In this work, we propose and numerically investigate a two‐dimensional microlaser based on the concept of bound states in the continuum (BIC). The device consists of a thin gain layer (Rhodamine 6G dye‐doped silica) sandwiched between two high‐contrast‐grating layers. The structure supports various BIC modes upon a proper choice of topological parameters; in particular it supports a high‐ Q quasi‐BIC mode when partially breaking a bound state in the continuum at Γ point. The optically‐pumped gain medium provides sufficient optical gain to compensate the quasi‐BIC mode losses, enabling lasing with ultra‐low pump threshold (fluence of 17 μJ/cm ² ) and very narrow optical linewidth in the visible range. This innovative device displays distinguished sensing performance for gas detection, and the emission wavelength sensitively shifts to the longer wavelength with the changing of environment refractive index (in order of 5 × 10 ⁻⁴ ). The achieved bulk sensitivity is 221 nm/RIU with a high signal to noise ratio, and a record‐high figure of merit reaches to 4420 RIU ⁻¹ . This ultracompact and low threshold quasi‐BIC laser facilitated by the ultra‐narrow resonance can serve as formidable candidate for on‐chip gas sensor.

A planar periodic leaky-wave antenna (PLWA) with continuous backward-to-forward beam-scanning capability and consistent gain is presented. The PLWA is made of a new type of periodically arranging meander line structures, in which the capacitive coupling between neighboring units plays the key role in achieving a high scanning rate. In detail, the beam-scanning rate of the proposed PLWA is efficiently tuned by varying the gap between two adjacent units, without considerably changing the working frequency band. To mitigate the open stopband (OSB) and to improve the impedance matching, several inductive open stubs are introduced into a single meander line unit cell to enhance the radiation. In the experiment, a prototype of the proposed PLWA was fabricated and measured. The simulated and measured beams show good agreement in terms of scanning range and radiation performance. A continuous beam scanning from -60° to +58° through broadside in the frequency band of 5.95-7.1 GHz is observed, and hence, a 102.6°/GHz scanning rate is realized in practice. Besides, the PLWA shows an average gain level of 11.96 dBi with a variation lower than 2 dB and a sidelobe below -10 dB at all the measured frequencies. The proposed PLWA may have potential applications in radar, microwave imaging, and wireless communication due to its compact structure, easy to fabricate, and dispersionless performance.

Distinct types of luminescence that are activated by various stimuli in a single material offer exciting developmental opportunities for functional materials. A versatile sensing platform that exhibits photoluminescence (PL), persistent luminescence (PersL), and mechanoluminescence (ML) is introduced, which enables the sensitive detection of temperature, pressure, and force/stress. The developed Sr₂MgSi₂O₇:Eu²⁺/Dy³⁺ material exhibits a linear relationship between ML intensity and force and can be used as an ML stress sensor. Additionally, the bandwidth of the PL emission band and the PL lifetime of this material are remarkably sensitive to temperature, with values of ≈0.05 nm K⁻¹ and 1.29%/K, respectively. This study demonstrates PersL pressure sensing for the first time, using long‐lasting (seconds) lifetime as a manometric parameter. The developed material functions as an exceptionally sensitive triple‐mode visual pressure sensor; specifically, it exhibits: i) a sensitivity of ≈−297.4 cm GPa⁻¹ (8.11 nm GPa⁻¹) in bandshift mode, ii) a sensitivity of ≈272.7 cm⁻¹/GPa (14.8 nm GPa⁻¹) in bandwidth mode, and iii) a sensitivity of 42%GPa⁻¹ in PL‐lifetime mode, which is the highest value reported to date. Notably, anti‐counterfeiting, night‐vision safety‐sign, 8‐bit optical‐coding, and QR‐code applications that exhibit intense PersL are demonstrated by 3D‐printing the studied material in combination with a polymer.

Light carries spin angular momentum, which, in the free space, is aligned to the direction of propagation and leads to intriguing spin Hall phenomena at an interface. Recently, it was shown that a transverse-spin (T-spin) state could exist for surface waves at an interface or for bulk waves inside a judiciously engineered metamaterial, with the spin oriented perpendicular to the propagation direction. Here, we demonstrate the spin Hall effect for transversely spinning light—a T-spin–induced beam shift at the interface of a metamaterial. It is found that the beam shift takes place in the plane of incidence, in contrast to the well-known Imbert-Fedorov shifts. The observed T-spin–induced beam shift is of geometrodynamical nature, which can be rendered positive or negative controlled by the orientation of T-spin of the photons. The unconventional spin Hall effect of light found here provides a previously unexplored mechanism for manipulating light-matter interactions at interfaces.