Abstract:
We investigate numerically a non-reciprocal switching behavior
in strongly modulated waveguide Bragg gratings (WBGs) having a longitudinally
asymmetric stopband configuration. The minimum power predicted
for a stable switching operation is found to be approximately 77 mW for
a realistic waveguide structure made of prospective materials; we assume
in this paper a nano-strip InGaAsP/InP waveguide having longitudinally
asymmetric modulation of the waveguide width. The analysis has been
performed with our in-house nonlinear finite-difference time-domain
(FDTD) code adapted to parallel computing. The numerical results clearly
show low-threshold Schmitt trigger operation, as well as non-reciprocal
transmission property where the switching threshold for one propagation
direction is lower than that for the other direction. In addition, we discuss
the modulation-like instability phenomena in such nonlinear periodic
devices by employing both an instantaneous Kerr nonlinearity and a more
involved saturable nonlinearity model.
