Kyocera Corporation (TSE: 6971) and Tohoku University have developed a technology to integrate optical isolators directly onto silicon photonics chips using localized laser annealing, addressing a key thermal challenge in building compact optical circuits for AI and data center applications.
The organizations said the technology enables a magneto-optical garnet material used in optical isolators to be heat-treated without exposing the rest of the silicon photonics chip to the high temperatures required by conventional processing. Kyocera describes the approach as the world’s first technology of its kind based on laser annealing, according to its July 2026 research assessment.
The research was published Sept. 2 in IEEE Access, an academic journal of the Institute of Electrical and Electronics Engineers. The paper, titled Monolithic Magneto-Optical Mach-Zehnder Isolator Using Laser-Annealed Iron Garnet on a Silicon Waveguide, documents the fabrication and experimental operation of the integrated device.
Laser Annealing Addresses a Key Integration Challenge
Silicon photonics uses optical signals rather than electrical signals to transmit and process data on silicon-based circuits. The technology is gaining importance as data centers handle increasingly demanding AI and generative AI workloads, while operators seek higher bandwidth and lower energy consumption.
The shift is also driving interest in co-packaged optics (CPO), which places optical and electronic circuits within the same semiconductor package to shorten signal paths and reduce signal loss and power requirements.
Optical isolators are important in such systems because they allow light to travel predominantly in one direction. Reflected optical signals can travel back toward a laser source, potentially degrading its performance.
Conventional optical isolators typically use magneto-optical garnet, a crystalline material that requires heat treatment at about 600°C or higher to achieve the properties needed for isolation. Applying that temperature across an entire silicon photonics chip, however, can damage electrodes, wiring and other components.
Kyocera and Tohoku University addressed the problem by applying a near-infrared laser only to the portion of the chip containing the isolator material.
The laser was directed at an approximately 700-by-700-micron region where a magneto-optical garnet film had been deposited. Localized heating crystallized the material while limiting thermal exposure to surrounding optical circuits and electrodes.
Integrated Device Demonstrates 13.6 dB Isolation
The research team fabricated an optical isolator on a silicon photonics chip using a structure based on light interference and then tested its operation.
The device achieved an isolation ratio of 13.6 dB across the optical communication wavelength range, according to the researchers. That corresponded to a reduction of approximately 95% in back-reflected light.
Electron microscopy also confirmed that the magneto-optical garnet in the laser-irradiated region had crystallized on the silicon waveguide, providing evidence that the localized treatment achieved the intended material transformation.
| Technology | Result |
|---|---|
| Laser treatment region | Approx. 700 × 700 μm |
| Heating method | Localized near-infrared laser annealing |
| Isolation ratio | 13.6 dB |
| Back-reflected light reduction | Approx. 95% |
| Integrated material | Magneto-optical garnet |
| Photonic platform | Silicon waveguide |
Implications for Co-Packaged Optics
The ability to fabricate an optical isolator directly on a silicon photonics substrate could help address one of the integration barriers facing compact optical systems.
CPO architectures are being developed to bring optical connectivity closer to high-performance processors and other electronic components. Reducing the physical distance between optical and electrical functions can help address bandwidth, signal integrity and power challenges as data rates rise.
For optical isolators, however, the requirement for high-temperature processing has made direct integration difficult. The laser-annealing approach allows the heat treatment to be concentrated where it is needed rather than exposing the entire photonic circuit to furnace temperatures.
That distinction could become increasingly relevant as optical engines move toward more highly integrated designs for AI infrastructure and high-performance computing.
Kyocera and Tohoku Target Commercialization
The latest work builds on previous collaboration between Kyocera and Tohoku University on integrated optical isolator technologies. In June 2026, the researchers published related work on a monolithically integrated magneto-optical isolator using nanocomposite garnet and an asymmetric Mach-Zehnder interferometer.
The organizations said their next objectives include reducing optical loss, improving efficiency and increasing productivity for eventual mass production.
The focus on manufacturing is significant because demonstrating an integrated device in a laboratory is only one step toward deploying the technology in commercial optical systems. Production throughput, process consistency and integration with established silicon photonics manufacturing flows will determine how readily the approach can move toward volume applications.
Kyocera is also expanding its semiconductor-related manufacturing capabilities. The company completed its Nagasaki Isahaya Plant in September, with production of fine ceramic components for semiconductor manufacturing equipment and semiconductor packages scheduled to begin in phases from spring 2027.
