M. Jagadeeswar Goud, Yesudasu Vasimalla, Bhishma Karki, Santosh Kumar
Advanced biosensors utilizing Surface Plasmon Resonance (SPR) are becoming powerful label-free optical sensing platforms for the real-time detection of biochemical interactions owing to their incredibly high sensitivity toward refractive index (RI) changes. Conventional metal-based SPR sensors typically suffer from optical losses, large resonance curves, and degraded detection sensitivity. The combination of widespread advances in high-RI dielectric materials and two-dimensional (2D) nanomaterials has greatly contributed to the improvement of SPR sensor performance, as a result of improved electromagnetic field confinement, enhanced biomolecular interactions, and higher overall sensing efficiency. This review summarizes the progress in dielectric- and 2D material-based SPR biosensors for both applications: ultrasensitive RI sensing and diverse biomedical, environmental, and chemical sensing. The basic concept of SPR, sensing performance indicators, and the nature of dielectric and 2D materials, multilayer devices, and theoretical modelling strategies are reviewed in detail. Moreover, the enhancement of RI sensing and biomarker detection is presented recently to analyze their benefits and obstacles experienced by different material platforms. Lastly, we gather the ongoing challenges in material stability, fabrication complexity, and clinical translation, along with the advent of new opportunities such as artificial intelligence-assisted sensor optimization, portable sensing systems, and next-generation hybrid plasmonic platforms. A holistic overview through this review will motivate researchers to develop cutting-edge SPR biosensors in the near future for advanced label-free detection applications.
An optimized dual-tunable terahertz (THz) absorber based on a graphene-ZnO-VO 2 hybrid architecture is proposed for tunable absorption, switching, and refractive-index sensing applications. The absorber consists of a connected four-cut graphene resonator integrated with a ZnO dielectric spacer and a VO 2 ground layer, enabling the dynamic control of the absorption response through both graphene chemical-potential modulation and VO 2 conductivity variation. The resonator geometry, dielectric thickness, and graphene relaxation time were systematically optimized to maximize the absorption efficiency and electromagnetic confinement. The optimized absorber exhibited four near-unity absorption resonances at 0.34, 5.14, 10.11, and 15.27 THz. Under metallic-state VO 2 conditions, strong localized electric-field, magnetic-field, and power-loss distributions confirm efficient electromagnetic energy trapping and resonance formation. By varying the VO 2 conductivity from 10 to 1 × 10 5 S/m, reversible broadband-narrowband switching behavior was achieved, while graphene chemical-potential tuning from 0.1 to 1.0 eV provided active spectral reconfigurability with a maximum tunability factor of 152.2% and modulation depth of 74.26%. The absorber also demonstrated polarization-insensitive performance and stable absorption characteristics up to an incidence angle of approximately 80°. Refractive-index sensing analysis over the range n = 1.0–2.0 reveals systematic resonance-frequency red shifts with a maximum sensitivity of 1.03 THz/RIU, a figure of merit of 0.26 RIU −1, and a Q-factor of 3.83 at the 15.27 THz resonance. The combination of quad-band absorption, dual tunability, broadband-narrowband switching, angular stability, and refractive-index sensing establishes the proposed graphene-ZnO-VO 2 absorber as a promising platform for terahertz sensing, biochemical detection, optical filtering, modulation, imaging, and reconfigurable-photonic applications. The present study is based entirely on full-wave numerical simulation; experimental fabrication and characterization are proposed as future work to validate these predicted results.
Silicon-based subwavelength gratings (SWG) have become important building blocks in integrated photonics because their engineered effective refractive index enables precise tailoring of optical confinement, dispersion, polarization, and light–matter interaction. However, significant challenges remain in the development of SWGs, limiting their cross-disciplinary applications, commercialization, and large-scale manufacturing. Unlike previous reviews focused primarily on SWG physics and device performance, this article examines the pathway from laboratory demonstration to scalable manufacturing and commercialization. We connect the physical sensitivities of SWG structures with experimental validation, design-for-manufacturability, process monitoring, photonic design kit development, testing, and packaging. We also propose a minimum reporting set and present roadmaps for benchmarking, foundry qualification, design automation, and commercial deployment. This review identifies the developments needed to transform SWGs from individually optimized research devices into reproducible and manufacturable photonic components.
Yixv Zhao, Lianghua Wen, Guochun Liu, Zhengcong Du, Jiaxun Li, Can Li
Adaptive optics (AO) is the key technology to correct wavefront aberrations. An adaptive optics system is composed of a wavefront sensor, a controller, and a wavefront corrector. Deformable mirror (DM) is the most popular wavefront corrector, which determines the effect of wavefront correction in some way. There are various driving methods for DMs, such as electrostatic forces, piezoelectric driving, and electromagnetic forces. The piezoelectric driving is the most common compelling method for DMs. The actuator made of traditional piezoelectric stack-driven has the advantages such as a large driving distance and high reliability. However, they are not suitable for low-cost AO systems. A design of potentially low-cost DM is proposed in this paper. The models of DMs are constructed, which are driven by unimorph piezoelectric actuator arrays with 19, 37, and 61 units. Then all kinds of parameters are obtained by using the finite element method. The simulations about wavefront aberrations fitting and the parameter optimizations are conducted. The results show that the DM with 19-actuators has moderate correction capability for the first 9 Zernike polynomial aberrations, the DM with 37-actuators exhibits favorable correction performance for the first 14 Zernike polynomial aberrations, and the DM with 61-actuators achieves optimal correction for the first 20 Zernike polynomial aberrations. In addition, the fundamental resonant frequencies of the DMs are 1.5 kHz, 2.7 kHz, and 5.5 kHz, respectively.
Michal Hausner, Martin Feiler, Martin Ziman, Ľuboš Podlucký, Soňa Kováčová, Jaroslav Kováč
Silicon oxynitride (SiON) is a highly adaptable material platform for photonic integrated circuits owing to its refractive index tunability and full CMOS compatibility. In this work, an integrated surface plasmon resonance (SPR) sensor based on a robust SiON rib waveguide is demonstrated. The sensor geometry and modal properties were optimized using two-dimensional finite element method (FEM) simulations. The sensor performance was evaluated by direct edge coupling within the 550–915 nm spectral range. The influence of the plasmonic layer was first investigated by tracking the resonance dip for gold thicknesses of 20–40 nm with dimethyl sulfoxide (DMSO, n = 1.47) as the analyte. The response was then simulated matching approximately volumetric water-isopropyl alcohol (IPA) mixtures (n = 1.33–1.38), yielding an averaged sensitivity of 158 nm/RIU changing from 80 (water) up to 350 (IPA) nm/RIU that increases with the analyte refractive index. The results confirm that matching the SiON core refractive index to the target analyte enhances the evanescent coupling and thereby the sensitivity. The combination of index tunability, robust architecture, and simple CMOS-compatible fabrication makes the presented platform a versatile candidate for lab-on-a-chip sensing.
