Lightmatter, a startup that uses light to link chips together and to do calculations for the deep learning necessary for AI, locked up a $400 million Series D led by new investor T. Rowe Price at a $4.4 billion valuation.

The new round nearly quadruples its previous valuation of $1.2 billion in December after a $155 million raise led by GV — which along with Fidelity Management and Research Co. also participated in the new round.

As Big Tech pours hundreds of billions of dollars into new AI data centers, Lightmatter is trying to solve the problems around energy consumption and scalability of those new centers.

The company’s tech uses silicon photonics that can speed up processes while also using less power. While the idea of using light in computing isn’t new, creating the components has historically been challenging.

Big money

The new Series D is Lightmatter’s largest to date, but the Boston-based company is not new to big raises. In May 2023, the startup locked up a $154 million raise before extending that round in December.

Founded in 2017, Lightmatter has raised $850 million, per the company.

Co-founder and CEO Nick Harris told Reuters, “This is probably our last private funding round.”

Lightmatter’s was not the only large raise by a photonic startup this week. Xscape Photonics — a New York-based startup also using photonics technology to address the energy, performance and scalability challenges of AI data centers — raised a $44 million Series A led by IAG Capital Partners and with investment from the likes of Cisco Investments and Nvidia.

Related reading:

• These AI Investors Are Following The Light By Giving This Startup $154M

Illustration: Dom Guzman