All-Optical Modulation in Si Quantum Dot-Doped SiO Micro-Ring Waveguide Resonator

Abstract

The Si quantum dot doped SiO x rib waveguide based free-carrier absorption modulator with enhanced all-optical modulation depth is demonstrated by integrating with a micro-ring waveguide resonator. The micro-ring waveguide resonator with a Q-factor of 6x10 3 induces a throughput transfer function in wavelength domain, such a transmittance notch can be blue-shifted by varying the excited free-carrier density of Si-QD. When injecting the continuous-wave probe at central wavelength of the transmittance notch, the probe signal can be inversely modulated by optically pumping the micro-ring waveguide resonator to blue-shift the notch away from its original wavelength. By optimizing the pump wavelengths, the largest free-carrier absorption (FCA) loss and highest free-carrier density can be enhanced to 2.9 cm -1 and 7.83×10 16 cm -3 , respectively. With the excited free-carrier density of ~1.3×10 16 cm -3 inside the micro-ring waveguide, the maximal wavelength of the transmittance notch can be blue-shifted by 0.033 nm. The optical pumping also induces the broadened linewidth of transmittance notch from 0.25 to 0.27 nm. With the integrated micro-ring waveguide resonator, the all-optical modulation depth can be further enhanced from 52.5% to 63.5% by shifting the notched transmission spectrum of the micro-ring waveguide with the excited free-carrier density of Si-QD at probe wavelength of 1563.5 nm.Index Terms-Si quantum dots, free-carrier absorption, ring waveguide resonator, data inverter. 1077-260X (c)

Realizing multi-functional all-optical data processing on nanoscale SiC waveguides

“…Among different mechanisms, the Si-QD embedded optoelectronic devices with strong quantum confinement effect have the most potential for signal processing beyond GHz. However, the bulk silicon also exhibits the two-photon absorption induced free-carrier absorption (FCA) effect 34 – 36 , which inevitably results in a recombination (or dissipation) time of ~1 ns to further limit the modulation speed. To meet this demand, nonlinear Kerr switching is proposed as an alternative to the FCA switching for implementing the ultrafast all-optical modulation 3 , 37 .…”