We propose a new method to generate terahertz perfect vortex beam with integer-order and fractional-order. A new optical diffractive element composed of the phase combination of a spherical harmonic axicon and a spira...We propose a new method to generate terahertz perfect vortex beam with integer-order and fractional-order. A new optical diffractive element composed of the phase combination of a spherical harmonic axicon and a spiral phase plate is designed and called spiral spherical harmonic axicon. A terahertz Gaussian beam passes through the spiral spherical harmonic axicon to generate a terahertz vortex beam. When only the topological charge number carried by spiral spherical harmonic axicon increases, the ring radius of terahertz vortex beam increases slightly, so the beam is shaped into a terahertz quasi-perfect vortex beam. Importantly, the terahertz quasi-perfect vortex beam can carry not only integer-order topological charge number but also fractional-order topological charge number. This is the first time that vortex beam and quasi-perfect vortex beam with fractional-order have been successfully realized in terahertz domain and experiment.展开更多
The mechanism of terahertz(THz) pulse coherent detection via two-color laser pulses of various frequency ratios in gas plasma is theoretically investigated.Our investigations demonstrate that except for the commonly u...The mechanism of terahertz(THz) pulse coherent detection via two-color laser pulses of various frequency ratios in gas plasma is theoretically investigated.Our investigations demonstrate that except for the commonly used frequency ratio of 2, other uncommon frequency ratios can also be utilized to detect THz pulse, such as 2 n, n + 1/2(n ≤ 3, n is a positive integer).The well-developed transient photocurrent model is extended to our terahertz detection process.Based on this model, our simulation results can be explained by analyzing the process of asymmetric electron ionization and electron acceleration.展开更多
It has been proposed previously that the coherent detection of a terahertz（THz） pulse can be achieved based on the time-resolved luminescence quenching. In this paper, we investigate the frequency response range of ...It has been proposed previously that the coherent detection of a terahertz（THz） pulse can be achieved based on the time-resolved luminescence quenching. In this paper, we investigate the frequency response range of this novel detection technology by simulating the motion of carriers in gallium arsenide（GaAs） by the ensemble Monte Carlo method. At room temperature, for a direct-current（DC） voltage of 20 kV/cm applied to the semiconductor（GaAs） and sampling time o140 fs, the luminescence quenching phenomena induced by terahertz pulses with different center frequencies are studied The results show that the quenching efficiency is independent of the THz frequency when the frequency is in a range o0.1 THz–4 THz. However, when the frequency exceeds 4 THz, the efficiency decreases with the increase of frequency Therefore, the frequency response range is 0.1 THz–4 THz. Moreover, when the sampling time is changed to 100 fs the frequency response range is extended to be approximately 0.1 THz–5.6 THz. This study of the frequency-dependen characteristics of the luminescence response to the THz pulse can provide a theoretical basis for the exploration of THz detection technology.展开更多
The mechanism of terahertz(THz)pulse generation with a static magnetic field imposed on a gas plasma is theoretically investigated.The investigation demonstrates that the static magnetic field alters the electron moti...The mechanism of terahertz(THz)pulse generation with a static magnetic field imposed on a gas plasma is theoretically investigated.The investigation demonstrates that the static magnetic field alters the electron motion during the optical field ionization of gas,leading to a two-dimensional asymmetric acceleration process of the ionized electrons.Simulation results reveal that elliptically or circularly polarized broadband THz radiation can be generated with an external static magnetic field imposed along the propagation direction of the two-color laser.The polarization of the THz radiation can be tuned by the strength of the external static magnetic field.展开更多
基金Project supported by the Fundamental Research Funds for the Central Universities,China (Grant No.2017KFYXJJ029)。
文摘We propose a new method to generate terahertz perfect vortex beam with integer-order and fractional-order. A new optical diffractive element composed of the phase combination of a spherical harmonic axicon and a spiral phase plate is designed and called spiral spherical harmonic axicon. A terahertz Gaussian beam passes through the spiral spherical harmonic axicon to generate a terahertz vortex beam. When only the topological charge number carried by spiral spherical harmonic axicon increases, the ring radius of terahertz vortex beam increases slightly, so the beam is shaped into a terahertz quasi-perfect vortex beam. Importantly, the terahertz quasi-perfect vortex beam can carry not only integer-order topological charge number but also fractional-order topological charge number. This is the first time that vortex beam and quasi-perfect vortex beam with fractional-order have been successfully realized in terahertz domain and experiment.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11574105,61475054,and 61405063)
文摘The mechanism of terahertz(THz) pulse coherent detection via two-color laser pulses of various frequency ratios in gas plasma is theoretically investigated.Our investigations demonstrate that except for the commonly used frequency ratio of 2, other uncommon frequency ratios can also be utilized to detect THz pulse, such as 2 n, n + 1/2(n ≤ 3, n is a positive integer).The well-developed transient photocurrent model is extended to our terahertz detection process.Based on this model, our simulation results can be explained by analyzing the process of asymmetric electron ionization and electron acceleration.
基金supported by the Wuhan Applied Basic Research Project,China(Grant No.20140101010009)the National Natural Science Foundation of China(Grant Nos.61405063,61475054,11574105,and 61177095)+1 种基金the Hubei Science and Technology Agency Project,China(Grant No.2015BCE052)the Fundamental Research Funds for the Central Universities,China(Grant No.2017KFYXJJ029)
文摘It has been proposed previously that the coherent detection of a terahertz（THz） pulse can be achieved based on the time-resolved luminescence quenching. In this paper, we investigate the frequency response range of this novel detection technology by simulating the motion of carriers in gallium arsenide（GaAs） by the ensemble Monte Carlo method. At room temperature, for a direct-current（DC） voltage of 20 kV/cm applied to the semiconductor（GaAs） and sampling time o140 fs, the luminescence quenching phenomena induced by terahertz pulses with different center frequencies are studied The results show that the quenching efficiency is independent of the THz frequency when the frequency is in a range o0.1 THz–4 THz. However, when the frequency exceeds 4 THz, the efficiency decreases with the increase of frequency Therefore, the frequency response range is 0.1 THz–4 THz. Moreover, when the sampling time is changed to 100 fs the frequency response range is extended to be approximately 0.1 THz–5.6 THz. This study of the frequency-dependen characteristics of the luminescence response to the THz pulse can provide a theoretical basis for the exploration of THz detection technology.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11574105,and 61475054)the Fundamental Research Funds for the Central Universities,China(Grant No.2017KFYXJJ029)
文摘The mechanism of terahertz(THz)pulse generation with a static magnetic field imposed on a gas plasma is theoretically investigated.The investigation demonstrates that the static magnetic field alters the electron motion during the optical field ionization of gas,leading to a two-dimensional asymmetric acceleration process of the ionized electrons.Simulation results reveal that elliptically or circularly polarized broadband THz radiation can be generated with an external static magnetic field imposed along the propagation direction of the two-color laser.The polarization of the THz radiation can be tuned by the strength of the external static magnetic field.
