We report on a one-dimensional photonic crystal (1DPhC) represented by a multilayer structure used for a surface plasmon-like sensing based on Bloch surface waves and radiation modes employing a structure comprising a glass substrate and four bilayers of TiO 2 /SiO 2 with a termination layer of TiO 2. We model the reflectance responses in the Kretschmann configuration with a coupling prism made of BK7 glass and express the reflectances for both (s and p) polarizations in the spectral domain for various angles of incidence to show that a sharp dip associated with the Bloch surface wave (BSW) excitation is obtained in p polarization when an external medium (analyte) is air. For s-polarized wave BSW is not excited and a shallow dip associated with the guided mode excitation is obtained for a liquid analyte (water). For decreasing angle of incidence, the dip depth is substantially increased, and resonance thus obtained is comparable in magnitude with resonance commonly exhibited by SPR-based sensors. In addition, we revealed that the resonances in s-polarization are obtained for other analytes. The surface plasmon-like sensing concept was verified experimentally in the Kretschmann configuration for the guided mode transformed into the radiation mode with a negative and constant sensitivity of −169 nm/RIU, and a detection limit of 5.9 ×10 −5 RIU.

We report on a highly sensitive measurement of the relative humidity (RH) of moist air using both the surface plasmon resonance (SPR) and Bloch surface wave resonance (BSWR). Both resonances are resolved in the Kretschmann configuration when the wavelength interrogation method is utilized. The SPR is revealed for a multilayer plasmonic structure of SF10/Cr/Au, while the BSWR is resolved for a multilayer dielectric structure (MDS) comprising four bilayers of TiO2/SiO2 with a rough termination layer of TiO2. The SPR effect is manifested by a dip in the reflectance of a p-polarized wave, and a shift of the dip with the change in the RH, or equivalently with the change in the refractive index of moist air is revealed, giving a sensitivity in a range of 0.042–0.072 nm/%RH. The BSWR effect is manifested by a dip in the reflectance of the spectral interference of s- and p-polarized waves, which represents an effective approach in resolving the resonance with maximum depth. For the MDS under study, the BSWRs were resolved within two band gaps, and for moist air we obtained sensitivities of 0.021–0.038 nm/%RH and 0.046–0.065 nm/%RH, respectively. We also revealed that the SPR based RH measurement is with the figure of merit (FOM) up to 4.7 × 10−4 %RH−1, while BSWR based measurements have FOMs as high as 3.0 × 10−3 %RH−1 and 1.1 × 10−3 %RH−1, respectively. The obtained spectral interferometry based results demonstrate that the BSWR based sensor employing the available MDS has a similar sensitivity as the SPR based sensor, but outperforms it in the FOM. BSW based sensors employing dielectrics thus represent an effective alternative with a number of advantages, including better mechanical and chemical stability than metal films used in SPR sensing.

Sensing abilities of a one-dimensional photonic crystal (1DPhC) represented by a multilayer dielectric structure are analyzed theoretically and experimentally, using a new wavelength interrogation interference method. The structure comprising a glass substrate and six bilayers of TiO2/SiO2 with a termination layer of TiO2 is employed in both gas sensing based on the Bloch surface wave (BSW) resonance and liquid analyte sensing based on a self-referenced guide-mode resonance (GMR). We model the spectral interference reflectance responses in the Kretschmann configuration with a coupling prism made of BK7 glass and show that a sharp dip with maximum depth associated with the BSW excitation is red-shifted as the refractive index (RI) changes in a range of 1–1.005. Thus, a sensitivity of 1456 nm per RI unit (RIU) and figure of merit (FOM) of 91 RIU−1 are reached. Similarly, we model the responses for aqueous solutions of ethanol to show that dips of maximum depth are associated with the GMRs, and the highest sensitivity and FOM reached are 751 nm/RIU and 25 RIU−1, respectively. Moreover, we show that one of the dips is with the smallest shift as the RI changes, and hence it can be used as a reference. The theoretical results are confirmed by the experimental ones when the BSW resonance is used in sensing of humid air with a sensitivity of 0.027 nm/%relative humidity (RH) and FOM of 1.4×10−3 %RH−1. Similarly, the GMR is used in sensing of aqueous solutions of ethanol, and the highest sensitivity and FOM reached 682 nm/RIU and 23 RIU−1, respectively. The reference dip is also resolved and this self-reference makes the measurement more accurate and repeatable, and less sensitive to optomechanical drifts.

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We report on a new, to the best of our knowledge, sensing concept based on Bloch surface waves (BSWs) and wavelength interrogation that utilizes the interference of s - and p -polarized waves from a one-dimensional photonic crystal (1DPhC), represented by a multilayer structure comprising a glass substrate and four bilayers of T i O 2 / S i O 2 with a termination layer of T i O 2 . We show that when a standard approach based on measurement of the reflectance of a p - or s -polarized wave in the Kretschmann configuration fails to confirm the excitation of the BSW, a new approach is successful. We demonstrate that the BSW excitation shows up as a dip with maximum depth, and resonance thus obtained is comparable in magnitude with resonance commonly exhibited by surface plasmon resonance (SPR). The new sensing concept is verified experimentally for ethanol vapors. The BSW resonances are resolved within two band gaps of the 1DPhC with sensitivities of 3272 nm/RIU and 1403 nm/RIU, and figures of merit of 43.7 R I U − 1 and 173.2 R I U − 1 , respectively. This research, to the best of the authors’ knowledge, is the first demonstration of a new SPR-like response that can be utilized in a wide range of sensing applications.