Necessary temporal condition for optimizing the switching window of the semiconductor-optical-amplifier-based ultrafast nonlinear interferometer in counter-propagating configuration

Characterization and optimization of SOA-based UNI recirculating shift register switching window

“…2 and 3 these include the SOA small signal gain, linewidth enhancement factor and carrier lifetime, the control pulse energy and width and the delay between the complementary clock pulses. However, the impact of the two latter parameters on the switching window of the SOA-based UNI in counter-propagating configuration, as it is the case for the shift register application, has been extensively studied and assessed in Zoiros et al (2006), which therefore means that there is no need to be re-examined within the frame of this paper. The remainder of them are set during the simulation process to 23 dB, 8, 125 ps and 75 fJ, respectively, whilst the default SOA parameters used for this purpose are E sat = 1pJ and ε = 0.2 W −1 , in accordance to typical values of bulk InGaAsP semiconductor materials operating at 1550 nm.…”

“…This quantity is equivalent to an effective recovery time that must not be much smaller neither larger enough than the operating period. In the former case, which occurs when T carrier T period assuming a constant, optimized T delay = 7 ps (Zoiros et al 2006), the time available for the switching procedure to be properly accomplished is rather short and the corresponding window declines and closes quickly after it has opened. In the latter, opposite case, the window opens but its side peaks do not have the same height because the switching procedure is abruptly interrupted from the new period that follows and which essentially intervenes and obstructs the preceding one in a sort of masking.…”

“…which is then appropriately adapted to the special case of the contra-directional UNI topology in the shift register application, as it has been extensively analyzed in Zoiros et al (2006), so as to find the time-dependent gains experienced by each clock pair constituent and replace them in (3), (1) and finally (5).…”

“…The above formula has been derived by making several valid assumptions (Zoiros et al 2007) and manipulating algebraically, based on the approach in Mecozzi and Mørk (1997), the relevant set of partial coupled differential equations that describe the propagation of pulses inside a SOA as well as the associated change of its gain dynamics (Tang et al 1998). Its solution can be obtained in a step-wise manner by slicing the optical pulse over its period in many small uniform temporal intervals, approximating the time derivative by a finite difference and applying the appropriate initial conditions at the end facets of a 1000 µm long SOA, according to the details stated in Zoiros et al (2006). The inserted clock pulses used in this procedure are assumed to be 10 Gb/s, return-to-zero (RZ), Gaussian-shaped…”

Theoretical Analysis of Directly Modulated Reflective Semiconductor Optical Amplifier Performance Enhancement by Microring Resonator-Based Notch Filtering

“…First, the RSOA temporal response is extracted by numerically solving for h(t) from (2). This is done by following the numerical method formulated in [37] but adapted to account for a temporal-dependent total injection current [38]. More specifically, for each information bit of duration T carried by the modulation current, (2) is solved in a step-wise manner by approximating the time derivative of h(t) by a finite difference and applying the appropriate initial conditions.…”