Three-dimensional ultra-compact straight-line tritter with uniform power splitting

Area of Science:

• Photonics and Optical Engineering
• Integrated Optics
• Quantum Technologies

Background:

• Multiport integrated photonic devices are essential for optical computing and quantum phenomena.
• S bends in traditional directional couplers (DCs) limit large-scale integration due to space constraints.

Purpose of the Study:

• To design and fabricate an ultra-compact three-dimensional (3D) tritter.
• To overcome space limitations in multiport DCs by eliminating S bends.

Main Methods:

• Utilized femtosecond laser direct writing for fabrication.
• Implemented a novel 3D coupling engineering strategy with straight input and coupling regions.
• Designed a tritter without S bends to reduce on-chip footprint.

Main Results:

• Achieved uniform power splitting ratios (e.g., 0.34:0.32:0.34).
• Reduced the cross-sectional area to ~2.37% of traditional tritters.
• Demonstrated controlled evanescent coupling in a smaller 3D scale.

Conclusions:

• The straight-line multiport DCs enable enhanced integration of 3D photonic circuits.
• This design offers a pathway for more complex and compact photonic devices.
• Femtosecond laser direct writing facilitates the creation of advanced 3D integrated photonic devices.