All dielectric reconfigurable metamaterials

• Main Author: Karvounis, Artemios
• Other Authors: Zheludev, Nikolay ; Macdonald, Kevin
• Published: University of Southampton 2017
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.759216

This thesis reports on my research efforts towards all-dielectric metamaterials with reconfigurable functionalities: • I have reported the first optomechanical nonlinear dielectric metamaterial. I have shown that such metamaterials provide extremely large optomechanical nonlinearities at near infrared, operating at intensities of only a few μW per unit cell and modulation frequencies as high as 152 MHz, thereby offering a path to fast, compact, and energy efficient all-optical metadevices. • I have experimentally demonstrated the first all-dielectric electro-optical nanomechanical modulator based on all-dielectric nanomembrane metamaterial. Furthermore, I have shown the dynamical control of optical properties of this device, with modulation frequency up to 7 MHz. I have also establish an encapsulation technique where any nano-membrane can be embedded within a fiber setup with electrical feedthroughs and pressure control. • I have studied for first time the optical properties of Diamond nano-membrane metamaterials. Diamond membranes after nanostructuring with Focus Ion Beam, present broadband, polarization-independent absorption that can be used as efficient coherent absorbers for optical pulses as short as 6 fs. This novel class of metamaterials have been used for coherent modulation with modulation contrast up to 40% at optical fluences of few nJ/cm2 across the visible spectrum. • I have reported the first optically-switchable, all-chalcogenide phase-change metamaterial. Germanium antimony telluride alloys (GST) after nanostructuring subwavelength-thickness films of GST present high-quality resonances that are spectrally shifted by laser-induced structural transitions, providing reflectivity and transmission switching contrast ratios of up to 5:1 (7 dB) at near-infrared wavelengths selected by design, or strong colour contrast in visible due to its plasmonic nature. • This work has introduced dielectric nano-membrane metamaterials, as a platform to provide optically switchable, nonlinear, reconfigurable responses. Due to nanomechanical actuation based on optical/electromagnetic forces, coherent modulation based on the diamond absorbers and phase change media of Chalcogenide glasses.