Coherent beam combining of optical phased array chips enabled by low-frequency half-wave voltage measurement

Area of Science:

• Optics and Photonics
• Semiconductor Devices
• Interferometry

Background:

• Optical phased arrays (OPAs) are crucial for beam steering applications.
• Enhancing far-field beam quality in OPAs remains a significant challenge.
• Existing methods often struggle with precise phase control for coherent combining.

Purpose of the Study:

• To introduce a novel OPA coherent combining architecture based on inter-chip interference.
• To develop a precise phase control method for low-frequency (DC-kHz) phasing requirements.
• To experimentally validate the proposed architecture's effectiveness in improving beam quality.

Main Methods:

• Proposed a novel OPA coherent combining architecture utilizing inter-chip interference.
• Employed phase modulators for inter-chip phase control, focusing on half-wave voltage parameters.
• Developed and applied a half-wave voltage measurement method for closed-loop coherent combining of two OPA chips.

Main Results:

• Successfully realized closed-loop coherent combining of two OPA chips.
• Demonstrated stable combination of the far-field beam into a single-main lobe.
• Reduced the beam divergence angle from 0.181° to 0.066°, significantly enhancing beam quality.

Conclusions:

• The proposed inter-chip interference architecture effectively enhances OPA far-field beam quality.
• The developed half-wave voltage measurement method enables high-precision phasing for coherent combining.
• The experimental results validate the proposed approach for stable and high-quality OPA beam formation.