Isotropic Perfect Absorber by VSRR and Sensor Application
Jia-Wern Chen1*, Chun Yen Liao1, Pin Chieh Wu1, Wei-Yi Tsai1, Din Ping Tsai1,2
1Department of Physics, National Taiwan University, Taipei, Taiwan
2Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
* presenting author:Jia-Wern Chen,
Metamaterials have been realized for fantasy optical phenomena which can’t be found in nature like negative refractive index and cloaking. Nowadays, people intend to be more precisely from fundamental physical response to specific functionalities in metamaterials on demand for the development on practical applications, such as optical switches, phase gradient surfaces, optical modulators, polarizer and waveplate, etc. One of the potential applications is the metamaterial based perfect absorber (MPA). Due to the strong electromagnetic field confinement arose from surface plasmon resonance, MPA provides a benefitting way for enhancing the efficiency in solar energy capture, nanoplasmonic sensor and bolometer. The commonly utilized structural configuration for MPAs is incorporating a metamaterial array with a perfect reflective mirror separated by a dielectric spacer. Because of the near-field interaction between metamaterials and its mirror images, a strong plasmon field confinement is involved and therefore dramatically enhances the absorption intensity.

In this work, we use vertical split-ring resonator (VSRR), because it not only utilizes contributions of the incident electric but also magnetic fields. Firstly, we show that a nearly 100% absorption can be achieved in a single VSRR based perfect absorber. Four-VSRRs are subsequently merged into a unit cell for the demonstration of isotropic perfect absorber which is examined by changing the polarization angles and angle of incidences. According to these results, the absorption can be maintained at a very high intensity even when the incident angle is up to 60˚ for both TE- and TM-polarized illumination. Furthermore, this proposed VSRR based perfect absorber can also be applied as a refractive index sensor with improved sensing performance, and therefore provides an efficient way for biosensor and optoelectronics applications.

Keywords: Metamaterials, Perfect absorber, Refractive index sensor, Isotropic