Kyocera and Tohoku University develop silicon photonic optical isolator technology

Kyocera Corporation and Tohoku University have developed a new technology to directly integrate optical isolators onto silicon photonic circuits using a process called ‘laser annealing’. This breakthrough addresses a critical challenge in the development of Co-Packaged Optics (CPO), which is essential for high-speed, low-power data transmission in AI data centers.

Optical isolators are vital components that prevent reflected light from returning to the laser source, which can destabilize communication. Traditionally, the magnetic-optical garnet material used in these isolators requires heat treatment exceeding 600°C. However, heating an entire chip to such temperatures can damage existing metal electrodes and wiring. The new method uses near-infrared laser light to provide localized heating, crystallizing the garnet only in specific areas without affecting the surrounding circuitry.

In experimental tests using a Mach-Zehnder interferometer structure, the researchers demonstrated an isolation ratio of 13.6 dB, effectively reducing reflected light to approximately one-twentieth of its original level. This advancement could lead to more compact, high-density optical circuits and simplified manufacturing processes for next-generation semiconductor packaging.