Bloch Surface Wave Sensor Research Articles

Design and optimization of Bloch surface wave sensor with high sensitivity and quality factor using LiNbO3

Design and optimization of Bloch surface wave sensor with high sensitivity and quality factor using LiNbO3

Theoretical investigation of transition metal dichalcogenides based Bloch surface wave sensors with mono and double absentee layers

In this paper, the performance of a transition metal dichalcogenides based Bloch surface wave (BSW) sensor with mono or double absentee layers is investigated. By adding mono absentee layer with high refractive index at some particular locations, the linewidth (FWHM) and the figure of merit (FOM) of the BSW sensor are improved. The BSW sensor with double absentee layers is also studied and the results indicate that FOM is further improved by using double absentee layers. In particular, the FOM of the BSW sensor with double GaAs absentee layers is up to 766.43 RIU−1, which is 5.83% higher than the one of a traditional BSW sensor without absentee layer. It is believed that the usage of absentee layers in a BSW sensor can improve its FOM, which is useful for the development of high-performance optical sensors.

Tunable Bloch surface wave constructed by two-dimensional lithium niobate grating for biosensor

In this study, a Bloch surface wave (BSW) biosensor coupled with a two-dimensional lithium niobate grating was designed. The influence of the nonlinear characteristics of lithium niobate on the BSW sensor was theoretically investigated, and the tunability of the BSW was studied using the excitation schemes of n e and n o. To confine the energy on the surface of the solution in contact with the sensor, we introduce a distributed Bragg reflector mirror (DBR) consisting of four pairs of 76% and 42% porosity porous silicon films. A layer of lithium niobate grating is deposited on top of DBR to excite Bloch surface waves(BSW) and introduce the concept of azimuth detection in the study of the tunable properties of lithium niobate. Then, the azimuth angle of the resonance peaks excited along the n e and n o directions of lithium niobate varied by approximately 5°.

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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.16\times10$ </tex-math></inline-formula> 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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8.62\times10$ </tex-math></inline-formula> −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.

Constrained optimization of transition metal dichalcogenide-based Bloch surface wave sensor using improved genetic algorithm

Constrained optimization of transition metal dichalcogenide-based Bloch surface wave sensor using improved genetic algorithm

Theoretical Model for a Highly Sensitive Near Infrared Biosensor Based on Bloch Surface Wave with Dirac Semimetal.

In this work, we present a theoretical model of a near-infrared sensitive refractive index biosensor based on the truncate 1D photonic crystal (1D PC) structure with Dirac semimetal. This highly sensitive near-infrared biosensor originates from the sharp reflectance peak caused by the excitation of Bloch surface wave (BSW) at the interface between the Dirac semimetal and 1D PC. The sensitivity of the biosensor model is sensitive to the Fermi energy of Dirac semimetal, the thickness of the truncate layer and the refractive index of the sensing medium. By optimizing the structural parameters, the maximum refractive index sensitivity of the biosensor model can surpass 17.4 × 103/RIU, which achieves a certain competitiveness compared to conventional surface plasmon resonance (SPR) or BSW sensors. Considering that bulk materials are easier to handle than two-dimensional materials in manufacturing facilities, we judge that 3D Dirac semimetal and its related devices will provide a strong competitor and alternative to graphene-based devices.

High-sensitivity Bloch surface wave sensor with Fano resonance in grating-coupled multilayer structures

A new type of device consisting of a lithium niobate film coupled with a distributed Bragg reflector (DBR) was theoretically proposed to explore and release Bloch surface waves for applications in sensing and detection. The film and grating made of lithium niobate (LiNbO3) were placed on both sides of the DBR and a concentrated electromagnetic field was formed at the film layer. By adjusting the spatial incidence angle of the incident light, two detection and analysis modes were obtained, including surface diffraction detection and guided Bloch detection. Surface diffraction detection was used to detect the gas molecule concentrations, while guided Bloch detection was applied for the concentration detection of biomolecule-modulated biological solutions. According to the drift of the Fano curve, the average sensor sensitivities from the analysis of the two modes were 1560 °/RIU and 1161 °/RIU, and the maximum detection sensitivity reached 2320 °/RIU and 2200 °/RIU, respectively. This study revealed the potential application of LiNbO3 as a tunable material when combined with DBR to construct a new type of biosensor, which offered broad application prospects in Bloch surface wave biosensors.

