Browsing by Author "Panajotov, Krassimir"

Now showing 1 - 6 of 6
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    PublicationOpen Access
    Experimental evidence of coherence resonance in a time-delayed bistable system
    (APS Physics, 2007) Arizaleta Arteaga, Mikel; Valencia, Miguel; Sciamanna, Marc; Thienpont, Hugo; López-Amo Sáinz, Manuel; Panajotov, Krassimir; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
    We report on the experimental observation of coherence resonance in a bistable system with delay. Our system consists of a vertical-cavity surface-emitting laser subject to time-delayed optical feedback simultaneously from a long and from an extremely short external cavity. Coherence resonance is experimentally proven by analysis of the residence time distribution of the polarization mode-hopping regime and of the signal to noise ratio in the power spectrum.
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    PublicationOpen Access
    Nonlinear dynamics of vertical-cavity surface-emitting lasers
    (Hindawi / Wiley, 2011) Panajotov, Krassimir; Sciamanna, Marc; Gatare, Ignace; Arizaleta Arteaga, Mikel; Thienpont, Hugo; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
    Nonlinear dynamics of Vertical-Cavity Surface-Emitting Lasers (VCSELs) induced by optical injection, optical feedback, current modulation and mutual coupling is reviewed. Due to the surface emission and cylindrical symmetry VCSELs lack strong polarization anisotropy and may undergo polarization switching. Furthermore, VCSELs may emit light in multiple transverse modes. These VCSEL properties provide new features to the rich nonlinear dynamics induced by an external perturbation. We demonstrate for the case of orthogonal optical injection that new Hopf bifurcation on a two-polarization-mode solution delimits the injection locking region and that polarization switching and injection locking of first-order transverse mode lead to a new resonance tongue for large positive detunings. Similarly, the underlying polarization mode competition leads to chaoticlike behavior in case of gain switching and the presence of two transverse modes additionally reduces the possibility of regular dynamics. The bistable property of VCSEL makes it possible to investigate very fundamental problems of bistable systems with time-delay, such as the coherence resonance phenomenon. We also demonstrate that the synchronization quality between unidirectionally coupled VCSELs can be significantly enhanced when the feedback-induced chaos in the master laser involves both orthogonal LP fundamental transverse modes.
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    PublicationOpen Access
    Polarized optical feedback from an extremely short external cavity for controlling and stabilizing the polarization of vertical cavity surface emitting lasers
    (AIP Publishing, 2007) Arizaleta Arteaga, Mikel; Parriaux, Olivier; López-Amo Sáinz, Manuel; Thienpont, Hugo; Panajotov, Krassimir; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
    The authors present experimental results showing that polarization selective optical feedback from an extremely short external cavity induces switching between the two fundamental transverse modes with orthogonal linear polarization of the otherwise without optical feedback polarization stable vertical cavity surface emitting laser. Moreover, when properly selecting the external cavity length within a subwavelength range the polarization state of the emitted light can be chosen in either of the two fundamental transverse modes and stabilized against injection current variations. The numerical results reported are in good agreement with experiments.
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    PublicationOpen Access
    Role of external cavity reflectivity for achieving polarization control and stabilization of vertical cavity surface emitting laser
    (AIP Publishing, 2007) Arizaleta Arteaga, Mikel; López-Amo Sáinz, Manuel; Thienpont, Hugo; Panajotov, Krassimir; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
    The authors present the experimental results showing how the external mirror reflectivity affects the polarization properties of a vertical cavity surface emitting laser subject to optical feedback from an extremely short external cavity. The amplitude of modulation of the polarization switching current with the external cavity length is found to be proportional to the external mirror reflectivity, confirming its key role in achieving polarization control and stabilization of such lasers using optical feedback. Numerical simulations presented here show good agreement with experiments.
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    PublicationOpen Access
    Study of light propagation in liquid crystal overlaying vertical-cavity surface-emitting laser
    (2011) Pardo Fanlo, Sara; Sevilla Moróder, Joaquín; Panajotov, Krassimir; Arizaleta Arteaga, Mikel; Escuela Técnica Superior de Ingenieros Industriales y de Telecomunicación; Telekomunikazio eta Industria Ingeniarien Goi Mailako Eskola Teknikoa; Vrije Universiteit Brussel (Bélgica); Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
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    PublicationOpen Access
    Tailoring light polarization in vertical cavity surface emitting lasers by isotropic optical feedback from an extremely short external cavity
    (AIP Publishing, 2006) Arizaleta Arteaga, Mikel; López-Amo Sáinz, Manuel; Thienpont, Hugo; Panajotov, Krassimir; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
    The authors experimentally show that isotropic optical feedback from an extremely short external cavity can induce switching between the two fundamental transverse modes with orthogonal linear polarization of otherwise without optical feedback polarization stable vertical cavity surface emitting laser. The switching currents and the hysteresis width can be widely tuned by varying the external cavity length. Moreover, by a proper choice of the optical feedback parameters, the emission can be stabilized in any of the two linearly polarized modes.