Yazar "Sayrac, Muhammed" seçeneğine göre listele

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    Computation of Atomic Dipole Spectra for Different Atoms by Considering Short and Long Electron Trajectories under the Intense Laser Pulse
    (9TH INTERNATIONAL ADVANCED TECHNOLOGIES SYMPOSIUM, 2021) Sayrac, Muhammed
    In this work, computation of the nonlinear dipole response of a single atom is performed by considering the ionization of the electron under the intense laser field. The dipole spectra for xenon (Xe) and argon (Ar) gases are obtained. Xe and Ar are the simples gas species having close ionization potentials. The interaction of these single atoms with the intense-short laser pulse leads to the laser-matter interaction. The short laser pulse is accepted as an ultra-short duration, i.e. the shorter time scale than the electron energy-lattice transfer process. The Keldysh parameter, which determines the ionization regime, is smaller than one because of the ionization potential of these gases. The harmonic spectra for Ar and Xe gas species are simulated by calculating the dipole spectrum considering the Lewenstein model by using a personal computer. After tunneling, the electron propagation in the short-trajectory and the combination of short and long trajectories are simulated. The effects of the short electron trajectory have noticeable effects on the dipole spectrum of a single electron.
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    Computation of Refractive Index Values of Inert Gases at Near-Infrared and XUV Region Based on Mathematica Software
    (Adiyaman University, 2021) Sayrac, Muhammed
    In this study, refractive indices in the visible, near-infrared, and extreme ultraviolet (XUV) regions are calculated based on Mathematica software. Atomic scattering factors are simulated for a high photon energy range (20-60 eV). By using the atomic scattering factors, the real and imaginary part of the index of refraction values are plotted as a function of photon energy. This work aims to present a computational program, which calculates the index of refraction of the inert gases at different wavelength regions. The refractive indices of gases, namely helium (He), neon (Ne), argon (Ar), and xenon (Xe) in the near-infrared and XUV region are computed by using Mathematica software. The applications of the index of refraction are discussed in the paper. The Mathematica program calculating the refractive indices is presented in the Appendix. © 2021, Adiyaman University. All rights reserved.
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    Effect of Ultrashort Laser Pulse Shape on the Dipole Spectrum of a Single Electron
    (International Conference on Advances in Engineering, Architecture, Science and Technology (ICAEAST 2021)), 2021) Sayrac, Muhammed
    In this study, the effects of ultrashort laser pulse shape for the laser-matter interaction have been considered. Three different pulse shapes, Gaussian, Super-Gaussian, and Cosine-Squared, are used to calculate the dipole spectrum of the single atom by considering the Lewenstein model. The ultrashort laser pulse shapes are presented, and it has been found that the super-Gaussian laser pulse, which has a spiky and strong tail, has been more effective in transferring energy to the electron. The electron is excited and gains kinetic energy under the ultrashort laser pulse. The laser pulse-electron interaction affects the ground state wave function and the returning electron wave packet. The optimum dipole spectrum, which is extended to higher photon energies, has been obtained under the Super- Gaussian pulse shape.
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    Exploring the Nonlinear Optical Behaviour of InGaAs/GaAs Triple Quantum Wells via Structural Modulations and External Electric Fields
    (Iranian Nano Society, 2023) Sayrac, Muhammed; Dakhlaoui, Hassen; Mora-Ramos, Miguel Eduardo; Ungan, Fatih
    The nonlinear optical properties of the InxGa1-xAs/GaAs triple quantum well structure are studied for different structure parameters and applied external electric field. Within the framework of the effective mass and envelope function approximations, the one-dimensional time-independent Schrödinger wave equation is solved using the diagonalization method to obtain the energy eigenvalues and eigenfunctions of the structure. The coefficients of nonlinear optical properties such as nonlinear optical rectification (NOR), second harmonic generation (SHG), and third harmonic generation (THG) of the structure are numerically evaluated from the corresponding expressions derived within the compact density matrix approximation. The influence of adjustable structure parameters and the applied external electric field affects the separation of subband energy levels and the magnitudes of dipole moment matrix elements. These changes in the electronic properties of the structure cause the NOR, SHG, and THG peak positions to shift towards lower or higher energy regions. It is expected that these results will enable the appropriate design of new optoelectronic devices. © (2023), (Iranian Nano Society). All Rights Reserved.
