Silicon photonics circuits are playing more and more important role in optical communication and interconnect fields [1, 2]. Many silicon CMOS technique compatible photonics integrated devices are reported [3, 4]. Most of those silicon components are based on optical waveguide. But conventional integrated optical waveguide is without memory feature. One hand, which makes us in trying to change the refractive index of the optical waveguide, must continually support energy to maintain the state of the waveguide, such as optical switch and modulators. And other hands, memory functional PIC into computer memory system, will solve van Neumann bottleneck issue.
In this presentation, I will introduce our group recent works that experimentally demonstrate two solutions for overcome those issues [5, 6]. First one is a non-volatile optical waveguide structure. It consists of a floating gate above an optical waveguide with a separated source and drain configuration.
For checking the memory functionality, we made a microring resonator by memory optical waveguide. By measuring the optical spectrum, the memory properties of maintain and retention are proved. And using different pulse voltage to drive electrons will cause multi-level state in the optical spectrum. Theoretically, this can be increased up to ~400 times using a 100 nm free spectral range broadband light source.
Another solution is using memristor device to control the optical waveguide property. Experimentally, we demonstrated SONOS (silicon-oxide-nitride-oxide-silicon) transistor as the memory cell, monolithically integrated with optical sense circuits (microring resonator, MRR). The SONOS series connect with P-N junction optical waveguide. The memristor situation determines the series current, thus change the optical waveguide states. Similarly, we fabricate a microring resonator with P-N junction waveguide. SONOS controlled current to modify the microring resonator’s oscillation wavelength. From optical spectrum, we will know the SONOS status. Results show that the effective reading speed can be enhanced by 1200 times with 100 nm spectrum ranges.
