  Here we show a photonic design for tunable dual-wavelength generation
deploying optical nonlinear mode coupling of two coupled III-V semiconductor
microring resonators (MRRs) connected to a pump and drop waveguide buses. Here
one of the two rings contains a grating, while the other has a planar surface.
The underling mechanism for the dual wavelength generation originates from the
resonance-detuning of the spectra resulting in non-linear mode mixing.
Tunability of the wavelengths is achieved by altering the grating depth of the
MRR and the power coupling coefficients. For the grating design of the MRR we
select a trapezoidal-profiled apodized grating to gain low reflectivity at
sidelobes. A time-domain travelling wave (TDTW) analysis gives a InGaAsP core
refractive index of 3.3 surrounded by a grating InP cladding with n=3.2. We
further confirm that the propagation of a Gaussian pulse input with 10 mW power
and bandwidth of 0.76 ps is well confined within the mode propagation of the
system. Taken together our results show a 2:1 fan-out of two spectrally
separate signals for compact and high functional sources on chip.
