Orthogonal-Sided Polished Microstructured Optical Fiber-Based SPR Sensor for Simultaneous Measurement of Temperature and Refractive Index

Abstract

We propose a concept of orthogonal-side polished microstructured optical fiber (MOF)-based surface plasmon resonance (SPR) sensor to implement the simultaneous sensing for two parameters. Two feasible structures, L-shaped MOF based and rectangular MOF based SPR sensors are investigated theoretically, which can support x-and y-polarized resonance peaks that can be used to measure and separate variations of the temperature and refractive index (RI). Our results show that the temperature coefficients (K Tx and K Ty ) are 8 pm/°C and 6 pm/°C, and the RI coefficients (K nx and K ny ) are 1470 nm/RIU and 1570 nm/RIU, for the L-shaped MOF-SPR sensor, while the K Tx and the K Ty are 10 pm/°C and 8 pm/°C, the K nx and K ny are 1460 nm/RIU and 1500 nm/RIU, for the rectangular MOF-based SPR sensor. Moreover, these coefficients can be further improved by choosing the appropriate structure parameters. The proposed SPR sensors with the advantages of simultaneously measuring two parameters and no need to be filled with the sensing media are expected to be more competitive in the MOF-based SPR sensor field.

Simulations of surface plasmon resonance sensor based on v-shaped microstructured optical fiber for temperature and refractive index sensing

“…In general, the gold layer thickness (m) can influence the coupling between the core mode and the plasmon mode, and thereby affecting the sensing performance 8 , 14 , 16 , 17 , 20 , 21 , 24 , 26 , 30 , 36 Figure 4. shows the effect of the m on the x- and y-polarized loss spectra of core modes of the sensor at T=25°C and n=1.34.…”

“…The polishing depths of the optical fiber are h1=1.2 and h2=1.3Λ, respectively. Compared with the double-sided polished structure that requires metal coating on two independently polished sides, 12 , 17 , 26 , 30 in this design, the gold is coated on the entire surface of the v-shaped part, which is expected to ensure the metal coating more uniform and operating more simply in sensor fabrication. The fiber material is assumed to be Silica and its RI (nsi) is determined by the Sellmeier equation 31 , 32 nsi2(λ,T)=(1.31552+0.690754×10−5T)+(0.788404+0.235835×10−4T)λ2λ2−(0.0110199+0.584758×10−6T)+(0.91316+0.548368×10−6T)λ2λ2−100,where λ is the wavelength in microns and …”

“…In general, the gold layer thickness (m) can influence the coupling between the core mode and the plasmon mode, and thereby affecting the sensing performance. 8,14,16,17,20,21,24,26,30,36 Figure 4 shows the effect of the m on the x-and y-polarized loss spectra of core modes of the sensor at T ¼ 25°C and n ¼ 1.34. As can be seen, the resonance peaks shift towards a longer wavelength and the peak loss decreases gradually as the m increases.…”