ACS Photonics最新文献

Single-photon emitters (SPEs) are essential for the advancement of quantum computing and information processing but face significant challenges. Current defect-based SPEs experience spectral diffusion and reduced photoluminescence efficiency due to electrons transitioning through dark states without photon emission. Additionally, these SPEs are highly sensitive to environmental fluctuations, affecting qubit stability. This study introduces a convenient optical coexcitation scheme to mitigate these issues in the SPE hosted in hexagonal boron nitride. This scheme repumps electrons from the metastable state to an intermediate state, enhancing their transition back to the excited state. This process significantly improves zero-phonon line emission while reducing phonon sideband intensity. Moreover, the coexcitation scheme increases tolerance to magnetic field and temperature variations. Long-duration photon count measurements demonstrate improved robustness of the SPE under this scheme. Overall, this research presents a simple strategy that enhances photon emission and stabilizes SPE performance against environmental disturbances, marking a notable advancement in quantum computing.

We designed and fabricated the first bifocal meta-lens with a high-quality AlN buffer on a sapphire substrate. According to the ellipsometry measurement, the refractive index of AlN is above 2.2, and the extinction coefficient is below 0.002 in the whole ultraviolet (UV) spectral region. The meta-atom library consists of nanofins with near-unity half-wavelength plate efficiency with a full 2π coverage in the effective propagation phase of the converted spin. Two independent lens profiles for right-circularly polarized (RCP) and left-circularly polarized (LCP) spins are constructed within a single closely packed metasurface by simultaneous modulation of the geometric phase and the effective propagation phase of the converted spin. The fabricated 100 μm × 100 μm bifocal meta-lens showed a ∼1.3 μm full width at half-maximum at both foci at 365 nm, which is close to the theoretical prediction. When the incident light is pure LCP or RCP spin, the signal-to-noise ratio between the two foci is above 40. The bifocal meta-lens can be applied to spin demultiplexing in proximity and space-division multiplexing in the UV spectral region.

This work introduces an enhanced terahertz (THz) imaging system based on a homodyne detection scheme with integrated resonant C-shaped complementary split-ring resonator metalenses, specifically designed for 253 GHz frequency to address the imaging challenges posed by low-absorbing dielectric materials. The system provides significant improvements over conventional direct imaging techniques, offering simultaneous imaging in both transmission and reflection geometries, thus enabling a comprehensive evaluation of the relative absorption properties. The integration of complementary split-ring resonator metalenses allows for subwavelength resolution, enhancing image contrast and delivering over twice the dynamic range of 68 dB for homodyne and 30 dB for direct imaging. The performance of the proposed imaging system based on a homodyne detection scheme is compared with the hyperspectral THz time-domain spectroscopy, and its superiority over the conventional direct THz imaging technique is revealed.

Liquid crystal (LC) lenses are widely used in augmented reality (AR) and virtual reality (VR) due to their high optical efficiency, lightweight, ease of fabrication, and electrically adjustable. To meet the demand for miniaturization and reduce the complexity of the optical system, an off-axis focusing lens, like a polarization volume lens (PVL), which realizes the light converging and beam steering with one structure, is proposed. However, the polarization dependence of LC devices greatly reduces the optical efficiency and restricts their application. A polarization-independent volume lens (PIVL) based on cholesteric liquid crystal (CLC) templates is proposed to realize polarization-independent of off-axis focusing. It integrates the right-handed CLC and left-handed CLC into a single layer with double photo alignment patterns. The PIVL greatly increases the optical efficiency with low polarization-dependent diffraction. The PIVL may be used not only in AR and VR displays but also in imaging and optical communication systems.

Halide perovskites such as methylammonium lead bromide (MAPbBr₃) host tightly bound three-dimensional excitons that are robust at room temperature. The excellent optical properties of MAPbBr₃ allow the design of optical single-mode waveguides and cavities in the frequency range close to excitonic transitions. Taken together, these results indicate that MAPbBr₃ is an excellent platform for probing exciton–polariton nonlinear phenomena at room temperature. Here, we investigate the ultrafast nonequilibrium dynamics of polaritons under nonresonant femtosecond-pulsed excitation. We demonstrate the presence of a stimulated acoustic phonon-assisted scattering regime above the threshold pump fluence, characterized by the explosive growth of emission intensity, a redshift of the emission spectral maximum, spectral narrowing, and subpicosecond emission dynamics. Our theoretical findings are confirmed by experimental measurements.