This is the final version.Atomic Weapons Establishment (AWE) plcEngineering and Physical Sciences Research Council (EPSRC

Bertolotti, J

Braid, G

Comley, A

Ruiz de Galarreta, C

Wright, CD

Open Research Exeter

Remote Thermal Sources for Switching Phase-Change Material-Based MetasurfacesG. Braid1, C. Ruiz de Galarreta1,2, A. Comley3, J. Bertolotti1, C. D. Wright11CMRI, University of Exeter, UK; 2IO-CSIC, Madrid, Spain; 3AWE Aldermaston, Reading UKgb512@exeter.ac.uk ex.ac.uk/GBraidwww.exeter.ac.uk/metamaterialsIntroduction Optical metasurfaces are 2D arrays of resonant subwavelength nanostructures that can change the phase, amplitude, or polarisation of incident light, enabling precise control of the optical wavefront [1]. A wider range of potential applications is achieved if the metasurface optical response can be actively controlled [1,2]. We do this by incorporating a chalcogenide PCM.The thermal impulse to switch a PCM metasurface is conventionally supplied by direct laser heating or embedded microheaters. However, these may not be feasible with all metasurfaces. We therefore here explore the switching of PCM-based metasurfaces by using remote thermal sources.DesignHan et al. [3] demonstrated thermal heat guide structures that can provide near-uniform heating over extended regions by conduction from a remote source. Although Han’s designs were on the macroscale (sizes in the cm range), we show that the approach is readily shrunk down to the microscale.ResultsReferences[1] Ruiz de Galarreta C et al., Journal of Optics, 2020, 22, 11, 114001.[2] Braid, G. et al., Nanomaterials, 2022, 12, 15, 2689.[3] Han, T. et al., Sci Rep, 2015,  34, 10242.However, similar control of heat can be achieved using simpler structures more suited to PCM metasurfaces, such as the design below. Here, heat sources are linked by straight tungsten arms to a central metasurface. Upon laser excitation of one or more of these arms, the metasurface can be heated and the PCM layers switched.Temperature/KHeat SourcesTungsten  ArmTemperature/KSteady state thermal simulations show a near-uniform temperature distribution can be achievedover the metasurface using the simplified remote heating approach. Dynamic thermal simulations show that the temperatures and cooling rates needed for successful crystallisation and amorphisation of the PCM layers in the metasurfacecan also be reached using the remote heating approach. Han’s design for uniform heating via remote sourcesSimplified remote heating design for use with PCM m etasurfacesSimulated temperature distribution for Han’s design and four remote sourcesTemperature distribution in simplified remote heating structure Schematic of generic PCM-based metasurfaceWe also simulated remote switching of a Ge2Sb2Se4Te PCM metasurface (as in [2]) using pulsed laser excitationof each end of the four tungsten arms (400 nmlaser, pulse power in tens of mW range).ConclusionWhere conventional approaches are not practicable, the switching of PCM-based metasurfaces should be possible using remote heating sources. Devices based on this concept are currently in the process of fabrication and testing.We show (in simulation) that Han’s structure produces a uniform temperature region on the microscale. 

Remote Thermal Sources for Switching Phase-Change Material-Based Metasurfaces

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Remote Thermal Sources for Switching Phase-Change Material-Based Metasurfaces

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