A Performance Study of Dielectric Metalens with Process-Induced Defects

Abstract

Metalenses based on dielectric nanostructures operating in the transmission mode are of great practical significances. As large-area, multifunctional metalenses are increasingly demanded at higher volumes nowadays, the quality and efficiency of the nanofabrication processes for these lenses are made even more important. Yet, no fabrication is without defects or errors. By using finite-difference time-domain (FDTD) calculation method, we study, in simulation, a set of common fabrication-induced errors such as inclined sidewall, critical dimension (CD) bias and process defects, and analyze their influences on the optical performances of two types of metalenses-one made of amorphous silicon and the other of silicon nitride. The study concludes that the lens behavior generally relies on the resonant nature of the nanostructure array. While most types of defects discussed in this work linearly decrease the focusing efficiency, a few would also influence the quality of the focal spot. Potential solutions to mitigate the effect of the process-induced defects are also investigated. The study provides the particular knowledge to understand the actual metalens performance when fabricated.

An All‐Silicon Metalens Integrated with a Mid‐Wave Infrared Black Phosphorus Photodiode

“…In contrast to periodic designs in which the centers between each nanostructure are fixed, we fixed the distance between the edges of each nanostructure. [41] By imposing a constant spacing g between the edges of the nanorod and unit cell, a greater number of unit cells can occupy the same area than if d + 2 g summed to a fixed period (i.e., g is not fixed). [24,41] Additionally, a fixed g ensures that two nanorods are never in direct contact each other, which aids fabrication processes and avoids unwanted coupling effects.…”

“…[41] By imposing a constant spacing g between the edges of the nanorod and unit cell, a greater number of unit cells can occupy the same area than if d + 2 g summed to a fixed period (i.e., g is not fixed). [24,41] Additionally, a fixed g ensures that two nanorods are never in direct contact each other, which aids fabrication processes and avoids unwanted coupling effects. [24] We designed our metalens with the fixed gap spacing constraint.…”

“…Nanorods, with the same diameter as the second nanorod, are then evenly distributed along a ring that is defined by the position of the second nanorod. [41] This process is repeated until the metalens design reaches the desired final size. In Figure 2c, as the nanorods' diameters decrease as their positions move further from the origin.…”

The Effect of Height Error on Performance of Propagation Phase-Based Metalens

“…Despite significant advancements in design theory enabling the creation of highly efficient metalenses, the introduction of fabrication errors during manufacturing has often led to final device performances falling short of expectations [23][24][25][26][27]. In recent years, some researchers have delved into the effects of sidewall tilting, lateral dimension variation, and process defects of structural units on the performance of metalenses [28,29]. They have discovered that sidewall tilting leads to the proximity of neighboring structures, resulting in stronger structural resonance, which affects the efficiency of the metalens.…”

Model-based optical proximity correction for immersion lithography-based flat optics platform

“…When the feature size and the pitch of the nanopillar array are comparable to the wavelength of the light source used in the photolithography, the diffraction and the optical proximity effect induce critical dimension (CD) errors of the nanopillar, which generates inaccurate phase modulation to reduce the performance of the flat optics devices 9 . Hence, optical proximity correction (OPC) technique is implemented to reduce the CD errors.…”