Surface lattice resonances (SLRs) on metasurfaces strongly enhance the interaction of light with the metasurface and can be used for obtaining very high-Q response, high spectral sensitivity, and strong optical nonlinearities. Here, we study experimentally and numerically the dynamic switching of SLRs in gold nanoantenna metasurfaces fabricated on top of indium tin oxide by use of electrically controlled liquid crystals. Experimental results show that the cumulative effects of the anisotropic optical response with an applied electric field and the alignment conditions of liquid crystal molecules significantly affect the formation as well as the strength of SLR modes. We achieve an electrical modulation of >50% in the SLR dips by applying 2 V on the device. The strength of the modulation can be further optimized by modifying the angle of incidence and the polarization of light. These findings demonstrate that plasmonic metasurfaces activated by liquid crystals enable a versatile platform to obtain electro-optical control over SLRs and open the door to various new applications of dynamic reconfigurable metasurfaces.
We study the optical response of plasmonic metasurface etalons in reflection. The etalons consist of a metallic mirror and a plasmonic metasurface separated by wavelength-scale dielectric spacer. We show that tuning the localized surface plasmon resonance and spacer thickness can be used to achieve both enhanced reflectivity and perfect absorption, in addition to full 2π range phase control, and tunable regions of normal and anomalous dispersion. We validate our claims by measuring the spectral reflection and phase response of metasurface etalons consisting aluminum nanodisks of different radii separated from an aluminum reflector by a SiO2 spacer. In addition, we use this approach to demonstrate a simple Hermite-Gaussian (HG) wavelength selective beam-shaping reflective mask. The concept can be further extended by using multilayers to obtain multi-functional elements.
The rapid growth in the development of new optical materials such as 2D materials, layered heterostructures, active phase changing materials, optical metasurfaces, and metamaterials, requires new methods which enable accurate, broadband, and real‐time microscopic characterization of their optical and physical properties. Here, this necessity is addressed and a novel method is presented to dynamically and accurately obtain the spectral phase of a microscopic sample, either in reflection or transmission. The method is based on a designed optical relay that couples the output port of a typical microscope setup to an imaging spectrometer. By post‐processing the acquired images, a stable, accurate, and easy‐to‐align broadband spectral microscopic interferometer is obtained. This approach is experimentally demonstrated by measuring the spectral phase response of two different types of metasurfaces in reflection and in transmission and also by accurately measuring the dispersion of a thick glass slab in transmission. Moreover, the method's applicability to broadband dynamic measurements is demonstrated by real‐time tracking the phase response of optically driven nematic to isotropic and isotropic to nematic phase transitions of a liquid crystal. Altogether this method enables accurate, dynamic, and easy microscopic phase characterization and can become widely used for materials characterization.
The emergence of optical anomalies in 3D plasmonic metamaterials upon excitation of volume collective modes is studied. These modes engage a collective response of all the meta‐atoms across the volume of the structure and arise due to coupling of localized plasmonic modes with Bloch modes of the 3D lattice. Two types of volume collective modes are introduced; a reflective mode resilient to the plasmonic absorption, exhibiting reflection that approaches unity with extremely low loss, through a distinct high‐Q spectral locking of the response of all the constituent plasmonic resonators in the volume; in addition, a transmissive mode that supports the emergence of lattice matched scattered waves within the volume, leading to full transmission through a spectral transparency window. These attractive optical properties of the volume collective modes may lead to a breakthrough in the design of low‐loss and efficient 3D plasmonic metamaterials for novel linear and nonlinear photonic applications.
We introduce a novel interferometric method for fast, broadband and microscopic phase characterization, based on common-path configuration. The method can be implemented by adding a simple optical relay to connect conventional microscope and imaging spectrometer.
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