Lightspring raises €3.5M to industrialize

French company Lightspring has closed a €3.1 million seed funding round and secured a €350,000 public grant, bringing its total financing to over €3.5 million. The investment, led by Atlantic and OVNI Capital, will be used to transition its 3D optical coupling technology from the laboratory to industrial production lines.

Lightspring designs and manufactures the optical interfaces for photonic integrated circuits (PICs). Its core innovation applies 3D lithography directly onto a chip to fabricate coupling structures. This approach aims to transform photonic packaging, which currently accounts for roughly half of a PIC's total cost, into a programmable and reproducible manufacturing step.

The AI packaging bottleneck

Advances in AI infrastructure are pushing optical components physically closer to computing processors. This trend, known as co-packaged optics, moves the optical interface from a system's faceplate directly onto the chip substrate. While photonic chip fabrication is now mature, the subsequent assembly and optical packaging step has not industrialized. According to the source, this packaging alone accounts for about 50% of a PIC's cost, compared to only 20% for the chip fabrication itself.

The current standard method, fibre-to-chip coupling, requires micrometre-scale active alignment performed part by part. This process is slow, has low throughput, and suffers from degraded yield. It also introduces significant optical loss, typically 2-3 dB, with no industry-wide standard.

A single-step fabrication process

Lightspring's technology uses two-photon polymerisation (2PP) 3D lithography to build optical components like microlenses, 3D waveguides, and beam-shaping elements directly on the chip surface in a single step. The company claims this process delivers several key advantages over traditional methods.

The company's intellectual property is centered on a Process Design Kit (PDK), the first dedicated to 3D optical coupling. This is paired with software-driven design tools and qualified fabrication recipes. The underlying technology was developed through publicly funded research at the FEMTO-ST Institute in Besançon, a leading European optics and micro-nanotechnology centre.

Investor and founder perspectives

Grégoire Bonnat, co-founder and CEO of Lightspring, stated the industry's core challenge. The whole industry is working on making photonic chips faster, yet light still loses most of its energy the moment it enters or leaves the device, he said. The funding, he added, will "turn a lab result into a qualified industrial building block."

Investors framed the opportunity around the demands of AI hardware. Quentin Calleja, Principal at lead investor Atlantic, said photonics is scaling quickly into AI infrastructure, but optical packaging remains slow and expensive. "Lightspring has developed a technology that finally makes it scalable," he said.

Thomas Renaudin, Founding Partner at co-lead OVNI Capital, noted that co-packaged optics is the inevitable endpoint of hardware trends. The industry has the roadmap; what it does not have is a way to manufacture the optical interface at volume. Lightspring is building that layer, he asserted.

Path to commercialization

The new capital will fund the further development of Lightspring's PDK and design software. It will also support expanding the team to 12 people, financing co-design programs with industrial partners, and scaling and qualifying its fabrication process for high-volume manufacturing. The company was also recently named a laureate of i-Lab, France's national deeptech innovation competition.