is derived by the density matrix theory. The results show that the applied external elements and internal parameters of this system have a strong influence on intraband nonlinear optical properties. It is hopeful that this tuning of the nonlinear optical properties of GaAs/Ga_(1-x)Al_(x)As QDs can make a greater contribution to preparation of new functional optical devices.展开更多
The 4H-SiC crystal is found to have great potential in terahertz generation via nonlinear optical frequency conversion due to its extremely high optical damage threshold,wide transparent range,etc.In this paper,optica...The 4H-SiC crystal is found to have great potential in terahertz generation via nonlinear optical frequency conversion due to its extremely high optical damage threshold,wide transparent range,etc.In this paper,optical rectification(OR)with tilted-pulse-front(TPF)setting based on the 4H-SiC crystal is proposed.The theory accounts for the optimization of incident pulse pre-chirping in the TPF OR process under high-intensity femtosecond laser pumping.Compared with the currently recognized LiNbO3-based TPF OR,which generates a single-cycle terahertz pulse within 3 THz,4HSiC demonstrates a significant advantage in producing ultra-widely tunable(up to over 14 THz,TPF angle 31◦–38◦)terahertz waves with high efficiency(~10–2)and strong field(~MV/cm).Besides,the spectrum characteristics,as well as the evolution from single-to multi-cycle terahertz pulses can be modulated flexibly by pre-chirping.The simulation results show that 4H-SiC enables terahertz frequency extending to an unprecedent range by OR,which has extremely important potential in strong-field terahertz applications.展开更多
We present the generation of high-repetition-rate strong-field terahertz(THz)pulses from a thin 4-N,N-dimethylamino-4’-N’-methyl-stilbazolium 2,4,6-trimethylbenzenesulfonate(DSTMS)organic crystal pumped by an ytterb...We present the generation of high-repetition-rate strong-field terahertz(THz)pulses from a thin 4-N,N-dimethylamino-4’-N’-methyl-stilbazolium 2,4,6-trimethylbenzenesulfonate(DSTMS)organic crystal pumped by an ytterbium-doped yttrium aluminum garnet laser.The generated THz pulse energy reaches 932.8 nJ at 1 kHz repetition rate,with a conversion efficiency of 0.19%and a peak electric field of 819 kV/cm.At a repetition rate of 10 kHz,it is able to maintain a peak electric field of 236 kV/cm and an average THz power of 0.77 mW.The high-repetition-rate,strong-field THz source provides a convenient tool for the study of THz matter manipulation and THz spectroscopy.展开更多
We observed sub-picosecond terahertz(THz)pulses generated from an electro-optic quartz plate using femtosecond optical pulses.The time-resolved THz radiation signal clearly indicates two separated THz pulses with oppo...We observed sub-picosecond terahertz(THz)pulses generated from an electro-optic quartz plate using femtosecond optical pulses.The time-resolved THz radiation signal clearly indicates two separated THz pulses with opposite polarity.Based on our results,a model based on optical-to-THz conversion via optical rectification is proposed to describe the twin pulsed THz emission mechanism of the quartz plate.Firstly,the two separated THz pulses are assigned to the forced and free THz pulses,respectively.With an optical pulse serving as an external source in the crystalline quartz,the forced THz pulse is a solution to linear Maxwell's equations and propagates at the velocity of the pump laser pulse,while the free THz pulse propagates with the group velocity in the THz frequency range.Finally,as a non-centrosymmetry material,the THz amplitude exhibits perfect threefold symmetry with respect to the azimuthal angle and twofold symmetry with respect to the pump polarization angle.展开更多
The second-harmonic generation （SHG） coefficient in an asymmetric quantum dot （QD） with a static magnetic field is theoretically investigated. Within the framework of the effective-mass approximation, we obtain th...The second-harmonic generation （SHG） coefficient in an asymmetric quantum dot （QD） with a static magnetic field is theoretically investigated. Within the framework of the effective-mass approximation, we obtain the confined wave functions and energies of electrons in the QD. We also obtain the SHC coefficient by the compact-density-matrix approach and the iterative method. The numerical results for the typical GaAs/AlGaAs QD show that the SHC coefficient depends strongly on the magnitude of magnetic field, parameters of the asymmetric potential and the radius of the QD. The resonant peak shifts with the magnetic field or the radius of the QD changing.展开更多
This paper presents a set of equations describing the terahertz generation and electro-optic detection based on optical rectification in zincblende crystals. The dependence of terahertz emission efficiency on the pola...This paper presents a set of equations describing the terahertz generation and electro-optic detection based on optical rectification in zincblende crystals. The dependence of terahertz emission efficiency on the polarization of incident beam and crystal-orientation is discussed. For the experimental setup with a transceiver which transmits and detects terahertz radiation in the same crystal, we have demonstrated the optimal combination of both parameters above to optimize the working efficiency. Equations supplied in this paper are valid for zincblende crystals with arbitrary crystal- orientation and every possible polarization of an incident beam, which are of great significance for the optimization of a system.展开更多
