Plasmon waveguide resonance sensor using
an Au–MgF
2
structure
Yanfei Zhou,
1,2,†
Pengfei Zhang,
1,2,†
Yonghong He,
1,2,
* Zihao Xu,
1,2
Le Liu,
3
Yanhong Ji,
4
and Hui Ma
1,2
1
Shenzhen Key Laboratory for Minimal Invasive Medical Technologies, Institute of Optical Imaging
and Sensing, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China
2
Department of Physics, Tsinghua University, Beijing 100084, China
3
Institute of Green Chemistry and Energy, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China
4
MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science, South China
Normal University, Guangzhou 510631, China
*Corresponding author: heyh@sz.tsinghua.edu.cn
Received 29 July 2014; revised 25 August 2014; accepted 25 August 2014;
posted 25 August 2014 (Doc. ID 219902); published 22 September 2014
We report an Au − MgF
2
plasmon waveguide resonance (PWR) sensor in this work. The characteristics of
this sensing structure are compared with a surface plasmon resonance (SPR) structure theoretically and
experimentally. The transverse-magnetic-polarized PWR sensor has a refractive index resolution of
9.3 × 10
−7
RIU, which is 6 times smaller than that of SPR at the incident light wavelength of 633 nm,
and the transverse-electric-polarized PWR sensor has a refractive index resolution of 3.0 × 10
−6
RIU. This
high-resolution sensor is easy to build and is less sensitive to film coating deviations. © 2014 Optical
Society of America
OCIS codes: (230.7400) Waveguides, slab; (240.6680) Surface plasmons; (310.6860) Thin films,
optical properties; (310.4165) Multilayer design.
http://dx.doi.org/10.1364/AO.53.006344
1. Introduction
Surface plasmon resonance (SPR) and plasmon
waveguide resonance (PWR) are two surface-
plasmon-based optical sensing methods that offer
high-sensitivity and label-free measurement [
1,2]
and have been widely used in diverse fields [
3].
The resonance conditions of both techniques are
sensitive to the refractive index change of analytes
in the evanescent fields. Because of the penet ration
depths of evanescent fields, the SPR and PWR sen-
sors are suitable for surface and bulk measurements,
respectively [
4].
To improve the measurement accuracy and quality,
a method for sensitivity enhancement of SPRs was
proposed by Lahav et al. [
5]. A thin dielectric layer
with a high value of the real part of the dielectric
function was coated above the SPR structure. The
method was demonstrated using electric field
enhancement to increase the sensitivity and the
misleading definition that the coating of dielectric
layer had no true sensitivity enhancement was re-
vised. Another method for enhancing the evanescent
field is increasing the thickness of the dielectric layer
to couple the surface plasmon wave to the waveguide
mode of the dielectric layer, which is called PWR [
6].
A PWR sensor has a narrow resonance curve,
which contributes to increasing its refractive index
resolution [
7], and large electric field penetration
depths [
8] for bulk sensing and large biomaterial
1559-128X/14/286344-07$15.00/0
© 2014 Optical Society of America
6344 APPLIED OPTICS / Vol. 53, No. 28 / 1 October 2014