Kyocera and Tohoku University Develop New Optical Chip Technology That Can Reduce Reflected Light by Up to 95%

Kyocera (Kyocera) and Tohoku University have jointly developed a new optical chip technology that could solve growing problems in high-speed data centers by reducing reflected light by approximately 95%, thereby improving performance. The technology utilizes laser annealing to directly integrate optical isolators onto silicon photonics chips, heating only the target area rather than exposing the entire chip to high temperatures. Optical isolators prevent light from propagating back toward the laser source, as reflected light can interfere with the laser and degrade the performance of optical communication systems.

As artificial intelligence workloads drive the need for data centers to process more information, silicon photonics technology is being developed to provide faster and more energy-efficient connections.

Technical Advantages of Optical Isolators

The technology uses light rather than electrical signals to transmit and process data, with laser heating addressing the integration issue. Traditional optical isolators typically rely on magneto-optical garnet, a crystalline material that needs to be heated to around 600 degrees Celsius or higher to develop the necessary properties to suppress reflected light. However, heating the entire silicon photonics chip to such temperatures could damage its electrodes, wiring, and other components. Kyocera and Tohoku University solve this problem by directing near-infrared laser light only at the area where the isolator is to be formed, with the laser focused on a region approximately 700 micrometers by 700 micrometers.

This localized heating causes the magneto-optical garnet to crystallize without subjecting the surrounding silicon photonics circuitry to the same thermal load.

Future Applications and Development

This method makes it easier to integrate optical isolators with compact optical circuits and co-packaged optics (CPO). CPO places optical and electronic components within the same semiconductor package, reducing signal paths and potentially lowering signal loss and power consumption. For optical links, as systems become more miniaturized and compact, it becomes increasingly important to keep light traveling in the intended direction. Therefore, directly fabricated isolators can remove a major integration barrier for compact photonic circuits used in future high-speed networks.

The researchers fabricated optical isolators on silicon waveguides and tested their ability to distinguish between forward-propagating light and backward-reflected light. The device achieved an isolation ratio of 13.6 decibels in the optical communication wavelength range, which, according to the researchers, corresponds to about a 95% reduction in reflected light. Electron microscope inspection showed that the laser-processed magneto-optical garnet had crystallized correctly on the silicon waveguide, supporting the operational results shown in the experiment. This achievement builds on earlier research by Kyocera and Tohoku University aimed at developing optical isolators that can be directly integrated into optical circuits.

The companies' current goal is to improve the technology by reducing optical losses, increasing efficiency, and making the process more suitable for large-scale production. If these improvements are realized, directly integrated optical isolators are expected to play a role in future high-density optical systems, particularly as data centers increasingly adopt silicon photonics and CPO to handle growing artificial intelligence-related workloads. The research has been published in the journal IEEE Access.

The Importance of the New Technology to Data Centers

As artificial intelligence drives the demand for high-speed data transmission in data centers, the collaboration between Kyocera and Tohoku University in developing new optical chip technology is particularly significant. By reducing reflected light and enhancing the integration of optical isolators, this technology not only improves the performance of optical communication systems but also effectively reduces power consumption, adapting to the needs of future high-density optical systems. As silicon photonics technology advances, the success of this technology will have a profound impact on the operational efficiency and sustainability of data centers.