Silicon photonics is potentially a viable technology to replace copper-based interconnects in multi-core computing chips with swelling demands on communication capacity and energy efficiency. This thesis proposes and demonstrates several building blocks for silicon photonic optical interconnects. ⁵...[ Read more ]

Silicon photonics is potentially a viable technology to replace copper-based interconnects in multi-core computing chips with swelling demands on communication capacity and energy efficiency. This thesis proposes and demonstrates several building blocks for silicon photonic optical interconnects.

On the photodetection front, we study the surface-state absorption (SSA) and the two-photon absorption (TPA) generated photocurrent in p-i-n diode embedded silicon microresonators. The microring resonator has large mode-field to waveguide surface overlapping which facilitates SSA-dominated photocurrent. We show 20-fold cavity-enhanced photocurrent generation with 0.12 mA/W responsivity in a Q~8000 microring resonator. The microdisk resonator supports high-Q multimode resonances (~10⁵) showing TPA-dominant photocurrent. The photocurrent at on-resonance wavelength is exceeding three orders of magnitude higher than that at off-resonance wavelength. We study microdisk photocurrent spectra with various p-i-n diode intrinsic region widths along the microdisk rim. Both devices are capable for wavelength-dependent optical power detection. The demonstrated cavity enhancement significantly improves the energy harvesting efficiency.

On the passive coupler front, we demonstrate three types of interference-based devices. 1) We design and fabricate a compact multimode-interference (MMI) based waveguide crossing. The MMI-crossing shows 0.4-dB insertion loss compared to 1.1-dB in plain crossing with a significantly suppressed crosstalk. 2) We fabricate and characterize an MMI-based 1 x 64 power splitter in a large-core square-shaped silicon waveguide in order to demonstrate the feasibility of two-dimensional (2-D) MMI couplers. The splitter shows 2-dB transmission flatness over a large number of 2-D array output ports. 3) We design an ultra-compact triplexer (a 1 x 3 wavelength-division multiplexer) using a photonic crystal (PhC) surface waveguide coupled with a conventional waveguide.