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    Wyświetlanie 1-6 z 6
    Tytuł:
    Inter-Landau Level Scattering Processes in Magnetic Field Assisted THz Quantum Cascade Laser
    Autorzy:
    Radovanović, J.
    Daničić, A.
    Milanović, V.
    Indjin, D.
    Ikonic, Z.
    Powiązania:
    https://bibliotekanauki.pl/articles/1503186.pdf
    Data publikacji:
    2011-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    72.10.-d
    73.21.Fg
    Opis:
    We present a detailed analysis of GaAs/AlGaAs terahertz quantum cascade laser in the presence of an intense external magnetic field. One of the objectives in further development of THz quantum cascade laser is the realization of structures operating at higher temperatures. This is difficult to obtain as the operating photon emission energy is smaller than the longitudinal-optical phonon energy in the semiconductor material. With increased temperature, electrons in the upper radiative state gain sufficient in-plane energy to emit an longitudinal-optical phonon, which represents a non-radiative scattering and reduces the optical gain. By applying strong magnetic field, two-dimensional continuous energy subbands become split into series of discrete Landau levels, and at particular values of B it is possible to quench these non-radiative channels. Numerical simulations are performed on two-well design quantum cascade laser operating at 4.6 THz, implemented in GaAs/$Al_{0.15}Ga_{0.85}As$, and the magnetic field is perpendicular to the epitaxial layers. Strong oscillations of carrier lifetimes for the upper state of the laser transition, as a function of magnetic field are observed, which can be attributed to interface roughness scattering and longitudinal-optical phonon scattering between Landau levels.
    Źródło:
    Acta Physica Polonica A; 2011, 120, 2; 227-230
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Quantum Cascade Laser Design for Tunable Output at Characteristic Wavelengths in the Mid-Infrared Spectral Range
    Autorzy:
    Daničić, A.
    Radovanović, J.
    Milanović, V.
    Indjin, D.
    Ikonić, Z.
    Powiązania:
    https://bibliotekanauki.pl/articles/1537879.pdf
    Data publikacji:
    2010-05
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    72.10.-d
    73.21.Fg
    Opis:
    We present a method for systematic optimization of quantum cascade laser active region, based on the use of the genetic algorithm. The method aims at obtaining a gain-maximized structure, designed to emit radiation at specified wavelengths suitable for direct absorption by pollutant gasses present in the ambient air. After the initial optimization stage, we introduce a strong external magnetic field to tune the laser output properties and to slightly modify the emission wavelength to match the absorption lines of additional compounds. The magnetic field is applied perpendicularly to the epitaxial layers, thus causing two-dimensional continuous energy subbands to split into series of discrete Landau levels. This affects all the relevant relaxation processes in the structure and consequently the lifetime of carriers in the upper laser level. Furthermore, strong effects of band nonparabolicity result in subtle changes of the lasing wavelength at magnetic fields which maximize the gain, thus providing a path for fine-tuning of the output radiation properties. Numerical results are presented for GaAs/$Al_{x}Ga_{1-x}As$ based quantum cascade laser structures designed to emit at particular wavelengths in the mid-infrared part of the spectrum.
    Źródło:
    Acta Physica Polonica A; 2010, 117, 5; 772-776
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Charge Carrier Transport in Quantum Cascade Lasers in Strong Magnetic Field
    Autorzy:
    Radovanović, J.
    Milanović, V.
    Indjin, D.
    Ikonić, Z.
    Harrison, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/1505456.pdf
    Data publikacji:
    2011-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    72.10.-d
    73.21.Fg
    Opis:
    We have developed a comprehensive rate equations based model for calculating the optical gain in the active region of a quantum cascade laser in magnetic field perpendicular to the structure layers, which takes into account all the relevant scattering channels. The model is applied to gain-optimized quantum cascade laser active region, obtained by a systematic optimization procedure based on the use of genetic algorithm, which we have previously set up for designing novel structures and improving performance of existing ones. It has proven to be very efficient in generating optimal structures which emit radiation at specified wavelengths corresponding to absorption fingerprints of particular harmful pollutants found in the atmosphere. We also illustrate another interesting prospective application of quantum cascade laser-type structures: the design of metamaterials with tunable complex permittivity, based on amplification via intersubband transitions. In this case, the role of the magnetic field is to assist the attainment of sufficient optical gain (population inversion), necessary to effectively manipulate the permittivity and fulfill the conditions for negative refraction (left-handedness).
