Mode properties of a coaxial
multi-layer hybrid surface
plasmon waveguide
Miao Sun
**
,2
, Jinping Tian
*
,1,2
, and Lu Li
2
1
Computer Center of Shanxi University, Taiyuan 030006, P. R. China
2
College of Physics and Electronics Engineering, Shanxi University, Taiyuan 030006, P. R. China
Received 11 December 2014, revised 7 April 2015, accepted 24 April 2015
Published online 18 May 2015
Keywords gain materials, mode confinement, propagating losses, surface plasmon polaritons, waveguides
*
Corresponding author: e-mail tianjp@sxu.edu.cn, Phone/Fax: þ86 0351 7010755
**
e-mail 281452063@qq.com, Phone: þ86 0188 3511 6303, Fax: þ86 0351 7010755
A novel type of coaxial circular multi-layer hybrid su rface
plasmonic waveguide is proposed and of which the mode
properties are analyzed theoretically at the t elecommunica-
tion wavelength of 1550 nm. Simulation results show that by
tuning the size of the waveguide, the mode propagation
properties could be effectively controlled to obtain enhanced
mode confinement as well as weaker propagating loss. It is
also found that the mode ca n be strongly localized in the
middle low-index dielectric media layer with sub- or deep
sub-wavelength scale. Further investigati on proves that the
mode propagation loss can be well compensate d by repla cing
the high-index dielectric media with gain material to obtain
longer propagation length w ith very tight mode confinement.
The proposed hybrid structu re can be used in nanophotonic
waveguides, high-quality nanolasers, optical trapping, and
biosensor s.
ß 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
1 Introduction With the emergence of nanophoton-
ics, manipulating light on scales much smaller than the
working wavelengths has attracted a lot of attention during
the last decade [1]. Surface plasmon polarition (SPP) [2, 3]
is one of the most promising candidates because of the sub-
wavelength optical confinement with the ability of breaking
the diffraction limit [4–8]. During the past years, advance-
ment in novel plasmon waveguide configurations has led
to the proposal and demonstration of numerous hybrid
plasmon waveguide structures [9–31], which combine the
advantages of both semiconductor and plasmon waveguides
and enable light transmission in the deep sub-wavelength
scale to achieve long distance propagating with very tight-
mode confinement. Among the reported results, hybrid
plasmonic waveguides (HPWs) [17–31] show great
advantages in both strong light confinement and reduced
propagating loss at the sub-wavelength or deep
sub-wavelength scale. So far, the main challenge to be
faced to in this area mainly comes from two aspects. The
first is the balance between the mode confinement and
propagating loss, and the second is the characteristics of
simple structure and easy to be manufactured. So, the design
of plasmon waveguide structures with better propagating
properties are still a hot spot.
In Ref. [28], the authors propose two types of coaxial
hybrid plasmonic nanowire waveguides. The first type
consists of a metal cladding, a sandwiched low index
dielectric layer, and a high index dielectric core which has
the property of less loss. The second type is the reverse
version of the first type which has the property of strong
confinement and enhanced optical fields in a low refractive
index region. In Refs. [29–31], the authors analytically
investigated the multi-layer planner SPPs waveguide and
they found that the electromagnetic mode can be well
confined in the low-index dielectric area with low loss. In
Ref. [32], a coaxial multi-layer hybrid plasmonic waveguide
was proposed and it was found that the electromagnetic
mode can be well confined in the two low-index dielectric
layers with low loss.
In this paper, a reverse version of coaxial circular hybrid
plasmonic waveguide studied in Ref. [32] is proposed. We
found the coupling between the plasmonic and waveguide
modes across the middle low-index dielectric media layer
enables “capacitor-like” energy storage that allows effective
Phys. Status Solidi B 252, No. 8, 1884–1889 (2015) / DOI 10.1002/pssb.201451761
basic solid state physics
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ß 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim