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International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD)

Ground and excited-state performance of an quantum-dot semiconductor amplifier

Benjamin Lingnau, Eckehard Schöll, Kathy Lüdge

Published Sep 1, 2014• 1 citation
Publisher

Abstract

Using an optimized delay-differential-equation model, we efficiently simulate the signal propagation through a quantum-dot semiconductor amplifier. We analyze the device performance by means of the signal quality factor when amplifying signals on either the ground or excited state transition, in dependence of pump current and signal power.

DOI
10.1109/nusod.2014.6935386

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Using an optimized delay-differential-equation model, we efficiently simulate the signal propagation through a quantum-dot semiconductor amplifier. We analyze the device performance by means of the signal quality factor when amplifying signals on either the ground or excited state transition, in dependence of pump current and signal power.
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The effect of additional optical pumping injection into the ground-state ensemble on the ultrafast gain and the phase recovery dynamics of electrically-driven quantum-dot semiconductor optical amplifiers is numerically investigated by solving 1088 coupled rate equations. The ultrafast gain and the phase recovery responses are calculated with respect to the additional optical pumping power. Increasing the additional optical pumping power can significantly accelerate the ultrafast phase recovery, which cannot be done by increasing the injection current density.
Quantum dot (QD)-based semiconductor optical amplifiers offer unique properties compared with conventional devices based on bulk or quantum well material. Due to the bandfilling properties of QDs and the existence of a nearby reservoir of carriers in the form of a wetting layer, QD semiconductor optical amplifiers may be operated in regimes of high linearity, i.e. with a high saturation power, but can also show strong and fast nonlinearities by breaking the equilibrium between discrete dot states and the continuum of wetting layer states. In this paper, we analyse the interplay of these two carrier populations in terms of a simple rate equation model. Based on the steady-state and small-signal properties of the model, we analyse and discuss the optical modulation response and the four-wave mixing properties of QD semiconductor optical amplifiers, in particular emphasizing the role of ultrafast gain dynamics.
The Pulse effect on the cross-gain modulation (XGM) in the quantum dot (QD) semiconductor optical amplifiers (SOAs) is investigated using the combining of the SOA power with the QD rate equations system. The QDs structure includes three regions: ground state (GS), excited state (ES) and wetting layer (WL). Thus, a set of rate equations for pump and probe signals is introduced for both steady-state and small-signal power values, which are solved numerically. The pulse shape was included in the analysis, for pump and probe signals. The theoretical results showed a good agreement with the experimental results. It was found that decreasing pulse width of pump/probe ratio is efficient to increase XGM efficiency and bandwidth.
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