Study of dual-directional high rate secure communication systems using chaotic multiple-quantum-well lasers

A scheme of synchronized injection multi-quantum-well （MQW） laser system using optical couphng-feedback is presented for performing chaotic dual-directional secure communication. The performance characterization of chaos masking is investigated theoretically, the equation of synchronization demodulation is deduced and its root is also given. Chaos masking encoding with a rate of 5 Gbit/s and a modulation frequency of 1 GHz, chaos modulation with a rate of 0.2 Gbit/s and a modulation frequency of 0.2 GHz and chaos shifting key with a rate of 0.2 Gbit/s are numerically simulated, separately. The ratio of the signal to the absolute synchronous error and the time for achieving synchronous demodulation are analysed in detail. The results illustrate that the system has stronger privacy and good performances so that it can be applied in chaotic dual-directional high rate secure communications.

Density cavities generated by plasma-field interactions in the far wake region of a space vehicle

Under the consideration of non-steady case, a set of equations is derived, which describes the non-steady nonlinear interactions between plasma and field in the far wake region of a space vehicle. Numerical calculations are also made and the numerical results show that density cavities and electromagnetic solitary waves are generated due to the modulation instability, if the envelope of high frequency modulation field is strong enough. This is of great significance to the detection of disguised space vehicles.

Small-Signal Analysis of Performance Characterization of Chaotic Masking Decoding in Injected Semiconductor Lasers

Performance characterization of chaotic masking encoding and decoding is studied in synchronization injected semiconductor lasers under condition of injected-feedback. The modulation response function of chaotic masking encoding and its response factor are theoretically deduced and analysed by small-signal analysis. It is numerically demonstrated that there are peak values between 1.52 GHz and 3.18 GHz when the injection coefficient is between 0.2 and 0.8. The chaotic synchronization error equation is theoretically deduced and its root is given by small- signal analysis under condition of chaotic masking encoding. The chaotic decoding formula is also theoretically demonstrated. There are the least dale values of synchronization errors between the modulation frequencies of 0.79GHz and 1.91 GHz when the injection coefficient is between 0.1 and 0.8 in numerical simulation. The numerical result is well consistent with the theoretical demonstration.

Theoretical model of optical fiber secure communication system with chaotic multiple-quantum-well lasers

Chaotic synchronization of injected multiple-quantum-well lasers of optical fiber system and a theoretical model of optical fiber chaotic secure communication system are presented by coupling a chaotic multiple-quantum-weU laser synchronization system and a fiber channel. A new chaotic encoding method of chaos phase shift keying On/Off is proposed for optical fiber secure communications. Chaotic synchronization is achieved numerically in long-haul fiber system at wavelength 1.55 μm. The effect of the nonlinear-phase of fiber is analyzed on chaotic signal and synchronization. A sinusoidal signal of 0.2 GHz frequency is simulated numerically with chaos masking in long-haul fiber analog communication at wavelength 1.55 μm while a digital signal of 0.5 Gbit/s bit rate is simulated numerically with c^1 haos masking and a rate of 0.05 Gbit/s are also simulated numerically with chaos shift keying and chaos phase shift keying On/Off in long-haul fiber digital communications at wavelength 1.55μm

Plasmon-Assisted Phase-Matched Second- and Third-Harmonic Generation in Single-Negative Heterostructures

Dispersion relations of surface plasmon polaritons （SPPs） in sandwiched optical systems are studied. The system is actually a kind of SPP waveguides, with two kinds of single negative material （SNG） as core and cladding layers, respectively. Since both TM and TE polarized SPPs can be excited in the structure, the dispersion of SPPs becomes more abundant and leads to colorful nonlinear opticM properties. The authors demonstrate the effective phase-matched second and third-harmonic generation （SHG, THG） assisted by the coupled SPPs. A cascaded second-order nonlinear process can Mso be achieved in the structure when the thickness of the core layer is properly selected, leading to the simultaneous SHG and THG. Further investigations show that much easier phase-matching can be fulfilled in the SNG waveguide array. Our results would be of potential use for surface-enhanced frequency conversion device such as light emitters or lasers.

Probing Quark Loop Effects on Dressed Gluon Propagator

We study the quark loop effects on the dressed gluon propagator and also on the quark propagator itself.We find that the gluon propagators are different in two phases.The quark mass effects on the gluon propagator aresmall but not negligible.We also study the current quark mass dependence on the bag constant.

Coupling effect of surface plasmon polaritons in single-negative lamellar heterostructure

Propagation characteristics of surface plasmon polaritons （SPPs） in the lamellar heterostructure, which is actually a SPP waveguide array, constructed by two kinds of single negative （SNG） material layers stacked alternatively are investigated. Based on the finite element method （FEM）, the negative-refraction （NR） property is demonstrated when the electromagnetic wave penetrates through free space into such SNG lamellar structure. A clear view of the underlying physics of NR is presented qualitatively that is mainly related to the coupled SPPs. The strong coupling effect leads to the novel SPP dispersion curves and then v the anomalous propagation characteristics.

All-optical chaotic MQW laser repeater for long-haul chaotic communications

We present an all-optical chaotic multi-quantum-well (MQW) laser repeater system to be used in long-haul chaotic communications. Chaotic synchronization is achieved among transmitter, repeater, and receiver. Chaotic repeater communications with a sinusoidal signal of 0.2-GHz modulation frequency and a digital signal of 0.4-Gb/s bit rate are numerically simulated, respectively. Calculation results illustrate that the signals are well decoded by the chaotic repeaters. Its bandwidth and the characteristics at much high bit rate are also analyzed. Simulation shows that the repeater can improve decoding quality, especially in higher bit rate chaotic communications.