Compact, Low Loss Edge Couplers for Hybrid Integration of Blue Lasers

Photonic integrated circuits (PICs) operating at blue wavelengths hold immense promise for applications ranging from quantum optics to biomedical detection [1]. While silicon nitride (Si<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>N<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf>) platforms are widely employed for visible wavelengths [2], achieving full integration of blue lasers into a Si<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>N<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> platform remains a significant challenge. The major limitation arises from the high aspect ratio of horizontal to vertical dimensions of the laser spatial output profile, imposing stringent requirements on the edge coupler design. To address this, we propose a compact, low loss (< 3 dB per facet) fork-shaped edge coupler, specifically designed for a gallium nitride (GaN) laser chip operating at 488 nm, providing a promising solution for the hybrid laser integration with flip-chip bonding [3].