Researchers have achieved a significant breakthrough in integrated photonics with the demonstration of a high-performance optical isolator based on a hybrid 2D material/silicon platform. By integrating a thin film of the 2D multiferroic material CuCrP2S6 (CCPS) onto a silicon microring resonator, they have created a compact and efficient device capable of non-reciprocal light transmission in the short-wave infrared (SWIR) spectrum, specifically around the crucial telecommunications wavelength of 1550 nm.
Optical isolators are essential components in optical systems as they allow light to pass in one direction while blocking it in the reverse, preventing detrimental back-reflections that can destabilize lasers and other sensitive optical sources. Achieving efficient and compact on-chip optical isolation has been a long-standing challenge. This new approach leverages the unique magneto-optic properties of CCPS. When an external magnetic field is applied, the ferromagnetic ordering within the 2D material induces a non-reciprocal phase shift for light propagating in opposite directions within the silicon resonator. This asymmetry in phase shift leads to the desired isolation effect.
The fabricated device exhibits impressive performance metrics, including a low insertion loss ranging from 0.15 dB to 1.8 dB, indicating minimal signal attenuation, and a high isolation ratio of 28 dB, signifying effective blocking of backward propagating light. The device also demonstrates a significant resonance wavelength splitting of 0.4 nm, supporting a 50 GHz optical bandwidth. Furthermore, it operates directly with the transverse electric (TE) polarization, the dominant mode in silicon photonics, simplifying integration and avoiding the need for additional polarization control components.
The use of a 2D material like CCPS offers significant advantages for integrated photonics. Its layered structure allows for easy integration onto silicon without the lattice mismatch issues associated with traditional 3D magneto-optic materials. The strong light-matter interaction in 2D materials, arising from quantum confinement and high refractive index, enables efficient magneto-optic effects in a very compact footprint. The demonstrated device has an interaction length of only 22–55 µm and a thickness of 39–62 nm.
This development represents a significant step forward in the quest for high-performance, chip-scale optical isolators compatible with silicon photonics. The low loss, high isolation, compact size, and direct TE mode operation of this hybrid CCPS/silicon device make it an ideal candidate for integration into advanced optical communication networks and other SWIR photonic systems where preventing back-reflections is critical for stable and reliable operation.
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