TY - JOUR A1 - Villasmunta, Francesco A1 - Heise, Patrick A1 - Breiter, Manuela A1 - Schrader, Sigurd A1 - Schenk, Harald A1 - Regehly, Martin A1 - Mai, Andreas T1 - Monolithically Integrated Optical Through-Silicon Waveguides for 3D Chip-to-Chip Photonic Interconnects JF - IEEE Journal of Selected Topics in Quantum Electronics N2 - The scaling limitations of electrical interconnects are driving the demand for efficient optical chip-to-chip links. We report the first monolithic integration of air-clad optical through-silicon waveguides in silicon, fabricated via Bosch and cryogenic deep reactive-ion etching. Rib, single-bridge, and double-bridge designs with 50 μm cores and up to 150 μm propagation lengths have been evaluated. Cryogenic-etched rib waveguides achieve the highest median transmission (66%, −1.80 dB), compared to Bosch-etched ribs (62%, −2.08 dB). Across all geometries, 3 dB alignment windows range from 9.3 μm to 49.2 μm, with Bosch-etched double-bridge waveguides providing the broadest tolerance. We show that geometric fidelity outweighs sidewall roughness for transmission and alignment in these large-core, multimode optical through-silicon waveguides. This technology provides a scalable, complementary metal-oxide semiconductor-compatible pathway toward 3D photonic interconnects. KW - optical waveguide KW - optical device fabrication KW - silicon KW - three-dimensional display KW - optical loss KW - optical interconnection KW - coupling KW - optical surface wave KW - optical coupling KW - coupler KW - silicon photonics KW - three-dimensional integrated circuit KW - through-silicon vias (TSV) Y1 - 2026 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-20828 VL - 32 IS - 2 PB - IEEE ER -