Polarisation and wavelength selective transmission through nanohole structures with multiple grating geometry

Polarization Multiplexing of Fluorescent Emission Using Multiresonant Plasmonic Antennas

Combining the ability to localize electromagnetic fields at the nanoscale with a directional response, plasmonic antennas offer an effective strategy to shape the far-field pattern of coupled emitters. Here, we introduce a family of directional multiresonant antennas that allows for polarization-resolved spectral identification of fluorescent emission. The geometry consists of a central aperture surrounded by concentric polygonal corrugations. By varying the periodicity of each axis of the polygon individually, this structure can support multiple resonances that 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 nanocuvette and manipulate the fluorescent response of colloidal-quantum-dot emitters coupled to the multiresonant antenna.

Polarization-independent split bull's eye antennas for infrared nano-photodetectors

Split bull’s eye (SBE) antennas exhibit much larger extraordinary optical transmission and strong polarization dependence rather than bull’s eye (BE) antennas in the infrared range due to the introduced sub-wavelength slit. Here, we demonstrate a dual-split bull’s eye (DSBE) antenna, which consists of two sub-wavelength slits crossing through the center of the BE antenna with an intersection angle θ. The polarization dependence in transmission can be flexibly tailored by adjusting the intersection angle, following a cos² (Φ + θ/2) angular dependence on polarization angle Φ. When θ = 90°, the DSBE antenna yields high and polarization-independent transmission enhancement over the entire infrared spectrum. It presents highly promising applications for polarization-insensitive photodetectors and other optoelectronic devices.

Polarization dependent transmission through a sub-wavelength hexagonal aperture surrounded by segmented polygonal grooves

We report enhanced optical transmission (EOT) through a hexagonal aperture surrounded by polygonal segmented grooves to explore its unique polarization dependence. Effects of light polarization on EOT through the hexagonal aperture were systematically investigated for three types of grooves: concentric hexagonal grooves, linear segmented grooves and wedge segmented grooves. Significant increase in EOT was observed for the polarization directed along the groove axis compared to the other orthogonal polarization, which can be further applied to polarization dependent photonic devices.

Optimization of bull's eye structures for transmission enhancement

We present an exhaustive exploration of the parameter space defining the optical properties of a bull's eye structure, both experimentally and theoretically. By studying the resonance intensity variations associated with the different geometrical features, several parameters are seen to be interlinked and scale laws emerge. From the results it is possible to give a simple recipe to design a bull's eye structure with optimal transmission properties.