High sensitive refractometers based on lossy mode resonances (LMRs) supported by ITO coated D-shaped optical fibers

Abstract

Tin doped indium oxide (ITO) coatings fabricated onto D-shaped optical fibers are presented as the supporting medium for Lossy Mode Resonances (LMRs) generation. The characteristic geometry of ITO-coated D-shaped optical fibers enables to observe experimentally LMRs obtained with both TM and TE polarized light (LMR(TM) and LMR(TE)). This permits to obtain a maximum transmission decay of 36 dB with a LMR spectral width of 6.9 nm, improving that obtained in previous works, where the LMRs were a combination of an LMR(TM) and an LMR(TE). Surrounding medium refractive index (SMRI) sensitivity characterization of LMR(TM) has been performed obtaining a maximum sensitivity of 8742 nm/RIU in the range 1.365-1.38 refractive index units (RIU) which overcomes that of surface plasmon resonance-based optical fiber devices presented in recent works.

Lossy Mode Resonance (LMR) Based Fiber Optic Sensors: A Review

“…Most recently, it is reported that spectral width reduction presented in [40] can be improved with D-shaped optical fibers [44]. In this work, highly sensitive LMR based ITO coated D-shaped optical fiber refractometers were presented with very narrow spectral width (6.9 nm) and high attenuation (36 dB).…”

High Sensitivity Refractive Index Sensor by D-Shaped Fibers and Titanium Dioxide Nanofilm

“…In general, a specified thin film coated onto a D-shaped fiber can generate LMR effect based on a modified Kretschmann configuration [10]. LMR phenomenon has been observed with metal oxides, such as indium tin oxide (ITO) [12], titanium oxide [13], and indium oxide [14]. Apart from this, LMR effect appears for both TM and TE polarized light, and the generation of multiple resonances without modifying the optical fiber geometry is also possible [15].…”

“…We also utilized a DC magnetron sputtering technique to deposit TiO 2 nanofilms on the polished surface of D-shaped fibers for the fabrication of liquid refractive index fiber sensors. The proposed D-shaped fiber sensor structure includes a low index upper cladding (about 3-5 m thick) between the fiber core and the TiO 2 layer that is different from an uncladded fiber structure in the literature [10][11][12]. Our fiber structure design will help in giving the D-shaped fiber good mechanical support after side-polishing.…”

Asymmetrically and symmetrically coated tapered optical fiber for sensing applications

“…The second material is ITO, with a real part of the refractive index ranging from 1.87 and 1.845 in the wavelength range analyzed, and with an imaginary part of 0.025 [11]. In Figure 2(c-d), for a 100 nm ITO SCTOF device, the HE and EH LMRs are separated from each other and they can be observed at 850 and 1400 nm.…”