elnaz irani

@modares.ac.ir

tarbiat modares university



           

https://researchid.co/elnazirani

RESEARCH, TEACHING, or OTHER INTERESTS

Atomic and Molecular Physics, and Optics, Physics and Astronomy

37

Scopus Publications

Scopus Publications


  • Investigating high harmonic yield from different alignments of WSe<inf>2</inf> semiconductor
    Amin Sadeghifaraz, Razieh Faghih-Latif, Elnaz Irani, and Mohammad Monfared
    Elsevier BV


  • Generation of the isolated highly elliptically polarized attosecond pulse using the polarization gating technique: TDDFT approach
    Ahmad Reza madhani, Elnaz Irani, and Mohammad Monfared
    Optica Publishing Group
    This paper theoretically investigates the generation of isolated elliptically polarized attosecond pulses with a tunable ellipticity from the interaction of Cl2 molecule and a polarization-gating laser pulse. A three-dimensional calculation based on the time-dependent density functional theory is done. Two different methods are proposed for generating elliptically polarized single attosecond pulses. The first method is based on applying a single-color polarization gating laser and controlling the orientation angle of the Cl2 molecule with respect to the polarization direction of the laser at the gate window. An attosecond pulse with an ellipticity of 0.66 and a pulse duration of 275 as is achieved by tuning the molecule orientation angle to 40° in this method and superposing harmonics around the harmonic cutoff. The second method is based on irradiating an aligned Cl2 molecule with a two-color polarization gating laser. The ellipticity of the attosecond pulses obtained by this method can be controlled by adjusting the intensity ratio of the two colors. Employing an optimized intensity ratio and superposing harmonics around the harmonic cutoff would lead to the generation of an isolated, highly elliptically polarized attosecond pulse with an ellipticity of 0.92 and a pulse duration of 648 as.

  • Investigation of parameters affecting the high harmonic generation from monolayer WS<inf>2</inf>
    Amin Sadeghifaraz, Elnaz Irani, and Mohammad Monfared
    Wiley
    AbstractThe effect of crystal symmetry in the high harmonic generation of monolayer WS2 is investigated using the three‐dimensional time‐dependent density functional theory. The role of linearly and elliptically polarized laser, as well as the crystall orientation in the enhancement of harmonics yield, is explored. Also, the wavelength dependence of the harmonic yield and the intensity dependence of cutoff harmonic order are studied. The former shows an exponential decay with increasing the driving laser wavelength, and the latter reveals a linear dependency of cutoff harmonic to the driving laser field. Moreover, a dual pulse system as a driving laser, a fundamental 1.3 μm laser pulse synthesized by its second harmonic, is proposed which could increase the cutoff harmonic order up to 24th (22 eV). Our results pave the way for controlling and enhancing high harmonic spectra from solids.

  • Influence of coherent vibrational excitation on the high-order harmonic generation of diatomic molecules
    Mohammad Monfared, Elnaz Irani, Christoph Lemell, and Joachim Burgdörfer
    American Physical Society (APS)
    The generation of high harmonics (HHG) in atomic systems by the highly non-linear response to an intense laser field is a prominent pathway to the synthesis of ever shorter laser pulses at increasingly higher photon energies. Extensions of this process to molecules add to the complexity but also offers novel opportunities as multi-center effects and the coupling to nuclear degrees of freedom can influence HHG. In this work we theoretically explore the impact of coherent vibronic excitations of diatomic molecules on the HHG spectrum within the framework of time-dependent density functional theory. We observe the appearance of novel interference structures in the HHG spectra controlled by resonances between the driving field and the vibronic wavepacket.



