Physics and Applications of Laser Diode Chaos

An overview of chaos in laser diodes is provided which surveys experimental achievements in the area and explains the theory behind the phenomenon. The fundamental physics underpinning this behaviour and also the opportunities for harnessing laser diode chaos for potential applications are discussed. The availability and ease of operation of laser diodes, in a wide range of configurations, make them a convenient test-bed for exploring basic aspects of nonlinear and chaotic dynamics. It also makes them attractive for practical tasks, such as chaos-based secure communications and random number generation. Avenues for future research and development of chaotic laser diodes are also identified.Comment: Published in Nature Photonic

Deterministic polarization chaos from a laser diode

Fifty years after the invention of the laser diode and fourty years after the report of the butterfly effect - i.e. the unpredictability of deterministic chaos, it is said that a laser diode behaves like a damped nonlinear oscillator. Hence no chaos can be generated unless with additional forcing or parameter modulation. Here we report the first counter-example of a free-running laser diode generating chaos. The underlying physics is a nonlinear coupling between two elliptically polarized modes in a vertical-cavity surface-emitting laser. We identify chaos in experimental time-series and show theoretically the bifurcations leading to single- and double-scroll attractors with characteristics similar to Lorenz chaos. The reported polarization chaos resembles at first sight a noise-driven mode hopping but shows opposite statistical properties. Our findings open up new research areas that combine the high speed performances of microcavity lasers with controllable and integrated sources of optical chaos.Comment: 13 pages, 5 figure

Modeling of optical synchronization of chaotic external-cavity VCSEL's

The performance of a master-slave configuration for effecting the synchronization of chaotic vertical-cavity sorface-emitting lasers (VCSEL's) is studied using numerical simulations. The dynamical evolution of optically coupled VCSEL's is examined using a traveling wave model which is valid in the strong optical feedback regime. It is shown that the proposed configuration is capable of effecting synchronization in a robust manner. The opportunity for exploiting synchronized chaos in secure optical communication systems is indicated.Peer Reviewe

Characteristics and applications of the short external cavity laser diode

The characteristics of the external cavity laser diode are investigated. Emphasis is placed on the short external cavity configuration. The general governing model equations which include the multiple reflection effect are derived. It is shown that the coupling coefficient becomes a complex function of the external cavity length and the near field beam size of the laser diode due to the diffraction loss of an open resonator. The validity of this open resonator model is proven experimentally by the asymmetry in optical power versus external cavity length characteristic curve. For analysis of the ultra short external cavity laser, it is necessary to include this complex coupling coefficient. As an example, the flying optical disk head is studied using this model. In some cases, especially when the external cavity length is longer than several micrometers, the external cavity may be simply regarded as a lossy resonator. With this constant loss per roundtrip approximation, the feedback operator can be reduced to the closed form. The stationary and transient solutions are investigated analytically and numerically. The single mode condition, and dynamical stability condition are derived. Also, the simple expression for the relaxation oscillation frequency of the short external cavity laser is given for the first time. With our model, it can not be expected to find the strange attractor for the constant biased autonomous operation. However, the chaotic behavior in the current modulated nonautonomous operation is investigated. It seems that the route to chaos in this system is not limited to the period-doubling route, which has been believed as the only route in the modulated solitary laser diode so far. Generally, it is suggested that the operating external cavity length should be close to the constructive interference position, as it will give superior properties. Some experimental results applying the short external cavity laser as a laser diode sensor are given

Nonlinear Dynamics in Optoelectronics Structures with Quantum Well

The author presents some results on nonlinear dynamics in optoelectronics nanostructures as lasers with quantum wells and quantum well solar cells using mathematical modeling and numerical simulations of the phenomena which take place in such kinds of structures. The nonlinear dynamics takes the complexity of the phenomena into account, which govern the field-substance interaction. Computational software was elaborated to study the nonlinear phenomena in such quantum devices, which put into evidence their complex nonlinear dynamics, characterized by bifurcation points and chaos, and the critical values of the parameters being determined. The mathematical modeling and numerical simulations for the quantum well solar cells for optimizing the values of their optical parameters (refraction index, reflectance, and absorption) were also analyzed, so that the conversion efficiency of the devices can be improved. Although in our study we have considered only rectangular quantum wells, the hybrid model allows computing the optimum values of the parameters whatsoever the form of the quantum wells. The developed numerical models and the obtained results are consistent with the existing data in the literature for the optoelectronics of quantum well structures, having important implications in the applications

Resonant Tunnelling Optoelectronic Circuits

Nowadays, most communication networks such as local area networks (LANs), metropolitan area networks (MANs), and wide area networks (WANs) have replaced or are about to replace coaxial cable or twisted copper wire with fiber optical cables. Light-wave communication systems comprise a transmitter based on a visible or near-infrared light source, whose carrier is modulated by the information signal to be transmitted, a transmission media such as an optical fiber, eventually utilizing in-line optical amplification, and a receiver based on a photo-detector that recovers the information signal (Liu, 1996)(Einarsson, 1996). The transmitter consists of a driver circuit along a semiconductor laser or a light emitting diode (LED). The receiver is a signal processing circuit coupled to a photo-detector such as a photodiode, an avalanche photodiode (APD), a phototransistor or a high speed photoconductor that processes the photo-detected signal and recovers the primitive information signa