Quantifying and mitigating optical surface loss in suspended GaAs photonic integrated circuits

Area of Science:

• Materials Science
• Optoelectronics
• Photonics

Background:

• Optical loss is a major challenge for high-performance photonic integrated circuits (PICs).
• Surface absorption and scattering are significant loss mechanisms in high refractive index contrast compound semiconductor (III-V) PICs.
• Gallium arsenide (GaAs) is a key material for III-V PICs, but its performance is limited by surface-related optical losses.

Purpose of the Study:

• To quantify optical propagation loss caused by surface state absorption in a suspended GaAs PIC platform.
• To investigate the origins of this surface-related optical loss.
• To demonstrate the effectiveness of surface passivation in mitigating these losses.

Main Methods:

• Quantification of optical propagation loss in suspended GaAs PICs.
• X-ray photoemission spectroscopy (XPS) to probe surface states.
• Spectroscopic ellipsometry to analyze surface properties.
• Surface passivation using alumina (Al2O3).

Main Results:

• Optical propagation loss due to surface state absorption was quantified in the GaAs PIC platform.
• The origins of the loss were identified through XPS and spectroscopic ellipsometry.
• Surface passivation with alumina significantly mitigated the measured optical loss.

Conclusions:

• Surface state absorption is a critical loss mechanism in suspended GaAs PICs.
• Alumina (Al2O3) surface passivation is an effective method for reducing optical propagation loss.
• This work provides a pathway for developing higher-performance III-V PICs.