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Fiber pump lasers are widely used in a variety of fields, such as optical fiber communication, national defense, and medical beauty due to their high beam quality and intense laser energy. However, the alignment errors of optical parameters can influence the beam quality in the packaging of the fiber pump lasers. It is necessary to analyze the reflector, focusing lens, fiber, and the laser diode on the coupling influence between for guiding the fiber pump laser packaging. Firstly, we establish the optical path between the laser diode, focusing lens and reflector based on the physical ray-tracing method. On the other hand, the high coupling efficiency of whole system is achieved by optimize the parameters of each optical element. The simulation result shows that the highest coupling efficiency is 98.6% based on optimizing the parameters of the optical path while the experimental result of coupling efficiency is 90.36%. Also, the effects of refractive index, wavelength and fiber diameter on coupling efficiency are further investigated. The experimental results show that the radial displacement has the greatest influence on the coupling efficiency. The simulation results show that increasing the fiber core diameter can effectively improve the coupling efficiency. The results of rigorous analysis will provide an effective reference for manufacturing compact, high coupling efficiency fiber pumped laser. [ABSTRACT FROM AUTHOR]

Data security is essential for applications that require a significant level of data privacy. Online banking and government mailing are good examples of data with security requirements. This paper demonstrates an enhanced secure fiber-optic communication system based on chaos using Optisystem 7.0 software. A 10 Gb/s externally modulated signal is transmitted over 100 km of standard single-mode fiber. The modulated data is hidden by a chaotic optical signal generated by controlling the rate parameters of a semiconductor laser. The results showed that chaos degrades the overall system performance and limits the transmission distance to 70 km. A chirped fiber-Bragg grating and erbium-doped fiber amplifier are introduced to compensate signal dispersion and to increase the transmission distance to 104 km (80% enhancement). Also, the results revealed that maximum Q-factor of 4.2 and a minimum bit error rate of 10 - 8 are successfully recovered the data at the receiver. [ABSTRACT FROM AUTHOR]

Structure optimisation of the GaAs-based GaInNAsSb/GaNAs quantum-well (QW) vertical-cavity surface-emitting diode lasers (VCSELs) has been carried out using the comprehensive three-dimensional self-consistent physical model of their room-temperature (RT) continuous-wave (CW) threshold operation. The model has been applied to investigate a possibility to use these devices as carrier-wave lasing sources in the third-generation optical-fibre communication. In this simulation, all physical (optical, electrical, thermal and gain) phenomena crucial for a laser operation including all important interactions between them are taken into consideration. As expected, the 1.5λ-cavity VCSEL has been found to demonstrate the lowest RT CW threshold. However, for many VCSEL applications, the analogous VCSEL equipped with a longer 3λ-cavity should be recommended because it exhibits only slightly higher threshold but manifest much better mode selectivity – the desired single-fundamental-mode operation has been preserved in these devices up to at least 380 K. The Auger recombination has been found to be decidedly the main reason of the threshold current increase at higher temperatures. A proper initial red detuning of the resonator wavelength with respect to the gain spectrum may drastically decrease CW lasing thresholds, especially at higher temperatures. [ABSTRACT FROM AUTHOR]

We present a multi-population rate equation model for the analysis of the static and dynamic characteristics of a quantum dot (QD) semiconductor laser. The model is applied to the extraction of the differential gain and linewidth enhancement factor of the QD laser simulating the same kind of experiments usually done in the laboratory. Coherently with the experimental results, we show the difference between the values of the differential parameters extracted in below and above threshold characterizations. We demonstrate that such discrepancy is due the complex dynamics of the carriers in those energy states, whose carrier concentration is not clamped by the stimulated emission process above threshold. [ABSTRACT FROM AUTHOR]

Quantum dot (QD) lasers exhibit many interesting and useful properties such as low threshold current, temperature insensitivity or chirpless behavior. In order to reach the standards of long-haul optical transmissions, 1.55 μm InAs QD lasers on InP substrate have been developed. Based on time resolved photoluminescence (PL) measurements, carrier dynamics behavior is at first investigated. Electroluminescence (EL) results are then shown at room temperature exhibiting a laser emission centered at 1.61 μm associated to a threshold current density as low as 820 A/cm2 for a six InAs QD stacked layers. Finally, a rate equation model based on the reservoir theory is used to model both time-resolved photoluminescence (TRPL) and electroluminescence results. It is shown that carrier dynamic calculations are in a good agreement with measurements since the saturation effect occurring at high injected power is clearly predicted. [ABSTRACT FROM AUTHOR]

Physical aspects of an operation of the GaAs-based InGaAs/GaAs quantum-well (QW) VCSELs with the intentionally detuned optical cavities have been considered in the present paper using the comprehensive three-dimensional self-consistent optical–electrical–thermal-gain simulation. In GaAs-based structures, very good DBR resonator mirrors and a very efficient methods to confine radially both the current spreading and the electromagnetic field with the aid of oxide apertures may be applied. It has been found using the above simulation that even currently available immature technology enables manufacturing the above devices emitting radiation of wavelengths over 1.20 μm. In particular, while the room-temperature 1.30-μm lasing emission is still beyond possibilities of the InGaAs/GaAs QW VCSELs, these structures may offer analogous 1.25-μm emission, especially for the high-power and/or high-temperature operation. [ABSTRACT FROM AUTHOR]