    Źródło:
    Acta Physica Polonica A; 2011, 119, 2; 99-102
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Enhancement of Electron Mobility and Photoconductivity in Quantum Well $In_{0.52}Al_{0.48}As//In_{0.53}Ga_{0.47}As//In_{0.52}Al_{0.48}As$ οn InP Substrate
    Autorzy:
    Kulbachinskii, V.
    Lunin, R.
    Yuzeeva, N.
    Galiev, G.
    Vasilievskii, I.
    Klimov, E.
    Powiązania:
    https://bibliotekanauki.pl/articles/1399881.pdf
    Data publikacji:
    2013-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    72.10.-d
    73.21.Fg
    73.63.Hs
    Opis:
    Isomorphic $In_{0.52}Al_{0.48}As//In_{0.53}Ga_{0.47}As//In_{0.52}Al_{0.48}As$ quantum well structure on InP substrate were grown by molecular beam epitaxy. We investigated the electron transport properties and mobility enhancement in the structures by changing of doping level, the width d of quantum well $In_{0.53}Ga_{0.47}As$ or by illumination using light with λ = 668 nm. Persistent photoconductivity was observed in all samples due to spatial separation of carriers. We used the Shubnikov-de Haas effect to analyze subband electron concentration and mobility. The maximal mobility was observed for quantum well width d = 16 nm.
    Źródło:
    Acta Physica Polonica A; 2013, 123, 2; 345-348
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Intervalley Scattering and the Role of Indirect Band Gap AlAs Barriers: Application to GaAs/AlGaAs Quantum Cascade Lasers
    Autorzy:
    Mc Tavish, J.
    Ikonić, Z.
    Indjin, D.
    Harrison, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/1813212.pdf
    Data publikacji:
    2008-03
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    72.10.-d
    73.21.Fg
    73.63.Hs
    Opis:
    We report on the results of our simulations of Γ-X scattering in GaAs/AlGaAs heterostructures, discussing the importance of the mole fraction, doping density, and lattice and electron temperature in determining the scattering rates. We consider three systems, a single quantum well (for the investigation of Γ-X scattering), a double quantum well (to compare the Γ-X-G and Γ-Γ scattering rates), and an example of a GaAs/AlGaAs mid-infrared quantum cascade laser. Our simulations suggest that Γ-X scattering can be significant at room temperature but falls off rapidly at lower temperatures. One important factor determining the scattering rate is found to be the energy difference between the Γ- and X-states.
    Źródło:
    Acta Physica Polonica A; 2008, 113, 3; 891-902
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    On the 2D quantum tunneling
    Autorzy:
    Mohammadpour, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/1159450.pdf
    Data publikacji:
    2016-09
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    72.10.-d
    72.10.Bg
    72.80.Vp
    72.90.+y
    73.21.Fg
    73.23.-b
    73.23.Ad
    73.40.Gk
    Opis:
    In this paper, we have solved a quantum tunneling problem for 2-dimensional systems, including electron gas and graphene. In spite of the one-dimensional scattering problems, in two dimensions, we observe phenomenon of tunneling at energies above the barrier. This effect is an analogue to the total internal reflection in optics. The scattering amplitudes inside the barrier region exhibit decaying behavior corresponding to optical evanescent-wave coupling, not only in energies below barrier height, but also above barrier. Velocity-selecting transmission, corresponding to angle-resolved beam filtering effect is one of the achievements of the paper. The famous Hartman effect which occurs normally at sub-barrier energies and has previously been studied for graphene is also addressed. The results manifest occurrence of the Hartman effect for over-barrier energies, as well.
    Źródło:
    Acta Physica Polonica A; 2016, 130, 3; 769-772
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-6 z 6

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