Citation: Escandell, L.;
Álvarez-Rodríguez, C.; Barreda, Á.;
Zaera, R.; García-Cámara, B.
All-Optical Nanosensor for
Displacement Detection in
Mechanical Applications.
Nanomaterials 2022, 12, 4107.
https://doi.org/10.3390/
nano12224107
Academic Editors: Deepak Kukkar,
Ki-Hyun Kim and
Antonios Kelarakis
Received: 3 October 2022
Accepted: 15 November 2022
Published: 21 November 2022
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Article
All-Optical Nanosensor for Displacement Detection
in Mechanical Applications
Lorena Escandell
1,
* , Carlos Álvarez-Rodríguez
1
, Ángela Barreda
2
, Ramón Zaera
3
and Braulio García-Cámara
1
1
Group of Displays and Photonics Applications, Carlos III University of Madrid, Avda. de la Universidad, 30,
Leganés, 28911 Madrid, Spain
2
Institute of Solid State Physics, Friedrich Schiller University Jena, Helmholtzweg 3, 07743 Jena, Germany
3
Department of Continuum Mechanics and Structural Analysis, Carlos III University of Madrid,
Avda. de la Universidad, 30, Leganés, 28911 Madrid, Spain
* Correspondence: lescande@ing.uc3m.es; Tel.: +34-9-1624-8397
Abstract:
In this paper, we propose the design of an optical system based on two parallel suspended
silicon nanowires that support a range of optical resonances that efficiently confine and scatter
light in the infrared range as the base of an all-optical displacement sensor. The effects of the
variation of the distance between the nanowires are analyzed. The simulation models are designed
by COMSOL Multiphysics software, which is based on the finite element method. The diameter of
the nanocylinders (d = 140 nm) was previously optimized to achieve resonances at the operating
wavelengths (
λ
= 1064 nm and 1310 nm). The results pointed out that a detectable change in their
resonant behavior and optical interaction was achieved. The proposed design aims to use a simple
light source using a commercial diode laser and simplify the readout systems with a high sensitivity
of 1.1
×
10
6
V/m
2
and 1.14
×
10
6
V/m
2
at 1064 nm and 1310 nm, respectively. The results may
provide an opportunity to investigate alternative designs of displacement sensors from an all-optical
approach and explore their potential use.
Keywords: optical sensor; nanowires; displacement sensor; light scattering resonances
1. Introduction
Current requirements in sensing technology are demanding further research about
their design and development to increase the sensitivity and improve the on-chip inte-
gration. In this sense, all-optical approaches and applications of silicon nanowires are
providing in recent decades promising solutions in topics such as nanoelectronics, opto-
electronics, and sensing/detection [1–3].
Micro- and more recently, nano-optoelectromechanical systems (M/NOEMS) have
been widely used to design a huge number of sensors for a large variety of applications, such
as health care, food quality control, or security [
4
–
9
]. They are mainly focused on sensing
displacement, mass [
10
], or force [
11
] as a consequence of the target phenomena such as
molecular bindings, mechanical vibrations, or external stress. As an example, MOEMS and
NOEMS are present in devices such as atomic force microscopes [
12
], accelerometers [
13
], or
biosensors [
14
]. Current trends show that optical solutions provide a better performance in
terms of sensitivity, resolution, and power consumption compared to other sensing methods
(e.g., piezoelectric or capacitive) [
15
]. In this sense, we can find in the literature many
proposed sensors based on interferometers [
16
], nanocavities [
17
], photonic crystals [
18
],
or nanocantilevers [
19
], offering quite interesting performances. However, the readout
system’s complexity and limited dynamic range or bandwidth of these proposals make it
necessary to continue searching for alternatives [20].
Due to the small signal produced by these nanostructures, resonant behaviors are
usually looked for in order to optimize the signal-to-noise ratio. Sensors based on plas-
Nanomaterials 2022, 12, 4107. https://doi.org/10.3390/nano12224107 https://www.mdpi.com/journal/nanomaterials
