Le laser à cavité verticale émettant par la surface (VCSEL ou Vertical-Cavity Surface-Emitting Laser) comporte des avantages compétitifs par rapport aux lasers émettant par le côté. Le VCSEL présente souvent deux modes de polarisation linéaire orthogonaux avec des fréquences et des gains optiques presque identiques. Dès lors, de faibles perturbations telles que des modifications du courant d injection ou de la température peuvent induire des basculements de polarisation. Toutefois, en utilisant un schéma d injection optique d un faisceau laser externe, il est possible de contrôler ces instabilités de polarisation. Nous nous intéressons au contrôle du basculement de polarisation, à la bistabilité de polarisation ainsi qu à la compétition des modes transverses d un VCSEL soumis à injection optique de polarisation orthogonale. En variant les paramètres d injection¡(puissance injectée et désaccord en fréquence entre le laser maître et le VCSEL), nous montrons que le basculement de polarisation implique des dynamiques non linéaires telles le mélange d ondes, le cycle limite, la résonance subharmonique ainsi qu une route de doublement de période vers le chaos optique. L analyse des bifurcations sous-jacentes permet de dresser une cartographie des dynamiques de basculement de polarisation du VCSEL. orthogonaux affecte la qualité de la synchronisation du chaos. Ces résultats sont intéressants dans le cadre du développement de liaisons de communication sécurisée par chaos optique. Dans notre thèse, nous étudions également la synchronisation du chaos de VCSELs dans un schéma de couplage unidirectionnel. Nous montrons que la compétition des modes de polarisation linéaire / Vertical-cavity surface-emitting lasers (VCSELs) have competitive advantages with respect to conventional edge-emitting lasers such as the fabrication of dense two-dimensional VCSEL arrays for optical interconnects. VCSELs exhibit intriguing polarization properties which are critical in polarization-sensitive applications. Polarization switching (PS) between two VCSEL s preferential orthogonal linearly polarized (LP) modes may be induced by changing the bias current, temperature or, externally, through orthogonally polarized optical injection. Depending on optical injection parameters, i.e., the injected power and the frequency detuning, injection-locking of the VCSEL can be achieved. We contribute to the study of polarization bistability, polarization switching (PS), injection-locking and transverse mode competition in a VCSEL subject to orthogonal continuous-wave optical injection. We experimentally show and theoretically demonstrate that PS and locking may involve rich nonlinear dynamics including wave mixing, limit cycle, subharmonic resonances or a period-doubling route to chaos. In particular, we analyze the interplay between PS and the underlying nonlinear dynamics, and unveil its bifurcation mechanisms. Our study brings a new insight into the physics of polarization dynamics in externally-driven VCSELs. Chaos synchronization of coupled VCSELs is also investigated. A feedback-induced chaotic light from the master VCSEL is unidirectionally injected into the slave VCSEL. We show that the synchronization quality can be significantly enhanced when chaos involves both orthogonal LP modes. This result is interesting for chaos communication schemes based on VCSELs.

Ulm, Univ., Diss., 2007.

Zugl.: Ulm, Universiẗat, Diss., 2008.

Münster (Westfalen), University, Diss., 2004. / Dateien im PDF-Format.

