Efficient Optical Sensing Based on Phase Shift of Waves Supported by a One-Dimensional Photonic Crystal

Abstract

Interferometric methods of optical sensing based on the phase shift of the Bloch surface waves (BSWs) and guided waves (GWs) supported by a one-dimensional photonic crystal are presented. The photonic crystal, composed of six SiO2/TiO2 bilayers with a termination layer of TiO2, is employed in the Kretschmann configuration. Under resonance condition, an abrupt phase change is revealed, and the corresponding phase shift is measured by interferometric techniques applied in both the spectral and spatial domains. The spectral interferometric technique employing a birefringent quartz crystal is used to obtain interference of projections of p- and s-polarized light waves reflected from the photonic crystal. The phase shifts are retrieved by processing the spectral interferograms recorded for various values of relative humidity (RH) of air, giving the sensitivity to the RH as high as 0.029 rad/%RH and 0.012 rad/%RH for the BSW and GW, respectively. The spatial interferometric technique employs a Wollaston prism and an analyzer to generate an interference pattern, which is processed to retrieve the phase difference, and results are in good agreement with those obtained by sensing the phase shift in the spectral domain. In addition, from the derivative of the spectral phase shifts, the peak positions are obtained, and their changes with the RH give the sensitivities of 0.094 nm/%RH and 0.061 nm/%RH for the BSW and GW, respectively. These experimental results demonstrate an efficient optical sensing with a lot of applications in various research areas.

Distributed Bragg Reflectors Employed in Sensors and Filters Based on Cavity-Mode Spectral-Domain Resonances

“…1DPhC was fabricated (Meopta, Přerov, Czech Republic) by a sputtering thin film deposition technique, and exact parameters such as layer thicknesses and dispersions were provided by techniques of scanning electron microscopy (SEM) and spectral ellipsometry. An SEM image (see Figure 1 a) captured by a scanning electron microscope (Quanta 650 FEG, FEI Company, Hillsboro, OR, USA) confirmed that the 1DPhC is composed of a system of six bilayers of TiO /SiO and a termination layer of TiO demanded for BSW-based sensing applications, as presented in a previous paper [ 52 ]. The SEM image obtained for a different magnification can also be found in the same paper.…”

“…In both cases, the resonance wavelength shift versus the RH can be well fitted by linear functions so that the sensitivity to RH, defined similarly to Equation ( 6 ) as the change of the position of the dip with respect to the change in the relative humidity , reaches 0.156 nm/%RH and 0.136 nm/%RH, respectively. Thus, sensing based on the cavity-mode resonances outperforms available techniques [ 35 , 52 ] utilizing surface plasmon and Bloch waves resonances, whispering gallery, and guided mode resonances as well. Using a similar relation to Equation ( 7 ), the FOM of the RH measurement reaches 0.047 %RH and 0.036 %RH , respectively.…”

“…We have found that six bilayers of TiO /SiO ( 1, ..., 6) had thicknesses of , and 76.9 nm and , and 125 nm, respectively, and the TiO termination layer of thickness nm is has a rough layer of thickness at nm, as schematically shown in Figure 1 b. From ellipsometric data, the refractive index dispersion of a glass substrate, TiO and SiO layers were obtained, as specified in [ 52 ].…”

One-Dimensional Photonic Crystal with a Defect Layer Utilized as an Optical Filter in Narrow Linewidth LED-Based Sources

“…, 10) have thicknesses t j , as schematically shown in Figure 2; their values are specified in Table 1. The refractive index dispersion of a glass substrate and the layers of SiO 2 and TiO 2 was obtained from the ellipsometric data for a 1DPhC including the same layer materials [61]. In the case of the glass substrate, the refractive index (RI) as a function of wavelength is expressed by the Cauchy formula:…”

Lab-on-a-chip sensor based on 1DPhC resonant cavity

“…Optical applications based on 1DPhCs with cavity-mode resonances represent an effective alternative to standard ones. They can be used as planar waveguides, and the guided waves can be used in sensing applications [3]. Moreover, the Bloch surface waves (BSWs) propagating along the interface of the 1DPhC and external medium are widely used in sensing area [4,5].…”