  • Mode-controlled random laser assisted by stimulated Raman scattering
    Mandana Sadat Hosseini, Elnaz Yazdani, Elnaz Irani, Batoo Sajad, Fariba Mehradnia, Sirous Bazire, and Amir Bayat
    Elsevier BV

  • Investigation of ablation efficiency during the pulsed laser ablation of a zinc metal target in a distilled water environment
    Mohammad Rasoul Khodaverdi and Elnaz Irani
    Optica Publishing Group
    In this study, the effect of Nd:YAG laser energy with a 9 ns time duration as one of the important parameters on the laser ablation of a zinc metal target in a distilled water environment has been investigated both experimentally and theoretically. The influence of plasma shielding on the ablation rate for 100–600 mJ energies is also considered. After investigating XRD, SEM, and UV-Vis results of each sample, it is determined that synthesized nanostructures are ZnO nanoparticles, and also the morphologies of the synthesized nanostructures are formed in two forms of hexagonal crystals and amorphous nanosheets. By increasing the laser energy to 400 mJ, the ablation rate on the zinc target increases. However, with increasing energy up to 600 mJ, the plasma shielding effect is evident and the ablation rate is reduced. Also, the theoretical two-fluid heat transfer model of nanosecond pulsed laser ablation is developed to visualize the evolution of temperature distributions, crater profile, and ablation depth.





  • Enhancing high harmonic generation by the global optimization of a two-color chirped laser field
    Mohammad Mofared, Elnaz Irani, and Rasoul Sadighi-Bonabi
    Royal Society of Chemistry (RSC)
    Enhanced high harmonics are generated by local and global optimization approaches to achieve a supercontinuum spectrum.

  • Controlling the properties of TiO<inf>2</inf> nanoparticles generated by nanosecond laser ablation in liquid solution
    Mahsa Pashazadeh, Elnaz Irani, Mir Maqsood Golzan, and Rasoul Sadighi-Bonabi
    IOP Publishing
    Laser ablation of titanium target in distilled water for synthesis of colloidal nanoparticles is studied both experimentally and theoretically. The effects of laser parameters such as wavelength, pulse energy, fluence and shot numbers on the ablation rate and size properties of colloidal nanoparticles are investigated. The experimental approach addresses the interesting issue for finding the optimal main experimental parameters of laser ablation. The theoretical thermal model of nanosecond pulsed laser ablation is developed to visualize the evolution of temperature distributions and ablation depth. The simulation result of ablation depth has been compared with the experimental result obtained by Nd:YAG laser, 1064 nm wavelength, 10 ns time duration and 200 µm spot size on the target. This comprehensive model has good agreement with experimental results and it can overcome the limitations of the experimental investigation technique and improves the pulsed laser ablation rate.

  • High-order harmonic generation of CO and N<inf>2</inf> molecules under linearly- and bi circularly-polarized laser pulses by TD-DFT
    A M Koushki, R Sadighi-Bonabi, M Mohsen-Nia, and E Irani
    IOP Publishing
    We present a method for high-order harmonics generation of N2 and CO molecules under two-color circularly polarized counter-rotating laser pulses at frequencies of and 2. Pulse envelope in this investigation is sin-squared and the intensity of each laser beam is with ten-optical cycle (o.c.). We show that an isolated pulse with a pulse duration shorter than 20 attosecond from the superposition of several harmonics can be generated. Both two-color linearly- and bicircularly-polarized laser pulses are considered. Our results have also been compared with the outcomes of the previous theoretical works as well as experiment observations. It is found that for CO molecule, the bicircularly-polarized laser pulses are superior and more efficient, and it can generate narrower attosecond pulses than the linearly-polarized pulses. While for N2 molecule, the two-color linearly-polarized pulses are more efficient, and it can generate narrower attosecond pulses than the bicircularly-polarized pulses. Furthermore, in order to demonstrate the origin of red- and blue-shifts in high-harmonic spectra, the effect of pulse duration on the high-order harmonics spectra is investigated. In addition, to obtain imaging on the temporal dependence of the electron densities, the time dependent electron localization function is used. Moreover, in order to study of the quantum trajectory of electrons, time-frequency analysis is utilized.

