The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
T. Otobe - One of the best experts on this subject based on the ideXlab platform.
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Analytical formulation for modulation of time-resolved dynamical Franz-Keldysh Effect by electron excitation in dielectrics
Physical Review B, 2017Co-Authors: T. OtobeAbstract:Analytical formulation of sub-cycle modulation (SCM) of dielectrics including electron excitation is presented. The SCM is sensitive to not only the time-resolved dynamical Franz-Keldysh Effect (Tr-DFKE) [T. Otobe, et al., Phys. Rev. B 93, 045124 (2016)], which is the nonlinear response without the electron excitation, but also the excited electrons. The excited electrons enhance the modulation with even-harmonics of pump laser frequency, and generate the odd-harmonics components. The new aspect of SCM is a consequence of i) the interference between the electrons excited by the pump laser and those excited by the probe pulse laser and ii) oscillation of the generated wave packed by the pump laser. When the probe- and pump-pulse polarizations are parallel, the enhancement of the even harmonics and the generation of the odd harmonics modulation appear. However, if the polarizations are orthogonal, the Effect arising from the electron excitations becomes weak. By comparing the parabolic and cosine band models, I found that the electrons under the intense laser field move as quasi-free particles.
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Time-resolved dynamical Franz-Keldysh Effect produced by an elliptically polarized laser
Physical Review B, 2016Co-Authors: T. OtobeAbstract:The analytical formula for the time-resolved dynamical Franz-Keldysh Effect (Tr-DFKE) under an elliptically polarized laser in sub-femtosecond time-scale is reported. The Houston function is assumed as the time-dependent wave function of the parabolic two-band system. The resulting formula shows the sub-cycle change of the optical properties for elliptically polarization; the modulation of the dielectric function becomes smaller than that of linear polarization. On the other hand, the subcycle modulation of the dielectric function disappears for a circularly polarized laser, which is a significant feature of the Tr-DFKE. This analytical formulas show good qualitative agreement with the first-principle calculation employing the time-dependent density functional theory for diamond.
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Analytical theory for the time-resolved dynamical Franz-Keldysh Effect under circularly polarized light
arXiv: Mesoscale and Nanoscale Physics, 2016Co-Authors: T. OtobeAbstract:We report here the analytical formula for the time-resolved dynamical Franz-Keldysh Effect (Tr-DFKE) under circularly polarized light. We assume the Houston function as the time-dependent wave function of the parabolic two-band system. Our formula shows that the sub-cycle change of the optical properties disappears, which is a significant feature of the Tr-DFKE under linear polarized light and is different from the static Franz-Keldysh Effect.
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Femtosecond time-resolved dynamical Franz-Keldysh Effect
Physical Review B, 2016Co-Authors: T. Otobe, Shunsuke A. Sato, Yasushi Shinohara, Kazuhiro YabanaAbstract:We theoretically investigate the dynamical Franz-Keldysh Effect in femtosecond time resolution, that is, the time-dependent modulation of a dielectric function at around the band gap under an irradiation of an intense laser field. We develop a pump-probe formalism in two distinct approaches: first-principles simulation based on real-time time-dependent density functional theory and analytic consideration of a simple two-band model. We find that, while time-average modulation may be reasonably described by the static Franz-Keldysh theory, a remarkable phase shift is found to appear between the dielectric response and the applied electric field.
D. S. Citrin - One of the best experts on this subject based on the ideXlab platform.
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High-field Franz-Keldysh Effect and exciton ionization in semiconductor quantum wires
Physical review letters, 2000Co-Authors: Stephen H. Hughes, D. S. CitrinAbstract:We investigate the Franz-Keldysh Effect and exciton ionization in semiconductor quantum wires. Absorption spectra are calculated near the band gap by solution of the low-density semiconductor Bloch equations in real space. The Sommerfeld factor and field-induced tunnel ionization of the exciton significantly affect the continuum portion of the absorption spectrum and remove the well known divergence problem associated with the 1D density of states at all field strengths. For reasonable electric field strengths substantial and tunable absorption oscillations appear above the band gap. Moreover, for very large fields, transparency can be achieved in the continuum for certain spectral positions.
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Dynamic Franz-Keldysh Effect: perturbative to nonperturbative regime.
