Research On Nonlinear Light-by-light Properties In Silicon Wire Waveguides

Compared with the traditional discrete optical-electric-optical processing technologies, photonic integrated chip is capable of the cost and complexity of the communications networks and then is considered as the most promising technology to meet the future development needs. SOI(Silicon-on-insulator) is a new type of silicon-based optoelectronic materials which is fully compatible with existing silicon LSIC technology, and has become the research focus of silicon photonics. Among them, silicon wire waveguide, as an important component of photonic integrated chip, has a sub-micron size structures, which helps to realize nonlinear photonic information processing functions by limiting strong light field. In this paper, relying on the National 973 Project "Research on ultrafast nonlinear light-by-light mechanism and Integrated chip of all-optical 2R/3R regeneration", we carry out the theoretical studies of four-wave mixing(FWM) in silicon wire waveguide and the main contents are as follows :1. The four-wave mixing coupled-mode equations for guided optical waves in silicon wire waveguides are calculated by using Runge-Kutta method. The impact of dispersion characteristics and the optical absorption losses(including linear transmission loss, two-photon absorption and carrier absorption) on the output idler optical power of degenerate four-wave mixing is analyzed in the case under, single-mode transmission condition in silicon line waveguide structure, and the FWM efficiency is dependent on the linear and nonlinear terms of the total phase-mismatching factor. Our calculations show that the dispersion curve can be moved downward when the height or width of silicon wire waveguides is increased or decreased, respectively. For the silicon wire waveguides with larger transmission loss, increasing the pump power or decreasing the waveguide length helps to achieve an optimal idler power at the output, two photon absorption and free-carrier absorption effect will lead to the attenuation of the pump power and then change the nonlinear phase mismatch factor and the FWM efficiency. According to the above analysis, we choose the silicon wire waveguide of 500 nm width and 250 nm height to verify the mode field distribution and dispersion curve, and the numerical results are in agreement with the FDTD simulation.2. The power transfer function(PTF) of data-pump FWM in the rectangular cross-section silicon wire waveguides is calculated and analyzed, including saturation point, mark and space threshold points. Calculation results show that, for the parameters used in the paper(including 1.2~2.0 cm long Si wire waveguide, the auxiliary light wavelength of 1500 ~ 1580 nm, and 0.5 ~ 4 dB/cm linear transmission loss), the resulting regenerator can provide an extinction ratio improvement by about 4.5 dB, in which the effective carrier lifetime should be greater than 2.5 ns.3. The phase sensitivity of degenerate FWM parametric process in Si wire waveguides is studied, according to the input and output phase transfer curve by defining the parameters such as input or output phase jitter tolerance and phase compression efficiency, which can be used to quantitatively evaluate the phase compression performance of multiple phase states, The influence of pump power, signal-to-idler power ratio, signal wavelength, and waveguide’s length, and loss on the compression performance is discussed, It is shown by calculation that the performance of phase regeneration can be optimized for the case at the pump power of 700 mw and signal-to-idler power ratio of 6 dB, which may provide a theoretical guidance for the future experiments.