Excitation of Bloch surface wave using silver nanoparticles for sensitivity enhanced biosensor

A silver nanoparticles array is introduced on the top layer of all-porous-silicon refractive index sensor. Bloch surface wave (BSW) resonance is realized at the interface between air and multilayer porous silicon structure, which can be excited by different coupling schemes: the Kretschmann prism and silver nanoparticles array. In addition to sustaining the BSW mode, the silver nanoparticles add an additional degree of freedom to the phase-matching conditions. We demonstrated the sharp BSW reflectivity dip with an ultra-narrow linewidth. The performance of the designed BSW sensor is numerically calculated by the rigorous coupled wave analysis (RCWA) method under s-polarized light. The optimized silver nanoparticles coupled BSW (AgNPs-BSW) sensor has a much higher figure of merit () than conventional prism-coupled BSW sensors. The azimuthal sensitivity can reach about 703°/RIU or even higher. The proposed silver nanoparticles coupled BSW (AgNPs-BSW) sensor exhibits the capacity to eliminate the adverse effects of inhomogeneous penetration of analytes. With such excellent performance, our study demonstrates its potential applications in the field of chemical and biological sensors in the future.

High Sensitivity Intensity-Interrogated Bloch Surface Wave Biosensor With Graphene

Bloch surface wave (BSW) is a surface state excited within the truncate defect layer at the surface of a dielectric 1-D photonic crystal (1DPC), which has been suggested as an attractive alternative to surface plasmon resonance (SPR) in chemical and biological sensors. In this paper, we propose an intensity-sensitive BSW sensor based on the truncate 1DPC with graphene. By optimizing the thickness of the defect layer and the layer number of graphene, the maximum intensity sensitivity of biosensor can surpass $3.5\times 10^{4}$ /RIU, which is greater than that for the conventional BSW or SPR sensors. With such excellent and interesting performance, we believe that the structure can be useful for many important applications in the field of chemical and biological sensors in the future.

Optimizing loss of the dielectric stack for Bloch-surface-wave sensors under different interrogation schemes

For enhancing the sensitivity of the Bloch surface wave-based sensing applications, the dependency of the Bloch surface wave (BSW) resonance dip and the associated phase change on the loss of a truncated one-dimensional photonic crystal structure is numerically analyzed and studied. Furthermore, through evaluating the sensitivity of a BSW sensor based on the intensity interrogation scheme and the phase detection method, a comparison is carried out to optimize the sensing performance. The results demonstrate that the sensing sensitivity of the BSW sensor is significantly affected by the applied sensing schemes. It is shown that the optimized device loss is not the same for different sensing schemes. Relatively high phase-detection sensing sensitivity can be maintained for low-loss BSW devices, while that of the intensity interrogation scheme may drop sharply. On the other hand, the performance of intensity interrogation scheme is less affected by the higher device loss. Our result could be useful for improving the performance of the BSW sensors and selecting the appropriate sensing scheme for such devices.

Plasmonic Photonic-Crystal Slabs: Visualization of the Bloch Surface Wave Resonance for an Ultrasensitive, Robust and Reusable Optical Biosensor

A one-dimensional photonic crystal (PhC) with termination by a metal film—a plasmonic photonic-crystal slab—has been theoretically analyzed for its optical response at a variation of the dielectric permittivity of an analyte and at a condition simulating the molecular binding event. Visualization of the Bloch surface wave resonance (SWR) was done with the aid of plasmon absorption in a dielectric/metal/dielectric sandwich terminating a PhC. An SWR peak in spectra of such a plasmonic photonic crystal (PPhC) slab comprising a noble or base metal layer was shown to be sensitive to a negligible variation of refractive index of a medium adjoining to the slab. As a consequence, the considered PPhC-based optical sensors exhibited an enhanced sensitivity and a good robustness in comparison with the conventional surface-plasmon and Bloch surface wave sensors. The PPhC biosensors can be of practical importance because the metal layer is protected by a capping dielectric layer from contact with analytes and, consequently, from deterioration.

