Petal-Inspired Diffractive Grating on a Wavy Surface: Deterministic Fabrications and Applications to Colorizations and LED Devices

Abstract

Interestingly, the petals of flowering plants display unique hierarchical structures, in which surface relief gratings (SRGs) are conformably coated on a curved surface with a large radius of curvature (hereafter referred to as wavy surface). However, systematic studies on the interplay between the diffractive modes and the wavy surface have not yet been reported, due to the absence of deterministic nanofabrication methods capable of generating combinatorially diverse SRGs on a wavy surface. Here, by taking advantage of the recently developed nanofabrication composed of evaporative assembly and photofluidic holography inscription, we were able to achieve (i) combinatorially diverse petal-inspired SRGs with controlled curvatures, periodicities, and dimensionalities, and (ii) systematic optical studies of the relevant diffraction modes. Furthermore, the unique diffraction modes of the petal-inspired SRGs were found to be useful for the enhancement of the outcoupling efficiency of an organic light emitting diode (OLED). Thus, our systematic analysis of the interplay between the diffractive modes and the petal-inspired SRGs provides a basis for making more informed decisions in the design of petal-inspired diffractive grating and its applications to optoelectronics.

Light‐Directed Soft Mass Migration for Micro/Nanophotonics

“…The gradient‐index (GRIN) lens is a representative example . Many other materials and device technologies, including holographic recording media, diffractive surface relief gratings (SRGs), photonic crystal color pixels and sensors, spatial light modulators, and metasurfaces, have undergone significant progress with the recent advances in methods that can control the refractive index of materials with micro and nanoprecision.…”

“…Aside from the concept of metasurfaces, where differently shaped, sized, and oriented antennas made of metals or highly transparent semiconductors are designed to be spatially arranged in a nonperiodic manner for a phase (or refractive index) discontinuity, the bulk refractive index of a homogeneous medium is generally defined by the material density. Accordingly, a spatially modulated density in a homogeneous medium has enabled the development of functional micro/nanophotonic materials and devices . Additionally, for a heterogeneous medium, the spatially controlled separation of different elements, which starkly contrast with each other in terms of their refractive indices, enables an efficient spatial variation in the refractive index .…”

“…Additionally, for a heterogeneous medium, the spatially controlled separation of different elements, which starkly contrast with each other in terms of their refractive indices, enables an efficient spatial variation in the refractive index . Overall, mass migration at the micro/nanoscale within a homogeneous or heterogeneous medium is the key to achieving such a spatially and precisely modulated refractive index …”

“…The potential produced by light is unique, particularly for micro/nanoscale mass migration. Noninvasive and remote control of mass migration can be achieved over a large area by illumination with light . Importantly, a rational mixing of wavevector and polarization‐controlled incident beams with the aid of the level‐set approach model can provide compelling advantages in the patterning of light, which in turn affords unprecedented flexibility in terms of micro/nanoscale mass migration …”

“…Notwithstanding, light‐directed mass migration can outperform its photolithographic counterpart in terms of its achievable structural complexity, functionality, heterogeneous integration of functional materials, and reconfigurability/adaptability . These aspects make light‐directed mass migration highly attractive for engineering sophisticated, functional micro/nanophotonic materials and devices.…”