Free-standing millimeter-range 3D waveguides for on-chip optical interconnects.

Area of Science:

• Photonics
• Materials Science
• Nanotechnology

Background:

• Next-generation photonic integrated systems, like neuromorphic chips, need efficient heterogeneous integration of light sources and detectors.
• Interconnecting these components in dense waveguide circuits is a significant challenge for upscaling photonic chips.

Purpose of the Study:

• To report on versatile, air-cladded, free-standing 3D polymer waveguides for heterogeneous photonic integration.
• To demonstrate their suitability for on-chip light coupling and non-connected 3D crossings in high-density optical circuits.

Main Methods:

• Microprinting of free-standing 3D polymer waveguides (OrmoCore, n≈1.5) up to 900 µm using two-photon polymerization (TPP).
• Utilizing a single laser source for both on-chip imaging and TPP microfabrication for precise alignment on microstructured substrates.
• Characterization of optical transmission losses at 635 nm and 830 nm.

Main Results:

• Achieved versatile, air-cladded, free-standing 3D polymer waveguides without intermediate supports.
• Demonstrated suitability for out-of-plane light coupling and non-connected 3D crossings.
• Measured optical transmission losses of 1.93 dB/mm at 635 nm and 3.71 dB/mm at 830 nm, compatible with GaAs-based microLEDs.
• Successfully interconnected two GaAs-based microLEDs using an on-chip microprinted 3D waveguide.

Conclusions:

• The developed 3D polymer waveguides overcome interconnection challenges in heterogeneous photonic chips.
• These waveguides are suitable for high-density optical circuits and serve as building blocks for future integrated photonic networks.
• The seamless integration of imaging and microfabrication enables accurate 3D printing on complex substrates.