Acceleration of gain recovery and dynamics of electrons in QD-SOA

The Composition Effect on the Dynamics of Electrons in Sb-Based QD-SOAs

“…So, ES is referred to as a reservoir for GS [8]. This is contradicted with the experimentally evidenced that carriers stay long in WL and short in ES [16]. Due to this and other reasons, discussed below, four REs system is more appropriate.…”

“…The energy subbands of the QD at each mole fraction are included through relaxation times (see Eqs. [15][16][17], thus a difference appears between curves. The carrier density in the barrier layer obtained here is in the range of (10 15 cm -3 ) which is near to the value of WL carrier density in [11] which assumes that carriers are injected directly to WL.…”

On the Feasibility of 320 Gb/S All-Optical and Gate Using Quantum-Dot Semiconductor Optical Amplifier-Based Mach-Zehnder Interferometer

“…When a critical layer thickness is exceeded, then three-dimensional islands are formed on top of the wetting layer [60,61]. QD-SOAs operating in the 1550-nm range consist of InAs QDs grown on InP substrate [44,62]. Assuming that the conduction band of a single QD has two discrete electronic states, namely the ground state (GS) and the exited state (ES), and that the wetting layer offers an additional energy level (WL), a QD-SOA is considered to be a three level system.…”

“…Similarly carriers from the ES relax to the GS, while the amplification process is incited by the stimulated radiative transition from the GS of the conduction band to the GS of the valence band. In this manner the states above the GS serve as a carrier reservoir for the GS [33,62,63], which accelerates the QD-SOA gain recovery and accordingly its response to ultrafast excitations.…”

“…In this case the QD ensemble should be divided into different groups with energies depending on their resonant frequencies. Then the QD-SOA dynamical behavior should be described by properly modifying the system of 3-level rate equations [63] while discriminating the modal gains of signals A and B by assuming a Gaussian-like distribution for their spectral profiles [62]. Nevertheless, although this possibility of XGM in QD-SOAs would be beneficial for multi-wavelength applications [45], yet the switching scheme we have proposed aims at realizing ultrafast Boolean logic operation on single channel data rates and hence at supporting alloptical signal processing in the context of Optical Time Division Multiplexing (OTDM) [69].…”