Mohammedhasanain Hadi mohsin Al-Jassani

The optical output of a semiconductor laser can fluctuate chaotically by modulating its direct current in limited conditions of the modulated current signal parameters in terms of modulation frequency and modulation index. In this work, single, double, and chaotic pulses of an InGaAsP laser with direct current modulation, are numerically presented through a bifurcation diagram. Numerically, the unidirectional optical coupling system realizes chaotic synchronization between two identical InGaAsP lasers with direct current modulation, as the transmitter/receiver configuration. The transmission time for transmitting light from the transmitted laser to the received laser is essential for controlling the quality of chaos synchronization. The transmission time applies on the order of nanoseconds. Chaos synchronization quality is estimated by a correlation plot and calculated by the cross-correlation coefficient. This study observed the best synchronization quality (complete chaos synchronization) when the two lasers are identical. On the other hand, the chaotic synchronization between two non-identical InGaAsP lasers was investigated. In this case, complete chaos synchronization is not found, and the quality of chaotic synchronization was observed to decrease as the mismatch between the parameters of the two lasers increased.

The synchronization of chaos in a quantum-dot laser diode (QDLD) is numerically proposed. The optical chaos is produced in a single-mode QDLD by an external loop of optoelectronic feedback. Chaos synchronization is performed by the injection of the electronic signal from the transmitter laser to the receiver laser. The numerical results of the chose synchronization quality are presented by calculating the correlation coefficient between the chaotic transmitter signal and the chaotic receiver signal.

The positive and negative feedback loop of optoelectronic in a standard quantum-dot semiconductor-laser model are investigated numerically. The time trace of the laser output (density of photon) and the phase portraits of charge carriers in the well are compared between a positive and negative feedback loop of optoelectronic. The identical behavior laser output is found at certain value of positive optoelectronic feedback strength with the corresponding value of negative feedback strength of optoelectronic.

In this work photo-luminescence epoxies samples by eosin y dye were fabricated. Eosin Y used as substance in the treating of epoxy resin to form photo-luminescence epoxies of five different concentrations ( 4x10^-5, 8x10^-5, 2x10^-4, 6x10^-4,1x10^-3) moles/L. The absorbance spectra and the florescence intensities of the all fabricated photo-luminescence epoxy samples were measured with spectrometer and fluorescence spectrophotometer respectively. The fluorescence quantum efficiency, fluorescence life-time ,and radiative life-time from all photo-luminescence epoxies were reported. Optimal fluorescence quantum efficiencies are between the extent of the limits of concentrations ( 2x10^-4- 1x10^-3 ) moles/L .The quantum efficiencies of fluorescence for photo-luminescence samples are (75.5%, 77%, 84.8%, 93%, 85.8%) respectively with the five different concentrations above.

In this numerical work, the one-way chaotic optical synchronization model in Ref. 12 was modified when we added the coupling time between the two chaotic optical systems, where every system consists of S-P LD subjected to sinusoidal modulation of its bias current. The coupling time between the emitting laser and the receiving laser controls the quality of chaos synchronization. In this work, the time series of the two laser outputs are plotted to display how well the chaotic photon numbers are synchronized between the two chaotic optical systems. On the other hand, the chaotic synchronization quality is estimated and calculated by the correlation plot and the correlation coefficient respectively. The results showed that the coupling time plays a decisive role in the quality of synchronization between the two chaotic systems, as the shorter the coupling time, the better the synchronization quality.

The delayed negative optoelectronic feedback DNOEF system of the self-assembled quantum dot (SA-QD) semiconductor laser with DNOEF is numerically investigated. Bifurcation diagrams, time traces, and frequency spectra of the laser output, and the 2-D phase space portraits, are used to analyze the nonlinear transitions of the DNOEF system. In this study, delay times of the feedback were applied that were neither much smaller nor much greater than the relaxation time of the laser, thus most results for nonlinear transitions in this feedback system indicated a strong interaction between the loop frequency and the relaxation frequency of the laser. These nonlinear transitions were included 2-P, RP, and 3-P states. On the other hand, the CP states of the laser output was found within a narrow range of feedback delay time. Through the results, it was found that the laser enters chaotic pulse states when the natural time delay increases from 1.433 to 1.6 and the feedback strength − 0.32.