131,449 research outputs found
Dynamics and bifurcations of a semiconductor laser with short external cavity
No full textWe present a theoretical study into the dynamics and bifurcations of a semiconductor laser subject to delayed optical feedback, as modelled by the Lang-Kobayashi equations. For the case of a short external cavity, of the order of a few centimeters, there is a limited number of external cavity modes (ECMs), which makes it possible to apply advanced techniques from dynamical systems, such as the continuation of ECMs and their bifurcations, and the computation of unstable manifolds. From the physical point of view, a short cavity is characterized by the fact that the delay time in the external cavity is of the same order of magnitude as the period of the relaxation oscillation of the laser. In this regime the optical feedback phase is known to play an important role. We provide a detailed overview of how the dynamics depends on the feedback phase, which is in good agreement with recent experimental measurements
Multi-longitudinal-mode dynamics in twin-stripe lasers
No full textSimulations for two laterally coupled Fabry-Perot type semiconductor lasers are presented. We show a threshold reduction effect and synchronization of the longitudinal modes in case of asymmetric pumping. For symmetric pumping 50% above threshold we find chaotic oscillations with frequencies well exceeding the single-stripe relaxation oscillation frequencies
The twin-stripe laser: a non-linear term in the coupling coefficient
No full textLaterally coupled laser-diode pairs, also called twin stripe lasers , are coupled by means of the evanescent em-field in between two dielectric laser cavities. The coupling strength between the two lasers is determined by the decay length of this evanescent em-field. This length depends on the indices of refraction of the material which separates the two cavities compared to the cavity material. However the index of refraction of the cavity material also depends on the inversion density in the lasing material. Therefore the coupling coefficient in the rate equation for the twin stripe device can be written as ¿0[1 + 1/2(ac(1) ¿1 + ac(2) ¿2)], where ¿1 and ¿2 are the inversion densities in the two stripes. We give an expression for ac>(i) in terms of the properties of the device
Silicon-based Broadband Amplifier Design
No full textDIMESElectrical Engineering, Mathematics and Computer Scienc
Dynamics of laterally coupled semiconductor lasers: transition to chaos.
No full textA method for the investigation of the dynamics of two semiconductor lasers, grown side-by-side on the same wafer to enhance the lateral optical coupling, is presented. Using steady state analysis, parameter regimes of relevant dynamics are identified. This is completed by a spectral analysis, were two routes to chaos are implicated. Finally, we confirm the calculations by showing an avoided crossing type of behavior for the coupling strength
Dynamical properties of mutually delayed coupled semiconductor lasers
No full textWe theoretically investigate the dynamical properties of a system of two semiconductor lasers (SLs) that are mutually coupled via their optical fields. An intrinsic feature of the coupling is its time delay which generically arises from the finite propagation time of the light form one SL to the other. In our system the coupling time is in the sub-ns range, which is of the same order of magnitude as the period of SL's internal relaxation oscillations. We model this system with Lang-Kobayashi-type rate equations where we account for the mutual coupling of the two SLs by a delay term. The resulting set of nonlinear delay differential equations, is analyzed by using recently developed numerical continuation. We consider the case of two nearly identical SLs with symmetrical coupling conditions but different frequencies, and present an analysis of the coupled laser modes (CLMs) of the system
Twin photons from small quantum dots
No full textDue to the large energy splitting of the single-electron levels in a small quantum dot, only one single electron level and one single hole level can be made resonant with the levels in the conduction band and valence band. This results in a closed system with nine distinct levels, which are split by the Coulomb interactions. We show that flat and tall cylindrically symmetric dots have level schemes with different selection rules. In both cases entangled photon pairs can be efficiently produced
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