We investigate the wavefronts depinning in current biased, infinitely long semiconductor superlattice systems by the method of discrete mapping and show that the wavefront depinning corresponds to the discrete mapping...We investigate the wavefronts depinning in current biased, infinitely long semiconductor superlattice systems by the method of discrete mapping and show that the wavefront depinning corresponds to the discrete mapping failure. For parameter values near the lower critical current in both discrete drift model (DD model) and discrete drift-diffusion model (DDD model), the mapping failure is determined by the important mapping step from the bottom of branch to branch α. For the upper critical parameters in DDD model, the key mapping step is from branch γ to the top of the corresponding branch α and we may need several active wells to describe the wavefronts.展开更多
This paper investigates the behaviour of a pair of electron and hole in semiconductor superlattice under an external electric field with the consideration of Coulomb interaction. By numerically calculating the corresp...This paper investigates the behaviour of a pair of electron and hole in semiconductor superlattice under an external electric field with the consideration of Coulomb interaction. By numerically calculating the corresponding probability in the nearest neighbour tight binding approximation, we find that the single electron (or the hole) can not be dynamically localized due to the Coulomb interaction, while the dynamic localization of exciton (the pair of the electron and hole) still exists. Moreover we find that with the increase of the intensity of electric field, the exciton can be dynamically localized more completely.展开更多
This paper studies both the intraband polarization and terahertz emission of a semiconductor superlattice in combined dc and ac electric fields by using the superposition of two identical time delayed and phase shifte...This paper studies both the intraband polarization and terahertz emission of a semiconductor superlattice in combined dc and ac electric fields by using the superposition of two identical time delayed and phase shifted optical pulses. By adjusting the delay between these two optical pulses, our results show that the intraband polarization is sensitive to the time delay. The peak values appear again for the terahertz emission intensity due to the superposition of two optical pulses. The emission lines of terahertz blueshift and redshift in different ac electric fields and dynamic localization appears. The emission lines of THz only appear to blueshift when the biased superlattice is driven by a single optical pulse. Due to excitonic dynamic localization, the terahertz emission intensity decays with time in different dc and ac electric fields. These are features of this superlattice which distinguish it from a supertattice generated by a single optical pulse to drive it.展开更多
The investigation of the polar optical vibration modes in semiconductor superlattices by different models are reviewed. It is emphasized that the simple analytic representations of the lattice modes calculated with th...The investigation of the polar optical vibration modes in semiconductor superlattices by different models are reviewed. It is emphasized that the simple analytic representations of the lattice modes calculated with the dipole oscillator model have introduced the double boundary condition that both the electrostatic potential and optical displacement vanish at the interfaces and have found wide acceptance. They have been referred to as the Huang Zhu model. It is pointed out that its improved simulation version is essentially the dielectric continuum model taking account of phonon dispersion and subject to the double boundary condition.展开更多
We present a theoretical investigation,based on the tight-binding Hamiltonian,of efficient electric-field-induced three-waves mixing(EFIM)in an undoped lattice-matched short-period superlattice(SL)that integrates quas...We present a theoretical investigation,based on the tight-binding Hamiltonian,of efficient electric-field-induced three-waves mixing(EFIM)in an undoped lattice-matched short-period superlattice(SL)that integrates quasi-phase-matched(QPM)SL straight waveguides and SL racetrack resonators on an opto-electronic chip.Periodically reversed DC voltage is applied to electrode segments on each side of the strip waveguide.The spectra ofχ_(xxxx)^((3))and of the linear suscepti-bility have been simulated as a function of the number of the atomic monolayers for“non-relaxed”heterointerfaces,and by considering all the transitions between valence and conduction bands.The large ob-tained values ofχ_(xxxx)^((3))make the(ZnS)3/(Si2)3 short-period SL a good candidate for realizing large effective second-order nonlinearity,en-abling future high-performance of the SLOI PICs and OEICs in the 1000-nm and 2000-nm wavelengths ranges.We have made detailed calculations of the efficiency of second-harmonic generation and of the performances of the optical parametric oscillator(OPO).The re-sults indicate that the(ZnS)N/(Si2)M QPM is competitive with present PPLN technologies and is practical for classical and quantum appli-cations.展开更多
Novel distributed Bragg reflectors (DBRs) with 4.5 pairs of GaAs/AlAs short period superlattice (SPS) used in oxide-apertured vertical-cavity surface-emitting lasers (VCSELs) were designed. The structure of a 22-perio...Novel distributed Bragg reflectors (DBRs) with 4.5 pairs of GaAs/AlAs short period superlattice (SPS) used in oxide-apertured vertical-cavity surface-emitting lasers (VCSELs) were designed. The structure of a 22-period Al0.9Ga0.1 As (69.5 nm)/4.5-pair [GaAs (10 nm)-AlAs (1.9 nm)] DBR was grown on an n+ GaAs substrate (100) 2° off toward <111>A by molecular beam epitaxy. The emitting wavelength was 850 nm with low threshold current of about 2 mA, corresponding to the threshold current density of 2 kA/cm2. The maximum output power was more than 1 mW. The VCSEL device temperature was increased by heating ambient temperature from 20 to 100℃ and the threshold current increased slowly with the increase of temperature.展开更多
基金Project supported in part by the State Key Program of National Natural Science of China (Grant No 70431002)the National Natural Science Foundation of China (Grant No 10575010)+1 种基金the National Basic Research Program of China (Grant No 2007CB814805)the Foundation of Doctoral Training of China (Grant No 20060027009)
文摘We investigate the wavefronts depinning in current biased, infinitely long semiconductor superlattice systems by the method of discrete mapping and show that the wavefront depinning corresponds to the discrete mapping failure. For parameter values near the lower critical current in both discrete drift model (DD model) and discrete drift-diffusion model (DDD model), the mapping failure is determined by the important mapping step from the bottom of branch to branch α. For the upper critical parameters in DDD model, the key mapping step is from branch γ to the top of the corresponding branch α and we may need several active wells to describe the wavefronts.
