Silicon photonics, with optical I/O chipsets made in high-volume commercial CMOS foundries, are well-suited to solve interconnection challenges in scaling up next-generation high-performance processors (XPUs) for AI, machine learning, and high-performance computing. Silicon microring modulators and resonators with high quality factors are essential for electronic-photonic integrated circuits. However, the current silicon carrier-plasma-effect-based device platform has limitations in modulator sensitivity, tuning power, and optical loss. These limitations may affect its ability to support interconnect scaling to keep up with processor progress. This thesis presents research on new efficient silicon modulators and electronic-photonic integrated transmitters in a CMOS platform while addressing additional performance metrics such as device footprint, bandwidth, and modulation depth. The work demonstrates cryogenic optical data output from a superconducting Josephson junction (JJ) based circuit chip operating at 4K temperature, an interface requiring high energy efficiency per bit. The demonstration involves a pre-amplified silicon ring modulator operating at cryogenic temperature with record shift efficiency. The presented improvements in the energy efficiency of silicon photonic links could enable advancements in microwave photonic signal processing for 5G/6G wireless communication and microwave remote sensing, as well as new computing technologies such as superconducting processors.
A second part of the thesis explores integrating electro-optic materials with a Pockels effect into photonic integrated circuit platforms, aiming to increase the shift efficiency or reduce the loss of ring modulators relative to conventional rings that rely on the silicon carrier plasma effect. Initially, electro-optic (EO) polymers are incorporated into two 45 nm CMOS foundry platforms, with monolithic electronic-photonic integration, to explore the concept of integrating materials post-foundry through the substrate from the back side. Initial results demonstrate the feasibility of this concept, providing a new method to introduce exotic materials into CMOS while preserving the integrity of electronic layers. Then, we successfully integrated a newly discovered liquid crystal material, ferroelectric nematic liquid crystal (FNLC), into a silicon photonics platform. Unlike EO polymers, FNLCs can provide modulation without needing a high-temperature poling step. FNLCs enable high-speed Pockels modulation and low-speed, substantial refractive index changes through molecular reorientation, which makes them a potential substitute for the power-hungry and unreliable thermo-optic tuning currently used in silicon photonics. Finally, the thesis demonstrates ultra-high Q silicon resonators and filters in conventional silicon photonics platforms aimed at microwave photonics applications and shows the first demonstration of higher-order bandpass filters with 200-800 MHz wide passbands and low insertion loss. The device-level advancements demonstrated in this thesis collectively address system-level challenges of electronic-photonic integrated circuits and enable various applications involving microwave signal processing. / 2025-09-24T00:00:00Z
| Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/49329 |
| Date | 24 September 2024 |
| Creators | Onural, Deniz |
| Contributors | Popović, Miloš A. |
| Source Sets | Boston University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
| Rights | Attribution-ShareAlike 4.0 International, http://creativecommons.org/licenses/by-sa/4.0/ |
Page generated in 0.0016 seconds