Browsing by Author "Kumar, Shubham"

Now showing items 1-13 of 13

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

      Kumar, Shubham; Perego, A.M.; Staliunas, Kestutis (2017-01-27)
      Article
      Open Access
      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 ...

    • Spatiotemporal stabilization proof of concept of Broad Area Semiconductor laser sources 

      Medina Pardell, Judith; Ahmed Waseem, Waqas Waseem; Kumar, Shubham; Botey Cumella, Muriel; Herrero Simon, Ramon; Staliunas, Kestutis (2018-02)
      Research report
      Open Access
      We provide a numerical proof of concept of a stabilization mechanism for BAS laser sources. The scheme is based on the simultaneous introduction of in-phase two-dimensional modulations on the refractive index and pump ...

    • Stabilization of Broad Area Semiconductor Amplifiers and Lasers by Double Modulation of Pump and Refractive Index 

      Ahmed Waseem, Waqas Waseem; Kumar, Shubham; Medina Pardell, Judith; Botey Cumella, Muriel; Herrero Simon, Ramon; Staliunas, Kestutis (Institute of Electrical and Electronics Engineers (IEEE), 2018)
      Conference report
      Restricted access - publisher's policy
      Broad Area Semiconductor Amplifiers and Lasers display instability of the homogeneous state typically related with self-focusing nonlinearities, inducing multi-transverse mode operation and filamentation that deteriorates ...

    • Stabilization of Broad Area Semiconductor Laser Sources 

      Medina Pardell, Judith; Ahmed Waseem, Waqas Waseem; Kumar, Shubham; Botey Cumella, Muriel; Herrero Simon, Ramon; Staliunas, Kestutis (Institute of Electrical and Electronics Engineers (IEEE), 2018)
      Conference report
      Open Access
      We numerically proof the stabilization of broad area semiconductor laser sources by introducing simultaneous in-phase two-dimensional modulations on the refractive index and on the pump (gain). We also examine the interplay ...

    • 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)
      Conference report
      Restricted access - publisher's policy
      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
      Open Access
      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
      Open Access
      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)
      Doctoral thesis
      Open Access
      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
      Restricted access - publisher's policy
      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 modulation instability in pump modulated flat-mirror VECSELs 

      Ahmed Waseem, Waqas Waseem; Kumar, Shubham; Herrero Simon, Ramon; Botey Cumella, Muriel; Radziunas, Mindaugas; Staliunas, Kestutis (International Society for Photo-Optical Instrumentation Engineers (SPIE), 2016)
      Conference report
      Restricted access - publisher's policy
      We show that modulation instability (MI) can be suppressed in vertical external cavity surface emitting lasers (VECSELs) by introducing a periodic spatio-temporal modulation of the pump profile which in turn allows a simple ...

    • 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
      Restricted access - publisher's policy

    • 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
      Open Access
      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)
      Master thesis
      Open Access
      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 ...