High-power terahertz(THz) generation in the frequency range of 0.1-10 THz has been a fast-developing research area ever since the beginning of the THz boom two decades ago, enabling new technological breakthroughs in ...High-power terahertz(THz) generation in the frequency range of 0.1-10 THz has been a fast-developing research area ever since the beginning of the THz boom two decades ago, enabling new technological breakthroughs in spectroscopy, communication, imaging,etc. By using optical(laser) pumping methods with near-or mid-infrared(IR) lasers, flexible and practical THz sources covering the whole THz range can be realized to overcome the shortage of electronic THz sources and now they are playing important roles in THz science and technology. This paper overviews various optically pumped THz sources, including femtosecond laser based ultrafast broadband THz generation, monochromatic widely tunable THz generation, single-mode on-chip THz source from photomixing, and the traditional powerful THz gas lasers. Full descriptions from basic principles to the latest progress are presented and their advantages and disadvantages are discussed as well. It is expected that this review gives a comprehensive reference to researchers in this area and additionally helps newcomers to quickly gain understanding of optically pumped THz sources.展开更多
We present a high-power and broadband terahertz(THz)time-domain spectroscopy setup utilizing the nonlinear organic crystal MNA both as an emitter and a detector.The THz source is based on optical rectification of near...We present a high-power and broadband terahertz(THz)time-domain spectroscopy setup utilizing the nonlinear organic crystal MNA both as an emitter and a detector.The THz source is based on optical rectification of nearinfrared laser pulses at a central wavelength of 1036 nm from a commercial,high-power Yb-based laser system and reaches a high THz average power of 11 mW at a repetition rate of 100 kHz and a broad bandwidth of more than 9 THz without a significant power fall-off in the higher THz frequency components.The conversion efficiency is high(0.13%)in spite of the high excitation average power of 8 W.We validate the high dynamic range and reliability of the source for applications in linear spectroscopy by measuring the broadband THz properties ofχ(2)nonlinear crystals up to 8 THz.This new high-repetition-rate source is very promising for ultra-broadband THz spectroscopy at high dynamic range and/or reduced measurement time.展开更多
Free-space strong-field terahertz(THz)pulses,generated via optical rectification of femtosecond lasers in nonlinear crystals,are pivotal in various applications.However,conventional Ti:sapphire lasers struggle to prod...Free-space strong-field terahertz(THz)pulses,generated via optical rectification of femtosecond lasers in nonlinear crystals,are pivotal in various applications.However,conventional Ti:sapphire lasers struggle to produce high-average-power THz sources due to their limited output power.While kilowatt ytterbium lasers are increasingly adopted,their application in THz generation faces challenges:low optical-to-THz conversion efficiency(attributed to long pulse duration and low energy)and crystal damage under high pumping power.Here,we report a high-average-power strong-field THz source using a lithium niobate crystal pumped by a 1030 nm,570 fs,1 mJ,50 kHz ytterbium femtosecond laser with tilted pulse front pumping(TPFP).By systematically optimizing TPFP implementations and comparing grating-and echelon-type configurations,we achieve a THz source with 64.5 mW average power at 42 W,50 kHz pumping,and focused peak electric field of 525 kV/cm at 0.83 mJ,1 kHz operation.Additionally,we observe Zeeman torque signals in cobalt-iron ferromagnetic nanofilms.This high-repetition-rate,high-average-power THz system,combined with its potential capabilities in high signal-to-noise ratio spectroscopy and imaging,promises transformative impacts in quantum matter manipulation,non-destructive testing,and biomedicine.展开更多
文摘By observing two-photon response and anisotropy of the light-induced voltage in Al-Si Schottky barrier potential,it is certified from the experimental and theoretical analysis that the built-in electric field generated by the Schottky barrier potential will induce the phenomena of optical rectification in Si photodiode.Thus,it is deduced that there must be double-frequency absorption caused by phase-mismatch in the mechanism of two-photon response of Si photodiode.If the intensity of the built-in electric field is strong enough,the double-frequency absorption will be the main factor of the two-photon response,which is different from the conventional opinion that the two-photon response is just the two-photon absorption.
