Broadband Polarization-Insensitive Wavelength Conversion Based on Non-Degenerate Four-Wave Mixing in a Silicon Nanowire

Abstract

We experimentally demonstrate broadband polarization-insensitive one-to-two wavelength conversion of a 10-Gb/s DPSK data signal based on non-degenerate four-wave mixing in a silicon nanowire with bit-error rate measurements. IntroductionAll-optical wavelength conversion (AOWC) may be an important functionality in future wavelength division multiplexing (WDM) networks. This functionality has been demonstrated in different devices including semiconductor optical amplifiers (SOAs) [1], periodically poled lithium niobate (PPLN) waveguides [2], and highly nonlinear fibers (HNLFs) [3], based on different nonlinear effects. Recently, nonlinear effects in silicon nanowires have attracted considerable research interests due to compactness, large conversion bandwidth and complementary metal-oxide-semiconductor (CMOS) compatibility. Due to the strong light confinement in silicon nanowires with sub-micron dimensions, the group velocity dispersion (GVD), which is a critical parameter for parametric processes, can be engineered, and thus one can achieve ultra-broadband wavelength conversion [4]-[6] based on four-wave mixing (FWM). The FWM process is normally highly polarization dependent and an efficient FWM process occurs when the input signal and pump waves are both aligned to either the transverse-electric (TE) mode or the transversemagnetic (TM) mode. However, a polarization insensitive operation is desired since the state of polarization (SOP) of the input signal fluctuates with time and distance in a real transmission system. Previously, a polarizationinsensitive FWM-based AOWC technique using an angled-pump scheme has been proposed [7]. However, it is challenging to realize a broadband polarization-insensitive conversion which requires simultaneous optimization of dispersion profiles of the silicon nanowire for both TE and TM polarizations. The conversion bandwidth can be enhanced if the dispersion requirements are relaxed by utilizing a dual-pump configuration [8], in which the two pumps have large frequency separation while the signal frequency is close to one of the pump frequencies. In this paper, we utilize a dual-pump scheme to experimentally demonstrate broadband polarization-insensitive AOWC of a 10-Gb/s differential phase-shift keying (DPSK) data signal based on non-degenerate FWM in a silicon nanowire.