Browsing by Subject "Sub-wavelength optics"

Now showing 1 - 3 of 3

Open Access
Beaming and enhanced transmission through a subwavelength aperture via epsilon-near-zero media
(Nature Publishing Group, 2017) Hajian, H.; Özbay, Ekmel; Caglayan, H.
We numerically validate and experimentally realize considerable funneling of electromagnetic energy through a subwavelength aperture that is covered with an epsilon-near-zero metamaterial (ENZ). The epsilon-near-zero metamaterial is composed of two layers of metasurfaces and operates at microwave frequencies. We demonstrate that the presence of the metamaterial at the inner and outer sides of the aperture not only lead to a significant enhancement in light transmission, but also cause a directional emission of light extracting from this hybrid system. In addition to these experimental results, we theoretically demonstrate the same concept in mid-IR region for a subwavelength gold aperture with indium tin oxide as an epsilon-near-zero material. Moreover, we found that using a dielectric spacer in-between the sunwavelength aperture and the ENZ medium, it is possible to red-shift the enhancement/directional frequency of the system.
Open Access
Disordered nanohole patterns in metal-insulator multilayer for ultra-broadband light absorption: atomic layer deposition for lithography free highly repeatable large scale multilayer growth
(Nature Publishing Group, 2017) Ghobadi, A.; Hajian, H.; Dereshgi, S. A.; Bozok, B.; Butun, B.; Özbay, Ekmel
In this paper, we demonstrate a facile, lithography free, and large scale compatible fabrication route to synthesize an ultra-broadband wide angle perfect absorber based on metal-insulator-metal-insulator (MIMI) stack design. We first conduct a simulation and theoretical modeling approach to study the impact of different geometries in overall stack absorption. Then, a Pt-Al2O3 multilayer is fabricated using a single atomic layer deposition (ALD) step that offers high repeatability and simplicity in the fabrication step. In the best case, we get an absorption bandwidth (BW) of 600 nm covering a range of 400 nm-1000 nm. A substantial improvement in the absorption BW is attained by incorporating a plasmonic design into the middle Pt layer. Our characterization results demonstrate that the best configuration can have absorption over 0.9 covering a wavelength span of 400 nm-1490 nm with a BW that is 1.8 times broader compared to that of planar design. On the other side, the proposed structure retains its absorption high at angles as wide as 70°. The results presented here can serve as a beacon for future performance enhanced multilayer designs where a simple fabrication step can boost the overall device response without changing its overall thickness and fabrication simplicity. © 2017 The Author(s).
Open Access
Metamaterial inspired enhanced far-field transmission through a subwavelength nano-hole
(WILEY, 2010-06-02) Alici, K. B.; Özbay, Ekmel
In the present study, we first demonstrate the polarization and orientation dependent transmission response of split ring resonators at the infrared and visible band. Then, we numerically demonstrate a configuration for the enhancement of power passing through an electrically small hole. By using deep subwavelength optical split ring resonator antennas and couplers we achieved a 400-fold enhanced transmission from a subwavelength aperture area of the electrical size Λ 2/25. The power was transmitted to the far field with 3.9 dBi directivity at 300 THz. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) Transmission through a subwavelength aperture at the optical regime is quite low. The Letter by Alici and Ozbay shows how it can be enhanced and transferred to the far field by using a metamaterial inspired configuration composed of nano-scale split ring resonator antennas and couplers. A 400-fold power enhancement was achieved.