Abstract :
The two-photon absorption (TPA), the free-carrier absorption (FCA), and the carrier plasma effect play important roles in Si-based photonic devices. These effects have been incorporated directly into a finite-difference time-domain (FDTD) simulator for the first time. To check the validity of the FDTD simulator, it has been applied to the simulation of nonlinear transmission of an ultrashort optical pulse in a short Si high-index-contrast waveguide. The results are consistent with those shown in the literature. The cause of the slight negative slope transmission has been explained as follows. Since the TPA-induced FCA makes the pulse-shape asymmetric, a pulse with a higher optical input intensity tends to have a longer tail. Therefore, a stronger optical pulse is subject to FCA for a longer period, resulting in the negative differential transmission.
Keywords :
elemental semiconductors; finite difference time-domain analysis; high-speed optical techniques; nonlinear optics; optical waveguide theory; silicon; two-photon processes; Si; carrier plasma effect; finite-difference time-domain simulator; free-carrier absorption; high-index-contrast waveguide; negative slope transmission; nonlinear transmission; optical input intensity; photonic devices; two-photon absorption; ultrashort optical pulse; Absorption; Finite difference methods; Nonlinear optics; Optical pulses; Optical waveguides; Plasma devices; Plasma simulation; Plasma waves; Tail; Time domain analysis; Finite-difference time-domain (FDTD) methods; nonlinear optics; optical pulses; optical waveguides; silicon;
