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High Performance Hybrid Silicon Evanescent Traveling Wave Electroabsorption Modulators

100%
Abedi K., Afrouz H.
Acta Physica Polonica A
|
2013
|
vol. 123
|
issue 2
415-417
EN
In this paper, for the first time, a high performance hybrid silicon evanescent traveling wave electroabsorption modulator based on asymmetric intra-step-barrier coupled double strained quantum wells active layer is introduced which has double steps at III/V mesa structure. Through this active layer, hybrid silicon evanescent traveling wave electroabsorption modulator will be advantages such as very low insertion loss, zero chirp, high extinction ratio, and large Stark shift and better figures of merit as compared with multiquantum well and intra-step quantum well structures. Furthermore, traveling wave electroabsorption modulator with double steps III/V mesa structure results in a wider bandwidth as compared with one-step III/V mesa and mushroom structures. For the modulator with double steps III/V mesa structure with a 200 μm length, the 3 dB bandwidths are obtained as 132 and 52 GHz for 25 and 40 Ω characteristic impedances, respectively.
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Multi-Electrode Tapered Waveguide Structure for Quantum-Dot Semiconductor Optical Amplifiers

100%
Abedi K., Mohadesrad E.
Acta Physica Polonica A
|
2013
|
vol. 123
|
issue 2
411-414
EN
In this paper, by employing two practical methods of multi-electrode design and tapered waveguide structure, compensation techniques to restore declining carrier density along the quantum dot semiconductor optical amplifier's waveguide are investigated. In the multi-electrode method, the effects of distributing current via electrodes on the gain and the cross-gain modulation for two, three and four-electrode structures are studied. These characteristics are also investigated for the quantum dot semiconductor optical amplifiers with a tapered waveguide structure for the first time, including waveguides with different profiles and width ratios. After due comparison between these two methods, optimum parameters of the two techniques will be used simultaneously along each other to form a combined method. Through these design developments, gain as the main feature of the quantum dot semiconductor optical amplifiers continuously increases, though cross-gain modulator results show that there is a trade-off between the modulation efficiency and improving structure capability of restoring carrier density.
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Sub-Nanosecond Phase Recovery in Quantum-Dot Semiconductor Optical Amplifiers

100%
Abedi K., Taleb H.
Acta Physica Polonica A
|
2013
|
vol. 123
|
issue 2
407-410
EN
In this paper, optimal design of a pumping scheme for achieving the best gain and phase response in quntum-dot semiconductor optical amplifiers is investigated. For the first time, the dynamic response of the quntum-dot semiconductor optical amplifier is evaluated under three different pumping schemes, known as optical pumping, electrical pumping, and electro-optical pumping. Simulation results show that the shortest gain recovery time in quntum-dot semiconductor optical amplifiers can be achieved under the electrical pumping scheme. However, under the optical pumping and electro-optical pumping schemes, the quntum-dot semiconductor optical amplifier represents a shorter phase recovery compared to the electrical pumping scheme. We found that a sub-nanosecond phase recovery in the quntum-dot semiconductor optical amplifier can be achieved under the OP and electro-optical pumping schemes, which can never be achieved under the electrical pumping, because of the slow carrier dynamics of the carrier reservoir. Also, it was found that the gain recovery process in an optically pumped quntum-dot semiconductor optical amplifier can be significantly accelerated at cryogenic temperatures. This result demonstrates the superiorities of the optical pumping scheme over the electrical pumping and electro-optical pumping schemes at low temperatures, where both the gain and phase recovery times of an optically pumped quantum-dot semiconductor optical amplifier are drastically decreased.
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