Lightspring raises 3.1 million euros to tackle the weak link in photonic chips

Lightspring, a French deeptech startup, has closed a 3.1 million euro seed round led by Atlantic and OVNI Capital. The funding will support the development of a 3D printing process that creates optical interfaces directly on photonic integrated circuits. The company emerged from research conducted at the FEMTO-ST laboratory in Besançon. Its goal is to overcome the primary barrier to mass production of photonic chips, which is not the fabrication of the circuits themselves but the connection of those circuits to fibers, lasers and other components. Industry analysts note that as optical interconnections become critical for artificial intelligence infrastructure, the alignment step that links photonic components is emerging as a major bottleneck. Current manufacturing platforms can produce photonic circuits in silicon, silicon nitride or indium phosphide, yet the assembly of those circuits with optical fibers and lasers remains poorly standardized. Precise alignment, often requiring submicrometer accuracy, is both costly and difficult to scale to the volumes typical of semiconductor production.

Lightspring estimates that packaging can account for up to half of a photonic chip’s total cost, compared with roughly 20 percent for front‑end fabrication. To address this, the startup employs two‑photon polymerization, a lithography technique capable of constructing three‑dimensional microstructures with high precision. Rather than aligning fibers and waveguides manually, Lightspring prints directly onto the chip an optical structure that matches their geometry. Microlenses, three‑dimensional waveguides and beam‑shaping elements can thus serve as intermediaries between components. The technology aims to achieve interface losses below 0.5 decibels and to eliminate active alignment for certain configurations. The company envisions a future in which designers can select a coupling architecture, embed it in their PIC design and automatically generate the necessary 3D structures and fabrication parameters. This approach would shift packaging from a discrete, end‑of‑line operation to a programmable layer defined at the design stage.

Lightspring is developing a Process Design Kit dedicated to three‑dimensional optical coupling, a concept that could become as foundational as standard PDKs in conventional semiconductor design. The founders, Grégoire Bonnat and Daniel Brunner, have been working on additive photonic integration at FEMTO‑ST for several years, focusing on CMOS‑compatible processes and hybrid photonic platforms. The rise of artificial intelligence is intensifying demand for more efficient optical interconnects, as an increasing share of data‑center energy is spent moving data between processors, memory and network equipment. By transforming the packaging step into a programmable, design‑time activity, Lightspring hopes to accelerate the commercialization of photonic chips for AI workloads.

Reported by FrenchWeb.