We propose to use a five-level cascade system to enhance self-Kerr nonlinearity under an electromagnetically induced transparency (EIT) condition. Using density-matrix theory, an expression of the self-Kerr nonlinear coefficient for a weak probe light is derived. Variations of the self-Kerr coefficient with respect to the frequency and intensity of a strong coupling light are investigated. The Kerr nonlinearity is basically modified and enhanced greatly in the spectral regions corresponding to EIT transparent windows. Furthermore, the sign, slope, and magnitude of the self-Kerr coefficient can be controlled with the frequency and intensity of the coupling light. Such a controllable Kerr nonlinearity can find interesting applications in optoelectronic devices working with low light intensity at multiple frequencies.

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Based on the Maxwell-Bloch equations, we considered a five-dimensional ODE system, describing the dynamics of a semiconductor laser. The system has rich dynamics with multiperiodic, chaotic and hyperchaotic states. In this analysis, we have investigated the hyperchaotic nature of the aforesaid model and proposed a communication scheme, the generalized form of chaos shift keys, where the coupled systems do not need to be in the synchronized state. The results are implemented with the hyperchaotic laser model followed by a comprehensive security analysis.

In this work, we study the influence of Doppler broadening on cross-Kerr nonlinearity in a four-level inverted-Y atomic system under electromagnetically induced transparency (EIT) condition. The first- and third-susceptibilities in the presence of Doppler effect are derived as a function of probe, signal and coupling beams and temperature of medium. Under EIT condition, cross-Kerr nonlinearity is enhanced several orders of magnitude compared to that without EIT. The Doppler effect leads to a reduction in the transparent efficiency and thus reduces the amplitude of cross-Kerr nonlinear coefficient. For hot atomic gaseous medium, such consideration of the Doppler effect may be useful for experimental observations and apply to photonic devices operating at different temperature conditions.

The paper presents the physical processes and operational characteristics of an original subpicosecond dye laser system which is designed and successfully developed at our laboratory basing on the combination use of three photonic processes of dye molecules: 1) Fast spectrotemporal evolutions in the broadband dye laser emissions; 2) Generation of a chain of ultrashort pulses (spikes) from low-Q micro-cavity dye lasers; and 3) Non-linear resonant interaction between ultrashort laser pulses and highly-saturated dye media. Such a laser system provides a stable generation of single 500 fs pulses with a peak power of 300 MW at 606 nm. Particularly, the whole sub-picosecond laser system is pumped by a single nanosecond laser (Q-switched Nd:YAG laser). The spectral and time processes involved in these pulse-shortening methods are analyzed with a rate-equation model extended to wavelengths. A white light continuum generation was obtained by focusing the 500 fs pulses into 2 cm water cell. As a result, it enables us to produce widely tunable ultrashort laser pulses with a spectral selection and amplification of the supercontinuum spectrum.