Widely Tunable GRIN Lenses Using Negative Dielectrophoretic Manipulation of Phosphate Nanosheets Colloid

Abstract

Tunable gradient refractive index (GRIN) lens has attracted increasing attention from researchers due to its promising applicability in various optical and electronic applications. However, the polarization‐insensitive, large sized, and focal‐length‐controllable GRIN lens is highly difficult to implement due to the lack of available functional materials with the property of tunable refractive index. Herein, a two dimensional (2D) α‐ZrP nanocolloid is introduced to fabricate a GRIN lens in which the 2D nanosheet density distribution is precisely controlled by negative dielectrophoresis. Interestingly, the geometrical 2D shape of nanosheets plays an essential role in reducing optical light scattering in colloids and enhancing the dielectrophoretic controllability of nanosheet distribution. Moreover, despite the nematic assembly of 2D nanosheets in colloids, the birefringence effect is negligible, and polarization‐independent properties are obtained. Using a simple nanocolloidal cell with designed electrodes and various thicknesses, not only tunable lenses with either positive or negative focal lengths but also wide tunable lenses across positive and negative focal lengths are successfully demonstrated. Thus, the results reveal new possibilities for 2D nanocolloids in tunable GRIN optical applications.

Nanocolloidal Lenses with Tunable Focal Length for an Augmented Reality System

“…Exfoliated α-ZrP nanocolloid with 1 wt % concentration was injected into two types of lens cells with dual ITO holes and a single ITO hole, as illustrated in the inset of Figure a. The dual ITO hole lens was designed and studied previously . To improve the control of particle redistribution of the dual ITO hole lens, a single ITO hole structure was introduced.…”

“…The synthesis of 2D α-ZrP was based on the same process reported in our previous work. 14 The hydrothermal method was used to synthesize inorganic thick α-ZrP [Zr(HPO 4 ) 2 •H 2 O] crystals. Zirconyl chloride octahydrate (ZrOCl 2 •8H 2 O, 98%, Alfa Aesar, Korea) was dissolved in 40 mL of 12 M phosphoric acid (H 3 PO 4 , 85%, Daejung, Korea) with vigorous stirring at 800 rpm for 2 h to obtain monodisperse α-ZrP crystals (4 g).…”

“…The dual ITO hole lens was designed and studied previously. 14 To improve the control of particle redistribution of the dual ITO hole lens, a single ITO hole structure was introduced.…”

“…This is another potential drawback of liquid crystal lenses in practical applications because larger aperture lenses require a greater thickness to maintain the tunable range of the focal length. 3,13 In general, chromatic aberration is more severe in diffractive type lenses than in GRIN lenses, 14 but it has been reported that chromatic aberration can be significantly reduced in diffractive lenses as well by adopting a new design of diffractive optical element. 15 Another type of tunable GRIN lens was recently proposed that utilized colloids of two-dimensional (2D) nanoparticles, 14 in which the medium refractive index was controlled using dielectrophoretic (DEP) manipulation of the concentration of nanoparticles.…”

Highly Efficient Double Microprism Polarizer with Microstructured Molecular Ordering

“…The crafted microstructure films with a pre-designed arrangement of the anisotropic refractive index profile exhibit excellent potential in controlling the propagation direction, [4] wavelength, [5] polarization, [6] phase front, [7] and fluorescence of light, [8,9] and have been used to drive remarkable advances in various photonic devices, such as displays, [2,10] holographic devices, [11] and lenses. [12][13][14] Nevertheless, as a photonic microstructure platform, the enormous potential of polymerized LC films has not been fully exploited; for example, a high transmission polarizer beyond the theoretical maximum value [6] can be a next innovative photonic application using polymerized LCs.…”