Investigation of Surface Plasmon Resonance (SPR) in MoS2- and WS2-Protected Titanium Side-Polished Optical Fiber as a Humidity Sensor.

Rozalina Zakaria,Muhammad Rusdi,Sulaiman Harun,Iraj Sadegh Amiri,Rosnadiya Rosli,Nur Zainuddin,Tan Leong

doi:10.3390/mi10070465

Rozalina Zakaria, Muhammad Rusdi + Show 5 more

Open Access

https://doi.org/10.3390/mi10070465

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Abstract

In this paper, we report the effects of a side-polished fiber (SPF) coated with titanium (Ti) films in different thicknesses, namely 5 nm, 13 nm, and 36 nm, protected by a thin layer of transition metal dichalcogenides (TMDCs) such as molybdenum disulfide (MoS2) and tungsten disulfide (WS2), which provide ultra-sensitive sensor-based surface plasmon resonance (SPR) covering from the visible to mid-infrared region. The SPF deposited with Ti exhibits strong evanescent field interaction with the MoS2 and WS2, and good optical absorption, hence resulting in high-sensitivity performance. Incremental increases in the thickness of the Ti layer contribute to the enhancement of the intensity of transmission with redshift and broad spectra. The findings show that the optimum thickness of Ti with 36 nm combined with MoS2 causes weak redshifts of the longitudinal localized surface plasmon resonance (LSPR) mode, while the same thickness of Ti with WS2 causes large blueshifts. The redshifts are possibly due to a reduced plasmon-coupling effect with the excitonic region of MoS2. The observed blueshifts of the LSPR peak position are possibly due to surface modification between WS2 and Ti. Changing the relative humidity from 58% to 88% only elicited a response in Ti/MoS2. Thus, MoS2 shows more sensitivity on 36-nm thickness of Ti compared with WS2. Therefore, the proposed fiber-optic sensor with integration of 2D materials is capable of measuring humidity in any environment.

Highlights

Surface plasmon resonance (SPR) is a well-known optical phenomenon that occurs on a metal-dielectric surface
Effect of transition metal dichalcogenides (TMDCs) with Different Thicknesses of Titanium We observed that no significant shifting occurred at the fixed or constant range of wavelength for a thinner layer of Ti (Figure 5a,b)
The selection of the transmission dip of different thickness in terms of surface plasmon resonance was based on the transverse mode related to the Maxwell equation

Summary

Introduction

Surface plasmon resonance (SPR) is a well-known optical phenomenon that occurs on a metal-dielectric surface. The transmission dip is formed wMihcreormeacthhineesre20fl1e9c, 1te0,d46l5ight resonates onto the surface plasmon after it passes through the SPR re4goiof n10 In this work, it was determined at the other end of the optical fiber as a function of wavelength [9]. Effect of TMDCs with Different Thicknesses of Titanium We observed that no significant shifting occurred at the fixed or constant range of wavelength for a thinner layer of Ti (Figure 5a,b). This indicates that the volume of 0.2 mL was not suitable with 5-nm and 13-nm thicknesses of Ti. In Figure 5c, the transmission dip for 36 nm of Ti layer shows a. The dip of transmission for different thickness of Ti was chosen based on the transverse mode

Effect of TMDCs with Different Thicknesses of Titanium

Findings

Conclusions