Optics letters, 2000Co-Authors: Stephen H. Hughes, D. S. CitrinAbstract:We study theoretically the dynamic Franz-Keldysh Effect for quantum wells excited by a cw optical field and a terahertz (THz) frequency driving field. By monitoring the THz sidebands one can show that for, increasing THz-field amplitudes, nonperturbative Effects become predominant, and one must account for THz-field-induced nonlinearities to all orders.
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Dynamic Franz–Keldysh Effect:?excitonic versus free-carrier excitation schemes
Optics letters, 1999Co-Authors: Stephen H. Hughes, D. S. CitrinAbstract:We theoretically investigate the dynamic Franz–Keldysh Effect for subpicosecond optical pulses on quantum wells as a function of detuning from the bandgap. For specific spectral excitation regimes we find dramatic nonlinear enhancement Effects that are due to the preferential creation of terahertz- (THz-) field-driven propagating excitons and free electron–hole pairs in the THz and the optical domains, respectively. Our results explain why previous measurements of THz sidebands in the optical domain were so weak; we suggest and demonstrate a remarkably better experiment.
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dynamical franz keldysh Effect in the terahertz regime
Radiative Processes and Dephasing in Semiconductors (1998) paper RMD7, 1998Co-Authors: S Hughes, D. S. CitrinAbstract:We study the dynamical Franz-Keldysh Effect in the THz regime by subjecting a semiconductor quantum well to both a THz-frequency driving field and a 50 fs optical pulse. The double excitation scenario produces harmonically-generated upshifted THz transients - the creation of highly anisotripic electron-hole wavepackets. The results are in qualitative agreement with recent experimental measurements. Coherent control of the propagating wavepackets is demonstrated.
Harold N. Spector - One of the best experts on this subject based on the ideXlab platform.
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Confined Franz–Keldysh Effect in ZnO quantum dots
Superlattices and Microstructures, 2010Co-Authors: Congxin Xia, Harold N. SpectorAbstract:Abstract Within the framework of the Effective mass approximation, the confined Franz–Keldysh Effect is investigated theoretically in a cylindrical ZnO quantum dot (QD). Numerical results show that the application of an electric field can decrease the strength and the threshold energy of the optical absorption coefficient in ZnO QD. There are additional oscillations in the absorption above the Effective band gap, which are due to the Franz–Keldysh Effect which occurs in the presence of the electric field. Our results also show that the electric field has a more obviously influence on the optical absorption in cylindrical ZnO QD with larger dot height.
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Franz–Keldysh Effect in ZnO quantum wire
Physica E: Low-dimensional Systems and Nanostructures, 2010Co-Authors: Congxin Xia, Shuyi Wei, Harold N. SpectorAbstract:Abstract Within the framework of the Effective mass, the electric field Effect on the optical absorption coefficient is investigated theoretically in cylindrical ZnO quantum wire (QWR). Numerical results show that the application of the electric field can decrease the strength and the threshold energy of the optical absorption coefficient in ZnO QWR. We find that there are additional oscillations in the absorption above the Effective band gap, which are due to the Franz–Keldysh Effect for the electric field parallel to the axis of the wire. In addition, quantum size Effects on the optical absorption of ZnO QWR are also calculated.
Jun Suda - One of the best experts on this subject based on the ideXlab platform.
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Phonon-assisted optical absorption due to Franz–Keldysh Effect in 4H-SiC p–n junction diode under high reverse bias voltage
Applied Physics Express, 2018Co-Authors: Takuya Maeda, Masahiro Horita, Jun Suda, Xilun Chi, Tsunenobu KimotoAbstract:Photocurrent in a 4H-SiC p–n junction diode under illumination with sub-bandgap light was investigated. Under a high reverse bias condition, the photocurrent significantly increased with an increase in the reverse bias voltage. We calculated the photocurrent taking into consideration the phonon-assisted optical absorption due to the Franz–Keldysh Effect. The calculated photocurrent showed good agreement with the experimental results. The photocurrent also increased at elevated temperatures, which could be quantitatively explained by the redshift of the 4H-SiC absorption edge (the shrinkage of the bandgap) and the increase in the phonon occupation number with rising temperature.
