The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform

Carlo Sirtori - One of the best experts on this subject based on the ideXlab platform.

  • inter landau level scattering and LO Phonon emission in terahertz quantum cascade laser
    Applied Physics Letters, 2007
    Co-Authors: Nicolas Perelaperne, Louisanne De Vaulchier, Y Guldner, Giacomo Scalari, Marcella Giovannini, Jerome Faist, Angela Vasanelli, G Bastard, S S Dhillon, Carlo Sirtori
    Abstract:

    A terahertz quantum cascade laser (QCL) structure based on a bound to continuum and LO-Phonon extraction stage is studied under a strong magnetic field. Two series of power oscillations as a function of magnetic field are observed. Comprehensive simulations of the lifetimes alLOw the first series to be assigned to interface roughness (elastic) and the second to LO-Phonon scattering (inelastic) of hot carriers in an excited Landau level, previously unobserved in terahertz QCL. The authors demonstrate that for the latter, the thermal electron distribution in the upper laser state leads to a breaking of the population inversion and hence laser action.

  • LO Phonon emission by hot electrons in terahertz quantum cascade lasers
    GDR Detecteurs et Emetteurs de radiation THz à semiconducteurs, 2006
    Co-Authors: Nicolas Perelaperne, Louisanne De Vaulchier, Y Guldner, Giacomo Scalari, Marcella Giovannini, Jerome Faist, Angela Vasanelli, Sukhdeep Dhillon, Carlo Sirtori
    Abstract:

    Recently, a new design of Quantum Cascade Lasers (QCL) operating in the terahertz (THz) domain that combines the advantages of the bound-to-continuum approach together with the use of a LO-Phonon resonance was proposed [1]. In this structure, the extraction miniband of the bound-to-continuum transition is aligned resonantly with the first excited state of a large coupled quantum well which exhibits a transition at roughly the LO-Phonon energy hwLO. This large energy separation was supposed to significantly reduce the LOwer state lifetime by alLOwing optical Phonon scattering of the electrons and also to reduce the thermal backfilling of the LOwer state. We present measurements performed on that particular structure under a strong magnetic field applied parallel to the growth axis. Each level of the QCL is split into a series of Landau levels (LLs). As previously reported, the lifetime of the upper state of the laser transition, and thus the output power, can be modulated by varying the magnetic field. A strong increase of the scattering rate, and therefore a output power minimum, is observed when two LLs are brought into resonance, since in that case electrons can scatter elastically, essentially as a result of the interface roughness. This leads to dramatic oscillations of the emission power which vary as B-1. Besides these features, a second series of oscillations is also clearly observed in this structure. Such minima cannot be accounted by inter-LL resonances or by resonant electron-electron scattering (Auger like effect) as previously observed in different structures. We show that they can be explained by LO-Phonon emission from hot electrons injected in the LLs of the upper level. For critical values of the magnetic field, these electrons can resonantly emit one LO-Phonon and relax directly to the fundamental LL of the laser transition, leading to a minimum in the output power. We are deveLOping a simple model to calculate the magnetic-field dependence of the upper state lifetime. The first predictions of this model, including both the interface roughness scattering and the LO-Phonon emission, account very well for the experimental data.

Y M Chang - One of the best experts on this subject based on the ideXlab platform.

  • ultrafast e1 LO Phonon and plasma dynamics in a plane wurtzite inn
    Journal of Applied Physics, 2008
    Co-Authors: Y M Chang, Y L Hong
    Abstract:

    Coherent Phonon spectroscopy of an a-plane wurtzite InN epitaxial thin film is demonstrated with time-resolved second-harmonic generation technique. Coherent E1(LO) Phonons are launched via a transient electric field screening process in the near surface region of the a-plane wurtzite InN. Because of the macroscopic electric dipole interaction between coherent E1(LO) Phonons and photoexcited plasmons, two hybridized vibration modes, Phononlike (L−) and plasmonlike (L+) E1(LO) Phonon-plasmon coupling modes, are identified. The investigation of these coupling modes alLOws us to understand the ultrafast carrier and Phonon dynamics in a-plane wurtzite InN.

  • determination of the electron effective mass of wurtzite inn by coherent upper branch a1 LO Phonon plasmon coupling mode
    Applied Physics Letters, 2007
    Co-Authors: Y M Chang, C H Shen, H Y Chen
    Abstract:

    Coherent A1(LO) Phonon and its coupling with photoexcited plasmon in wurtzite InN were generated and detected with time-resolved second-harmonic generation. The experimental results directly reveal that the plasma damping time constant is about 60∼120fs, which depends on the photoexcited plasma density in InN. The frequency of the upper-branch A1(LO) Phonon-plasmon coupling mode shifts as a function of the photoexcited plasma density. This frequency shift can be fitted consistently with different InN films by solving the InN dielectric response function and leads to the determination of the electron effective mass m‖*=(0.033±0.003)me, parallel to the c axis of wurtzite InN.

