Hassan Ashour - Academia.edu (original) (raw)
Papers by Hassan Ashour
Anesthesia and Analgesia, 2009
The paper considers the effect of the defects on the electronic transmission properties in binomi... more The paper considers the effect of the defects on the electronic transmission properties in binomially tailored waveguide quantum wires, in which each Dirac delta function potential strength have been weight on the binomial distribution law. We have assumed that a single free-electron channel is incident on the structure and the scattering of electrons is solely from the geometric nature of the problem. We have used the transfer matrix method to study the electron transmission. We found this novel structure has a good defect tolerance. We found the structure tolerate up to 20% ± in strength defect and 5% ± in position defect for the central Dirac delta function in the binomial distribution. Also, we found this structure can tolerate both defect up to 20% ± in strength and 5% ± in position dislocation.
In this paper, we propose a new method to tune intrinsic GaAs semiconductor laser lasing frequenc... more In this paper, we propose a new method to tune intrinsic GaAs semiconductor laser lasing frequency and reducing the laser linewidth using an external deriving field. We used the developed Floquet S-matrix which determines the transmission probabilities and the shape and position of the induced quasibound state, which accumulated incident electrons. We solve the S-matrix numerically to the system parameters. We found that the oscillating field amplitude 1 V plays a curial rule in defining the profile of electrons accumulations in the quasibound state, and the field's strength made shift the position of the quasibound state. This shift in the bound state energy due field's strength is used to tune the lasing frequency and the output of the semiconductor laser linewidth is improved by changing the field's amplitude the deriving field.
In this study, we propose a new method to tune the semiconductor laser lasing frequency and reduc... more In this study, we propose a new method to tune the semiconductor laser lasing frequency and reducing the laser linewidth using an external deriving field. We redeveloped Floquet S-matrix which determines the transmission probabilities and the shape and position of the induced quasibound state, which accumulated incident electrons. We explored the S-matrix numerically for various system parameters. We found that the oscillating field amplitude V1 plays a curial rule in defining the profile of electrons accumulations in the quasibound state and the field's strength made sift the position of the quasibound state. This sift in the bound state energy due field's strength is used to tune the lasing frequency and the output of the semiconductor laser linewidth is improved by changing the field's amplitude the deriving field. By narrowing down the electron accumulations profile the laser linewidth would be narrower.
Journal of The Optical Society of America, 2007
A model of microcavity semiconductor lasers in which both the cavity field and the gain medium ar... more A model of microcavity semiconductor lasers in which both the cavity field and the gain medium are quantized is presented. The equation of motion for the elements of the reduced density matrix for the field in the photon number representation is developed and numerically solved to find the steady-state photon number distribution and the laser linewidth for a variety of operating conditions. For typical semiconductor microcavity operating conditions, the intensity noise is smaller and the laser linewidth is larger for lasers with a larger fraction of spontaneous emission into the cavity mode. However, for very-low-loss microcavity lasers, if the rate of spontaneous emission into the cavity mode exceeds the loss rate, the laser can appear to turn on at pump rates for which the gain medium is not inverted. In this anamolous regime, the laser intensity noise increases with an increased fraction of spontaneous emission into the cavity mode.
Physica Status Solidi (a), 2000
A phenomenological model is developed to study the transient behaviour of the photocurrent due to... more A phenomenological model is developed to study the transient behaviour of the photocurrent due to detrapping of carriers from a double impurity in semi-insulating semiconductors. The model predicts a peak in the transient curve at constant temperature. An Arrhenius plot of t p (the time at the peak) yields the second ionization energy of the double impurity. The activation energy determined from the photoinduced current transient spectroscopy (PICTS) analysis corresponds to the first ionization energy of the impurity. The model explains the appearance of a negative peak in the PICTS spectrum which was reported by previous authors on a number of semiconductors. Experimental investigation of the current decay curves on Mg x Zn 1Àx Te (x 0:10; 0:14; 0:30) showed that for x 0:10 the behaviour of the photocurrent decay at different temperatures and the PICTS spectrum can be interpreted in terms of the double impurity model. The ionization energies of the impurity were determined to be 0.082 AE 0.007 eV and 0.12 to 0.13 eV.
Physica Status Solidi (a), 2001
The trap levels in CdS thin films prepared by rf magnetron sputtering have been investigated usin... more The trap levels in CdS thin films prepared by rf magnetron sputtering have been investigated using Photoinduced Current Transient Spectroscopy (PICTS). Trap levels in the range 0.08-1.06 eV have been detected. Those levels are tentatively attributed to native defects and foreign impurities (particularly Cu and Ag).
Physica Status Solidi (a), 2000
A phenomenological model is developed to study the transient behaviour of the photocurrent due to... more A phenomenological model is developed to study the transient behaviour of the photocurrent due to detrapping of carriers from a double impurity in semi-insulating semiconductors. The model predicts a peak in the transient curve at constant temperature. An Arrhenius plot of t p (the time at the peak) yields the second ionization energy of the double impurity. The activation energy determined from the photoinduced current transient spectroscopy (PICTS) analysis corresponds to the first ionization energy of the impurity. The model explains the appearance of a negative peak in the PICTS spectrum which was reported by previous authors on a number of semiconductors. Experimental investigation of the current decay curves on Mg x Zn 1Àx Te (x 0:10; 0:14; 0:30) showed that for x 0:10 the behaviour of the photocurrent decay at different temperatures and the PICTS spectrum can be interpreted in terms of the double impurity model. The ionization energies of the impurity were determined to be 0.082 AE 0.007 eV and 0.12 to 0.13 eV.
