Facile fabrication of close-packed microlens arrays using photoinduced surface relief structures as templates

Abstract

We demonstrate the cost-effective and facile method of fabricating close-packed microlens arrays using photoinduced two-dimensional (2-D) surface relief structures as original templates. 2-D surface relief structures are produced by successive inscription of two beams interference patterns with different grating vectors on azopolymer films. The employed exposure dose of 1st inscription stage and 2nd inscription stage are optimized to obtain symmetrical modulation heights. These photoinduced 2-D surface relief structures on azopolymer films are used directly to mold PDMS, and PDMS molds were then transferred onto photopolymer to imprint microlens arrays. Using this method, tetragonally and hexagonally close-packed microlens arrays are successfully fabricated in rapid and cost-effective way.

Directional Superficial Photofluidization for Deterministic Shaping of Complex 3D Architectures

“…Furthermore, the azobenzene materials with the specific structures could be converted into other materials, for example, by replication process. 42 The absorption spectrum of PDO 3 is presented in Figure S2. Laser beam parameters were then changed, resulting in different 3D structures.…”

“…21 This fluidic behavior, however, is quite extraordinary, as the "flow", 4 herein, is highly directional, typically parallel to the light polarization, in contrast to the heatinduced isotropic counterparts, 5,6, 11,13,[16][17][18][19]23,26 and is spatially controlled by the light irradiation pattern in a non-trivial way. 14,16,[42][43][44][45][46][47][48] When the irradiation stops, everything becomes "frozen" again, and the reconfigured structural fidelity of azo-materials is hence quite stable. [42][43][44][45][46][47][48] Even if, all previous works has been highly limited to 2D reconfiguration of pristine structures (e.g., inscription of two orthogonal gratings or 2D directional photofluidic reconfiguration of a micron scaled, simple line shape into a ellipsoidal hole with nanoscale), [42][43][44][45][46][47][48] such synergistic properties can make the photofluidization highly amendable to a deterministic 3D shaping of architectures in an unprecedented way.…”

Azopolymer‐based micro‐ and nanopatterning for photonic applications

“…This has significantly broadened the application potential of azopolymer SRGs, since they can now be used as a starting point for creation of periodic (or self‐assembled quasiperiodic) structures out of essentially any material or combination of materials, and in a variety of shapes. In addition to the already discussed azopolymer‐based diffraction gratings that can indeed be used to control light emission, absorption, and transmission, one can also create such photonic elements as microlens arrays for optical signal processing and wavefront sensing, molecular alignment layers for liquid‐crystal displays, and various nondiffractive subwavelength gratings that can be used, for example, as ultrathin broadband polarizers and phase retarders, moth‐eye‐type broadband AR coatings, and plasmonic microstructures and nanostructures for near‐field optical applications including surface‐enhanced Raman scattering (SERS) and optics of metamaterials . We notice that essentially all these periodic structures can be fabricated also with the help of other microfabrication and nanofabrication techniques, such as traditional photoresist‐based optical lithography and electron‐beam lithography.…”

Efficiency Enhancement of Organic Solar Cells by Fabricating Periodic Surface Textures using Direct Laser Interference Patterning

“…[14,15] For instance, laser interference lithography (LIL) on photoresist or as photofluidization lithography have emerged as a technology capable to fabricate templates by irradiating an azo-polymer or a photoresist with interference patterns obtained by using two or more coherent laser beams (typically UV radiation, e.g., using an Ar laser), mostly operating in continuous wave (cw) mode. [16][17][18] Therefore, these methods can offer scalable and parallel nanotexturing with controlled complexity [19] and can be applied to improve the efficiency of solar cells. [20] In addition, electron beam [21] and ion beam lithography [22] have been used to produce structures with high precision at the required scale.…”