Using One-Step, Dual-Side Nanoimprint Lithography to Fabricate Low-Cost, Highly Flexible Wave Plates Exhibiting Broadband Antireflection

Abstract

In this study, we used dual-side nanoimprint lithography to prepare sub-wavelength periodical grating (SPG)-based wave plates on flexible substrates. Without employing any etching, we directly imprinted SPGs on both sides of a polycarbonate (PC) substrate through a one-step imprinting process. This dual-side nanoimprint lithography process dramatically decreases the typical imprinting pressure required in conventional resist-based nanoimprint lithography. With this low-cost formation of PC-based wave plates, any degree of phase retardation could be obtained merely by stacking a set of wave plates with designed depths and working wavelengths. Our SPG-based wave plates exhibited the excellent broadband antireflection properties of sub-wavelength structures possessing refractive index gradients on both sides of the PC substrates. The high flexibility, low cost, and low surface reflection of these dual-side SPG-based wave plates make them attractive alternatives to commonly used birefringent crystal-based wave plates, suggesting that this phase retardation technique has promising potential for use in the development of next-generation flexible optoelectronic devices and systems.Wave plates are key components in various optoelectronic systems because they can modulate the polarization state of light through phase retardation effects along their fast and slow axes. 1 In an optics system, a 0.5p phase retardation is usually obtained using a quarter-wave plate. When light passes through a quarterwave plate, a 0.5p phase retardation is applied to the electric field passing through the slow axis; therefore, a 0.5p phase difference exists between the electric fields emitted from the fast and slow axes of the wave plate. Meanwhile, a 0.5p phase retardation would be achieved when stacking two 1/8-wave plates together. The eventual polarization state of the light would be identical to that of light that had passed directly through a quarter-wave plate. Thus, arbitrary phase retardation could be achieved if we precisely stacked numbers of wave plates with designed phase retardation. Under this consideration, low-cost wave plates were in demand.Commercial wave plates are typically made of highly crystalline birefringent crystals, such as quartz, calcite, and MgF 2 , which exhibit different refractive indices along their different crystalline orientations. 2-4 Difficulties encountered during the cutting, grinding, and polishing of these crystal-based wave plates mean that they are generally expensive. Moreover, because birefringent crystals exhibit intrinsically high reflection at their surfaces, additional antireflection coatings on both surfaces of a plate are necessary to ensure high transmittance of incident light and to eliminate stray light.Recently, phase retarders made of liquid crystal cells have been developed as alternatives to inorganic crystals. The large birefringence of these liquid crystals makes them promising phase modulators. A liquid crystal cell has the potential to behave both as a phase rotation and retarda...

Soft biomimetic tapered nanostructures for large-area antireflective surfaces and SERS sensing

“…Polycarbonate (PC) was chosen due to its hightransmittance, biocompatibility, durability, high impact resistance, and wide usage in electronic components. 42,43 On the other hand, the utilized PC material possesses a moderate refractive index and ignorable absorption in the visible wavelengths, which makes it feasible for optical applications. Besides the antireection feature, produced tapered structures exhibit highly hydrophobic properties (145 water contact angle).…”

Influence of Rapid Thermal Annealing and Substrate Terrace Width on Self-Organizing Formation of Periodic Straight Nanogroove Array on NiO(111) Epitaxial Thin Film

“…Nanopatterning techniques are the subject of intensive research in many diverse areas of nanotechnology. [1][2][3][4][5][6][7][8] Artificial nanostructural construction has been conducted by employing various methods such as extreme ultraviolet interference lithography, 9) nanoimprint lithography, [10][11][12][13][14][15] and high speed scanning CW laser method. 16) Recently, nanotechnology using self-organizing phenomena has been attracting much attention owing to its low-cost and applicability for large-scale patterning.…”

Nanoimprint technology for patterning functional materials and its applications

“…Similar to the NIL on resist layer, the direct NIL on plastic substrates was performed at an elevated temperature around Tg of the plastic substrate [70]. Polycarbonate (PC) is commonly used as a high-transmittance polymer-based substrate, and it is considered as a promising candidate for fabricating optical components or devices.…”

“…For example, the sub-wavelength periodical gratings (SPGs) prepared by direct NIL exhibited the birefringence [70]. The SPG structure resulted in different degrees of phase retardation of the TE and TM modes of light.…”