Two‐Photon Absorption‐Free Ultrafast Optical Switching in Carbon‐Rich Si_xC_1−x Microring

Ultrafast Kerr effect switching in near‐infrared two‐photon absorption (TPA)‐free and free‐carrier‐absorption (FCA)‐free nonstoichiometric silicon carbide (Si_xC_1−x) microring waveguides is performed and investigated. With pulsed return‐to‐zero on–off‐keying (PRZ‐OOK) stream for the Si‐rich Si_xC_1−x‐based all‐optical switches, the inversely modulated probe reveals an asymmetric bit shape data extinction ratio (ER) of only 8.7 dB owing to the TPA + FCA effect. By eliminating the FCA effects in nearly stoichiometric Si_xC_1−x microring waveguide, the high‐speed wavelength conversion of a data stream with an ER of 14 dB can be observed when coinciding the probe wavelength with the transmission dip. Slightly deviating the probe wavelength from the transmission dip, most probe power still remains in bus waveguide to cause a strong FCA effect to degrade the ER down to 7.4 dB. A symmetrically converted and inverted data stream with high on/off extinction can be observed in the C‐rich Si_xC_1−x‐based microring waveguide with completely suppressed trailing‐edge response. To further approach the upper limitation on bandwidth, the wavelength‐converted and sign‐reversible PRZ‐OOK data switching at a bit rate up to 12 Gbit s⁻¹ can be obtained with similar ER of better than 20 dB, as contributed mainly by the enhanced Kerr nonlinearity in the C‐rich Si_xC_1−x.