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B Krauskopf

Publications and source records attributed to B Krauskopf.

6 recordsLinked to original sources
PubMed2006

Frequency versus relaxation oscillations in a semiconductor laser with coherent filtered optical feedback.

We investigate the dynamics of a semiconductor laser subject to coherent delayed filtered optical feedback. A systematic bifurcation analysis reveals that this system supports two fundamentally different types of oscillations, namely relaxation oscillations and external roundtrip oscillations. Both occur stably in large domains under variation of the feedback conditions, where the feedback phase is identified as a key quantity for controlling this dynamical complexity. We identify two separate parameter regions of stable roundtrip oscillations, which occur throughout in the form of pure frequency oscillations.

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PubMed2003

Delay dynamics of semiconductor lasers with short external cavities: bifurcation scenarios and mechanisms.

We present a comprehensive study of the emission dynamics of semiconductor lasers induced by delayed optical feedback from a short external cavity. Our analysis includes experiments, numerical modeling, and bifurcation analysis by means of computing unstable manifolds. This provides a unique overview and a detailed insight into the dynamics of this technologically important system and into the mechanisms leading to delayed feedback instabilities. By varying the external cavity phase, we find a cyclic scenario leading from stable intensity emission via periodic behavior to regular and irregular pulse packages, and finally back to stable emission. We reveal the underlying interplay of localized dynamics and global bifurcations.

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PubMed2001

Unnested islands of period doublings in an injected semiconductor laser.

We present a theoretical study of unnested period-doubling islands in three-dimensional rate equations modeling a semiconductor laser subject to external optical injection. In this phenomenon successive curves of period doublings are not arranged in nicely nested islands, but intersect each other. This overall structure is globally organized by several codimension-2 bifurcations. As a consequence, the chaotic region existing inside an unnested island of period doublings can be entered not only via a period-doubling cascade but also via the breakup of a torus, and even via the sudden appearance of a chaotic attractor. In order to fully understand these different chaotic transitions we reveal underlying global bifurcations and we show how they are connected to codimension-2 bifurcation points. Unnested islands of period doublings appear to be generic and hence must be expected in a large class of dynamical systems.

Journal Article↗
PubMed1999

Excitability and coherence resonance in lasers with saturable absorber.

We show that a laser with a saturable absorber, described by the Yamada model, displays excitability just below threshold. A small perturbation, for example, a small input pulse, can trigger a single high output pulse, after which the system relaxes back to the off state. In order to study possible applications, such as pulse reshaping and clock recovery, approximate expressions are given for the excitability threshold and the delay between input and output pulses. Under the influence of optical noise, the system displays coherence resonance: below threshold the laser produces pulse trains with minimal jitter for a particular optimal noise level. This all-optical coherence resonance allows direct experimental verification.

Journal Article↗
PubMed1966

Genetic analysis of the ViA-his chromosomal region in Salmonella.

Johnson, E. M. (Walter Reed Army Institute of Research, Washington, D.C.), Barbara Krauskopf, and L. S. Baron. Genetic analysis of the ViA-his chromosomal region in Salmonella. J. Bacteriol. 92:1457-1463. 1966.-The relative chromosomal location of the ViA determinant, a gene required for Vi antigen expression in Salmonella typhosa (and present also in S. typhimurium), was examined in S. typhimurium x S. typhosa matings. The position of this gene was determined with respect to the histidine (his) and methionine (metG) biosynthesis markers, and to the genetic determinants of somatic antigens 5 (O-5) and 4 (O-4) of S. typhimurium. The gene order established by analyses of the hybrid classes resulting from the genetic crosses was ViA-O-5-metG-O-4 (his). This order suggests that neither ViA nor O-5 is a member of the complex of functionally related structural genes which constitute the O-4 locus. It allows for the possibility, however, of a functional relationship between the genes of the ViA and O-5 loci.

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