Robust Helical Dichroism on Microadditively Manufactured Copper Helices via Photonic Orbital Angular Momentum

Selective and Tunable Absorption of Twisted Light in Achiral and Chiral Plasmonic Metasurfaces

The symmetry of achiral metasurfaces suggests selective absorption is nonexistent when irradiated either by circularly polarized Gaussian or twisted light beams carrying orbital angular momentum (OAM). In chiral metasurfaces, the lack of symmetry leads to differential absorption when probed with chiral light either in the form of circular polarization (circular dichroism) or helical phase fronts (helical dichroism). Here, we demonstrate differential absorption of asymmetric twisted light beams, known as helical dichroism, which exist in an array and a single achiral structure and can be controlled. When extended to chiral structures, these asymmetrical chiral light modes enable to enhance and tune chiroptical sensitivity. Our technique offers more control parameters than just changing the OAM value, as presented in previous studies. Selective response to asymmetric helical light beams is qualitatively explained in terms of induced multipole moments. The presence of dichroism in achiral nanostructures offers a significant fabrication advantage over complex chiral structures and enables the development of next-generation plasmonic-based chiroptical spectroscopy and molecular sensing.

Integration of cross-scale milli/microlenses by ion beam etching and femtosecond laser modification

Integrated cross-scale milli/microlenses offer irreplaceable functions in modern integrated optics with the advantage of reducing the size of the optical system to millimeters or microns. However, the technologies for fabricating millimeter-scale lenses and microlenses are always incompatible, which makes the successful fabrication of cross-scale milli/microlenses with a controlled morphology challenging. Here, ion beam etching is proposed as a means to fabricate smooth millimeter-scale lenses on various hard materials. In addition, by combining femtosecond laser modification and ion beam etching, an integrated cross-scale concave milli/microlens (27,000 microlenses on a lens with a diameter of 2.5 mm) is demonstrated on fused silica, and can be used as the template for a compound eye. The results provide a new, to the best of our knowledge, route for the flexible fabrication of cross-scale optical components for modern integrated optical systems.