Anesthesia and Analgesia, 2009
The paper considers the effect of the defects on the electronic transmission properties in binomi... more The paper considers the effect of the defects on the electronic transmission properties in binomially tailored waveguide quantum wires, in which each Dirac delta function potential strength have been weight on the binomial distribution law. We have assumed that a single free-electron channel is incident on the structure and the scattering of electrons is solely from the geometric nature of the problem. We have used the transfer matrix method to study the electron transmission. We found this novel structure has a good defect tolerance. We found the structure tolerate up to 20% ± in strength defect and 5% ± in position defect for the central Dirac delta function in the binomial distribution. Also, we found this structure can tolerate both defect up to 20% ± in strength and 5% ± in position dislocation.
In this paper, we propose a new method to tune intrinsic GaAs semiconductor laser lasing frequenc... more In this paper, we propose a new method to tune intrinsic GaAs semiconductor laser lasing frequency and reducing the laser linewidth using an external deriving field. We used the developed Floquet S-matrix which determines the transmission probabilities and the shape and position of the induced quasibound state, which accumulated incident electrons. We solve the S-matrix numerically to the system parameters. We found that the oscillating field amplitude 1 V plays a curial rule in defining the profile of electrons accumulations in the quasibound state, and the field's strength made shift the position of the quasibound state. This shift in the bound state energy due field's strength is used to tune the lasing frequency and the output of the semiconductor laser linewidth is improved by changing the field's amplitude the deriving field.
In this study, we propose a new method to tune the semiconductor laser lasing frequency and reduc... more In this study, we propose a new method to tune the semiconductor laser lasing frequency and reducing the laser linewidth using an external deriving field. We redeveloped Floquet S-matrix which determines the transmission probabilities and the shape and position of the induced quasibound state, which accumulated incident electrons. We explored the S-matrix numerically for various system parameters. We found that the oscillating field amplitude V1 plays a curial rule in defining the profile of electrons accumulations in the quasibound state and the field's strength made sift the position of the quasibound state. This sift in the bound state energy due field's strength is used to tune the lasing frequency and the output of the semiconductor laser linewidth is improved by changing the field's amplitude the deriving field. By narrowing down the electron accumulations profile the laser linewidth would be narrower.
Journal of The Optical Society of America, 2007
A model of microcavity semiconductor lasers in which both the cavity field and the gain medium ar... more A model of microcavity semiconductor lasers in which both the cavity field and the gain medium are quantized is presented. The equation of motion for the elements of the reduced density matrix for the field in the photon number representation is developed and numerically solved to find the steady-state photon number distribution and the laser linewidth for a variety of operating conditions. For typical semiconductor microcavity operating conditions, the intensity noise is smaller and the laser linewidth is larger for lasers with a larger fraction of spontaneous emission into the cavity mode. However, for very-low-loss microcavity lasers, if the rate of spontaneous emission into the cavity mode exceeds the loss rate, the laser can appear to turn on at pump rates for which the gain medium is not inverted. In this anamolous regime, the laser intensity noise increases with an increased fraction of spontaneous emission into the cavity mode.
Physica Status Solidi (a), 2000
A phenomenological model is developed to study the transient behaviour of the photocurrent due to... more A phenomenological model is developed to study the transient behaviour of the photocurrent due to detrapping of carriers from a double impurity in semi-insulating semiconductors. The model predicts a peak in the transient curve at constant temperature. An Arrhenius plot of t p (the time at the peak) yields the second ionization energy of the double impurity. The activation energy determined from the photoinduced current transient spectroscopy (PICTS) analysis corresponds to the first ionization energy of the impurity. The model explains the appearance of a negative peak in the PICTS spectrum which was reported by previous authors on a number of semiconductors. Experimental investigation of the current decay curves on Mg x Zn 1Àx Te (x 0:10; 0:14; 0:30) showed that for x 0:10 the behaviour of the photocurrent decay at different temperatures and the PICTS spectrum can be interpreted in terms of the double impurity model. The ionization energies of the impurity were determined to be 0.082 AE 0.007 eV and 0.12 to 0.13 eV.
Physica Status Solidi (a), 2001
The trap levels in CdS thin films prepared by rf magnetron sputtering have been investigated usin... more The trap levels in CdS thin films prepared by rf magnetron sputtering have been investigated using Photoinduced Current Transient Spectroscopy (PICTS). Trap levels in the range 0.08-1.06 eV have been detected. Those levels are tentatively attributed to native defects and foreign impurities (particularly Cu and Ag).
Physica Status Solidi (a), 2000
A phenomenological model is developed to study the transient behaviour of the photocurrent due to... more A phenomenological model is developed to study the transient behaviour of the photocurrent due to detrapping of carriers from a double impurity in semi-insulating semiconductors. The model predicts a peak in the transient curve at constant temperature. An Arrhenius plot of t p (the time at the peak) yields the second ionization energy of the double impurity. The activation energy determined from the photoinduced current transient spectroscopy (PICTS) analysis corresponds to the first ionization energy of the impurity. The model explains the appearance of a negative peak in the PICTS spectrum which was reported by previous authors on a number of semiconductors. Experimental investigation of the current decay curves on Mg x Zn 1Àx Te (x 0:10; 0:14; 0:30) showed that for x 0:10 the behaviour of the photocurrent decay at different temperatures and the PICTS spectrum can be interpreted in terms of the double impurity model. The ionization energies of the impurity were determined to be 0.082 AE 0.007 eV and 0.12 to 0.13 eV.