We investigate the stability of an array of three laterally coupled semiconductor lasers. This study of the
simplest system with an underlying structure that is also found in larger arrays constitutes a first step towards
understanding the stability properties of large arrays. We use a composite-cavity model, where the individual
lasers are described by the transverse modes of the entire composite-cavity system. Specifically, we analyze
the stable locking region, where the laser array exhibits continuous wave emission for different detunings and
coupling strengths between the individual lasers. We find that the optical fields in the outer lasers are out of
phase with the middle laser.
We consider a semiconductor laser device, where the active region consists of parallel stripes in the longitudinal
direction. In the composite cavity model, the stripes are coupled via the transversal modes of the entire
compound laser device. By calculating the spatial mode profiles we accurately account for the frequency
detuning between the modes as well as for the gain and coupling of the individual modes, which are determined
by spatial overlap integrals of the mode profiles. In particular, we show the nonlinear dependence of these
quantities on the geometry of the laser device. The temporal dynamics of the composite cavity modes are
described by corresponding rate equations. Bifurcation analysis of these rate equations, which are coupled to
the spatial mode equations, unravels the dynamics of a twin-stripe laser. We identify different locking regions
as well as regions with possibly chaotic dynamics.
We consider a system of two identical, but possibly detuned, spatially separated semiconductor lasers that are
mutually coupled via their optical fields. In a rate equation approach this system can be modeled by a set
of delay differential equations, where the delay takes into account the propagation time of the light from one
laser to the other. The delay introduces a complicated structure the compound laser modes (CLMs) whose
interaction may lead to complicated dynamics.
In this paper we present a bifurcation study of the CLM structure for the relevant system parameters,
including the pump current and the detuning. Initially stable CLMs can destabilizes in Hopf bifurcations that
lead to complicated dynamics on different time scales. In particular, we concentrate on the dynamics near the
boundary of locked dynamics of the two lasers. Depending on the pump current we find different scenarios for
the route to locking as a function of the detuning between the two lasers.
In the filtered optical feedback (FOF) scheme a part of the emission of the laser is spectrally filtered, for example by a Fabry-Perot filter, and than fed back into the laser. If a semiconductor laser is subject to such delayed FOF qualitative different types of oscillations are possible: the well known relaxation oscillations and, more remarkably, frequency oscillations. We explain how the continuous wave operation of the FOF laser - the external filtered modes - lose their stability and the different types of oscillations arise due to the presence of the filter. This study is restricted to the case of a narrow filter. This means that there are only a few external filtered modes within the width of the filter, so that the influence of the feedback phase can be studied explicitly.
We investigate the continuous wave solutions of a system of two mutually delay coupled semiconductor lasers. These continuous wave solutions, which we refer to as compound laser modes (CLMs), are locked solutions of the coupled laser system where both lasers lase at a common frequency. We model the system by a set of delay differential rate equations, where we assume that, apart from a possible detuning in their free running optical frequencies, the lasers are identical. We show how the structure and the stability of the CLMs depend on the main parameters, namely, the feedback phase, the feedback rate, the pump parameter, and the detuning. We identify two mechanisms for creating CLMs. First, CLMs emerge from the off-state of the coupled laser system in Hopf bifurcations. Second, CLMs are created in pairs in saddle-node bifurcations. For the special case of zero detuning we also find pitchfork bifurcations that organize the CLM structure. We show in which parameter regions CLMs exist, where they are stable, and which bifurcation curves form the boundary of the stable locking region.
We theoretically investigate the dynamical properties of a system
of two semiconductor lasers 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 laser 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 laser's internal relaxation
oscillations. We model this system with Lang-Kobayashi-type rate equations where we account for the mutual coupling of the two lasers 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 lasers with symmetrical coupling conditions but different frequencies, and present an analysis of the coupled laser modes (CLMs) of the system.
We 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.
A model is presented to study self diffusion effects of silylated polymers during dry development. The effect is discussed in connection with mechanisms of the formation of the oxide mask during different O2-RIE conditions. Furthermore, the influence on the CD control is outlined.
Process simulation based on a two dimensional diffusion model for the reaction of the hexamethyldisilazan (HMDS) within the resist considering the crosslinks between photo active component (PAC) and resin and the following dry development is outlined. Results of silylation and etching simulation are discussed. Furthermore the influence of the resin composition and the conditions of silylation will be presented for an ORWO-resist.
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