Holographic Recording and Hierarchical Surface Patterning on Periodic Submicrometer Pillar Arrays of Azo Molecular Glass via Polarized Light Irradiation

Abstract

Periodic submiocrometer pillar arrays are fabricated from a photoresponsive azo molecular glass (IA-Chol) by soft-lithographic hot embossing with elastomeric poly(dimethylsiloxane) (PDMS) modes. Through deformation of each submicrometer-sized pillar in response to the local amplitude and polarization of the superimposed electric waves, optical holograms are recorded on the IA-Chol pillar arrays. When the interference pattern is formed by two polarized beams with opposite-circular polarizations, the recorded patterns mainly reflect the polarization state variations with spatial phase difference of the interfering waves. When two plane waves with the same linear polarizations are superimposed, where the polarization direction is almost the same as the writing beams, the intensity variation of the superimposed electric waves is recorded by the pillar arrays changing spatially with the phase variations. Various ordered surface patterns with distinct hierarchical configurations are successfully developed by the intensity and polarization modulations of the interfering waves. This approach not only allows to directly visualize the intensity and polarization of the coherent light captured by the holograms, but also provides a powerful platform to fabricate various complex surface patterns. The submicrometer pillar arrays can also be used to record polarization hologram and the images are reconstructed by reference light in diffracted spots.

Light‐Directed Soft Mass Migration for Micro/Nanophotonics

“…Thus far, a sub‐30 nm structural pattern has been produced with photoisomerization‐driven directional mass migration of azomaterials . This resolution is comparable to that of current semiconducting technologies, such as extreme UV lithography and directed self‐assembly . Additionally, photochromic NSOM imaging can guarantee a resolution of a few nanometers, exceeding that of scattering‐based conventional NSOM .…”

“…Wang et al reported another promising application of the directional mass migration of azomaterials for advancing metasurfaces, as shown in Figure . Pristine nanoscale, azomaterial posts, which are regular arrays over a large area, can be individually reconfigured into a graded unit array by a one‐shot illumination with an interference pattern (Figure a–f).…”

“…Most metasurfaces developed so far have relied on serial‐type lithographic techniques (e.g., electron beam lithography) . Therefore, massive and parallel mass migration of azomaterials through one‐shot light illumination can effectively address the cost and scalability issues of the fabrication of metasurfaces . This field also needs to be further explored; we will separately report on this pursuit in the near future.…”

“…The illumination time is gradually increased from top to bottom panels: a,b) 8 s; c,d) 10 s, and e,f) 12 s. g,h) The reconstructed volume hologram image, recorded in a nanopillar array. (a)–(h) Reproduced with permission . Copyright 2018, Wiley‐VCH.…”

Symmetry‐Breaking Response of Azo Molecular Glass Microspheres to Interfering Circularly Polarized Light: From Shape Manipulation to 3D Patterning

“…By exploiting the directional mass transfer feature, SRGs have been efficiently inscribed on the azo polymer films by using the interfering CPL with opposite circulations . To be utilized for such applications, amorphous molecular materials containing azo chromophores (azo molecular glasses) show some unique advantages, such as well‐defined structures, high chromophore density, easy purification, no chain entanglements of polymers, and good processibility . Although molecular weights are much lower than those of their polymeric counterparts, azo molecular glasses can be feasibly used to prepare optical quality solid films, which are highly stable for storage in the glassy state below glass transition temperature ( T g ) .…”