French deeptech startup Lightspring has closed a €3.1 million seed round to industrialise its 3D optical coupling technology for photonic integrated circuits. The Besançon-based company, which designs and manufactures the optical interfaces of photonic chips, was backed by Atlantic and OVNI Capital as lead investors. Concept Ventures, Ixcore, Plug and Play Ventures, and industry business angels also participated, while an i-Lab laureate grant of €350,000 and additional public innovation funding bring total financing to over €3.5 million.
The Optical Packaging Bottleneck
Lightspring is targeting one of the most expensive and least reproducible steps in photonic chip production. While photonic integrated circuit fabrication is now handled by mature foundries at roughly 20 percent of a chip's cost, assembly and optical packaging account for about half. Fibre-to-chip coupling is still performed part by part through micrometre-scale active alignment, causing typical optical losses of 2 to 3 decibels, low throughput, and inconsistent yield.
A Programmable Manufacturing Step
The startup applies 3D lithography, also known as two-photon polymerisation, directly onto the chip to fabricate microlenses, 3D waveguides, and beam-shaping elements. This single process step supports fibre-to-chip, laser-to-chip, and chiplet-to-chiplet coupling with target losses below 0.5 decibels per interface. It removes the need for precision pre-alignment, is materials-agnostic and equipment-agnostic, and reduces design cycles from several months to under two weeks.
Intellectual Property and Research Origins
Lightspring's core intellectual property is concentrated in the design layer through what it describes as the first Process Design Kit dedicated to 3D optical coupling. The proprietary platform pairs with software-driven design tools and qualified fabrication recipes to make optical packaging programmable. The underlying technology originates from nationally and EU-funded research at the FEMTO-ST Institute in Besançon, a CNRS-UMLP joint research unit of more than 700 staff, where co-founder Daniel Brunner serves as CNRS Research Director.
Founder Perspectives
Lightspring co-founder and CEO Grégoire Bonnat said the industry is working on faster photonic chips, yet light still loses most of its energy when entering or leaving the device. He explained that the company is building the optical interface the same way the rest of the chip is built, in one reproducible process step. Bonnat added that the funding will help turn a laboratory result into a qualified industrial building block.
Investor Views and Strategic Plans
Atlantic's Quentin Calleja said that photonics is scaling into AI infrastructure quickly, but optical packaging remains slow and expensive, and that Lightspring's approach can make it scalable. OVNI Capital's Thomas Renaudin added that the industry has a roadmap for co-packaged optics but lacks a method to manufacture the optical interface at volume. The capital will support development of the PDK and design tools, expand the team to 12 people, fund co-design programmes with industrial partners, and scale and qualify fabrication for industrial use.
Lightspring's technology addresses a structural constraint in photonic packaging as AI systems push optics closer to compute. By transforming a manual, low-yield assembly process into a programmable step, the company aims to provide the missing industrial layer for co-packaged optics. The new financing positions the startup to move from laboratory results toward a qualified production process for a global market.