Thermally reconfigurable metalens

Abstract

Reconfigurable metalenses are compact optical components composed by arrays of meta-atoms that offer unique opportunities for advanced optical systems, from microscopy to augmented reality platforms. Although poorly explored in the context of reconfigurable metalenses, thermo-optical effects in resonant silicon nanoresonators have recently emerged as a viable strategy to realize tunable meta-atoms. In this work, we report the proof-of-concept design of an ultrathin (300 nm thick) and thermo-optically reconfigurable silicon metalens operating at a fixed, visible wavelength (632 nm). Importantly, we demonstrate continuous, linear modulation of the focal-length up to 21% (from 165 μm at 20 °C to 135 μm at 260 °C). Operating under right-circularly polarized light, our metalens exhibits an average conversion efficiency of 26%, close to mechanically modulated devices, and has a diffraction-limited performance. Overall, we envision that, combined with machine-learning algorithms for further optimization of the meta-atoms, thermally reconfigurable metalenses with improved performance will be possible. Also, the generality of this approach could offer inspiration for the realization of active metasurfaces with other emerging materials within field of thermo-nanophotonics.

Integrated-resonant metadevices: a review

“…Tunability provides metadevices with more flexibility and functionality, promoting their practical applications. [79][80][81][82][83][84][85][86][87][88][89][90][91] Polarization direction of incident light is a straightforward way to dynamically tune the metadevice. Acosta et al 79 demonstrated a tunable metalens using asymmetric rectangular TiO 2 nanoposts with polarization-dependent responses [Fig.…”

“…Yu et al 80 ∼290. Tagliabue et al 81 reported a thermally reconfigurable metalens consisting of coupled anisotropic silicon nanofins with thermo-optic effects, as illustrated in Fig. 6(b).…”

Electrically switchable metallic polymer metasurface device with gel polymer electrolyte

“…What is more, by combining metasurfaces with active materials, unique and novel functionalities become possible as the optical properties can be dynamically adjusted [ 19 ], [ 20 ], [ 21 ], [ 22 ]. In such way, active metalenses [ 23 ], [ 24 ], [ 25 ], [ 26 ], [ 27 ], [ 28 ], [ 29 ], [ 30 ], [ 31 ], beam switching [ 25 , 32 ], [ 33 ], [ 34 ] and steering devices [ 6 , 35 ], [ 36 ], [ 37 ], active holograms [ 38 , 39 ], dynamic displays [ 40 ], [ 41 ], [ 42 ], or spatial light modulators [ 43 ] have been demonstrated. Recently, a new concept for active nanoantennas and metasurfaces based on polymers has been introduced [ 23 , 33 , 44 ], [ 45 ], [ 46 ].…”

Ultrathin Tunable Optomechanical Metalens

“…A metalens is a two-dimensional (2D) metasurface − that controls the amplitude, polarization, and phase of the impinging light using engineered sub-wavelength resonators, also known as meta-atoms (MA), judicially arranged in periodic or quasi-periodic arrays. ,− To date, metalenses are the center of intense research efforts and have shown great potential to replace bulky optical elements, sometimes even with superior performance . However, the intrinsic passive nature of metalenses limits their use where active operation is required, such as adaptive vision and imaging. − To address this challenge, various approaches have emerged that rely on changing the optical properties of the meta-atoms themselves or their surrounding medium. ,− In particular, promising advances were reported using electro-optic control, ,− temperature-induced effects, , light-induced effects, − phase change media, and mechanical actuation. ,− Despite this progress, it remains challenging to combine compactness, fast operation speed, and low energy consumption. For instance, a phase-change material-based metasurface provides large tunability and ultrafast switch ON time (up to MHz) but suffers from long switch OFF time .…”

“…5−12 To address this challenge, various approaches have emerged that rely on changing the optical properties of the meta-atoms themselves or their surrounding medium. 6,12−26 In particular, promising advances were reported using electro-optic control, 12,16−18 temperature-induced effects, 19,20 light-induced effects, 21−25 phase change media, 26 and mechanical actuation. 6,13−15 Despite this progress, it remains challenging to combine compactness, fast operation speed, and low energy consumption.…”