Compact deep-groove-assisted bends on SiN platform for monolithic integrated laser.

Area of Science:

• Materials Science
• Photonics
• Integrated Optics

Background:

• Photonic integration platforms require micro-meter scale passive layers alongside III-V layers for monolithically integrated light sources.
• Low-temperature plasma-enhanced chemical vapor deposition (PECVD) silicon nitride (SiN) is suitable for back-end-of-line (BEOL) integration due to its amorphous structure enabling thick, defect-free layers.
• Optimized SiN waveguides are thick and rib-shaped, but bends suffer high radiation losses, necessitating large bending radii (800 µm) for compact photonic integrated circuits (PICs).

Purpose of the Study:

• To address the challenge of high radiation losses in thick SiN waveguide bends for compact PICs.
• To introduce and demonstrate a novel SiN bending structure that significantly reduces bending radii and associated losses.
• To investigate the performance of micro-ring resonators (MRRs) incorporating these novel bending structures.

Main Methods:

• Fabrication of a novel SiN bending structure featuring a deep etched groove along the outer side.
• Characterization of the bending loss and minimum bending radius of the novel SiN structures.
• Investigation of compact MRRs utilizing the deep etched groove bending structures.

Main Results:

• The novel SiN bending structure achieved a significantly reduced bending radius of 37 µm.
• The demonstrated bending loss was as low as 0.1 dB/90°.
• MRRs with deep etched grooves showed enhanced free spectral range (FSR) and a passband of 39.1 GHz compared to standard rib waveguide MRRs.

Conclusions:

• The novel deep etched groove SiN bending structure dramatically reduces bending radii and losses in photonic integrated circuits.
• This advancement enables the creation of significantly more compact PICs.
• The improved performance of MRRs and waveguides paves the way for compact integrated emitters on a single substrate.