Now showing items 21-40 of 114

    • Ferroelectric domain engineering by focused infrared femtosecond pulses 

      Chen, Xin; Karpinski, Pawel; Shvedov, Vladlen; Koynov, Kaloian; Wang, Bingxia; Trull Silvestre, José Francisco; Cojocaru, Crina; Krolikowski, Wieslaw; Sheng, Yan (2015-10-05)
      Article
      Open Access
      We demonstrate infrared femtosecond laser-induced inversion of ferroelectric domains. This process can be realised solely by using tightly focused laser pulses without application of any electric field prior to, in conjunction ...
    • Ferroelectric domain patterning with ultrafast light 

      Chen, Xin; Shvedov, Vladlen; Karpinski, Pawel; Koynov, Kaloian; Boes, A.; Mitchell, A.; Trull Silvestre, José Francisco; Cojocaru, Crina; Krolikowski, Wieslaw; Sheng, Yan (2016-12-01)
      Article
      Open Access
    • Fiber optical parametric oscillator 

      García Sánchez, Enric (Universitat Politècnica de Catalunya, 2015-02-24)
      Master thesis (pre-Bologna period)
      Open Access
      Covenantee:   Danmarks tekniske universitet
      The parametric gain of a four-wave mixing (FWM) process in a configuration of a fiber optical parametric oscillator (FOPO) is one option to achieve the conversion of high peak power pulses at frequencies reachable with ...
    • Field concentration by Axisymmetric local PT-symmetry 

      Ahmed Waseem, Waqas Waseem; Botey Cumella, Muriel; Herrero Simon, Ramon; Staliunas, Kestutis (2016)
      Conference report
      Open Access
      We propose a new class of systems holding PT-symmetry only locally; the potential fulfills: U(r-r0)=U*(-r+r0 ) in a small neighborhood of any point r0, whereas on a global scale the system is only Parity symmetric: ...
    • First-passage times for a marginal state driven by colored noise 

      Ramírez de la Piscina Millán, Laureano; Sancho, Jose Maria (The American Physical Society, 1991-01-18)
      Article
      Open Access
      The dynamical process through a marginal state (saddle point) driven by colored noise is studied. For small correlation time of the noise, the mean first-passage time and its variance are calculated using standard methods. ...
    • Frequency-Doubling of Femtosecond Pulses in “Thick” Nonlinear Crystals With Different Temporal and Spatial Walk-Off Parameters 

      Apurv Chaitanya, N.; Aadhi, A.; Chaitanya Kumar, S.; Jabir, M. V.; Samanta, G. K.; Ebrahim-Zadeh, Majid (IEEE, 2016-12-01)
      Article
      Open Access
      We present a comparative study on frequency-doubling characteristics of femtosecond laser pulses in thick nonlinear crystals with different temporal and spatial walk-off parameters. Using single-pass second harmonic ...
    • Gain through losses in nonlinear optics 

      Perego, A.M.; Turitsyn, S.K.; Staliunas, Kestutis (2018-08-01)
      Article
      Open Access
      Instabilities of uniform states are ubiquitous processes occurring in a variety of spatially extended nonlinear systems. These instabilities are at the heart of symmetry breaking, condensate dynamics, self-organisation, ...
    • Gain-through-filtering enables tuneable frequency comb generation in passive optical resonators 

      Bessin, Florent; Perego, Auro M.; Staliunas, Kestutis; Turitsyn, Sergei K.; Kudlinski, Alexandre; Conforti, Matteo; Mussot, Arnaud (2019-10-03)
      Article
      Open Access
      Optical frequency combs (OFCs), consisting of a set of phase-locked, equally spaced laser frequency lines, have enabled a great leap in precision spectroscopy and metrology since seminal works of Hänsch et al. Nowadays, ...
    • Generation of intrinsically CEP-stable few-cycle pulses in the mid-IR 

      Sánchez Peacham, Daniel Alexander (Universitat Politècnica de Catalunya, 2013-09-10)
      Master thesis
      Open Access
      [ANGLÈS] The generation of few cycle pulses in the mid-IR is investigated through a numerical non linear propagation code as a seed pulse for an OPCPA system
    • Generation of polarization entangled photon pairs in Bragg reflection waveguides 

      Vallés Marí, Adam (Universitat Politècnica de Catalunya, 2012-09-06)
      Master thesis
      Open Access
      [ANGLÈS] We report the observation of polarization entangled photon pairs generated by means of type-II spontaneous parametric down-conversion (SPDC) within an AlGaAs Bragg reflection waveguide (BRW). Even though SPDC in ...
    • Globally-linked vortex clusters 

