Fast and Transparent Adaptive Lens Based on Plasmonic Heating

Abstract

In the current trend toward miniaturization, integrated micro-optical elements play a central role in the development of various applications including high-density data storage and imaging. In these operations, fine alignment and focus adjustment are usually performed mechanically, thus, limiting the accuracy, size and speed of devices. Here, we propose a novel reconfigurable microlens based on the engineering of the temperature distribution induced by a patterned plasmonic surface shined with a resonant nearinfrared light. The refractive index change generated in a surrounding thermo-optical material acts as an effective lens whose parameters are remotely adjusted by the control nearinfrared light. We demonstrate focal distance tunability of tens of microns with subnanometer accuracy along with timeresponses down to 200 μs. The applicability of this photothermal lens is proved in the framework of optical microscopy and adaptive optics.

A review of dielectric optical metasurfaces for wavefront control

“…Thermal tuning is another method of changing the response of metasurfaces. Thermo-optical modulation of metasurfaces have been proposed for spatial light modulation [204,268]. Figure 9d shows a high-speed silicon-based device for phasedominant spatial light modulation through the thermo-optic effect in α-Si.…”

Highly tunable elastic dielectric metasurface lenses

“…Some efforts have recently been focused on developing tunable and reconfigurable metasurfaces using different stimuli for tuning the meta-atoms. Examples include frequency response tuning using substrate deformation [6,7], refractive index tuning via thermo-optic effects [8,9], phase change materials [10,11], and electrically driven carrier accumulation [12,13].Stretchable substrates have been used to demonstrate tunable diffractive and plasmonic metasurface components [14-16], but they have exhibited low tunability, poor efficiency, polarization dependent operation, or significant optical aberrations. Here we present mechanically tunable dielectric metasurfaces based on elastic substrates, simultaneously providing a high tuning range, polarization independence, high efficiency, and diffraction limited performance.…”

“…Some efforts have recently been focused on developing tunable and reconfigurable metasurfaces using different stimuli for tuning the meta-atoms. Examples include frequency response tuning using substrate deformation [6,7], refractive index tuning via thermo-optic effects [8,9], phase change materials [10,11], and electrically driven carrier accumulation [12,13].…”

Eppur Si Riscalda - and yet, It (Just) Heats Up: Further Comments on “Quantifying Hot Carrier and Thermal Contributions in Plasmonic Photocatalysis”

“…Either way, these claims were raised in [17,18] in the quite different context of a single illuminated NP configuration, where temperature-induced changes to the metal permittivity are dominant. As shown below, in the current context of a mm-scale composite that contains a very large number of sparsely dispersed NPs, the nonlinear thermo-optic response originates from the host (as it occupies the vast majority of the sample volume), see also [19]. Since the permittivity of dielectric materials is far less sensitive to heat, the nonlinear thermo-optic response manifests itself at much higher temperatures -several hundreds of degrees.…”