Non-volatile logic operations using phase change materials in silicon photonics

Phase change materials (PCMs) on waveguides provide enormous flexibility for programmable integrated photonics. These materials show a large contrast in the optical properties (such as refractive index and optical loss) between the two stable states (i.e., amorphous to crystalline) of the PCM. These states are reversible and reproducible with external stimuli which could be optical, thermal or electrical. We first present directed logic architectures that achieve low insertion losses as well as multi-bit and broadband operations using directional coupler switches and low loss combiners. The switches consist of directional couplers with non-volatile phase change material-clad waveguides. A low loss broadband combiner is designed using an angled-MMI structure. We demonstrate the directed-logic operations with multi-bit operation capability. Moreover, the designs of the logic-circuits show low insertion-losses (< 1 dB), high extinction-ratios (⪆10 dB) with broadband operations (~ 100 nm) operating in the telecommunication C-band. This study provides a practical technique to design future high-speed nanoscale non-volatile photonic integrated circuits for computing applications. A non-volatile broadband hybrid EO plasmonic switch based on a phase-change material embedded in a plasmonic slot waveguide was also designed and modeled. The proposed switch exhibits excellent performance in several important categories, including large extinction ratio (⪆28 dB), high bandwidth (BW ⪆ 400 nm), and low power consumption. It was demonstrated that basic logic-gates, a plasmonic combinational logic-circuits, as well as plasmonic asynchronous sequential latch-circuits can be implemented using the plasmonic switches as the active elements.