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Nonlinear dynamical properties of semiconductor lasers have attracted considerable attention, and their rich behaviors enable many popular research topics. The research effort of this thesis has emphasized on two areas - one is photonic microwave generation based on period one dynamic of semiconductor lasers; the other is laser's chaotic dynamic. Microwave photonics has attracted considerable attention recently because of its practical applications in radio-over-fiber (RoF) communications links. A stable photonic microwave allows it to convey, in a cost-effective manner, wideband signals over optical fibers with low loss, large bandwidth and immunity of electromagnetic interference. Microwave photonics technologies consist of photonic microwave generation, processing, control and distribution. Many photonic microwave generation techniques have been proposed, which includes direct modulation, optical heterodyne technique, external modulation, mode-locked semiconductor lasers, optoelectronic oscillator (OEO) and period one (P1) dynamic of semiconductor lasers. Among these techniques, photonic microwave generation based on P1 oscillation dynamic has gained special attention due to its many advantages, such as: widely tunable oscillation frequency, and nearly single sideband (SSB) spectrum. The aim of this thesis in the photonic microwave generation area is to produce photonic microwaves based on P1 dynamic using low-cost vertical-cavity surface-emitting lasers (VCSELs). The technical contents in this area cover two parts. The first part is to generate broadly tunable photonic microwaves. Continuous tuning of the microwave frequency from 4GHz to up to an instrumentation limited 15GHz is experimental achieved through the adjustment of the injection power and the frequency detuning between the master laser and the VCSEL. Numerical simulations using a common spin flip model are also carried out, which agree qualitatively with the experimental results. The second part of the photonic microwave generation in this thesis is to explore effective approaches to not only reduce the linewidth but also improve the stability of the generated microwave. Due to spontaneous emission noise in the semiconductor laser, P1 dynamic inherently imposes phase noise, which increases the microwave linewidth of the generated microwave. This considerably affect the signal transmission performance of the modulated microwave signal in RoF applications. To address this challenge, single optical feedback and double optical feedback are applied in the experiments. The experimental results demonstrate that both single feedback and double feedback can reduce the linewidth of the generated microwave to about one tenth of linewidth without the optical feedback. However, single optical feedback may induce many side peaks due to external cavity frequency from the feedback cavity, the feedback phase needs to be carefully adjusted to suppress the side peaks. The side peaks can be suppressed by introducing the second optical feedback. The double optical feedback can also significantly enhance the stability of the generated microwave. The results of the numerical simulations are in good agreement with the experimental results. The other important dynamic of semiconductor lasers is chaos, which has attracted considerable research interest due to its many potential applications in secure communications, chaotic optical time-domain reflectors, chaotic lidars and physical random number generators. Optical feedback is the simplest method to generate chaos in semiconductor lasers, but a typical chaos generated by optical feedback has unwanted recurrence features termed time delay (TD) signature because of the optical round trip in the external cavity. The complexity, bandwidth and TD signature of chaos are the three main parameters for evaluating its applicability in abovementioned application scenarios. In order to find the correct operating parameters to achieve low TD signature and high complexity of chaos simultaneously, in this thesis, the influence of bias current and the feedback strength on the complexity and time-delay signature of chaotic signals in semiconductor lasers with optical feedback is investigated experimentally and theoretically. In the experiment, the effect of the data acquisition method on quantification of complexity is also examined. The experimental results show that the TD signature is approximately in an inverse relationship with the complexity of chaos when the semiconductor laser is subject to low or strong optical feedback. However, the inverse relationship disappears when the laser operates at higher bias currents with intermediate feedback strength. Numerical simulation based on Lang Kobayashi laser equations show qualitative agreements with the experimental results.

This research studied the polarization switching during theturned on of a VCSEL. The switching periods and beam profilewere investigated by the variation of the driving current and heat sink temperature of the laser. The laser would present a series of polarization switching before it achieved the stable state. At a laser¡¦s current of 5.5 mA, the laser first output in Y-polarization for a period of T1 after the laser was turned on. Then the laser switched to X-polarization and maintained for a period of T2. In the third period of T3, the laser switched to Y-polarization and followed by a final switch to X-polarization. We found that the switching periods would decrease under higher temperature and larger driving current, while the ratio of T2 /T1 and T3/T2 did not change, approximating to a constant of e2.We also found that the beam profile of X-polarization would change periodically with a period of 0.32 mA in the region of 3.5 to 6.0 mA. These results will help to understand the mechanism of the polarization switching when the laser is turned on.

¡uGaAs VCSEL Contact Process and Feature Analysis ¡vIn this article, we talk about the process of metalization on sample of epied GaAs VCSEL structure. We deposit Au/Ge-Au on n-GaAs substrate for n-type contact ¡Fand Au/Be-Au on p-DBR for p-type contact by thermal evaporation. To lower threshold current, and increase laser output power, ohmic contact is a necessary condition. Furthermore a lot of analysis is done for injection current-EL spectrum; VCSEL structure-EL spectrum; output aperture-laser output power. And check the laser mode with gain Spectrum ¡Bresonant cavity mode ¡B spontaneous emission of active layer. Throughout the analysis mention above, we hope to find a reasonable and reliable way of VCSEL structure design, so that we can reduce the heat effect to vertical cavity surface emitting laser.

Zugl.: Zürich, Techn. Hochsch., Diss., 2009

Univ., Diss., 2008--Kassel.