Gryga Michal, Ciprian Dalibor, Hlubina Petr
Department of Physics, Technical University Ostrava, 17. listopadu 2172/15, 708 00 Ostrava-Poruba, Czech Republic.
Sensors (Basel). 2020 Sep 8;20(18):5119. doi: 10.3390/s20185119.
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 -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 - and -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 %RH-1, while BSWR based measurements have FOMs as high as 3.0 × 10-3 %RH-1 and 1.1 × 10 %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.
我们报告了一种利用表面等离子体共振（SPR）和布洛赫表面波共振（BSWR）对潮湿空气相对湿度（RH）进行高灵敏度测量的方法。当采用波长询问法时，两种共振在Kretschmann配置中都能分辨出来。对于SF10/Cr/Au的多层等离子体结构可观察到SPR，而对于由四层TiO2/SiO2双层和一层粗糙TiO2终端层组成的多层介质结构（MDS）可分辨出BSWR。SPR效应表现为p偏振波反射率的下降，并且发现该下降随RH的变化而移动，或者等效地随潮湿空气折射率的变化而移动，灵敏度范围为0.042 - 0.072 nm/%RH。BSWR效应表现为s偏振波和p偏振波光谱干涉反射率的下降，这是一种以最大深度分辨共振的有效方法。对于所研究的MDS，BSWR在两个带隙内被分辨出来，对于潮湿空气，我们分别获得了0.021 - 0.038 nm/%RH和0.046 - 0.065 nm/%RH的灵敏度。我们还发现基于SPR的RH测量的品质因数（FOM）高达4.7×10 %RH-1，而基于BSWR的测量的FOM分别高达3.0×10-3 %RH-1和1.1×10 %RH-1。基于光谱干涉测量获得的结果表明，采用现有MDS的基于BSWR的传感器与基于SPR的传感器具有相似的灵敏度，但在FOM方面优于SPR传感器。因此，采用电介质的基于BSW的传感器是一种有效的替代方案，具有许多优点，包括比SPR传感中使用的金属膜具有更好的机械和化学稳定性。
