2, Universidad Autónoma de Madrid, Madrid, , Spain
Specific design of nanostructured surfaces allows enhanced and directional in- and out-coupling of light for targeted wavelengths , . Moreover, the ability to control both the polarization-dependent response of an antenna and the polarization state of the outgoing light, offers an effective strategy to structure electromagnetic fields , . Thanks to these properties, optical nanoantennas represent a powerful tool in a wide range of applications including optical imaging, light harvesting, and sensing .
One of the most successful examples of directional plasmonic antennas are the so-called bull’s eye structures [5-7]. Using concentric circular grooves, these single-resonant antennas provide spectrally selective and directional transmission of light [5,6,8]. Here, inspired by these structures, we introduce a new class of bull’s eye antennas, consisting of concentric polygons . In contrast to the traditional circular bull’s eyes, our polygonal bull’s eyes can accommodate multiple resonances by introducing variations in the periodicity along the different axes of the structure. As such, this structure can provide independent control over emission directionality for multiple wavelengths. Moreover, since each resonant wavelength is directly mapped to a specific polarization orientation, spectral information can be encoded in the polarization state of the out-scattered beam. To demonstrate the potential of such structures in enabling simplified detection schemes and additional functionalities in sensing and imaging applications, we use the central subwavelength aperture as a built-in nano-cuvette and manipulate the fluorescent response of colloidal quantum dot emitters coupled to the multiresonant antenna.
Extending the concept of our multiresonant bull’s eyes beyond the plasmonic antenna structure, we translate our design to structures made entirely out of colloidal quantum-dots . Efficient Bragg scattering of the quantum dot fluorescence yields a high degree of directional and polarization control. Our results on plasmonic and quantum dot structures will be discussed in the context of polarimetric applications that may generate new forms of structured light and enable advanced concepts in spectroscopy and display applications.
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