Passive Photonics in an Unmodified CMOS Technology With No Post-Processing Required

Abstract

Passive photonic components consisting of sub-micrometer waveguides, grating couplers, and ring resonators are demonstrated in an unmodified commercial complementary metal-oxide-semiconductor (CMOS) process. Waveguides demonstrate propagation losses of approximately 1 dB/mm at 1.3-µm wavelengths. Grating couplers achieve better than −5.8-dB coupling efficiencies. Ring resonators exhibit Qs greater than 5000 with extinction ratios of more than 20 dB. Furthermore, due to the utilization of front-end-of-the-line design layers for creating the waveguide cores coupled with a relatively thick buried-oxide layer standard within the process, no post-processing is required at the chip or wafer level to achieve the reported device performance. Hence, for the first time, designers without processing capabilities may design custom CMOS photonic circuits for a broad range of applications. One such application which may appropriately leverage the low-cost platform could be disposable bio-photonic sensor arrays.

Resolving the thermal challenges for silicon microring resonator devices

“…Applications such as these stress the traditional portfolio of optical components, rebalancing the emphasis from expensive high-performance components towards low-cost high-volume components that can be closely integrated with electronics. With these considerations in mind, the silicon photonics platform has received wide attention for its ability to deliver the necessary bandwidth required at an economy-of-scale that will be enabled by its compatibility with CMOS fabrication processes [3].…”

“…Applications such as these stress the traditional portfolio of optical components, rebalancing the emphasis from expensive high-performance components towards low-cost high-volume components that can be closely integrated with electronics. With these considerations in mind, the silicon photonics platform has received wide attention for its ability to deliver the necessary bandwidth required at an economy-of-scale that will be enabled by its compatibility with CMOS fabrication processes [3].Within the silicon photonic platform, traditional optical components such as low-loss waveguides [4], lowloss waveguide crossings [5], high-speed mach-zhender modulators (MZM) [6], arrayed waveguide-gratings [7], and efficient photodetectors [8,9] have been demonstrated. Leveraging the high index contrast between silicon and silicon-on-insulator, the aforementioned components have been shown with much smaller footprints than their counterparts in more conventional optical platforms.…”