Optimization of angularly resolved Bloch surface wave biosensors.

Bloch surface wave (BSW) sensors to be used in biochemical analytics are discussed in angularly resolved detection mode and are compared to surface plasmon resonance (SPR) sensors. BSW supported at the surface of a dielectric thin film stack feature many degrees of design freedom that enable tuning of resonance properties. In order to obtain a figure of merit for such optimization, the measurement uncertainty depending on resonance width and depth is deduced from different numerical models. This yields a limit of detection which depends on the sensor's free measurement range and which is compared to a figure of merit derived previously. Stack design is illustrated for a BSW supporting thin film stack and is compared to the performance of a gold thin film for SPR sensing. Maximum sensitivity is obtained for a variety of stacks with the resonance positioned slightly above the TIR critical angle. Very narrow resonance widths of BSW sensors require sufficient sampling but are also associated with long surface wave propagation lengths as the limiting parameter for the performance of this kind of sensors.

Phase-sensitive Bloch surface wave sensor based on variable angle spectroscopic ellipsometry.

In this paper, we propose a phase-sensitive Bloch surface wave sensor based on the variable angle spectroscopic ellipsometry and numerically simulate the phase behavior of the sensor. The simulation results show that the dependence of resonant phase is step-like when BSWs are excited. In contrast to the reflectance behavior, even though losses of the dielectric layers are very small, the resonance dip in the reflectivity will be shallow while the step-like change of the reflection phase of the BSW still be remarkable. This means that phase detection is an alternative to reflectivity intensity detection for the sensing applications of the BSWs in this case. Our experimental results indicate that phase detection for the BSW sensors has the potential to achieve the higher sensitivity and the lower limit of detection.

High-sensitivity sensing based on intensity-interrogated Bloch surface wave sensors

A high-sensitivity sensing scheme based on Bloch surface wave is presented with the simple intensity interrogation configuration. The p-polarized electromagnetic surface wave is designed to be excited in a one-dimensional photonic crystal band-gap structure, and support a rather steep resonance dip, much sharper than that of the well-known surface plasmon resonance (SPR). Although the angular shift of this Bloch-surface-wave-based sensor is not as sensitive, the intensity measurement proves to be a more suitable scheme for Bloch surface wave based sensors, thanks to the sharpness of their resonance. Through detection of glycerol in water solution for different concentrations, the intensity sensitivity of our Bloch-surface-wave-based sensor significantly surpasses that of the conventional SPR-based sensors. Experimental results show that the sensor could achieve a detection limit as low as 7.5×10−7 refractive index units in a simple lab setup, which is much simpler than many of the much more complicated SPR-based platforms.

Efficiency of optical sensing by a plasmonic photonic-crystal slab

A one-dimensional photonic crystal with termination by a noble metal film—a plasmonic photonic-crystal slab—is theoretically analysed for its optical response at the variation of the dielectric permittivity of an analyte. A sharp attenuation peak associated with a ‘noble metal-visualized’ Bloch surface wave is observed due to plasmon absorption in the metal. We investigate the sensing performance of the slab and show that it is tolerant to the variation of probing conditions and the slab's structural parameters. As a consequence, the considered sensor exhibits an enhanced sensitivity and good robustness in comparison with conventional surface-plasmon and Bloch surface wave sensors.

Direct comparison of the performance of Bloch surface wave and surface plasmon polariton sensors

We report on the direct experimental comparison of the sensitivity and figure of merit of biosensors based either on surface plasmon polaritons on metal layers or on Bloch surface waves on one dimensional photonic crystals. The comparison was carried out by making use of a commercial surface plasmon resonance platform that was slightly adapted for these experiments. Although the experimental conditions are not optimized for Bloch surface waves, our experiments demonstrate that both types of biosensors show a similar figure of merit for biochips deposited on low cost molded plastic substrates. For glass substrates with better optical quality, the increased homogeneity of the photonic crystals results in the Bloch surface wave sensors outperforming the surface plasmon polariton sensors by a factor 1.7 in terms of figure of merit. Considerations on the illumination bandwidth indicate options to further increase such a factor.