Abstract
We propose and theoretically demonstrate a novel type of optical Yagi-Uda nanoantennas tunable via variation of the free-carrier density of a semiconductor disk placed in a gap of a metallic dipole feeding element. Unlike its narrowband all-metal counterparts, this nanoantenna exhibits a broadband unidirectional emission and demonstrates a bistable response in a preferential direction of the far-field zone, which opens up unique possibilities for ultrafast control of subwavelength light not attainable with dipole or bowtie architectures.
Highlights
Owing to recent advances in nanotechnology, plasmonic nanoantennas have become a subject of considerable theoretical and experimental interest [1,2]
Unlike its narrowband all-metal counterparts, this nanoantenna exhibits a broadband unidirectional emission and demonstrates a bistable response in a preferential direction of the far-field zone, which opens up unique possibilities for ultrafast control of subwavelength light not attainable with dipole or bowtie architectures
Plasmonic resonances in nanoantennas allow breaking through the fundamental diffraction limit [3], opening up novel opportunities for controlling light–matter interactions within subwavelength volumes
Summary
Owing to recent advances in nanotechnology, plasmonic nanoantennas have become a subject of considerable theoretical and experimental interest [1,2]. Several potential applications of nanoantennas have been considered in topics such as spectroscopy and highresolution near-field microscopy [2], subwavelength light confinement and enhancement [4], photovoltaics [5], sensing [6], molecular response enhancement [7], non-classical light emission [8], and communication [9]. In many of these applications, controlling and modifying the far-field of a nanoantenna is an important issue that is interesting for obtaining directional beaming effects, which have been demonstrated e.g. with Yagi-Uda architectures [10,11,12,13,14]. Large spectral tunability can be obtained using electrically controlled liquid crystals [32,33,34], but a very slow response of liquid crystals is not suitable for many application and, in general, a solid-state implementation is more suitable for on-chip integration of nanoantennas
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