Photonic devices are outpacing electronic circuits in bandwidth and speed, yet the seamless integration of photonics and electronics remains a critical challenge for high-performance computing and communication. While planar microring resonators are common, their large footprint restricts high-density integration.
Three-dimensional (3D) microtube resonators formed by rolled-up nanomembranes offer a solution with a significantly smaller footprint. However, conventional microtubes suffer from light leakage along the axial direction of microtube, which degrades the quality factor (Q-factor) and limits performance. Furthermore, integrating photodetection capabilities into these resonators without destroying their optical storage properties has proven difficult.
In a new paper published in Light: Science & Applications , a team of scientists led by Professor Yongfeng Mei from Fudan University and Doctor Binmin Wu from Shanghai Institute of Technical Physics has developed a novel 3D photonic-electronic platform. They utilized strain-engineered self-rolling technology to fabricate silicon nitride (SiN x ) microtube resonators integrated with graphene, featuring a specialized "lobe" geometry.
The core innovation lies in the light localization in the lobe structures. The engineered lobe-shaped architecture in the microtube facilitates axial mode quantization. This design creates a gradient refractive index that acts like a quantum potential well, trapping light within specific regions of the tube and preventing it from escaping axially.
This structural innovation leads to a significant performance boost. By tuning the length of the integrated graphene, the team achieved an optimal balance between optical confinement and electrical readout efficiency. The graphene-integrated microtube resonators with the lobe structure demonstrate an efficient optical resonance (Q ≈ 2008) and high photoresponsivity (2.80 A W⁻¹).
Additionally, the rolling process naturally breaks the rotational symmetry of the nanomembrane. This asymmetry grants the device polarization sensitivity, allowing it to distinguish between transverse electric (TE) and transverse magnetic (TM) modes with a polarization ratio of approximately 4.3.
"The overall characteristics present a promising platform for optical manipulation and multidimensional detection of integrated photonic and optoelectronic systems," the scientists forecast. This technology provides a scalable foundation for realizing complex three-dimensional integrated photonic systems with unprecedented functionality and miniaturization.
Graphene-integrated microtube whispering-gallery mode resonators for polarization-sensitive optical modulation and photodetection