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With the development of the information age, photonic integrated circuits (PICs) have become indispensable for advancements in optical communications, quantum computing, artificial intelligence, and LiDAR technologies.Traditional isolators, based on the Faraday effect in magneto-optic materials, rely on bulky permanent magnets and complex optical designs, making them incompatible with the miniaturization, low-power consumption, and high integration requirements of modern PICs. With the development of silicon photonics, on-chip integrated optical isolators have become a research focus.

Associate Researcher Zhang Hao and Associate Professor Yang He from Beihang University summarized recent developments in on-chip isolators based on magneto-optic, acousto-optic, electro-optic, and nonlinear optical effects, while critically analyzing their advantages, challenges, and future directions. 1. Magneto-optic isolators rely on the Faraday rotation effect, achieved through heterogeneous integration of magneto-optic materials (e.g., Ce: YIG , Bi: YIG ) with silicon-based waveguides. 2.Acousto-optic isolators enable nonreciprocal transmission via phase-matched photon-phonon interactions, without the need for magneto-optic materials, offering low power consumption and dynamic reconfigurability. 3. Electro-optic isolators achieve nonreciprocal transmission by controlling the phase of optical waves through the electro-optic effect. 4. Nonlinear optical isolators break the reciprocity of light transmission through nonlinear optical effects such as the Kerr effect or four-wave mixing, offering advantages such as broad bandwidth and high flexibility.

Finally, they explores future development directions and potentialapplications