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    Generation of Coherent Extreme Ultraviolet Radiation in an Air Gas Cell with a High Power Femtosecond Laser System
    (Springer, 2021) Sayrac, Muhammed
    High harmonic generation (HHG) in air medium is experimentally produced by using a state-ofthe-art high power laser system. The harmonic orders up to 35th harmonic are well observed. Optical power dependence of harmonic spectrum is obtained. Dynamics of a free electron in an intense laser field presents good agreement with the experimental results. The air medium is used as an interaction medium since air is a ready source in abundance. The harmonic spectral distribution is similar to that obtained in noble gases. Experimental results of harmonics produced in air medium follows same trends in terms of plateau region and cutoff harmonic order, which extends and enhances with increasing laser field.
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    Generation of coherent XUV radiation at different interaction lengths using the ultrashort laser system
    (World Scientific Publ Co Pte Ltd, 2024) Sayrac, Muhammed
    Generation of short wavelengths is obtained using the gas cells having different lengths. A Ti:sapphire laser system at 1kHz or 10Hz repetition rate is used to produce high harmonic generation (HHG). The gas cell producing optimum harmonic spectrum is determined using the 1kHz laser system. The optimum harmonic signal is obtained under the phase-matched condition. The total harmonic yield is increased by adjusting argon gas pressure in the different gas cell lengths (length of the interaction mediums). Harmonics up to the 27th order are obtained. The 1D model is used for the calculation of harmonic yield at different interaction lengths. The high-power laser system at the 10Hz repetition rate is used to generate high-order harmonics. The harmonic orders are extended to the 35th harmonic in argon gas. A harmonic spectrum in H2 gas is generated using different pump laser power. The power dependence of the harmonic signal from H2 gas is obtained. The variation of the harmonic spectrum for the different cell parameters is explained as a constructive or destructive buildup of generated harmonics while they propagate through the gas cell.
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    Generation of Coherent XUV Radiation in N2 molecule and its Mixture with Ne Gas using Sub-terawatt Laser System
    (2024) Sayrac, Muhammed
    High harmonic generation (HHG) in pure nitrogen (N2) and its mixture with neon (Ne) gas was produced. The external laser field producing 6mJ optical pulse energy with 50fs pulse duration at 10Hz repetition rate was focused into a gas jet producing high harmonics. The N2 and Ne gas have different ionization potentials. The strong harmonic signal in pure N2 was produced, and a weak harmonic signal in a mixture of N2-Ne was generated compared to that in pure N2. The increase of Ne contribution in the N2-Ne mixture resulted in a decrease in harmonic signal. Harmonic signal increase and decrease were observed for different N2:Ne ratios. The harmonic generation mechanism was discussed in that the ionization of Ne is difficult compared to N2, and the neutral Ne atom leads to neutral atomic dispersion (phase mismatch), so the harmonic yield decreases.
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    Generation of even and odd harmonics in the XUV region with controlling the relative delay and polarization of two-color fields
    (Elsevier, 2021) Sayrac, Muhammed; Kolomenskii, Alexandre A.; Dong, Jian; Schuessler, Hans A.
    We report high harmonic generation in the extreme ultraviolet (XUV) region by using two-color laser fields at the wavelengths of 800 nm and 400 nm. With a Ti: sapphire femtosecond laser at a 10 Hz repetition rate efficient high harmonic generation was obtained in an argon gas medium with the IR field (ω) and its second harmonic (2ω) with parallel and perpendicular polarizations. The relative delay between the pulses is controlled via a Michelson interferometer arrangement. In addition to the odd high harmonic spectrum with frequencies (2n+1)ω, where n - integer number, also even spectral components 2nω are obtained, when the fields of the two colors are temporally overlapped and interact with the argon gas. Due to this overlap, the yield of odd harmonics can be increased as well. The calculations of electron trajectories within the semiclassical approach show differences in the action of the fields with parallel and perpendicular polarizations. For the former, there exist broad time intervals for returning electrons, and in the latter case there are only narrow intervals for possible solutions for each of the electron returns to the parent ion for a fixed phase difference between the ω and 2ω fields. By varying the relative delay between the two laser fields it is possible to spectrally enrich and enhance the produced XUV radiation or suppress it. The conclusions of the semi-classical approach were confirmed by calculations of the harmonic intensities within the strong field dipole approximation.
