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Silicon photonics has established itself as a leading technology for the development of integrated photonic circuits, taking advantage of the microelectronics industry’s existing manufacturing technologies. This compatibility enables cost-effective, large-scale manufacturing of high-density photonic circuits.

Power dividers are key components in photonic circuits, necessary to efficiently distribute and route optical signals within a chip. However, current dividers still face challenges such as limited bandwidth, optical signal losses, and sensitivity to manufacturing errors. In this work, the research team has overcome the limits of current power dividers by developing a new architecture based on a symmetric Y junction assisted by subwavelength metamaterials. This new design not only enables multimode and dual-polarization operation with minimal losses in a record bandwidth, but also improves robustness against manufacturing imperfections. These features make it a key component for photonic applications requiring high precision, low losses, and a wide operating spectrum.

In this study, the researchers designed and fabricated a 3 dB power divider for the silicon-on-insulator (SOI) platform. The device is based on a symmetric Y junction that was optimized by including subwavelength metamaterials (SWG) with two different geometries. These SWG metamaterials are made up of nanometric periodic structures that allow precise control of light propagation through them. Using three-dimensional simulations, the team tuned the geometry of the SWG metamaterials to minimize optical losses and maximize operating bandwidth, covering the wavelength range from 1300 to 2000 nm.

The devices were then fabricated and their optical properties were experimentally validated. Measurements demonstrated that the splitter maintains low losses (<0.2 dB) not only in the fundamental electrical transverse (TE0) and first-order (TE1) modes, but also in the fundamental magnetic transverse polarization (TM0) mode over a wide spectral range. Moreover, even considering fabrication variations of up to ±10 nm, the proposed device demonstrates the robustness and consistency of its high performance.

Subwavelength grating metamaterials

Subwavelength grating metamaterials are composed of periodic distributions of structures with a spacing much smaller than the wavelength of the light that propagates through them. With these subwavelength nanostructures, the light is allowed to propagate through the grating as if it were a new homogeneous material (what is known as metamaterial), with the advantage that its optical properties can be adjusted at will.

Article: Raquel Fernández de Cabo, David González Andrade, Pavel Cheben, Aitor V. Velasco “Extending the spectral operation of multimode and polarization-independent power splitters through subwavelength nanotechnology”. Optics & Laser Technology. Volume 181, Part B, February 2025, 111921

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