Method for determining antiphase dynamics in a multimode laser

We measure the cross spectrum of the intensity fluctuations of pairs of modes for a multilongitudinal mode neodymium-doped yttrium aluminum garnet laser operating in the steady state regime. From the data we build up a picture of how the longitudinal mode fluctuations interfere and directly show the antiphase dynamics of the intensity fluctuations.T. Hill, L. Stamatescu and M. W. Hamilto

Antiphase dynamics and self-pulsing due to a low-frequency spatial population grating in a multimode laser

We study analytically equations that extend the Tang-Statz-deMars rate equations for a multimode Fabry-Perot laser by including the low-spatial-frequency population grating and the inhomogeneous pumping rate along the cavity axis [Quant. Semiclassic Opt. 5, L17 (1997)]. First, we prove the theorem that is the foundation of the antiphase dynamics: The total intensity transients are characterized by only one frequency, the single-mode relaxation oscillation. Second, we study the three-mode laser operation. In this context, we derive analytic expressions for the steady-state intensities, their linear stability, and the bifurcation points. We prove that strictly multimode solutions display a Hopf bifurcation leading to passive Q-switched solutions. Numerically, we have found that these time-periodic regimes may bifurcate to quasiperiodic and chaotic states and that there are many domains of bistability.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Interacting pairs of periodic solutions lead to tori in lasers subject to delayed feedback

Models of class-B lasers subject to either an optoelectronic or an optical feedback are investigated analytically and numerically. We derive slow time amplitude equations from the laser delay differential equations and find multiple bifurcating and isolated branches of periodic solutions. We then show that secondary bifurcations to tori result from the interaction of pairs of Hopf bifurcations. The branches emerging from these bifurcations are followed numerically using a continuation method developed for delay differential equations.Journal Articleinfo:eu-repo/semantics/publishe

Stability and rupture of bifurcation bridges in semiconductor lasers subject to optical feedback

The bifurcation diagram of a single-mode semiconductor laser subject to a delayed optical feedback is examined by using numerical continuation methods. For this, we show how to cope with the special symmetry properties of the equations. As the feedback strength is increased, branches of modes and antimodes appear, and we have found that pairs of modes and antimodes are connected by closed branches of periodic solutions (bifurcation bridges). Such connections seem generically present as new pairs of modes and antimodes appear. We subsequently investigate the behavior of the first connection as a function of the linewidth enhancement factor and the feedback phase. Our results extend and confirm existing results and hypotheses reported in the literature. For large values of the linewidth enhancement factor (alpha=5-6), bridges break through homoclinic orbits. Changing the feedback phase unfolds the bifurcation diagram of the modes and antimodes, allowing different types of connections between modes.Journal Articleinfo:eu-repo/semantics/publishe

Bridges of periodic solutions and tori in semiconductor lasers subject to delay

For semiconductor lasers subject to a delayed optical feedback, branches of steady states sequentially appear as the feedback rate is increased. But branches of time-periodic solutions are connecting pairs of steady states and provide bridges between stable and unstable modes. All bridges experience a change of stability through a torus bifurcation point. Close to the bifurcation point, the torus remains localized near a specific fixed point in phase space. As the feedback rate increases, the torus envelope suddenly unfolds and its trajectory visits two or more unstable fixed points, anticipating the rich dynamics observed at larger feedback rates.Journal ArticleSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Intensity coherence of a multimode Nd-doped yttrium aluminum garnet laser

We measure the power spectral densities, at relaxation oscillation frequencies, of the individual longitudinal modes and the total intensity of a Nd-doped yttrium aluminum garnet laser at low pumping rate. We then test relationships between these quantities that are derived from the modal rate equations theory. The theoretical relations for the two mode case are confirmed by the experiment. However, in the three-mode regime, theory and experiments do not agree well. 5555 2002 The American Physical Society.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Retrieval of vertical profiles of atmospheric refraction angles by inversion of optical dilution measurements

In this paper, we consider occultations of celestial bodies through the atmospheric limb from low Earth orbit satellites and we show how the usual change of tangent altitude associated with atmospheric refraction is inseparably connected to a variation of the observed apparent intensity, for extended and pointlike sources. We demonstrate, in the regime of weak refraction angles, that atmospheric optical dilution and image deformation are strictly concomitant. The approach leads to the integration of a simple differential equation related to the observed transmittance in the absence of other absorbing molecules along the optical path. The algorithm does not rely on the absolute knowledge of the radiometer pointing angle that is related to the accurate knowledge of the satellite attitude. We successfully applied the proposed method to the measurements performed by two past occultation experiments: GOMOS for stellar and ORA for solar occultations. The developed algorithm (named ARID) will be applied to the imaging of solar occultations in a forthcoming pico-satellite mission

Secure communication scheme using chaotic laser diodes subject to incoherent optical feedback and incoherent optical injection

International audienceWe propose a secure communication scheme based on anticipating synchronization of two chaotic laser diodes respectively subjected to incoherent optical feedback and incoherent optical injection. This scheme does not require fine tuning of the optical frequencies of both lasers as it does for other schemes based on chaotic laser diodes subject to coherent optical feedback and injection. Our secure communication scheme is therefore attractive for experimental investigation