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International audience; Free-space optics constitutes a growing technology offering higher bandwidth with fast and cost-effective deployment compared to fiber technology. Multiple applications are envisioned like private communications. In such a case, the secret message is encoded into a chaotic waveform from which the information is extremely hard for an eavesdropper to extract. For free-space optics applications, the operating wavelength is an important parameter that has to be chosen wisely to reduce the impact of the environmental parameters. In this context, quantum cascade lasers are highly relevant semiconductor lasers because the lasing wavelength can be properly adjusted in the mid-infrared domain, typically at wavelengths for which the atmosphere is highly transparent. The simplest way to generate a chaotic optical carrier from a quantum cascade laser is to feed back part of its emitted light into the device after a certain time delay, beyond which chaos synchronization between the drive and the response lasers occurs. In this paper, we discuss about how quantum cascade laser's chaos can be used to develop private communication lines. We also give realistic perspectives for further developing mid-infrared private communications using chaotic waves.

PubMed ID: 27415263 In this paper we analyze the rogue wave spectra of the Kundu-Eckhaus equation (KEE). We compare our findings with their nonlinear Schrodinger equation (NLSE) analogs and show that the spectra of the individual rogue waves significantly differ from their NLSE analogs. A remarkable difference is the one-sided development of the triangular spectrum before the rogue wave becomes evident in time. Also we show that increasing the skewness of the rogue wave results in increased asymmetry in the triangular Fourier spectra. Additionally, the triangular spectra of the rogue waves of the KEE begin to develop at earlier stages of their development compared to their NLSE analogs, especially for larger skew angles. This feature may be used to enhance the early warning times of the rogue waves. However, we show that in a chaotic wave field with many spectral components the triangular spectra remain as the main attribute as a universal feature of the typical wave fields produced through modulation instability and characteristic features of the KEE's analytical rogue wave spectra may be suppressed in a realistic chaotic wave field. Publisher's Version