All-Optical Cross-Absorption-Modulation Based Gb/s Switching With Silicon Quantum Dots

In silicon quantum dots (Si-QDs), the sub-bandgap cross-absorption-modulation (XAM) has been preliminarily observed and confirmed as a new kind of wavelength conversion process to enable ultrafast optical switching. By using the Si-QD doped Si-rich SiC
_x
micro-ring resonator waveguide with a quality factor of 1.7 × 10
⁴
under an optimized gap spacing of 700 nm away from the bus waveguide, the XAM effect induces a wavelength-converted picosecond all-optical switching between pump and probe signals, which is attributed to a specific free-carrier absorption at probe wavelength caused by the two-photon-absorption induced carriers. The non-degenerate pump-probe analysis also shows a weak Kerr nonlinearity related ultrafast switching response from the changing envelope of the XAM probe pulse at red-shifted wavelength. These observations declare that the nano-scale Si-QDs can provide sufficiently large XAM effect to enable the ultrafast all-optical switching capability for pulsed optical logic applications. To confirm, the Si-QDs doped Si-rich SiC
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waveguide modulator-based 1.2 Gb/s all-optical format inversion of a PRZ-OOK data-stream is demonstrated for the first time.