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We present experimental evidence for the synchronization of two semiconductor lasers exhibiting chaotic emission on subnanosecond time scales. The transmitter system consists of a semiconductor laser with weak to moderate coherent optical feedback and therefore exhibits chaotic oscillations. The receiver system is realized by a solitary semiconductor laser in which a fraction of the transmitter signal is coherently injected. We find that for a considerably large parameter range, synchronized receiver output can be achieved. We discuss the physical mechanism and demonstrate that the receiver acts as a chaos pass filter, which reproduces the chaotic fluctuations of the transmitter laser, but suppresses additionally encoded signals. Signal extraction at frequencies of up to 1 GHz has been achieved. Thus we provide a simple and robust optical chaos synchronization system that is promising for the realization of communication by sending signals with chaotic carriers.

We experimentally demonstrate random bit generation using multi-bit samples of bandwidth-enhanced chaos in semiconductor lasers. Chaotic fluctuation of laser output is generated in a semiconductor laser with optical feedback and the chaotic output is injected into a second semiconductor laser to obtain a chaotic intensity signal with bandwidth enhanced up to 16 GHz. The chaotic signal is converted to an 8-bit digital signal by sampling with a digital oscilloscope at 12.5 Giga samples per second (GS/s). Random bits are generated by bitwise exclusive-OR operation on corresponding bits in samples of the chaotic signal and its time-delayed signal. Statistical tests verify the randomness of bit sequences obtained using 1 to 6 bits per sample, corresponding to fast random bit generation rates from 12.5 to 75 Gigabit per second (Gb/s) ( = 6 bit x 12.5 GS/s).

Laser action on a single spatially chaotic wave function is obtained as a final stable state in a nonlinear dynamical model of a stadium shaped resonant cavity with an active medium. The stable single-mode lasing state corresponds to a particular metastable resonance of the cavity which wins a competition among multiple modes with positive net linear gain and has a distinct lasing threshold.

We propose a secure key distribution scheme based on correlated physical randomness in remote optical scramblers driven by common random light. The security of the scheme depends on the practical difficulty of completely observing random optical phenomena. We describe a particular realization using the synchronization of semiconductor lasers injected with common light of randomly varying phase. We experimentally demonstrate the feasibility of the scheme over a distance of 120 km.

Scar wave functions in a fully chaotic cavity are obtained numerically by an extended Fox-Li method. Lasing on the scar modes are observed in a semiconductor microcavity with a selective excitation of different scars controlled by corresponding shape of electrodes for current injection.

This paper presents a distributed algorithm to direct evacuees to exits through arbitrarily complex building layouts in emergency situations. The algorithm finds the safest paths for evacuees taking into account predictions of the relative movements of hazards, such as fires, and evacuees. The algorithm is demonstrated on a 64 node wireless sensor network test platform and in simulation. The results of simulations are shown to demonstrate the navigation paths found by the algorithm.

We present a comprehensive experimental characterization of the dynamics of semiconductor lasers subject to polarization-rotated optical feedback. We find oscillatory instabilities appearing for large feedback levels and disappearing at large injection currents, which we classify in contrast to the well-known conventional opticalfeedback-induced dynamics. In addition, we compare our experiments to theoretical results of a single-mode model assuming incoherence of the optical feedback, and we identify differences concerning the average power of the laser. Hence, we develop an alternative model accounting for both polarizations, where the emission of the dominant TE mode is injected with delay into the TM mode of the laser. Numerical simulations using this model show good qualitative agreement with our experimental results, correctly reproducing the parameter dependences of the dynamics. Finally, we discuss the application of polarization-rotated-feedback induced instabilities in chaotic carrier communication systems.