Performance analysis of optical fiber surface plasmon resonance sensor in single-mode operation region

Abstract

A new approach for studying the performance of single-mode optical fiber surface plasmon resonance sensor for refractive index sensing is presented. Intensity interrogation technique is used to observe and examine the effect of changing the value of the operating wavelength, within the single-mode operation region, on sensor performance. Effect of changing metal thickness, which is a critical parameter of the sensor structure, is also investigated. The results show that the selected operating wavelength within the mentioned region plays a very important role and has a significant impact on the sensor sensitivity. As the operating wavelength increases beyond the cut-off wavelength, above which the first higher-order mode disappears, the sensitivity increases while the refractive index range, for which the sensitivity is above its half maximum value, becomes narrower. In the proposed sensor structure, for a metal thickness of 25 nm, the maximum sensitivity reaches 2554 RIU−1 for analyte refractive index of 1.439 at a wavelength of 1500 nm. This sensitivity corresponds to a resolution of order 106 RIU by assuming 1% minimum reflectivity variation. The operating wavelength should be carefully selected and changed according to the refractive index values intended to be measured to ensure high sensor sensitivity at these values. The analysis provided in this paper enables to select and change the desired range of the sensed refractive index using low cost technique by just changing the operating wavelength in the single-mode operation region.

Few-mode optical fiber surface plasmon resonance sensor with controllable range of measured refractive index

“…and 𝜃 is the angle of the incident light with respect to the normal to the core-cladding interface and can be determined as provided in [23]. The total reflectivity 𝑅 for the sensor of sensing length 𝑙 and with number of reflections 𝑚 is determined using (10) [29], 𝑅 = 𝑅′ 𝑚 (10) where 𝑚 = 𝑙/(2𝑑 1 𝑡𝑎𝑛𝜃).…”

“…This is very important since monitoring the various responses of the modes may significantly develop new sensing techniques, such as enabling simultaneous measurements of multiple parameters [1]. In the previous work [23], the performance of the fundamental linear polarized (LP01) mode in optical fiber SPR sensor has been studied for different operating wavelengths, where the study was related only to single-mode fiber. In this paper, the performance of guided modes in SPR sensor is examined for some selected few-mode fibers, which are an ideal compromise between singlemode and multimode fibers [24].…”