基金supported by the National Natural Science Foundation of China(Grant No.11364028)the Major Projects of the Natural Science Foundation of Inner Mongolia Autonomous Region,China(Grant No.2013ZD02)the Project of "Prairie Excellent" Engineering in Inner Mongolia Autonomous Region,China
文摘The polaron effect on the optical rectification in spherical quantum dots with a shallow hydrogenic impurity in the presence of electric field is theoretically investigated by taking into account the interactions of the electrons with both confined and surface optical phonons. Besides, the interaction between impurity and phonons is also considered. Numerical calculations are presented for typical Zn1-xCdxSe/ZnSe material. It is found that the polaronic effect or electric field leads to the redshifted resonant peaks of the optical rectification coefficients. It is also found that the peak values of the optical rectification coefficients with the polaronic effect are larger than without the polaronic effect, especially for smaller Cd concentrations or stronger electric field.
基金Project supported by Support National Natural Science Foundation of China(Grant Nos.52174161,12174161,51702003,61775087,and 11674312)the Natural Science Foundation of Anhui Province(No.1508085QF140)Plan Fund for Outstanding Young Talents in Colleges and Universities(No.gxyq ZD2018039)。
文摘We consider the effects of quantum dot radius,confinement potential depth and controllable effective mass on the optical rectification coefficient(ORC)in spherical quantum dots,which is confined with Modified Kratzer-Coulomb Potential(MKCP).Using the Nikiforov-Uvarov method and compact density matrix theory,the ground state energy,ORC and wave function of electrons under the combined action of many factors are calculated.The results show that they affect the optical rectification response from different angles,including the position of peak and formant.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.51702003,61775087,11674312,52174161,and 12174161)。
文摘We investigate the nonlinear optical rectification(NOR) of spherical quantum dots(QDs) under Hulthén plus Hellmann confining potential with the external tuning elements. Energy and wavefunction are determined by using the Nikiforov–Uvarov method. Expression for the NOR coefficient is derived by the density matrix theory. The results show that the applied external elements and internal parameters of this system have a strong influence on intraband nonlinear optical properties. It is hopeful that this tuning of the nonlinear optical properties of GaAs/Ga_(1-x)Al_(x)As QDs can make a greater contribution to preparation of new functional optical devices.
基金This work was supported by the National Natural Science Foundation of China(No.62175184)the Key Laboratory of Micro Opto-electro Mechanical System Technology,Ministry of Education.
文摘The 4H-SiC crystal is found to have great potential in terahertz generation via nonlinear optical frequency conversion due to its extremely high optical damage threshold,wide transparent range,etc.In this paper,optical rectification(OR)with tilted-pulse-front(TPF)setting based on the 4H-SiC crystal is proposed.The theory accounts for the optimization of incident pulse pre-chirping in the TPF OR process under high-intensity femtosecond laser pumping.Compared with the currently recognized LiNbO3-based TPF OR,which generates a single-cycle terahertz pulse within 3 THz,4HSiC demonstrates a significant advantage in producing ultra-widely tunable(up to over 14 THz,TPF angle 31◦–38◦)terahertz waves with high efficiency(~10–2)and strong field(~MV/cm).Besides,the spectrum characteristics,as well as the evolution from single-to multi-cycle terahertz pulses can be modulated flexibly by pre-chirping.The simulation results show that 4H-SiC enables terahertz frequency extending to an unprecedent range by OR,which has extremely important potential in strong-field terahertz applications.
