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K Panajotov

Publications and source records attributed to K Panajotov.

5 recordsLinked to original sources
PubMed2005

Two-mode injection locking in vertical-cavity surface-emitting lasers.

We report on the dynamics that accompany polarization switching induced by orthogonal optical injection in a vertical-cavity surface-emitting laser (VCSEL). As the injection strength increases, the VCSEL bifurcates to injection-locked steady states and time-periodic and possibly chaotic dynamics. Of particular interest is a two-mode injection-locking solution, i.e., locking of the two VCSEL polarization modes. A detailed stability analysis unveils new bistability mechanisms in optical injection problems.

Journal Article↗
PubMed2003

Optical feedback induces polarization mode hopping in vertical-cavity surface-emitting lasers.

Vertical-cavity surface-emitting lasers subjected to weak polarization-insensitive optical feedback are studied experimentally and theoretically. We find that the feedback induces random anticorrelated hopping between the two orthogonal linearly polarized modes. This polarization mode hopping is accompanied by rapid anticorrelated oscillations in the linearly polarized intensities at the external-cavity frequency. The study of a simple stochastic delay differential equation suggests that these oscillations generated by the delay are typical of any hopping phenomenon between states.

Journal Article↗
PubMed2003

Nonlinear polarization dynamics in directly modulated vertical-cavity surface-emitting lasers.

A current-modulated vertical-cavity surface-emitting laser is shown to exhibit interesting nonlinear dynamics in its two orthogonal linearly polarized (LP), fundamental transverse modes. The intensities of the two LP modes may exhibit in-phase time-periodic dynamics or chaotic regimes with combination of in-phase and antiphase dynamics at two different time scales. Chaotic dynamics are found in a large range of laser and modulation parameters.

Journal Article↗
PubMed2001

Photorefractive beam-fanning effect and self-pulsations in coated LiNbO3 slabs.

We investigate the dynamical behavior of optical Fabry-Perot resonators consisting of LiNbO3 slabs (x and c cut) that are coated with different (absorbing or lossless) dielectric multilayers deposited on both sides of the slabs. Bistable switching is observed experimentally. The buildup of beam fanning with time leads to destructive interference for a portion of the incident beam, inducing a change in absorption and heating, hence to switching off. As a result, self-pulsations appear whose frequency depends strongly on the input light intensity, the spot size, and the focusing. Switching and self-pulsations are not observed in the case of lossless coatings or for bare LiNbO3 slabs, although strong photorefractive beam fanning is still present. We also study the influence of the incident-beam characteristics (width and focusing) on the beam-fanning process and the pulsating behavior.

Journal Article↗