The High-Sensitivity Phase Interrogation of Bloch Surface Wave Sensor Based on 1-D Photonic Crystal

The Bloch surface wave (BSW) is excited in a 1-D photonic crystal and supports a rather steep resonance dip, much sharper than that of traditional surface plasmon resonance (SPR). A highly sensitive sensor based on BSW was fabricated by electron beam evaporation, the structure was characterized by scanning electron microscopy (SEM) and ellipsometry spectrometer, and the sensitivity in wavelength and phase interrogation was achieved experimentally by an optical system based on a Mach–Zehnder interferometer. The wavelength sensitivity and the phase sensitivity can reach 219 nm/RIU and $1.16\times10$ 4 deg/RIU, respectively. After comparison, we demonstrate that the phase interrogation has a higher sensitivity than the wavelength interrogation and is more suitable for BSW sensors. Experimental results show that the detection limit of the sensor is $8.62\times10$ −7 RIU in phase interrogation, which proves that the sensor could become a valuable and promising tool to replace traditional SPR sensors for the application of ultralow concentration detection. This sensor, only composed of TiO2 and SiO2 materials, has the advantages of mechanical and chemical stability, easy fabrication, and low cost, which can be used as an alternative to traditional SPR sensors in the fields of biomedicine, chemical analysis, and environmental monitoring.