Novel Bloch wave excitation platform based on few-layer photonic crystal deposited on D-shaped optical fiber

Enhancement of lossy mode resonance sensing properties by the introduction of an intermediate low-refractive-index layer

Devices based on the lossy mode resonance (LMR) effect have found numerous sensing applications. Herein, the enhancement of the sensing properties by the introduction of an intermediate layer between the substrate and the LMR-supporting film is discussed. Experimental results for a silicon oxide (SiO₂) layer of tuned thickness between a glass slide substrate and a thin film of titanium oxide (TiO₂) prove the possibility of significantly increasing the LMR depth and the figure of merit (FoM) for refractive index sensing applications, which is supported by a numerical analysis using the plane wave method for a one-dimensional multilayer waveguide. The application of the intermediate layer allows the introduction of a new, to the best of our knowledge, degree of freedom into the design of LMR-based sensors, resulting in improved performance for demanding fields such as chemical sensing or biosensing.

Refractometric sensitivity of Bloch surface waves: perturbation theory calculation and experimental validation

The sensitivity of one-dimensional Bloch surface wave (BSW) sensors to external refractive index variations using Kretschmann's configuration is calculated analytically by employing first-order perturbation theory for both TE and TM modes. This approach is then validated by comparison with both transfer matrix method simulations and experimental results for a chosen photonic crystal structure. Experimental sensitivities of (8.4±0.2)×10² and (8.4±0.4)×10² nm/RIU were obtained for the TE and TM BSW modes, corresponding to errors of 0.02% and 4%, respectively, when comparing with the perturbation theory approach. These results provide interesting insights into photonic crystal design for Bloch surface wave sensing by casting light into the important parameters related with sensor performance.

Bloch surface wave-atom coupling in one-dimensional photonic crystal structure

Considering efforts for hot atomic vapor-nanophotonics integration as a new paradigm in quantum optics, in this paper, we introduce 1D photonic crystal-Rb vapor cell as structure with miniaturized interaction volume. The Bloch surface wave (BSW) excited on surface of a photonic crystal as electromagnetic hosting photonic mode, and altered the optical response of Rb atoms in the vicinity of surface. Coupling of atomic states with BSW confined modes would lead to quantum interference effects and results in nonlinearities in resonant coupling of atoms with BSW. We show Bloch surface wave induced transparency is highly stable under a change of incidence angle. Our results show slight changes in transitions detuning's due to nonlinear interactions like the Casimire-Polder effect under change of localized density of optical states.

Research Advances on Fiber-Optic SPR Sensors with Temperature Self-Compensation

The fiber-optic surface plasmon resonance sensor has very promising applications in environmental monitoring, biochemical sensing, and medical diagnosis, due to the superiority of high sensitivity and novel label-free microstructure. However, the influence of ambient temperature is inevitable in practical sensing applications, and even the higher the sensitivity, the greater the influence. Therefore, how to eliminate temperature interference in the sensing process has become one of the hot issues of this research field in recent years, and some accomplishments have been achieved. This paper mainly reviews the research results on temperature self-compensating fiber-optic surface plasmon sensors. Firstly, it introduces the mechanism of a temperature self-compensating fiber-optic surface plasmon resonance sensor. Then, the latest development of temperature self-compensated sensor is reviewed from the perspective of various fiber-optic sensing structures. Finally, this paper discusses the most recent applications and development prospects of temperature self-compensated fiber-optic surface plasmon resonance sensors.

Simulation of High-Performance Surface Plasmon Resonance Sensor Based on D-Shaped Dual Channel Photonic Crystal Fiber for Temperature Sensing

This paper presents and numerically analyzes a refractive index sensor based on side-polished D-shaped two-channel photonic crystal fiber (PCF) and surface plasmon resonance (SPR). The effects of pore duty ratio, polishing depth, and thickness of a Nano-Titania sensitizing layer on sensor performance are studied, and the sensor performance is analyzed and optimized. The results show that the sensitivity of the Nano-Titania sensitized sensor can reach 3392.86 nm/RIU and temperature sensitivity of the sensor is increased to 1.320 nm/K, and the amplitude sensitivity of the unsensitized sensor can reach 376.76 RIU^-1. In addition, the influence of titanium dioxide layer on the mode field diameter of PCF fiber core is also studied. It is found out that the sensor with a 50 nm thick titanium dioxide film has a larger mode fiber diameter, and is more conducive to coupling with single-mode fiber. Our detailed results contribute to the understanding of SPR phenomena in hexagonal PCF and facilitate the implementation and application of SPR-PCF sensors.

