Optical sensors based on lossy-mode resonances

Generation of Lossy Mode Resonances in Planar Waveguides Toward Development of Humidity Sensors

“…This idea again agrees well with what was observed with optical fibre, where tapered optical fibres with reduced diameter presented deeper resonances than standard multimode fibre [22]. According to the design rules of LMR-based sensors, the highest sensitivity is obtained with the first LMR [3,8]. However, as it was observed in the simulation, the first LMR with an ITO coating is almost undetectable, because it disappears as the deposition is being built up and the LMR moves to longer wavelengths ( Fig.…”

“…This effect can also be observed in Fig. 5, where the spectra of the second LMRTE, the second LMRTM and the transmission average value between both of them is shown, proving the overlap between both polarizations [3]. Comparing the first and the second LMR, it is also evident that the depth of the resonance for the first LMR is very small compared to the second LMR.…”

“…obtained when the real part of the thin-film permittivity is negative and higher in magnitude than both its own imaginary part and the permittivity of the material surrounding the thinfilm, whereas LMRs occur when the real part of the thin-film permittivity is positive and higher in magnitude than both its own imaginary part and the material surrounding the thin-film [3,6]. In view of the previous conditions, one would think that it is not possible to simultaneously observe both phenomena, SPR and LMR.…”

“…Some important differences between SPRs and LMRs were observed. LMRs can be excited with both transverse electric (TE) and transverse magnetic (TM) polarized light, whereas SPRs can only be obtained at TM polarization [3]. The second difference is that, unlike SPR, the position of LMRs in the optical spectrum depends directly on the coating thickness, which allows for simple tuning of the resonance wavelength [8].…”

Sensitivity enhancement of lossy mode resonance-based ethanol sensors by graphene oxide coatings

“…A shift of this resonance peak can be observed when the optical conditions of the system change, i.e., when there is a variation in the refractive index of the coating or the surrounding medium. Consequently, if a thin-film sensitive to some analyte is deposited onto a waveguide and used as resonance-supporting coating, a variation in the concentration of this analyte will produce a measurable shift of the LMR peak [5].…”