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franz keldysh Effect in gan p n junction diode under high reverse bias voltage
Applied Physics Letters, 2018Co-Authors: Takuya Maeda, Tetsuo Narita, Masakazu Kanechika, Tsutomu Uesugi, Tetsu Kachi, Tsunenobu Kimoto, Masahiro Horita, Jun SudaAbstract:Photocurrent induced by sub-bandgap light absorption due to the Franz-Keldysh Effect was observed in GaN p-n junction diodes under a high reverse bias voltage. The photocurrent increased with the reverse bias voltage and the increase was found to be more significant as the wavelength approached the absorption edge of GaN. The photocurrent was calculated with consideration of light absorption induced by the Franz-Keldysh Effect in the depletion layer. The calculated curves showed excellent agreement with the experimental curves. The photocurrent also increased with an increase in temperature and this could be quantitatively explained by the red-shift of the GaN absorption edge with the increase in temperature.Photocurrent induced by sub-bandgap light absorption due to the Franz-Keldysh Effect was observed in GaN p-n junction diodes under a high reverse bias voltage. The photocurrent increased with the reverse bias voltage and the increase was found to be more significant as the wavelength approached the absorption edge of GaN. The photocurrent was calculated with consideration of light absorption induced by the Franz-Keldysh Effect in the depletion layer. The calculated curves showed excellent agreement with the experimental curves. The photocurrent also increased with an increase in temperature and this could be quantitatively explained by the red-shift of the GaN absorption edge with the increase in temperature.
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Franz–Keldysh Effect in n-type GaN Schottky barrier diode under high reverse bias voltage
Applied Physics Express, 2016Co-Authors: Takuya Maeda, Masahiro Horita, Masaya Okada, Masaki Ueno, Yoshiyuki Yamamoto, Jun SudaAbstract:The photocurrent of GaN vertical Schottky barrier diodes was investigated under sub-bandgap wavelength light irradiation. Under a low reverse bias voltage, the photocurrent is induced by internal photoemission, while under a high reverse bias voltage, the photocurrent increases significantly with the bias voltage. This is due to sub-bandgap optical absorption in a depletion region due to the Franz–Keldysh Effect. The voltage and wavelength dependences of the photocurrent are successfully explained quantitatively.
P. K. Basu - One of the best experts on this subject based on the ideXlab platform.
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Study of Si-Ge-Sn based Heterobipolar Phototransistor (HPT) exploiting Quantum Confined Stark Effect and Franz Keldysh Effect with and without resonant cavity
Physica E: Low-dimensional Systems and Nanostructures, 2019Co-Authors: Soumava Ghosh, Bratati Mukhopadhyay, Gopa Sen, P. K. BasuAbstract:Abstract We have studied the performance of a Quantum Confined Stark Effect (QCSE) dominated resonant cavity enhanced (RCE) Heterobipolar Phototransistor (HPT) using an absorption layer of Ge 0.992Sn0.008 QW with Si0.3Ge0.61Sn0.09 barrier between base and collector. Further the QW is replaced by bulk GeSn so that Franz-Keldysh Effect (FKE) becomes predominant. Main analysis was concentrated on finding the Quantum Efficiency (QE), Responsivity of RCE-HPT. Finally the Optical gain, Gain-Bandwidth product are estimated and compared with the structure without resonant cavity.
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Study of GeSn/SiGeSn RCE photodetectors based on Franz–Keldysh Effect and quantum confined Stark Effect
Optical and Quantum Electronics, 2015Co-Authors: Vedatrayee Chakraborty, Bratati Mukhopadhyay, P. K. BasuAbstract:We have studied the performance of a resonant cavity enhanced photodetector using multiple quantum wells made with GeSn as the well and SiGeSn as the barrier. The structure shows type I band alignment and the GeSn well possess a direct gap. Strong quantum confined Stark Effect in GeSn leads to strong absorption and high quantum efficiency. Similar parameters for a bulk GeSn with comparable width exhibiting Franz–Keldysh Effect are found to be substantially lower.
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GeSn/SiGeSn RCE photodetectors: A comparative study based on Franz-Keldysh Effect and quantum confined stark Effect
2012 5th International Conference on Computers and Devices for Communication (CODEC), 2012Co-Authors: Vedatrayee Chakraborty, Bratati Mukhopadhyay, P. K. BasuAbstract:Ge-based photodetectors are currently studied for providing cheap solution to long haul and short distance communication and optical interconnects. Tensile strained Ge layers grown with suitable barriers show direct gap type I band alignment. We have worked on resonant cavity enhanced (RCE) photodetectors using GeSn/SiGeSn type I structure. Performance of photodetectors using strong Quntum Confined Stark Effect, and Franz-Keldysh Effect in these structures and properties related to photodetection are studied in this paper.
