Lesiones parciales del ligamento cruzado anterior Cruz Cámara, Antonio; Villalba Aramburu, Alfredo; García Barcenilla, Rebeca ...
Revista Española de Artroscopia y Cirugía Articular,
09/2020, Volume:
27, Issue:
3
Journal Article
We report a first experimental study of the polarization-resolved nonlinear dynamics of a 1550 nm single-mode vertical-cavity surface-emitting laser (VCSEL) subject to orthogonal optical injection. ...Stability maps identifying the boundaries between regions of different nonlinear dynamics are reported for two different values of the bias current. A rich variety of nonlinear behaviors including periodic, period doubling, and irregular dynamics are observed for both polarizations. Polarization switching and injection locking induced by the optical injection are also included in the mapping. Analysis is given also in terms of the frequency detuning between the injected light and the orthogonal linear polarization of the VCSEL. When the frequency detuning is positive polarization switching can be observed in a periodic dynamical regime, including both period one and period two behaviors. For positive frequency detuning, the only polarization that contributes to the dynamics of the total power is the orthogonal polarization. For negative frequency detunings both linear polarizations contribute to the dynamics of the total power.
An all-optical inverter using polarization switching (PS) of a long-wavelength single-mode vertical-cavity surface-emitting laser (VCSEL) is experimentally demonstrated. PS appears when linearly ...polarized light is injected orthogonally to the linear polarization of the solitary VCSEL. The dynamic behavior of an all-optical inverter under different pulsed optical inputs is analyzed. Time traces, rise and fall times of the linearly polarized output signals are reported. The dependence of these quantities on the bias current and injected optical power is investigated. This analysis permits us to identify proper operation conditions for the all-optical inversion. The PS-based all-optical inverter is demonstrated with a 2.5-Gb/s non-return-to-zero input signal.
The transverse mode selection induced by optical injection in a VCSEL emitting in two transverse modes is analyzed from a theoretical point of view. Different pairs of transverse modes with parallel ...or orthogonal polarizations are considered. In general, we show that transverse mode selection can be achieved when the two modes have parallel or orthogonal polarizations. The selection is not possible only when both modes have parallel polarizations and the mode with the lowest threshold current has a lower injection rate than the other mode. Different forms of the selection region in the injected power-injection current plane appear depending on the polarization of the transverse modes. When both transverse modes are orthogonally polarized the mode with the lowest threshold is selected when the injected power surpasses a value that depends on the injection current. However when both modes have parallel polarizations the selection region has a completely different shape because the selection of the mode is no longer possible if the injected power or the injected current are large enough. We also show that the modal selection is favoured as the frequency of the injected light becomes smaller than the frequency of the mode to be selected.
We present experimental and theoretical results of noise-induced attractor hopping between dynamical states found in a single transverse mode vertical-cavity surface-emitting laser (VCSEL) subject to ...parallel optical injection. These transitions involve dynamical states with different polarizations of the light emitted by the VCSEL. We report an experimental map identifying, in the injected power-frequency detuning plane, regions where attractor hopping between two, or even three, different states occur. The transition between these behaviors is characterized by using residence time distributions. We find multistability regions that are characterized by heavy-tailed residence time distributions. These distributions are characterized by a -1.83±0.17 power law. Between these regions we find coherence enhancement of noise-induced attractor hopping in which transitions between states occur regularly. Simulation results show that frequency detuning variations and spontaneous emission noise play a role in causing switching between attractors. We also find attractor hopping between chaotic states with different polarization properties. In this case, simulation results show that spontaneous emission noise inherent to the VCSEL is enough to induce this hopping.
An analytical calculation of relative intensity noise spectra of weakly index-guided vertical-cavity surface-emitting lasers (VCSELs) in a multimode regime is performed. We obtain analytical ...expressions that incorporate the spatial dependence of electrical field and carrier density profiles. Expressions are derived for single-mode and two-transverse-mode operation. Our analysis shows that single-mode noise spectrum depends on the spatial mode profile through a modal effective volume. Two-mode noise spectra also incorporate the dependence on the degree of spatial overlapping between the modes. Two resonance peaks appear in the noise spectra of the individual modes and total power of the two-mode VCSEL. We analytically show that those peaks appear at frequencies that correspond to the relaxation oscillation frequencies of the multimode laser. Simple analytical expressions are also derived for noise spectra at zero frequency.
Modal selection induced by parallel polarized optical injection is studied experimentally in a vertical-cavity surface-emitting laser (VCSEL) with emission in two transverse modes. We report that the ...selection of the fundamental transverse mode can be achieved when the two transverse modes have parallel polarizations. The selection of the fundamental mode is accompanied by locking of that mode to the optically injected signal for large enough values of the wavelength detuning between the fundamental mode and the externally injected signal. The injected power needed to induce modal selection grows as the VCSEL bias current is increased and exhibits a minimum with respect to the injection wavelength at a value ¿ min that is slightly longer than the wavelength of the fundamental mode of the solitary VCSEL. We also report that the selection process exhibits a bistable behaviour when the wavelength of optical injection increases beyond ¿ min . The width of the observed bistable region grows linearly with the wavelength of the optically injected signal. Selection of the higher order transverse mode is achieved when the optical injection wavelength is close to that of the higher order transverse mode. The qualitative behavior associated with the selection of the higher order mode is similar to that of the fundamental mode.
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