Direct imprint of optical quasiparticles to materials

Takashige Omatsu^1,2,3*

¹Graduate School of Engineering, Chiba University, Chiba, Japan
²Molecular Chirality Reseach Center, Chiba University, Chiba, Japan
³National Yang Ming Chiao Tung University, Hsinchu, Taiwan

* Presenter:Takashige Omatsu, email:takashige.omatsu@gmail.com

Optical vortices, known as the most conventional structured light fields, carry an annular spatial form and an orbital angular momentum (OAM) owing to an on-axis phase/polarization singularity, and they have been widely utilized across versatile applications, including optical trapping and manipulation, optical and quantum communication, and scanning microscopy with a high spatial resolution beyond the diffraction limit. Furthermore, it is discovered that their OAM can exert a force that twists irradiated materials, such as metals, semiconductors, and azopolymers, to fabricate chiral surface structures at a nano/micron scale. Such exotic light and matter interaction opens new avenues towards advanced materials processing and manipulation.
Beyond the conventional optical vortices, structured light fields currently involve particle-like optical waveforms with spatially inhomogeneous polarization structures in two- or three-dimensional space, referred herein optical quasiparticles, such as optical skyrmions and optical hopfions. Optical skyrmions encompass all polarization states mapped on a Poincaré sphere (referred topologically protected polarization textures) instead of spin textures of magnetic skyrmions, and they have been experimentally demonstrated by coherently superposing orthogonally oriented, circularly polarized fundamental Gaussian and Laguerre–Gaussian (LG) modes with the appropriate relative phase. Interestingly, their topological characteristics remain invariant under propagation through turbulent media, and thus, they have been rapidly collecting much attention in advanced applications, such as free-space communications under turbulent conditions, polarization nanoscale-metrology, and super-resolution microscopy with a sub-wavelength spatial resolution. However, in contrast to more conventional structured light fields, such as optical vortices, optical skyrmions are still in their infancy as a research topic. In fact, there is a lack of studies detailing the interaction between optical skyrmions and matters.
In this presentation, we review the structured light fields, including optical quasiparticles, and report on the experimental demonstration of the direct imprint of the polarization textures of optical skyrmions onto a material (a photosensitive azopolymer film). Interestingly, the fabricated structures onto the film possess sub-wavelength-scale periodical ripples that reflect the polarization textures of optical skyrmions. This demonstration gives rise to a new and modern approach to materials manipulation, and it also provides new insights into fundamental laser physics.

Keywords: Optical Physics , Structured Optics, Optical Angular Momentum