We present energy coupling (EC) and power coupling (PC) formalisms for analyzing optical instability in coupled microring resonators having instantaneous intensity dependent nonlinear refractive index. Analysis of a chalcogenide double-microring resonator is performed to investigate and compare instability phenomena predicted by both formalisms. It is shown that the EC formalism fails to predict Ikeda instability in the double-microring resonator and generally yields results that drastically deviate from those of the more rigorous PC formalism at high input powers and large phase detunings. We also show that the input threshold powers for reaching self-pulsation and Ikeda instabilities in a double-microring resonator can be minimized by proper selection of the coupling parameters. In particular, self-pulsation can be reached in a chalcogenide double-microring with input powers as low as tens of milliwatts, while the threshold power for Ikeda instability can be reduced by more than 20% compared to the value required in a single microring.
We propose a novel and compact all-optical tunable filter with embedded preamplifier and channel selector. This filter is based on cross-Raman scattering (XRS) in a silicon nanowire waveguide, suitable for multichannel optical communications. Tuning is performed by means of tuning the pump center wavelength. With this tuning approach the separation between the pump wavelength and that of the desired channel should equal the Raman shift in Si. Spanning over 40 optical communication channels following the ITU-T G.694.1 standard (100 GHz grid), our simulation results have demonstrated an excellent channel selectivity and tunabilty for the proposed all-optical filter. The XRS process in Si nanowire has amplified the desired channel by about 11.5+/-0.38 dB, while the suppression ratios for the first and the second neighboring channels are about 28+/-0.25 and 33.6+/-0.31 dB, respectively.
We propose a new numerical model to analyze heat induced by two-photon absorption and free-carrier absorption, while high intensity optical pulses propagate along silicon-on-insulator (SOI) nanowaveguides (NWGs). Using this model, we demonstrate that such induced heat causes a shift in the amount of wavelength conversion and hence deteriorates the converter output characteristics for pulses in the picosecond regime. The wavelength shift induced by a pulse with maximum input intensity and full width at half-maximum of I(max)=1.5x10(10) W x cm(-2) and T(FWHM)=30 ps, propagating along a SOI NWG with an effective cross-sectional area of a(eff)=0.15 microm(2), is shown to be Delta lambda(s) approximately 8 pm. We also demonstrate that such a shift can be compensated by tuning the pump intensity down by approximately 6.33%.
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