Optical pulling and pushing forces via Bloch surface waves

For flexible tailoring of optical forces, as well as for extraordinary optomechanical effects, additional degrees of freedom should be introduced into a system. Here, we demonstrate that photonic crystals are a versatile platform for optical manipulation due to both Bloch surface waves (BSWs) and the complex character of the reflection coefficient paving a way for controlled optomechanical interactions. We demonstrate enhanced pulling and pushing transversal optical forces acting on a single dipolar bead above a one-dimensional photonic crystal due to directional excitation of BSWs. Our results demonstrate angle- or wavelength-assisted switching between BSW-induced optical pulling and pushing forces. Easy to fabricate for any desired spectral range, photonic crystals are shown to be prospective for precise optical sorting of nanoparticles, which are difficult to sort with conventional optomechanical methods. Our approach opens opportunities for novel, to the best of our knowledge, optical manipulation schemes and platforms, and enhanced light-matter interaction in optical trapping setups.

Pulse modulation by Bloch surface wave excitation

Considering dielectric multilayers with N identical bilayers and an additional terminating layer, we address the effect of Bloch surface wave excitation on the temporal characteristics of short optical pulses. When such a resonant excitation occurs within the spectrum of the incident pulse, the reflected pulse splits into leading and trailing parts, the latter having an exponentially decaying tail. The role of the number of bilayers and the level of absorption in the multilayer stack is illustrated.

Figure of Merit Comparison Between Surface Plasmon Resonance and Bloch Surface Waves

The sensing performance of two types of electromagnetic surface waves are compared, a Surface Plasmon Polariton, where a gold thin film is used, being a standard material in biosensing applications; and a Bloch Surface Wave, using a photonic crystal made of a stack of silica and titanium dioxide layers. It is verified that the sensing performance (as measured by the Figure of Merit) of the gold film is higher, even though the Bloch Surface Waves can serve specific applications due to its narrow bandwidth. At the same time, it is concluded that further research must be made in order to choose the right set of parameters that maximize the Bloch Surface Wave performance.

Sensitivity Enhanced Refractive Index Fiber Sensor Based on Long-Range Surface Plasmon Resonance in SiO2-Au-TiO2 Heterostructure

Long-range surface plasmon resonance (LRSPR), generated from a coupled plasmon polariton in a thin metal slab sandwiched by two dielectrics, has attracted more and more attention due to its merits, such as longer propagation and deeper penetration than conventional single-interface surface plasmon resonance. Many useful applications related to light–medium interaction have been demonstrated based on the LRSPR effect, especially in the sensing area. Here, we propose and demonstrate an LRSPR-based refractive index sensor by using a SiO2-Au-TiO2 heterostructure, in which a D-shaped honeycomb-microstructure optical fiber (MOF) is designed as the silica substrate and then deposited with a gold film and thin-layer titanium dioxide (TiO2). By using the full-vector finite-element method (FEM), this heterostructure is numerically investigated and demonstrated to excite LRSPR without a buffer layer, which is usually necessary in previous LRSPR devices. Through comprehensive discussion about the influence of structural parameters on the resonant wavelength, the excitation of the LRSPR in the proposed heterostructure is revealed to be highly related to the effective refractive index of MOF’s fundamental core mode, which is mainly determined by the MOF’s pitch, the thicknesses of the silica web and the planar-layer silica. Moreover, the thin-layer TiO2 plays an important role in significantly enhancing the resonance and the sensitivity to analyte’s refractive index as well, when it is coated on the top of the Au film rather than between the metal and waveguide. Finally, the proposed LRSPR sensor based on SiO2-Au-TiO2 heterostructure shows an ultra-high wavelength sensitivity of 20,100 nm/RIU and the corresponding minimum resolution is as low as 4.98×10−7 RIU. Thus, the proposed LRSPR device offers considerable potential for sensing applications in biomedical and biochemical areas.