The high harmonic generation(HHG)by few-cycle laser pulses is essential for research in strong-field solid-state physics.Through comparison of high harmonic spectra of solids generated by laser pulses with varying dur...The high harmonic generation(HHG)by few-cycle laser pulses is essential for research in strong-field solid-state physics.Through comparison of high harmonic spectra of solids generated by laser pulses with varying durations,we discovered that lasers with good dispersion compensation are capable of producing a broad spectrum of high harmonics.As the pulse duration is further compressed,several interference peaks appear in the broad spectrum.Moreover,we conducted simulations using the semiconductor Bloch equation,considering the effect of Berry curvature,to better understand this process.Our work provides a valuable approach for studying HHG by few-cycle laser pulses in solid materials,expanding the application of HHG in attosecond physics.展开更多
We study high-order harmonic generation(HHG) from multi-center asymmetric linear molecules numerically and analytically. Our simulations show that odd and even HHG spectra of the asymmetric multi-center system respond...We study high-order harmonic generation(HHG) from multi-center asymmetric linear molecules numerically and analytically. Our simulations show that odd and even HHG spectra of the asymmetric multi-center system respond differently to the change of the molecular structure. Specifically, when the internuclear distances between these nuclei of the molecule have a small change, the odd spectra usually do not change basically, but the even spectra differ remarkably. Based on this phenomenon, a simple procedure is proposed to probe the positions of these nuclei with odd–even HHG. Our results shed light on attosecond probing of the structure of multi-center molecules using HHG.展开更多
提出了一种利用高频谐波场增强阿秒脉冲强度的方法。计算结果表明,当适当地加入一束13次谐波或者27次谐波场到双色激光场时,谐波强度比原双色场时分别增强了2个或5个数量级。尤其是当采用27次谐波光源时,谐波光谱形成了一个465 e V的超...提出了一种利用高频谐波场增强阿秒脉冲强度的方法。计算结果表明,当适当地加入一束13次谐波或者27次谐波场到双色激光场时,谐波强度比原双色场时分别增强了2个或5个数量级。尤其是当采用27次谐波光源时,谐波光谱形成了一个465 e V的超长平台区。最后通过适当地叠加谐波,可分别获得脉宽仅为50 as和40 as的孤立阿秒脉冲,其强度比原双色场情况下产生的阿秒脉冲增强了2个或5个数量级。展开更多
We theoretically study the high-order harmonic generation(HHG) in a two-color laser field using the Bohmian mechanics. Our results show that, for the case of a weak second-color laser field, the simulation of the HHG ...We theoretically study the high-order harmonic generation(HHG) in a two-color laser field using the Bohmian mechanics. Our results show that, for the case of a weak second-color laser field, the simulation of the HHG with only one central Bohmian trajectory is in a good agreement with the ab initio time-dependent Schr o¨dinger equation(TDSE) results.In contrast, with the increase of the amplitude of the second-color laser field, the HHG spectra from the single central Bohmian trajectory deviate from the TDSE results more and more significantly. By analyzing the Bohmian trajectories,we find that the significant deviation is due to the fact that the central Bohmian trajectory leaves the core quickly in the two-color laser field with the breaking of inversion symmetry. Interestingly, we find that another Bohmian trajectory with different initial position, which keeps oscillating around the core, could qualitatively well reproduce the TDSE results. Furthermore, we study the HHG spectrum in a two-color laser field with inversion symmetry and find that the HHG spectrum in TDSE can be still well simulated with the central Bohmian trajectory. These results indicate that, similar to the case of one color laser field, the HHG spectra in a two-color laser field can be also reproduced with a single Bohmian trajectory,although the initial position of the trajectory is dependent on the symmetry of the laser field. Our work thus demonstrates that Bohmian trajectory theory can be used as a promising tool in investigating the HHG process in a two-color laser field.展开更多
Using a nonperturbative quantum electrodynamics theory of high-order harmonic generation (HHG),a scaling law of HHG is established.The scaling law states that when the atomic binding energy E b,the wavelength λ and t...Using a nonperturbative quantum electrodynamics theory of high-order harmonic generation (HHG),a scaling law of HHG is established.The scaling law states that when the atomic binding energy E b,the wavelength λ and the intensity I of the laser field change simultaneously to kE b,λ/k,and k 3 I,respectively.The characteristics of the HHG spectrum remain unchanged,while the harmonic yield is enhanced k 3 times.That HHG obeys the same scaling law with above-threshold ionization is a solid proof of the fact that the two physical processes have similar physical mechanisms.The variation of integrated harmonic yields is also discussed.展开更多
We investigate high-order harmonic generation(HHG) of Li^+ ion driven by an intense infrared(IR) laser field in combination with a weak XUV pulse. To achieve this, we first construct an accurate single-active electron...We investigate high-order harmonic generation(HHG) of Li^+ ion driven by an intense infrared(IR) laser field in combination with a weak XUV pulse. To achieve this, we first construct an accurate single-active electron angular-momentumdependent model potential of Li^+ ion, by which the accurate singlet energy levels of Li^+ for the ground state and excited states with higher quantum numbers can be obtained. Then, we solve numerically the three dimensional time-dependent Schr o¨dinger equation of Li^+ ion by means of the generalized pseudospectral method to obtain HHG. Our results show that the strength of assisted XUV is not amplified during the harmonic generation process, but the yield of HHG power spectrum in the whole plateau has a significant enhancement. Furthermore, the optimal phase delay between the IR and XUV pulses allows the production of ultrabroadband supercontinuum spectra. By superposing some harmonics, a strong new single 27-attosecond ultrashort pulse can be obtained.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.91850209 and 11974416)。
文摘The high harmonic generation(HHG)by few-cycle laser pulses is essential for research in strong-field solid-state physics.Through comparison of high harmonic spectra of solids generated by laser pulses with varying durations,we discovered that lasers with good dispersion compensation are capable of producing a broad spectrum of high harmonics.As the pulse duration is further compressed,several interference peaks appear in the broad spectrum.Moreover,we conducted simulations using the semiconductor Bloch equation,considering the effect of Berry curvature,to better understand this process.Our work provides a valuable approach for studying HHG by few-cycle laser pulses in solid materials,expanding the application of HHG in attosecond physics.
