Transparent amorphous silicon channel waveguides and high-Q resonators using a damascene process

Area of Science:

• Materials Science
• Photonics
• Optical Engineering

Background:

• Amorphous silicon (a-Si) is a promising material for integrated photonics due to its CMOS compatibility.
• Fabricating high-performance a-Si optical components faces challenges related to thermal stability and optical loss.
• Existing fabrication methods may not meet the stringent requirements for advanced photonic integrated circuits.

Purpose of the Study:

• To demonstrate a novel damascene process for fabricating amorphous silicon optical channel waveguides and racetrack resonators.
• To evaluate the optical performance and thermal stability of a-Si waveguides produced by the new process.
• To achieve high quality factors (Q) and extinction ratios in a-Si racetrack resonators.

Main Methods:

• Fabrication of amorphous silicon (a-Si) single-mode optical channel waveguides and racetrack resonators using a damascene process.
• Characterization of optical transmission loss at 1,550 nm for TE mode.
• Measurement of quality factors (Q) and extinction ratios for racetrack resonators.
• Investigation of process compatibility with thermal budget limitations for a-Si phase stability.

Main Results:

• The damascene process is compatible with thermal budget limitations for a-Si phase stability.
• Average measured transmission loss coefficient of 2.5+/-0.1 dB/cm at 1,550 nm for TE mode.
• Racetrack resonators achieved mid-10(4) to 10(5) quality factors (Q).
• Extinction ratios as high as 25 dB were recorded for the resonators.

Conclusions:

• The demonstrated damascene process enables the fabrication of high-performance amorphous silicon optical waveguides and resonators.
• The process offers improved optical transmission and facilitates hydrogen encapsulation for waveguide cores.
• The achieved performance is comparable to single crystalline silicon counterparts, opening possibilities for advanced a-Si photonic devices.