Interdisciplinary analysis and optimization of digital photonic devices for meta-photonics.

With the continuous integration and development of AI and natural sciences, we have been diligently exploring a computational analysis framework for digital photonic devices. Here, We have overcome the challenge of limited datasets through the use of Generative Adversarial Network networks and transfer learning, providing AI feedback that aligns with human knowledge systems. Furthermore, we have introduced knowledge from disciplines such as image denoising, multi-agent modeling of Physarum polycephalum, percolation theory, wave function collapse algorithms, and others to analyze this new design system. It represents an accomplishment unattainable within the framework of classical photonics theory and significantly improves the performance of the designed devices. Notably, we present theoretical analyses for the drastic changes in device performance and the enhancement of device robustness, which have not been reported in previous research. The proposed concept of meta-photonics transcends the conventional boundaries of disciplinary silos, demonstrating the transformative potential of interdisciplinary fusion.

Investigation of unidirectional coupling of dipole emitters in valley photonic heterostructure waveguides.

Photonic heterostructure has recently become a promising platform to study topological photonics with the introduction of mode width degree of freedom (DOF). However, there is still a lack of comprehensive analysis on the coupling of dipole emitters in photonic heterostructures, which constrains the development of on-chip quantum optics based on chiral dipole sources. We systematically analyze the unidirectional coupling mechanism between dipole emitters and valley photonic heterostructure waveguides (VPHWs). With the eigenmode calculations and full-wave simulations, the Stokes parameters are obtained to compare the coupling performance of two types of valley-interface VPHWs. Simulation results show that compared to the zigzag interface with inversion symmetry, the strategy of bearded interface with glide symmetry is easier to realize high-efficiency coupling. By adjusting the position and chirality of dipole emitters in VPHWs, the transmission of light reverses with guided modes coupled to different directions. Furthermore, a topological beam modulator is realized based on VPHWs, which maintains the robustness to large-area potential barriers and sharp corners. Our work supplies a powerful guide for chiral light-matter interaction, which is expected to be applied to increasingly compact and efficient on-chip optical platforms in the future.

An all-silicon design of a high-efficiency broadband transmissive terahertz polarization convertor.

Polarization, a fundamental behavior of electromagnetic waves, holds immense potential across diverse domains such as environmental monitoring, biomedicine, and ocean exploration. However, achieving efficient modulation of terahertz waves with wide operational bandwidth poses significant challenges. Here, we introduce an all-silicon polarization converter designed specifically to operate in the terahertz range of the electromagnetic spectrum. Simulation results demonstrate that the average conversion efficiency of cross-linear waves exceeds 80% across a wide frequency range spanning from 1.00 to 2.32 THz, with the highest conversion efficiency peaking at an impressive 99.97%. Additionally, our proposed structure facilitates linear-to-circular polarization conversion with an ellipticity of 1 at 0.85 THz. Furthermore, by rotating the cross-shaped microstructure, active control over arbitrary polarization states can be achieved. To summarize, the proposed structure offers remarkable flexibility and ease of integration, providing a reliable and practical solution for achieving broadband and efficient polarization conversion of terahertz waves.

Terahertz narrowband filter metasurfaces based on bound states in the continuum.

The electromagnetically induced transparency (EIT) effect realized by metasurfaces have potential for narrowband filtering due to their narrow bandwidth. In optics, bound states in the continuum (BIC) can produce strong localized resonances, which means that light can be trapped and stored for long periods of time to produce very high Q-factors. This has potential applications in designing highly efficient sensors and narrow bandpass filters. Here, we present two metal-flexible dielectric metasurfaces consisting of copper structures and polyimide substrates. Quasi BICs are obtained by breaking C2 symmetry of the metal structures. Resonance-captured quasi-BICs with ultra-high q-factor resonances satisfy the dark modes required to realize the EIT and couple to the bright modes in the structure to achieve narrowband filtering. The peak transmission rates are around 0.9 at 0.29 THz-0.32 THz and 0.23 THz-0.27 THz, respectively. Our results have practical implications for the realization of low-frequency terahertz communications.

All-dielectric terahertz metasurfaces with dual-functional polarization manipulation for orthogonal polarization states.

All-dielectric metasurfaces have led to a surge of activities in the field of polarization converters due to their extremely significant potential in the manipulation of terahertz waves. Herein, a versatile all-dielectric metasurface platform that can realize dual-functional polarization manipulation for the orthogonal states of polarization in the terahertz frequency range is proposed. Furthermore, such metasurface platform exhibits the properties of a full-waveplate for one circularly polarized light, and a quarter-waveplate for the orthogonal circularly polarized light. For experimental demonstrations of strategy verification, several representative metasurfaces consisting of subwavelength-scaled all-silicon elliptical cylinders were designed, fabricated, and characterized to demonstrate the capability of dual-functional polarization manipulation, including bifunctional waveplate, near-field imaging, and focusing. The metasurface platform demonstrated here may provide an alternative perspective for the development of compact, versatile polarization terahertz devices, and the design concept can be extended to other frequency ranges as well.