文摘This paper investigates the behaviour of a pair of electron and hole in semiconductor superlattice under an external electric field with the consideration of Coulomb interaction. By numerically calculating the corresponding probability in the nearest neighbour tight binding approximation, we find that the single electron (or the hole) can not be dynamically localized due to the Coulomb interaction, while the dynamic localization of exciton (the pair of the electron and hole) still exists. Moreover we find that with the increase of the intensity of electric field, the exciton can be dynamically localized more completely.
基金Project supported by the National Natural Science Foundation of China (Grant No 10647132)the Scientific Research Fundof Hunan Provincial Education Department of China (Grant No 05B014)
文摘This paper studies both the intraband polarization and terahertz emission of a semiconductor superlattice in combined dc and ac electric fields by using the superposition of two identical time delayed and phase shifted optical pulses. By adjusting the delay between these two optical pulses, our results show that the intraband polarization is sensitive to the time delay. The peak values appear again for the terahertz emission intensity due to the superposition of two optical pulses. The emission lines of terahertz blueshift and redshift in different ac electric fields and dynamic localization appears. The emission lines of THz only appear to blueshift when the biased superlattice is driven by a single optical pulse. Due to excitonic dynamic localization, the terahertz emission intensity decays with time in different dc and ac electric fields. These are features of this superlattice which distinguish it from a supertattice generated by a single optical pulse to drive it.
文摘The investigation of the polar optical vibration modes in semiconductor superlattices by different models are reviewed. It is emphasized that the simple analytic representations of the lattice modes calculated with the dipole oscillator model have introduced the double boundary condition that both the electrostatic potential and optical displacement vanish at the interfaces and have found wide acceptance. They have been referred to as the Huang Zhu model. It is pointed out that its improved simulation version is essentially the dielectric continuum model taking account of phonon dispersion and subject to the double boundary condition.
基金supported by the Air Force Office of Scientific Research under Grant FA9550-21-1-0347.
文摘We present a theoretical investigation,based on the tight-binding Hamiltonian,of efficient electric-field-induced three-waves mixing(EFIM)in an undoped lattice-matched short-period superlattice(SL)that integrates quasi-phase-matched(QPM)SL straight waveguides and SL racetrack resonators on an opto-electronic chip.Periodically reversed DC voltage is applied to electrode segments on each side of the strip waveguide.The spectra ofχ_(xxxx)^((3))and of the linear suscepti-bility have been simulated as a function of the number of the atomic monolayers for“non-relaxed”heterointerfaces,and by considering all the transitions between valence and conduction bands.The large ob-tained values ofχ_(xxxx)^((3))make the(ZnS)3/(Si2)3 short-period SL a good candidate for realizing large effective second-order nonlinearity,en-abling future high-performance of the SLOI PICs and OEICs in the 1000-nm and 2000-nm wavelengths ranges.We have made detailed calculations of the efficiency of second-harmonic generation and of the performances of the optical parametric oscillator(OPO).The re-sults indicate that the(ZnS)N/(Si2)M QPM is competitive with present PPLN technologies and is practical for classical and quantum appli-cations.
文摘Novel distributed Bragg reflectors (DBRs) with 4.5 pairs of GaAs/AlAs short period superlattice (SPS) used in oxide-apertured vertical-cavity surface-emitting lasers (VCSELs) were designed. The structure of a 22-period Al0.9Ga0.1 As (69.5 nm)/4.5-pair [GaAs (10 nm)-AlAs (1.9 nm)] DBR was grown on an n+ GaAs substrate (100) 2° off toward <111>A by molecular beam epitaxy. The emitting wavelength was 850 nm with low threshold current of about 2 mA, corresponding to the threshold current density of 2 kA/cm2. The maximum output power was more than 1 mW. The VCSEL device temperature was increased by heating ambient temperature from 20 to 100℃ and the threshold current increased slowly with the increase of temperature.