A High-Efficiency Multispectral Filter Based on Plasmonic Hybridization between Two Cascaded Ultrathin Nanogratings.

Bo Zhao,Jianjun Yang,Lei Zhang,Chunlei Guo,Zhenfen Huang,Rajagopal S Joshya

doi:10.3390/molecules24112038

Abstract

Overcoming the disadvantages of low transmission and broad peak bandwidth of previously reported plasmonic color filters, a high-efficiency multispectral plasmonic color filter is theoretically proposed with two cascaded ultrathin metallic nanogratings separated by two heterogeneous dielectric layers, and its optical properties are theoretically investigated using the finite-difference time-domain method. The transmission spectrum presents three near-unity peak bands accompanied with three near-null dip bands adjacent around them. Both transmission efficiencies of above 90% and ultranarrow peak bandwidth of 20 nm are achieved in the visible regime. The peak band positions can be flexibly tailored by varying the structural parameters. The filter selects the visible color with high signal noise ratio at the peak bands. The outstanding spectral properties of this filter indicate significant improvement for the high-accuracy color filtering and multispectral imaging applications. The simulated near-field electromagnetic distributions suggest that the excitation of the hybrid antisymmetric surface plasmon polariton (SPP) leaky mode and metal-insulator-metal waveguide modes are responsible for the peak transmission bands, while the formation of the hybrid SPP bound modes confined on the bottom nanograting makes the dip transmission bands, all of which are the consequence of the plasmonic hybridization between the two neighboring metallic nanogratings.

Highlights

Since the pioneering report of the extraordinary transmission (EOT) phenomenon by Ebbesen [1], metallic subwavelength structures have been an attractive subject of intense study due to the capabilities for manipulating the light at subwavelength scales by the excitation of surface plasmon polariton (SPP) [2,3,4,5,6], which is essentially a hybrid electromagnetic mode originating from the coupling of the light with the collective oscillations of free electrons at the metal/dielectric interface
The calculated transmission spectra of the multispectral plasmonic color filter with respect to the wavelengths and the upper nanogratings thicknesses tu is shown in Figure 2A, where the fixed bottom nanograting thickness is tb = 30 nm, and other geometric parameters are given by Λ = 500 nm, w = 150 nm, and td = ta = 50 nm
The dip bands of D1 and D2 in the visible regime possess the same full-width at half-maximum (FWHM) at the scale of tens of nanometers as that of the peak bands P1 and P2, while the dip band D3 in the near infrared region has an FWHM of hundreds of nanometers

Summary

Introduction

Since the pioneering report of the extraordinary transmission (EOT) phenomenon by Ebbesen [1], metallic subwavelength structures have been an attractive subject of intense study due to the capabilities for manipulating the light at subwavelength scales by the excitation of surface plasmon polariton (SPP) [2,3,4,5,6], which is essentially a hybrid electromagnetic mode originating from the coupling of the light with the collective oscillations of free electrons at the metal/dielectric interface. Obtaining a narrow peak bandwidth and high transmission efficiency have been experimentally reported for plasmonic color filters, which consist of the multilayer stacks with metallic nanostructured films and dielectric layers to support a multitude of hybridized SPP modes [15,16,17,18]. Through five alternative layers of Ag and SiO2 as a multilayer slot-mode plasmonic filter (MSPF) in the visible regime, it is capable of achieving a single peak bandwidth as narrow as 17 nm and 40% transmission efficiency [18]. All these MIM structures still have the problems of either relative low transmission efficiency or relative broad bandwidth. Complex multilayer designs composed of two-dimensional nanoparticle arrays are required

Methods

Results

Conclusion