Photonic Orbital Angular Momentum Dichroism on Three-Dimensional Chiral Oligomers

Chiral oligomers in optics are photonic metamaterialsinspiredby the concept of chiral centers in chemistry. In recent years, chiraloligomers have attracted increasing attention in recent years dueto their simple construction and unique chiroptical response. To date,research has predominantly focused on the photonic spin angular momentum(SAM)-dependent chiroptical response: circular dichroism (CD). However,for another photonic dimension parallel to the SAM, orbital angularmomentum (OAM)-dominated chiroptical response of chiral oligomersstill remains elusive. Here, we theoretically and experimentally demonstratethe individual three-dimensional (3D) chiral tetramers can exhibita gigantic response to the photonic OAM with a maximum helical dichroism(HD) of similar to 23%. Meanwhile, we also reveal the origin of the HDvia simulation analysis of electric current distribution, reflectedelectric field, and the discrete OAM spectroscopy. Furthermore, byfemtosecond direct laser writing, 3D oligomers with tailoring geometricparameters can be flexibly fabricated in one step for varying HD responses.Our research fills the gap of OAM-related chiroptical response ofchiral oligomers, which has great implications for chiroptical spectroscopyand photonic angular momentum engineering.

Automated summary

Chiral oligomers in optics are photonic metamaterials inspired by the concept of chiral centers in chemistry. Recent research has focused on the photonic spin angular momentum (SAM)-dependent chiroptical response, but the orbital angular momentum (OAM)-dominated chiroptical response of chiral oligomers is still unknown. In this study, we demonstrate that individual three-dimensional (3D) chiral tetramers can exhibit a significant response to the photonic OAM, and we also reveal the origin of this response. Furthermore, we show that 3D oligomers with tailored geometric parameters can be fabricated using femtosecond direct laser writing for varying responses. This research has implications for chiroptical spectroscopy and photonic angular momentum engineering.