A surface plasmon resonance (SPR) based graphene biosensor is presented. It consists of a graphene sheet coated above a gold thin film, which has been proposed and experimentally fabricated recently [ChemPhysChem 11, 585 (2010)]. The biosensor uses attenuated total reflection (ATR) method to detect the refractive index change near the sensor surface, which is due to the adsorption of biomolecules. Our calculations show that the proposed graphene-on-gold SPR biosensor (with L graphene layers) is (1 + 0.025 L) × γ (where γ > 1) times more sensitive than the conventional gold thin film SPR biosensor. The improved sensitivity is due to increased adsorption of biomolecules on graphene (represented by the factor γ) and the optical property of graphene.

Optical sensors are widely used for refractive index measurement in chemical, biomedical, and food processing industries. Due to specific field distribution of the resonances, optical sensors provide high sensitivity to ambient refractive index variations. The sensitivity of an optical sensor is highly dependent on material and structure of the sensor. Here, six major categories of optical refractive index sensors using plasmonic and photonic structures are reviewed: i) metal‐based propagating plasmonic eigenwave structures, ii) metal‐based localized plasmonic eigenmode structures, iii) dielectric‐based propagating photonic eigenwave structures, iv) dielectric‐based localized photonic eigenmode structures, v) advanced hybrid structures, and vi) 2D material integrated structures. Representative configurations working in the wavelength range of 400–2000 nm will be selected and compared in terms of bulk refractive index sensitivities, figures of merit, and working wavelengths. A technology map is established in order to define the standard and development trend for optical refractive index sensors.

MXene, a new class of two-dimensional nanomaterials, have drawn increasing attention as emerging materials for sensing applications. However, MXene-based surface plasmon resonance sensors remain largely unexplored. In this work, we theoretically show that the sensitivity of the surface plasmon resonance sensor can be significantly enhanced by combining two-dimensional ${\mathrm{Ti}}_3{\mathrm{C}}_2{\mathrm{T}}_x$ MXene and transition metal dichalcogenides. A high sensitivity of ${198}^{\circ }$ /RIU (refractive index unit) with a sensitivity enhancement of 41.43% was achieved in aqueous solutions (refractive index ∼1.33) with the employment of monolayer ${\mathrm{Ti}}_3{\mathrm{C}}_2{\mathrm{T}}_x$ MXene and five layers of ${\mathrm{WS}}_2$ at a 633 nm excitation wavelength. The integration of ${\mathrm{Ti}}_3{\mathrm{C}}_2{\mathrm{T}}_x$ MXene with a conventional surface plasmon resonance sensor provides a promising approach for bio- and chemical sensing, thus opening up new opportunities for highly sensitive surface plasmon resonance sensors using two-dimensional nanomaterials.

Surface plasmons allow electromagnetic fields to be confined to subwavelength scale, well beyond the classical optical diffraction limit. With continuous reduction of optical mode volume into the deep subwavelength scale, a new era of quantum plasmonics opens up that investigates the quantum behavior of surface plasmons and their interactions with matter. This emerging and exciting field creates many new opportunities in advancing the boundaries of fundamental science and applied quantum technology. This review covers recent breakthroughs from three unique and important perspectives: the fundamental quantum properties of plasmon-polaritons, plasmon-polaritons interacting with quantum emitters, and plasmon-polaritons stepping into quantum technology. A clear development map of quantum plasmonics is also established for the reader.

Controlling and channeling light emissions from unpolarized quantum dots into specific directions with chiral polarization remains a key challenge in modern photonics. Stacked metasurface designs offer a potential compact solution for chirality and directionality engineering. However, experimental observations of directional chiral radiation from resonant metasurfaces with quantum emitters remain obscure. In this paper, we present experimental observations of unidirectional chiral emission from a twisted bi-layer metasurface via multi-dimensional control, including twist angle, interlayer distance, and lateral displacement between the top and bottom layers, as enabled by doublet alignment lithography (DAL). First, maintaining alignment, the metasurface demonstrates a resonant intrinsic optical chirality with near-unity circular dichroism of 0.94 and reflectance difference of 74%, where a high circular dichroism greater than 0.9 persists across a wide range of angles from −11 to 11 degrees. Second, engineered lateral displacement induces a unidirectional chiral resonance, resulting in unidirectional chiral emission from the quantum dots deposited onto the metasurface. Our bi-layer metasurfaces offer a universal compact platform for efficient radiation manipulation over a wide angular range, promising potential applications in miniaturized lasers, grating couplers, and chiral nanoantennas.