Nicolas Perelaperne - One of the best experts on this subject based on the ideXlab platform.

  • inter landau level scattering and LO Phonon emission in terahertz quantum cascade laser
    Applied Physics Letters, 2007
    Co-Authors: Nicolas Perelaperne, Louisanne De Vaulchier, Y Guldner, Giacomo Scalari, Marcella Giovannini, Jerome Faist, Angela Vasanelli, G Bastard, S S Dhillon, Carlo Sirtori
    Abstract:

    A terahertz quantum cascade laser (QCL) structure based on a bound to continuum and LO-Phonon extraction stage is studied under a strong magnetic field. Two series of power oscillations as a function of magnetic field are observed. Comprehensive simulations of the lifetimes alLOw the first series to be assigned to interface roughness (elastic) and the second to LO-Phonon scattering (inelastic) of hot carriers in an excited Landau level, previously unobserved in terahertz QCL. The authors demonstrate that for the latter, the thermal electron distribution in the upper laser state leads to a breaking of the population inversion and hence laser action.

  • LO Phonon emission by hot electrons in terahertz quantum cascade lasers
    GDR Detecteurs et Emetteurs de radiation THz à semiconducteurs, 2006
    Co-Authors: Nicolas Perelaperne, Louisanne De Vaulchier, Y Guldner, Giacomo Scalari, Marcella Giovannini, Jerome Faist, Angela Vasanelli, Sukhdeep Dhillon, Carlo Sirtori
    Abstract:

    Recently, a new design of Quantum Cascade Lasers (QCL) operating in the terahertz (THz) domain that combines the advantages of the bound-to-continuum approach together with the use of a LO-Phonon resonance was proposed [1]. In this structure, the extraction miniband of the bound-to-continuum transition is aligned resonantly with the first excited state of a large coupled quantum well which exhibits a transition at roughly the LO-Phonon energy hwLO. This large energy separation was supposed to significantly reduce the LOwer state lifetime by alLOwing optical Phonon scattering of the electrons and also to reduce the thermal backfilling of the LOwer state. We present measurements performed on that particular structure under a strong magnetic field applied parallel to the growth axis. Each level of the QCL is split into a series of Landau levels (LLs). As previously reported, the lifetime of the upper state of the laser transition, and thus the output power, can be modulated by varying the magnetic field. A strong increase of the scattering rate, and therefore a output power minimum, is observed when two LLs are brought into resonance, since in that case electrons can scatter elastically, essentially as a result of the interface roughness. This leads to dramatic oscillations of the emission power which vary as B-1. Besides these features, a second series of oscillations is also clearly observed in this structure. Such minima cannot be accounted by inter-LL resonances or by resonant electron-electron scattering (Auger like effect) as previously observed in different structures. We show that they can be explained by LO-Phonon emission from hot electrons injected in the LLs of the upper level. For critical values of the magnetic field, these electrons can resonantly emit one LO-Phonon and relax directly to the fundamental LL of the laser transition, leading to a minimum in the output power. We are deveLOping a simple model to calculate the magnetic-field dependence of the upper state lifetime. The first predictions of this model, including both the interface roughness scattering and the LO-Phonon emission, account very well for the experimental data.

F Jahnke - One of the best experts on this subject based on the ideXlab platform.

  • rabi oscillations in semiconductor quantum dots revisited influence of LO Phonon collisions
    Applied Physics Letters, 2009
    Co-Authors: K Schuh, J Seebeck, M Lorke, F Jahnke
    Abstract:

    Coherence properties of semiconductor quantum dots are of central importance for a variety of applications. Previous studies of decoherence in these systems mainly focused on the interaction with LA Phonons, only giving rise to dephasing. In contrast, the interaction with LO Phonons additionally causes carrier scattering. To show the importance of the combined influence of dephasing and carrier scattering, we revisit the case of Rabi oscillations in semiconductor quantum dots using a quantum-kinetic treatment of the carrier-LO-Phonon interaction.

Y L Hong - One of the best experts on this subject based on the ideXlab platform.

  • ultrafast e1 LO Phonon and plasma dynamics in a plane wurtzite inn
    Journal of Applied Physics, 2008
    Co-Authors: Y M Chang, Y L Hong
    Abstract:

    Coherent Phonon spectroscopy of an a-plane wurtzite InN epitaxial thin film is demonstrated with time-resolved second-harmonic generation technique. Coherent E1(LO) Phonons are launched via a transient electric field screening process in the near surface region of the a-plane wurtzite InN. Because of the macroscopic electric dipole interaction between coherent E1(LO) Phonons and photoexcited plasmons, two hybridized vibration modes, Phononlike (L−) and plasmonlike (L+) E1(LO) Phonon-plasmon coupling modes, are identified. The investigation of these coupling modes alLOws us to understand the ultrafast carrier and Phonon dynamics in a-plane wurtzite InN.