基金supported by the National Key Research and Development Program of China(No.2022YFA1604401)the National Natural Science Foundation of China(Nos.12325409,62105346 and 12388102)+2 种基金the CAS Project for Young Scientists in Basic Research(No.YSBR-059)the Basic Research Project of the Shanghai Science and Technology Innovation Action Plan(No.20JC1416000)the Shanghai Pilot Program for Basic Research–Chinese Academy of Sciences,Shanghai Branch。
文摘We present the generation of high-repetition-rate strong-field terahertz(THz)pulses from a thin 4-N,N-dimethylamino-4’-N’-methyl-stilbazolium 2,4,6-trimethylbenzenesulfonate(DSTMS)organic crystal pumped by an ytterbium-doped yttrium aluminum garnet laser.The generated THz pulse energy reaches 932.8 nJ at 1 kHz repetition rate,with a conversion efficiency of 0.19%and a peak electric field of 819 kV/cm.At a repetition rate of 10 kHz,it is able to maintain a peak electric field of 236 kV/cm and an average THz power of 0.77 mW.The high-repetition-rate,strong-field THz source provides a convenient tool for the study of THz matter manipulation and THz spectroscopy.
基金Project supported by the National Key Research and Development Program of China(Grant No.2023YFF0719200)the National Natural Science Foundation of China(Grant Nos.62322115,U24A20226,61988102,and 62435010)+1 种基金111 Project(Grant No.D18014)Science and Technology Commission of Shanghai Municipality(Grant Nos.22JC1400200 and 21S31907400)。
文摘We observed sub-picosecond terahertz(THz)pulses generated from an electro-optic quartz plate using femtosecond optical pulses.The time-resolved THz radiation signal clearly indicates two separated THz pulses with opposite polarity.Based on our results,a model based on optical-to-THz conversion via optical rectification is proposed to describe the twin pulsed THz emission mechanism of the quartz plate.Firstly,the two separated THz pulses are assigned to the forced and free THz pulses,respectively.With an optical pulse serving as an external source in the crystalline quartz,the forced THz pulse is a solution to linear Maxwell's equations and propagates at the velocity of the pump laser pulse,while the free THz pulse propagates with the group velocity in the THz frequency range.Finally,as a non-centrosymmetry material,the THz amplitude exhibits perfect threefold symmetry with respect to the azimuthal angle and twofold symmetry with respect to the pump polarization angle.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10975125)
文摘The second-harmonic generation （SHG） coefficient in an asymmetric quantum dot （QD） with a static magnetic field is theoretically investigated. Within the framework of the effective-mass approximation, we obtain the confined wave functions and energies of electrons in the QD. We also obtain the SHC coefficient by the compact-density-matrix approach and the iterative method. The numerical results for the typical GaAs/AlGaAs QD show that the SHC coefficient depends strongly on the magnitude of magnetic field, parameters of the asymmetric potential and the radius of the QD. The resonant peak shifts with the magnetic field or the radius of the QD changing.
基金supported by the National Natural Science Foundation of China (Grant No. 10974063)the Natural Science Foundation of Hubei Province of China (Grant No. 2010CDA001)+2 种基金Ph. D. Program Foundation of the Ministry of Education of China (Grant No. 20100142110042)the Fundamental Research Funds for the Central Universities (Grant No. HUST:2010MS041)the National "973" Project (Grant No. 2007CB310403)
文摘This paper presents a set of equations describing the terahertz generation and electro-optic detection based on optical rectification in zincblende crystals. The dependence of terahertz emission efficiency on the polarization of incident beam and crystal-orientation is discussed. For the experimental setup with a transceiver which transmits and detects terahertz radiation in the same crystal, we have demonstrated the optimal combination of both parameters above to optimize the working efficiency. Equations supplied in this paper are valid for zincblende crystals with arbitrary crystal- orientation and every possible polarization of an incident beam, which are of great significance for the optimization of a system.
基金supported by the National Basic Research Program of China(Grant No.2014CB339802)the National Natural Science Foundation of China(Grant Nos.61675146,61471257,61505089,61275102&61271066)
文摘High-power terahertz(THz) generation in the frequency range of 0.1-10 THz has been a fast-developing research area ever since the beginning of the THz boom two decades ago, enabling new technological breakthroughs in spectroscopy, communication, imaging,etc. By using optical(laser) pumping methods with near-or mid-infrared(IR) lasers, flexible and practical THz sources covering the whole THz range can be realized to overcome the shortage of electronic THz sources and now they are playing important roles in THz science and technology. This paper overviews various optically pumped THz sources, including femtosecond laser based ultrafast broadband THz generation, monochromatic widely tunable THz generation, single-mode on-chip THz source from photomixing, and the traditional powerful THz gas lasers. Full descriptions from basic principles to the latest progress are presented and their advantages and disadvantages are discussed as well. It is expected that this review gives a comprehensive reference to researchers in this area and additionally helps newcomers to quickly gain understanding of optically pumped THz sources.
基金Ministerium für Kultur und Wissenschaft des Landes Nordrhein-Westfalen(terahertz.NRW program Netzwerke 2021)Ruhr-Universit?t Bochum(DFG Open Access Publication Funds)Deutsche Forschungsgemeinschaft(SFB/TRR196 MARIE project M01 and C07,PR1413/3-2,EXC-2033-Projektnummer390677874-RESOLV)。
文摘We present a high-power and broadband terahertz(THz)time-domain spectroscopy setup utilizing the nonlinear organic crystal MNA both as an emitter and a detector.The THz source is based on optical rectification of nearinfrared laser pulses at a central wavelength of 1036 nm from a commercial,high-power Yb-based laser system and reaches a high THz average power of 11 mW at a repetition rate of 100 kHz and a broad bandwidth of more than 9 THz without a significant power fall-off in the higher THz frequency components.The conversion efficiency is high(0.13%)in spite of the high excitation average power of 8 W.We validate the high dynamic range and reliability of the source for applications in linear spectroscopy by measuring the broadband THz properties ofχ(2)nonlinear crystals up to 8 THz.This new high-repetition-rate source is very promising for ultra-broadband THz spectroscopy at high dynamic range and/or reduced measurement time.
基金Scientific Research Innovation Capability Support Project for Young(ZYGXQNJSKYCXNLZCXMI3)National Key Research and Development Program of China(2022YFA1604402)+1 种基金National Natural Science Foundation of China(U23A6002,92250307)Open Project Program of Wuhan National Laboratory for Optoelectronics(2022WNLOKF006)。
文摘Free-space strong-field terahertz(THz)pulses,generated via optical rectification of femtosecond lasers in nonlinear crystals,are pivotal in various applications.However,conventional Ti:sapphire lasers struggle to produce high-average-power THz sources due to their limited output power.While kilowatt ytterbium lasers are increasingly adopted,their application in THz generation faces challenges:low optical-to-THz conversion efficiency(attributed to long pulse duration and low energy)and crystal damage under high pumping power.Here,we report a high-average-power strong-field THz source using a lithium niobate crystal pumped by a 1030 nm,570 fs,1 mJ,50 kHz ytterbium femtosecond laser with tilted pulse front pumping(TPFP).By systematically optimizing TPFP implementations and comparing grating-and echelon-type configurations,we achieve a THz source with 64.5 mW average power at 42 W,50 kHz pumping,and focused peak electric field of 525 kV/cm at 0.83 mJ,1 kHz operation.Additionally,we observe Zeeman torque signals in cobalt-iron ferromagnetic nanofilms.This high-repetition-rate,high-average-power THz system,combined with its potential capabilities in high signal-to-noise ratio spectroscopy and imaging,promises transformative impacts in quantum matter manipulation,non-destructive testing,and biomedicine.
