Demonstration of > 2π reflection phase range in optical metasurfaces based on detuned gap-surface plasmon resonators

Abstract

Plasmonic metasurfaces, representing arrays of gap-surface plasmon (GSP) resonators and consisting of arrays of metal nanobricks atop thin dielectric layers supported by thick metal films, constitute an important subclass of optical metasurfaces operating in reflection and enabling the realization of numerous, diverse and multiple, functionalities. The available phase variation range is however limited to being $$<\! 2\pi$$ < 2 π , a circumstance that complicates the metasurface design for functionalities requiring slowly varying phases over the whole range of $$2\pi$$ 2 π , e.g., in holographic applications. The available phase range also determines the wavelength bandwidth of metasurfaces operating with linearly polarized fields due to the propagation (size-dependent) nature of the reflection phase. We suggest an approach to extend the phase range and bandwidth limitations in the GSP-based metasurfaces by incorporating a pair of detuned GSP resonators into a metasurface elementary unit cell. With detailed simulations related to those for conventional single-resonator metasurfaces and proof-of-concept experiments, we demonstrate that the detuned-resonator GSP metasurfaces designed for beam steering at $${900}\,\,\hbox {nm}$$ 900 nm wavelength exhibit the extended reflection phase and operation bandwidth. We believe that the considered detuned-resonator GSP metasurfaces can advantageously be exploited in applications requiring the design of arbitrary phase gradients and/or broadband operation with linearly polarized fields.

Dynamic piezoelectric MEMS-based optical metasurfaces

“…5B ). The deviation between the required and available phase profiles results mostly from the achievable phase coverage of ~270°, a limitation that could be circumvented by including more complex unit cell elements such as detuned GSP resonators ( 62 ) that can also be constructed square-like to ensure the polarization-independent operation or by using cross-like nanobricks, allowing for a wider phase coverage ( 57 ).…”

“…5B). The deviation between the required and available phase profiles results mostly from the achievable phase coverage of ~ 270⁰, a limitation that could be circumvented by including more complex unit cell elements such as detuned GSP resonators (58).…”

Experimental Implementation of Achromatic Multiresonant Metasurface for Broadband Pulse Delay

“…Metasurfaces (MSs), that is, ultrathin periodic configurations of subwavelength resonant meta-atoms, have attracted considerable interest in recent years for an abundance of applications, − ranging from perfect absorption − to polarization , and wavefront control. − MSs can impart a nontrivial phase delay on an impinging wave, as they temporarily store energy due to their resonant nature; this phase, however, is typically limited to 0–2π (in the case of electric and magnetic response) and features a very specific dispersive spectral profile dictated by the underlying (Lorentzian) resonance. As a result, thus far, metasurfaces have found limited use when it comes to dispersion engineering − and particularly applications relying on large and spectrally engineered phase profiles.…”

Chiral-Selective Tamm Plasmon Polaritons

“…The dimensions of the unit cell with a nanobrick fabricated using electron beam lithography are shown (please see Supplementary Materials ). The SiO layer and bottom metal film are used to control the phase of the reflected light [ 24 , 25 , 26 , 27 , 28 , 29 ]. This design allows the handedness of reflected light to be preserved and the polarization-matching condition fulfilled.…”