Applied Engineering Sciences Deng (Ed.)
© 2015 Taylor & Francis Group, London, 978-1-138-02649-0
Research on the transmission enhancement properties of a novel
subwavelength grating structure and mechanism
H.X. Chang, M.Q. Li, S. Zhang & Y. Ding
Key Laboratory of Intelligent Computing & Signal Processing, Ministry of Education,
Anhui University, Hefei, China
ABSTRACT: The subwavelength metal grating is designed and simulated by using the finite difference time
domain (FDTD) algorithm.The transmission characteristics of subwavelength metal grating structure are studied
based on the Lossy Drude dispersive medium model. The influence of grating geometry parameters on the
transmission characteristics are analyzed, especially for the zero transmission point location of the spectrum.
The difference between the designed and conventional gratings is that the former introduces the resonant cavity.
Results show that, compared with the single-layer grating, the triple-layer grating has a better filtering effect,
and the transmission spectrum peak is in excess of 82%. It concludes that the transmission peak drift is analyzed
by using the waveguide Fabry-Perot (F-P) cavity resonance effect, and the zero transmission point location of
the spectrum is independent of the metal layer thickness. The influence rules provide an available reference for
the design of the band-pass filters.
1 INTRODUCTION
When light passes through a metallic film with
subwavelength arrays of holes, it will produce an
extraordinary transmission phenomenon under cer-
tain wavelengths and its broad application prospects
have sparked extreme great interest since the work
of Ebbesen et al. [1]. In recent years, subwavelength
structures have mostly been studied around a hole
array periodic structure, square hole arrays and slit
grating [2]. However, this paper designed a triple-
layer subwavelength grating with the resonant cavity.
Based on Lossy Drude’s dispersive medium model
[3], a dispersion 2-d FDTD iteration equation was
deduced under the resonance of the metal surface
plasma membrane dispersion, to solve the instability
of the dispersion medium numerical calculation, and
study the cavity length, slit width, the refractive index
of the medium and other parameters for enhanced
transmission characteristics.
2 LOSSY DRUDE DISPERSIVE MEDIUM
FDTD ALGORITHM
When the dielectric constant of metal materials is
related to the frequency, the metal has dispersion char-
acteristic. The dispersion relationship of the Lossy
Drude model is given by [4]:
where ω is the bulk plasma frequency; ω
p
is the metal
plasma oscillation frequency; and γ is the damping
coefficient. The model formula (1) is substituted into
Maxwell’s equations by using the ADE method [5,6]
to transform the time-frequency domain operator. The
differential equations of the light transmission in the
metal are then given by [7]:
where E and H are respectively the electric field inten-
sity and magnetic field intensity; J is the current
density; ε
0
, µ
0
are respectively the vacuum permit-
tivity and permeability. The difference and discrete
Eq. (2b) is given by:
13

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