• Linear and Nonlinear Bullets of the Bogoliubov-de Gennes Excitations 

    Kumar, Shubham; Perego, A.M.; Staliunas, Kestutis (2017-01-27)
    Article
    Accés obert
    We report on the focalization of Bogoliubov–de Gennes excitations of the nonlinear Schrödinger equation in the defocusing regime (Gross-Pitaevskii equation for repulsive Bose-Einstein condensates) with a spatially modulated ...
  • Stabilization of broad area semiconductor lasers 

    Kumar, Shubham; Ahmed Waseem, Waqas Waseem; Herrero Simon, Ramon; Botey Cumella, Muriel; Staliunas, Kestutis (International Society for Photo-Optical Instrumentation Engineers (SPIE), 2018)
    Text en actes de congrés
    Accés restringit per política de l'editorial
    Broad Area Semiconductor edge-emitting lasers typically display self-focusing nonlinearity due to the refractive index dependence on the population inversion. It induces the homogeneous solution instability, multi-transverse ...
  • Stabilization of broad-area semiconductor laser sources by simultaneous index and pump modulations 

    Waseem Ahmed, Waqas; Kumar, Shubham; Medina Pardell, Judith; Botey Cumella, Muriel; Herrero Simon, Ramon; Staliunas, Kestutis (2018-06-01)
    Article
    Accés restringit per política de l'editorial
    We show that the emission of broad-area semiconductor amplifiers and lasers can be efficiently stabilized by introducing two-dimensional periodic modulations simultaneously on both the refractive index and the pump (gain–loss) ...
  • Stabilization of flat-mirror vertical-external-cavity surface-emitting lasers by spatiotemporal modulation of the pump profile 

    Ahmed Waseem, Waqas Waseem; Kumar, Shubham; Herrero Simon, Ramon; Botey Cumella, Muriel; Radziunas, Mindaugas; Staliunas, Kestutis (2015-10-20)
    Article
    Accés obert
    We propose and demonstrate theoretically that vertical-external-cavity surface-emitting lasers (VECSELs) with external flat mirrors can be stabilized by applying a periodic spatiotemporal modulation of the pump current. ...
  • Suppression and control of modulation instability 

    Kumar, Shubham (Universitat Politècnica de Catalunya, 2017-06-21)
    Tesi
    Accés obert
    Dynamical instabilities which lead to spontaneous pattern formation are present in a wide variety of nonlinear dynamical systems, both in nature as well as in technological areas. The instabilities may be saturating, leading ...
  • Suppression of modulation instability in broad area semiconductor amplifiers 

    Kumar, Shubham; Herrero Simon, Ramon; Botey Cumella, Muriel; Staliunas, Kestutis (2014-10-01)
    Article
    Accés restringit per política de l'editorial
    We show that a two-dimensional periodic modulation of the pump profile (modulation both along and perpendicular to the optical axis) can suppress the modulation instability in broad emission area semiconductor amplifiers. ...
  • Suppression of pattern-forming instabilities by genetic optimization 

    Kumar, Shubham; Herrero Simon, Ramon; Botey Cumella, Muriel; Staliunas, Kestutis (American Chemical Society (ACS), 2016-07-13)
    Article
    Accés restringit per política de l'editorial
  • Taming of modulation instability by spatio-temporal modulation of the potential 

    Kumar, Shubham; Herrero Simon, Ramon; Botey Cumella, Muriel; Staliunas, Kestutis (Macmillan Publishers, 2015-08-19)
    Article
    Accés obert
    Spontaneous pattern formation in a variety of spatially extended nonlinear systems always occurs through a modulation instability, sometimes called Turing instability: the homogeneous state of the system becomes unstable ...
  • Transformation Optics in Coupled Waveguides 

    Kumar, Shubham (Universitat Politècnica de Catalunya / Universitat Autònoma de Barcelona, 2011-09-08)
    Projecte Final de Màster Oficial
    Accés obert
    English: The technique of transformation optics is applied to a system of three coupled waveguides undergoing adiabatic passage of a light beam. We show that it is possible, by applying different transformations to different ...