Novel Ridge-Type Gold Film Waveguide for Surface Plasmon
Received: 28 March 2018 /Accepted: 28 May 2018
Springer Science+Business Media, LLC, part of Springer Nature 2018
Surface plasmon polariton lasers are the basis for photonic circuits, but their losses, thresholds, and some other problems remain
thorny issues. In this study, we put forward a novel ridge-type gold film surface plasmon polariton laser. The device adopts a
multi-layer hybrid waveguide structure, where the bottom layer is a gold film, and a gold ridge is formed over the center of the
gold film. We symmetrically place the two SiO
layers on both sides of the gold ridge as buffer layers and deposit a gold
nanoribbon on the top of gold ridge. Two air gaps are formed between the gold ridge and SiO
buffer layers. We numerically
study the structure, and the results show that at the operating wavelength of 1550 nm, the effective mode area reaches 1.375 ×
, and the confinement factor reaches 0.75. When the width of the SiO
layer is 2 nm, the height of the ridge is 10 nm, and
the angle of the ridge is 80°, the waveguide can effectively enhance the light field confinement so as to limit the energy to a very
small range and exhibits the minimum gain threshold. The waveguide can provide a solution for the optical source device of the
surface plasma excitation circuits and has great application potential in the ultra-small and high-density optical chips.
Keywords Surface plasmon polariton laser
Surface plasmon polaritons (SPPs) are evanescent waves prop-
agating along the interface between mental and dielectric [1–4].
Due to their unique properties, they attract great attention and
have wide application potential in many fields, such as biosen-
sor, medicine, nanolithography, and information storage [5–10].
Because of the diffraction limit, the size of a conventional semi-
conductor laser must be above half of the wavelength. However,
SPPs waveguide can break the diffraction limit [11–14], so a
variety of SPPs waveguide lasers have been proposed. As early
as 2001, M.H. Huang et al. used a semiconductor nanowire
array to realize ultraviolet lasing at room temperature .
However, due to the diffraction limit and the limitation of the
fabrication process, the size of the structure is not suitable for
application in integrated photonic devices. Mark Stockman
studied the nanoparticle surface plasmon amplification that
stimulated by emission of radiation  and theoretically pro-
posed the working principle of surface plasmon polariton lasers.
M.A. Noginov et al. of Norfolk State University designed the
world’s smallest laser at that time. The size of the laser is only
44 nm  and successfully verified it from experiments, which
had been widely noticed. Hill et al. designed a metal-insulator-
metal sub-wavelength plasmonic waveguide filled with electri-
cally pumped semiconductor core ,andthelaserofthis
structure has a fast response. Nezhad at the University of
California, San Diego, demonstrated a sub-wavelength cylindri-
cal metallo-dielectric laser which can emit laser light at room
temperature by optical pumping . This kind of laser works at
the visible and infrared waveband with bigger wavelength. It is
of great significance for practical application. Oulton et al. pro-
posed a multi-layer structure  and found that adding a high
refractive-index dielectric layer near the metal layer can achieve
strong light field confinement ability. However, the above struc-
tures are severely limited by the transmission loss of SPPs.
These lasers have weak resonance characteristics, and the gain
threshold is very likely to oscillate, resulting in a high gain
Jian Lou and Jun Zhu contributed equally to this work.
* Jun Zhu
* Duqu Wei
* Frank Jiang
College of Electronic Engineering, Guangxi Normal University,
Guilin 541004, China