基金Project supported by the National Natural Science Foundation of China(Grants No.91750111)the Youth Foundation of Hebei Province Education Department,China(Grant No.QN2017028)+2 种基金the Fundamental Research Funds for Hebei GEO University,China(Grant No.BQ2017047)the Natural Science Foundation of Hebei Province,China(Grant No.A2015205161)the Fundamental Research Funds for the Central Universities,China(Grant No.SNNU.GK201801009)
文摘We study high-order harmonic generation(HHG) from multi-center asymmetric linear molecules numerically and analytically. Our simulations show that odd and even HHG spectra of the asymmetric multi-center system respond differently to the change of the molecular structure. Specifically, when the internuclear distances between these nuclei of the molecule have a small change, the odd spectra usually do not change basically, but the even spectra differ remarkably. Based on this phenomenon, a simple procedure is proposed to probe the positions of these nuclei with odd–even HHG. Our results shed light on attosecond probing of the structure of multi-center molecules using HHG.
文摘提出了一种利用高频谐波场增强阿秒脉冲强度的方法。计算结果表明,当适当地加入一束13次谐波或者27次谐波场到双色激光场时,谐波强度比原双色场时分别增强了2个或5个数量级。尤其是当采用27次谐波光源时,谐波光谱形成了一个465 e V的超长平台区。最后通过适当地叠加谐波,可分别获得脉宽仅为50 as和40 as的孤立阿秒脉冲,其强度比原双色场情况下产生的阿秒脉冲增强了2个或5个数量级。
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11334009,11474321,and 11527807)
文摘We theoretically study the high-order harmonic generation(HHG) in a two-color laser field using the Bohmian mechanics. Our results show that, for the case of a weak second-color laser field, the simulation of the HHG with only one central Bohmian trajectory is in a good agreement with the ab initio time-dependent Schr o¨dinger equation(TDSE) results.In contrast, with the increase of the amplitude of the second-color laser field, the HHG spectra from the single central Bohmian trajectory deviate from the TDSE results more and more significantly. By analyzing the Bohmian trajectories,we find that the significant deviation is due to the fact that the central Bohmian trajectory leaves the core quickly in the two-color laser field with the breaking of inversion symmetry. Interestingly, we find that another Bohmian trajectory with different initial position, which keeps oscillating around the core, could qualitatively well reproduce the TDSE results. Furthermore, we study the HHG spectrum in a two-color laser field with inversion symmetry and find that the HHG spectrum in TDSE can be still well simulated with the central Bohmian trajectory. These results indicate that, similar to the case of one color laser field, the HHG spectra in a two-color laser field can be also reproduced with a single Bohmian trajectory,although the initial position of the trajectory is dependent on the symmetry of the laser field. Our work thus demonstrates that Bohmian trajectory theory can be used as a promising tool in investigating the HHG process in a two-color laser field.
基金supported by the National Natural Science Foundation of China (Grant Nos.10774153 and 61078080)the National Basic Research Program of China (Grant Nos.2010CB923203 and 2011CB808103)
文摘Using a nonperturbative quantum electrodynamics theory of high-order harmonic generation (HHG),a scaling law of HHG is established.The scaling law states that when the atomic binding energy E b,the wavelength λ and the intensity I of the laser field change simultaneously to kE b,λ/k,and k 3 I,respectively.The characteristics of the HHG spectrum remain unchanged,while the harmonic yield is enhanced k 3 times.That HHG obeys the same scaling law with above-threshold ionization is a solid proof of the fact that the two physical processes have similar physical mechanisms.The variation of integrated harmonic yields is also discussed.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11465016,11664035,11764038,and 11765018)the Foundation of Northwest Normal University,China(Grant No.NWNU-LKQN-17-1)
文摘We investigate high-order harmonic generation(HHG) of Li^+ ion driven by an intense infrared(IR) laser field in combination with a weak XUV pulse. To achieve this, we first construct an accurate single-active electron angular-momentumdependent model potential of Li^+ ion, by which the accurate singlet energy levels of Li^+ for the ground state and excited states with higher quantum numbers can be obtained. Then, we solve numerically the three dimensional time-dependent Schr o¨dinger equation of Li^+ ion by means of the generalized pseudospectral method to obtain HHG. Our results show that the strength of assisted XUV is not amplified during the harmonic generation process, but the yield of HHG power spectrum in the whole plateau has a significant enhancement. Furthermore, the optimal phase delay between the IR and XUV pulses allows the production of ultrabroadband supercontinuum spectra. By superposing some harmonics, a strong new single 27-attosecond ultrashort pulse can be obtained.
