2024 Theses Doctoral

Application Specific Silicon Photonic Integrated Circuits

Gopal, Vignesh V.

Modern telecommunications face growing challenges from the exponential increase in high-performance computing and AI, as well as the demand for widespread global connectivity.

This thesis demonstrates how Silicon Photonics (SiP) can help alleviate these bottlenecks. SiP has shown great potential in developing high-bandwidth optical interconnects to meet the rising demands of data centers. Additionally, this thesis explores SiP’s role in creating reconfigurable and dynamic optical transceivers for satellite-based communications. SiP is a promising platform for both applications, offering high bandwidth, low power consumption, and compatibility with complementary metal-oxide-semiconductor (CMOS) technology.

To address the need for higher bandwidth interconnects within exascale data centers, on-chip SiP resonator-based devices have emerged as a strong candidate for dense wavelength division multiplexing (DWDM). Multiple resonators, each operating at distinct wavelengths, can be cascaded on a single bus, thereby enabling a massively parallel platform for data transmission. One of the most promising light sources to power these interconnects is the Kerr frequency comb, operating in the normal group velocity dispersion regime. This approach can generate hundreds of independent wavelength channels.

Early demonstrations of data transmission using Kerr frequency comb sources were limited to bulk telecom components for modulating, filtering, and receiving individual frequencies. However, recent studies have achieved error-free Kerr-comb-driven SiP transmitters, modulating individual comb lines at data rates of up to 32 Gb/s per wavelength (𝜆) using cascaded microdisk modulator (MDM) arrays. Furthermore, we have experimentally validated a scalable transceiver architecture capable of modulating channels beyond a single free spectral range (FSR) of a resonator. Typically, the number of usable wavelengths is limited by the FSR of the modulator divided by the channel spacing of the laser source, as aliased resonances can interfere with orthogonal signals.

SiP also holds promise for providing more widespread internet access globally. Since the early 2000s, thousands of Low-Earth Orbit (LEO) satellites have been launched, creating numerous incompatible LEO constellations with mismatched communication standards, such as modulation format, data rate, and polarization. In response, we demonstrate a reconfigurable transceiver architecture capable of transmitting and receiving both intensity-modulated and coherent signals on a single chip. Our approach supports successful modulation of multiple formats, including OOK, BPSK, and QPSK, at moderate speeds suitable for modern satellite communication demands.