  • Controlling the multi-electron dynamics in the high harmonic spectrum from N<inf>2</inf>O molecule using TDDFT
    M. Monfared, E. Irani, and R. Sadighi-Bonabi
    AIP Publishing
    In this study, high harmonic generation from a multi-atomic nitrous oxide molecule was investigated. A comprehensive three-dimensional calculation of the molecular dynamics and electron trajectories through an accurate time-dependent density functional theory was conducted to efficiently explore a broad harmonic plateau. The effects of multi-electron and inner orbitals on the harmonic spectrum and generated coherent attosecond pulses were analyzed. The role of the valence electrons in controlling the process and extending the harmonic plateau was investigated. The main issue of producing a super-continuum harmonic spectrum via a frequency shift was considered. The time-frequency representation by means of a wavelet transform of the induced dipole acceleration provided a good insight into the distorted effects from the nonlinear processes in high harmonic emission. The effect of the chirped laser pulse on the production of broadband amplitude was justified in this model. By adjusting the optimal laser parameters to an input intensity of 2.5 × 1014 W cm−2, an isolated 68 as pulse was generated.

  • The control of electron quantum trajectories on the high-order harmonic generation of CO and N<inf>2</inf> molecules in the presence of a low frequency field
    A. M. Koushki, R. Sadighi-Bonabi, M. Mohsen-Nia, and E. Irani
    AIP Publishing
    In the present work, an efficient method is theoretically investigated for extending high-order harmonics and ultrashort attosecond pulse generation in N2 and CO molecules by using the time-dependent density functional theory approach. Our results show that by utilizing chirped laser field in the presence of a low frequency field, not only is the harmonic cutoff extended remarkably but also the single short quantum trajectory is selected to contribute to the harmonic spectra. When a low frequency field is added to the two-color chirped laser field, the long quantum trajectories are suppressed and only the short quantum trajectories contribute to the higher harmonic emission mechanism. As a result, the spectral modulation is significantly decreased and an intense ultrashort pulse can be generated from the supercontinuum region of high harmonics. With such a scheme, the isolated ultrashort attosecond pulses can be generated in length, velocity, and acceleration gauges. Furthermore, these results are explained by using the classical and quantum time-frequency analyses.


  • Selective photo-dissociative ionization of methane molecule with TDDFT study
    E. Irani, A. Anvari, and R. Sadighi-Bonabi
    Elsevier BV



  • The Effect of Chirped Intense Femtosecond Laser Pulses on the Argon Cluster
    H. Ghaforyan, R. Sadighi-Bonabi, and E. Irani
    Hindawi Limited
    The interaction of intense femtosecond laser pulses with atomic Argon clusters has been investigated by using nanoplasma model. Based on the dynamic simulations, ionization process, heating, and expansion of a cluster after irradiation by femtosecond laser pulses at intensities up to 2×1017 Wcm−2are studied. The analytical calculation provides ionization rate for different mechanisms and time evolution of the density of electrons for different pulse shapes. In this approach, the strong dependence of laser intensity, pulse duration, and laser shape on the electron energy, the electron density, and the cluster size is presented using the intense chirped laser pulses. Based on the presented theoretical modifications, the effect of chirped laser pulse on the complex dynamical process of the interaction is studied. It is found that the energy of electrons and the radius of cluster for the negatively chirped pulses are improved up to 20% in comparison to the unchirped and positively chirped pulses.

  • Optical absorption and electronic spectra of chlorophylls a and b
    Leila Hedayatifar, Elnaz Irani, Mahmood Mazarei, Soroush Rasti, Yavar T. Azar, Ali T. Rezakhani, Alireza Mashaghi, Farzaneh Shayeganfar, Mehrnaz Anvari, Tiam Heydari,et al.
    Royal Society of Chemistry (RSC)
    We report optical and electronic properties of the two main chlorophylls in green plants, namely, chlorophylls a and b. We estimate the electric moments of these molecules and study absorption spectra of the chlorophylls.