Laser-Assisted Tailored Patterning of Au Nanoparticles over an Inch-Sized Area: Implications for Large Aperture Meta-optics

Abstract

We investigate laser-induced dewetting of Au films to form nanoparticles with a controlled distribution and to alter these properties spatially with laser parameters for applications of large aperture meta-optics. By performing laser line scans under various parameter space conditions (power, speed, and beam size), we observe that laser power is an effective knob for adjusting the dewetting process while scan speed is not. Temperature numerical calculations show that the scan speeds used in this parameter space do not introduce a large temperature variation but the laser power does. By correlating calculated temperatures and associated experimental dewetting results, we confirm that local temperature is the driving factor in the laser-induced dewetting process. Furthermore, based on in situ thermal emission imaging, the thermal response time is estimated as ∼2 ms and a self-terminating characteristic of the laser-induced dewetting process is observed. This self-terminating effect results in an insignificant change in subsequent laser scans, contributing to the robustness of this process for large area dewetting patterning by beam rastering. Based on these findings, we successfully demonstrate an inch round globe-shaped pattern consisting of Au nanoparticles.

All-glass metasurface laser optics for lensing, antireflections, and waveplates

“…By adjusting the local induced temperature with scanning laser we pattern the local effective index. Parameter studies of laser power and dwell time (raster speed) have been conducted on various metal layer thickness, showing that there is high and monotonic dependence on laser power and low sensitivity to laser scan [11]. Therefore, the laser power is being used as a patterning knob, whereas scan speed a potential direction for speeding up the process while scaling up the patterned area.…”

“…These set of requirements for large aperture size scalability and laser power-energy durability and the challenges described to the more typical "shape-sensitive" MS are addressed with the "averaged-index" MS approach we have developed [2][3][4][5][6][7][8][9][10][11][12][13][14], as will be describe next. However, for these "averaged index" MS to become a viable solution there were different obstacles and challenges that had to be overcome first, such as substantial increase in the MS layer thickness.…”

All‐Glass Metasurfaces for Ultra‐Broadband and Large Acceptance Angle Antireflectivity: from Ultraviolet to Mid‐Infrared

“…[29] Spatial patterning of the mask has also been demonstrated, through usage of a laser raster with varying laser power at the mask formation step, to vary the end-result patterned effective index across the optics aperture. [33,36] In this work, we discuss progress made toward fabricating large-aperture substrate engraved metasurfaces, and the performance of these structures as ultra-broadband AR layers. Specifically, we present the optical performance when the aspect ratio of nanoscale metasurface features is increased as large as ≈14, where the mean base diameter of the cone-like feature is 62 nm.…”

“…[ 29 ] Spatial patterning of the mask has also been demonstrated, through usage of a laser raster with varying laser power at the mask formation step, to vary the end‐result patterned effective index across the optics aperture. [ 33,36 ]…”

Linear-to-circular polarization conversion with full-silica meta-optics to reduce nonlinear effects in high-energy lasers

“…In addition to bandwidth constraints and aperture size limitations induced by optics manufacturing techniques, one of the main challenges is to increase laser damage resistance of optical materials in operating conditions. Several efforts are being made to improve the performance of laser optics manufacturing processes such as fused silica finishing process improvements 14,15 , multi-layer dielectric coatings optimization 15,16 , nanostructures engineering [17][18][19][20][21][22][23] . More disruptive concepts such as replacing optical materials by plasmas 24,25 were also proposed but still need to be developed and implemented.…”