      Crasovan, L C; Vekslerchik, V; Mihalache, Dumitru; Pérez Torres, Juan; Perez-Garcia, V M; Torner Sabata, Lluís (Kluwer, 2004-09-30)
      Part of book or chapter of book
      Restricted access - publisher's policy
      We show the existence of a rich variety of fully stationary vortex structures made of an increasing number of vortices nested in paraxial wave fields confined by symmetric and asymmetric harmonic trapping potentials in ...
    • Graphene based laser dynamics and applications 

      Peralta Amores, Albert (Universitat Politècnica de Catalunya, 2017-07-07)
      Bachelor thesis
      Open Access
      Self-starting stretched-pulse operation in a Mode-locked Erbium fiber laser is demonstrated for both; Graphene Oxide and pure graphene Mode-lockers. The -3 dB spectral width is 36.8 nm. Pulse temporal width of 43.65 ps and ...
    • Harmonic generation from metal-oxide and metal-metal boundaries 

      Escalora, M.; Vincenti, M. A.; de Ceglia, Domenico; Akozbek, Neset; Bloemer, M. J.; De Angelis, C.; Haus, J.W.; Vilaseca Alavedra, Ramon; Trull Silvestre, José Francisco; Cojocaru, Crina (American Physical Society (APS), 2018-08-20)
      Article
      Open Access
      We explore the outcomes of detailed microscopic models by calculating second- and third-harmonic generation from thin-film surfaces with discontinuous free-electron densities. These circumstances can occur in structures ...
    • High-coherence light source for atom trapping and cooling 

      Palacios Álvarez, Silvana (Universitat Politècnica de Catalunya, 2012-09-06)
      Master thesis
      Open Access
      [ANGLÈS] A master clock (frequency reference) for experiments related to cold and trapped rubidium atoms was developed. From a telecommunication fibre laser source at 1560 nm, frequency-doubling was optimized to obtain an ...
    • High-performance polymer solar cells using an optically enhanced architecture 

      Martinez Otero, Alberto; Elías Castells, Xavier; Betancur, Rafael; Martorell Pena, Jordi (2013-01-31)
      Article
      Restricted access - publisher's policy
    • High-power, continuous-wave optical parametric oscillators from visible to near-infrared 

      Samanta, Goutam Kumar (Universitat Politècnica de Catalunya, 2009-07-01)
      Doctoral thesis
      Open Access
      This thesis presents the development of a new class of high-power, continuous-wave (cw) optical parametric oscillators (OPOs) with extended tunability from visible to near-infrared (near-IR). While lasers have been in use ...
    • High-power, high-repetition-rate performance characteristics of β-BaB2O4 for single-pass picosecond ultraviolet generation at 266 nm 

      Kumar, S. Chaitanya; Canals Casals, J.; Wei, Junxiong; Ebrahim-Zadeh, Majid (OSA, 2015-10-16)
      Article
      Open Access
      We report a systematic study on the performance characteristics of a high-power, high-repetition-rate, picosecond ultraviolet (UV) source at 266 nm based on β-BaB2O4 (BBO). The source, based on single-pass fourth harmonic ...
    • Hybrid bloch-anderson localization of light 

      Stützer, Simon; Kartashov, Yaroslav V.; Vysloukh, Victor A.; Konotop, Vladimir V; Nolte, Stefan; Torner Sabata, Lluís; Szameit, Alexander (2013-04-26)
      Article
      Restricted access - publisher's policy
      We investigate the interplay of Bloch oscillations and Anderson localization in optics. Gradual washing out of Bloch oscillations and the formation of nearly stationary averaged intensity distributions, which are symmetric ...
    • Image encryption system based on a nonlinear joint transform correlator for the simultaneous authentication of two users 

      Vilardy Ortiz, Juan Manuel; Millán Garcia-Varela, M. Sagrario; Pérez Cabré, Elisabet (2019-01-01)
      Article
      Open Access
      We propose a new encryption system based on a nonlinear joint transform correlator (JTC) using the information of two biometrics (one digital fingerprint for each user) as security keys of the encryption system. In order ...
    • Images encryption system based on a fractional joint transform correlator and nonlinear filtering 

      Vilardy Ortiz, Juan Manuel; Millán Garcia-Varela, M. Sagrario; Pérez Cabré, Elisabet (2014)
      Article
      Open Access
      A new optical security system for image encryption based on a fractional joint transform correlator and nonlinear filtering is proposed. The position of the lens in the proposed optical encryption setup can be chosen, so ...