Thin Film Lithium Niobate, abbreviated TFLN, is an advanced material that leverages the superior electro-optic properties of lithium niobate in a thin-film format. By bonding a thin layer of lithium niobate onto a substrate like silicon dioxide or sapphire, TFLN combines the best of both worlds.
Lithium niobate has one of the highest electro-optic coefficients among optical materials, enabling efficient modulation and a high electro-optic coefficient. Its thin-film approach allows for smaller, more integrated optical components in a compact form factor. Lastly, TFLN can deliver low optical losses while operating at higher transmission speeds beyond 1Tb/s.
The dominant chip technology approach used for up to 800Gb/s along some of the new 1.6Tb/s optics, silicon photonics has been instrumental in the rapid advancement of high-speed, high-bandwidth optical communications. Industry experts and reports expect this to continue as silicon photonics will continue to play a prevalent role in the optical transmission arena for the foreseeable future. However, as companies strive to deliver 1Tb/s and beyond, silicon photonic technologies face a few known constraints and challenges for achieving this efficiently.
Silicon's material properties limit its ability to support higher modulation speeds without substantial signal degradation, resulting in bandwidth limitations. Modulation in silicon photonics faces electron mobility limitations, which is a fixed physical limit. Therefore, silicon photonics cannot surpass a 50GHz modulation rate (equivalent to 200G with PAM4 modulation), so achieving higher data rates of 800Gb/s, 1.6Tb/s, etc requires more parallel channels, thus adding complexity along with increased power consumption and dissipation.
In terms of power consumption, achieving higher data rates with this approach has meant requiring more power, making solutions less energy-efficient as data rates increase. As with most systems and devices, higher power consumption results in greater heat generation, complicating thermal management while potentially impacting performance. Finally, the necessity to integrate more active and passive components on a silicon substrate leads to greater complexity at higher frequencies and for manufacturing purposes.
The use of TFLN technology has been shown to successfully address some of the limitations of silicon photonics. The key entities and players leading this developing technology all appear to agree on a few stated advantages of TFLN:
Similar to most promising technologies, multiple entities around the world are focused on advancing TFLN technology by designing and manufacturing TFLN components and solutions. While HyperLight, based in the United States, continues to be a recognized pioneer in the TFLN space primarily manufacturing packaged modulators, other new entities are also entering the TFLN arena. All are supported by optimism from the investment community, a positive sign for growth and confidence in the TFLN technology market as a whole.
One such company is Lightium AG, a Swiss-based company founded just a year ago in September 2023. In the last few months since May 2024, Lightium received approximately a USD $3M grant from InnoSuisse, along with a new seed round this month in September 2024 of USD $7M. An entity providing pure-play TFLN foundry and design services, the company offers production-grade prototyping through high-volume manufacturing of CMOS-compatible, 200mm wafers.
"Lithium niobate is notoriously challenging to process. At Lightium, we have now developed the manufacturing capability to provide this technology at scale for the industry. What used to be limited to academic and R&D cleanrooms has now become an accessible reality for the industry to adopt”, states Dr. Amir Ghadimi (PhD), CEO and Co-Founder of Lightium.
As the necessary demand for transceiver optics delivering 1Tb/s and beyond continues to rapidly grow in the years to come, TFLN is beginning to establish itself as a technology with the potential to play a significant role in paving the way to achieving these levels of performance. Along with supporting higher bandwidth levels, the energy savings that can be realized by utilizing TFLN is another attractive benefit, given the anticipated volumes of devices expected to be deployed in networks across the globe amidst growing energy consumption concerns.
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