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    Influence of hydrostatic pressure, temperature, and terahertz laser field on the electron-related optical responses in an asymmetric double quantum well
    (Springer, 2021) Sayrac, Muhammed; Turkoglu, Aslan; Ungan, Fatih
    In this study, the effects of hydrostatic pressure, temperature, and high-frequency intense laser field on the nonlinear optical properties of an asymmetric GaAs/AlGaAs double quantum well was theoretically investigated. For this, firstly, the energy eigenvalues and eigenfunctions of the system have been obtained using the effective-mass and parabolic band approximation. Later, the nonlinear optical properties of the structure are calculated using the compact-density matrix approach. The obtained numerical results show that when the magnitude of the intense laser field applied to the structure is increased, the amplitudes of both the total optical absorption coefficients (TOACs) and the relative refractive index changes (RRICs) peaks increase and shift towards higher energies. In addition, it was also observed that the increase in temperature had a similar effect on the TOACs and RRICs with the intense laser field, whereas the increase in hydrostatic pressure has an opposite effect.
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    Intensity-dependent nonlinear optical properties in an asymmetric Gaussian potential quantum well-modulated by external fields
    (Springer, 2021) Sayrac, Muhammed; Turkoglu, Aslan; Mora-Ramos, M. E.; Ungan, Fatih
    In this paper, the efects of external electric, magnetic and non-resonant intense laser felds on the nonlinear optical rectifcation (NOR), second-harmonic (SH), and third harmonic (TH) generation in a GaAs quantum well with asymmetrical Gaussian potential are theoretically investigated. Firstly, the energy eigenvalues and eigenfunctions of a single electron confned in the structure are obtained by using the diagonalization method within the framework of the efective-mass and parabolic band approaches. Then, using these energy eigenvalues and eigenfunctions, expressions derived within the compact density matrix approximation have been employed to calculate the coefcients of the nonlinear optical response in the structure. The obtained simulation results show that the infuence of the external felds leads to signifcant changes in the coefcients of nonlinear optical rectifcation, second and third harmonic generation in the system. As a result, it has been seen that the amplitude and position of the peaks of nonlinear optical rectifcation, second and third harmonic coefcients can be controlled by changing the applied external felds.
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    Investigation of the Structural and Thermodynamic Parameters on the Nonlinear Optical Properties of InGaAs/InP Triple Quantum Well Exposed to an External Electric Field
    (Iranian Nano Society, 2023) Sayrac, Muhammed; Dakhlaoui, Hassen; Mora-Ramos, Miguel Eduardo; Ungan, Fatih
    In this study, the effects of both tunable physical parameters and thermodynamic variables on the linear and nonlinear optical properties of the InGaAs/InP triple quantum well are theoretically investigated in detail. In addition, the effect of an external static electric field applied parallel to the growth direction of the structure was also studied. To carry out this analysis, firstly, the energy eigenvalues and eigenfunctions of the system were obtained as a result of solving the time-independent Schrödinger equation using the diagonalization method, under the effective mass and envelope function approach. Then, using these energy eigenvalues and eigenfunctions, the nonlinear optical properties of the structure were calculated from the expressions derived within the compact density matrix approach via the iterative method. The effect of adjustable structure parameters and applied external fields affects the difference in subband energy levels at which transitions occur and the magnitudes of the dipole moment matrix elements. These changes in the electronic properties of the structure cause the peak positions of the total (linear plus nonlinear) optical absorption coefficient and total relative refractive index change coefficient (RRIC) to shift towards lower or higher energy regions. These results are expected to enable the proper design of new optoelectronic devices. © (2023), (Iranian Nano Society). All Rights Reserved.
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    Numerical Simulation of Diffraction Patterns with Different Illumination Laser Wavelength
    (International Conference on Engineering Technologies (ICENTE'21), 2021) Sayrac, Muhammed
    In this study, a computer simulation program generating Fresnel diffraction patterns from the apertures by using the different illumination wavelength sources has been studied. Changing the aperture-screen distance and the illumination wavelength provides a clear transition of diffraction patterns from the Fresnel to the Fraunhofer region. The diffraction patterns obtained by the Fresnel integral method have been compared with those simulated by the Fraunhofer calculation. There is a good agreement between the results. Certain conditions have been investigated that Fresnel diffraction patterns approach the Fraunhofer diffraction patterns. The simulations have been performed using a personal computer with Matlab software.