{"ID":23620896,"CreatedAt":"2026-09-18T06:47:37.825099056Z","UpdatedAt":"2026-09-18T06:47:37.825099056Z","DeletedAt":null,"paper_url":"https://arxiv.org/abs/2609.20686","arxiv_id":"2609.20686","title":"Volumetric Evanescent Edge Coupling for Fiber-to-Chip Optical I/O","abstract":"Scaling optical input/output for co-packaged optics is limited by the fiber-to-chip interface. Conventional edge coupling offers low loss and broad bandwidth but confines channels to a single row along the chip facet. On the other hand, surface couplers are either narrowband or difficult to fabricate with high yield and, importantly, compete with back-end metal routing. In this work, we introduce volumetric edge coupling, in which the chip edge is structured in three dimensions so that optical coupling can occur over a two-dimensional region rather than along a single line, providing a route toward interfacing multiple waveguides with multiple cores of a multicore fiber while preserving optical access from the chip perimeter. We investigate a single-channel realization based on total-internal-reflection (TIR)-mediated evanescent coupling through the 54.7$^\\circ$ sidewall of a KOH-etched silicon cavity, with the coupling profile shaped by a wedged buried-oxide ridge. Finite-difference time-domain simulations predict a peak coupling efficiency of 88% (-0.56 dB) at 1550 nm and a 1-dB bandwidth of 86.45 nm spanning the C-band. The design further exhibits a vertical alignment tolerance of approximately $\\pm$2 $μ$m, weak sensitivity to transverse offsets up to 5 $μ$m, and a $\\pm$0.8$^\\circ$ 1-dB angular tolerance. The reflected optical field also provides a potential alignment signal, offering a path toward reduced active alignment overhead in future multicore implementations.","short_abstract":"Scaling optical input/output for co-packaged optics is limited by the fiber-to-chip interface. Conventional edge coupling offers low loss and broad bandwidth but confines channels to a single row along the chip facet. On the other hand, surface couplers are either narrowband or difficult to fabricate with high yield an...","url_abs":"https://arxiv.org/abs/2609.20686","url_pdf":"https://arxiv.org/pdf/2609.20686v1","authors":"[\"Hamdy Elshehaby\",\"Omar Bakheet\",\"Mohamed A. Swillam\",\"Mohamed Elkabbash\"]","published":"2026-09-17T16:55:39Z","proceeding":"physics.optics","tasks":"[\"physics.optics\",\"physics.app-ph\"]","methods":"[]","has_code":false}