In this paper we are interested in modeling, performance evaluation, and measurement of a quadrant detector. Photodiode is modeled using its differential equations then implemented and solved using ORCAD-pspise. The model validation was performed by comparing the model results with the experimental measurements using a proposed setup. The model was used to investigate the effect of the photodiode donor concentrations, acceptor concentrations and intrinsic region concentrations. The simulation results showed that the donor concentrations should be kept as small as possible in order to improve the photodiode performance, the acceptor concentrations has a small effect on the performance, and as the intrinsic region concentration increases the photocurrent increases and the junction capacitance decreases with a small increase in the dark current.

Fiber lasers technology has grown rapidly due to the rapid advances in high power diodes, diode-to-fiber coupling schemes and doped fiber design and fabrication.Erbium-Ytterbium (Er 3+ /Yb 3+ ) co-doped fiber is an attractive active medium for the fiber lasers in which Ytterbium is co-doped with Erbium to produce a spectrum in third telecoms window around 1550nm which makes them suitable sources for long range applications. In this paper the Er 3+ /Yb 3+ fiber laser pumped by a laser diode at 980 nm is simulated using the Optiwave software. The pump source was swept from 1.25 to 5 w to extract the slope efficiency. The pump radiation was focused into the Er 3+ /Yb 3+ fiber through an input mirror, which was 98% reflecting at 1550 nm and 99% transmitting at 980 nm. A length of 0.1 m of Er 3+ /Yb 3+ fiber was used with an N.A. of 0.22, Er 3+ ion density of 25.4 x 10 24 m -3 , and Yb 3+ ion density of 320 x 10 24 m -3 . The output mirror was 50% reflecting at 1550 nm. Then the length of the fiber was swept from 1m to 5m in order to obtain optimized fiber length. The simulation results demonstrated that a laser output power of 0.8 W was obtained at 1550 nm for a launched power of 2 W with a slope efficiency of 40% and a lasing threshold of 0.4 W of launched pump power. The results also showed that the optimized fiber length was achieved at 2 m which is in a good agreement with the published similar experimental schemes.

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In this paper, we present an enhanced high-power extrinsic diode side-pumped solid-state laser (DPSSL) model to accurately predict the dynamic operations and pump distribution under different practical conditions. We introduce a new implementation technique for the proposed model that provides a compelling incentive for the performance assessment and enhancement of high-power diode side-pumped Nd:YAG lasers using cooperative agents and by relying on the MATLAB, GLAD, and Zemax ray tracing software packages. A large-signal laser model that includes thermal effects and a modified laser gain formulation and incorporates the geometrical pump distribution for three radially arranged arrays of laser diodes is presented. The design of a customized prototype diode side-pumped high-power laser head fabricated for the purpose of testing is discussed. A detailed comparative experimental and simulation study of the dynamic operation and the beam characteristics that are used to verify the accuracy of the proposed model for analyzing the performance of high-power DPSSLs under different conditions are discussed. The simulated and measured results of power, pump distribution, beam shape, and slope efficiency are shown under different conditions and for a specific case, where the targeted output power is 140 W, while the input pumping power is 400 W. The 95% output coupler reflectivity showed good agreement with the slope efficiency, which is approximately 35%; this assures the robustness of the proposed model to accurately predict the design parameters of practical, high-power DPSSLs.

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