ACS Photonics最新文献

In this work, we demonstrated the first ultraviolet (UV) superluminescent diodes (SLDs) with AlGaN/GaN-based multiple quantum wells (MQWs), emitting at 360 nm. The UV SLD samples were grown on the c-plane sapphire substrates using molecular beam epitaxy (MBE) and were processed into ridge waveguides with inclined facets. The epitaxial structure exhibits excellent crystalline quality with low dislocation density. Optical mode simulations reveal strong confinement within the QWs, with a confinement factor of 3.2%. Moreover, the fabricated UV SLDs achieve a maximum optical power of 8 mW and an external quantum efficiency (EQE) of 7.6% at a current density of 3.5 kA/cm². These results represent a significant advancement in III-nitride light-emitting devices, paving the way for UV superluminescent light sources for applications such as UV optical communications, photolithography, and medical imaging.

Self-assembled supraparticles (SPs) of colloidal semiconductor nanocrystals act as solution-processable microlasers, where optical gain couples to whispering-gallery modes supported by the microspherical cavity. Here, multicolor lasing is demonstrated from SPs composed of standard-size (5.5–6.5 nm), graded thin-shell CdS_xSe_1–x/ZnS quantum dots (QDs) by exploiting their electronic transitions. While lasing from higher-order states typically requires engineered thick-shell QDs, we achieve this using conventional thin-shell QDs through composite SPs that integrate two QD populations: one with an absorption edge above the pump wavelength (625 nm) and another with an edge near (540 nm) or below (450 nm) the pump (532 nm). At low pump fluence, lasing occurs in the red region (2.00–2.04 eV) from 1S transitions. With increased fluence, lasing shifts to the yellow region (2.14–2.18 eV), arising from 1P transitions. This fluence-controlled red-to-yellow shift establishes composite SPs as a versatile platform for tunable, multicolor microlasers based on standard-sized QDs.

Semiconductor radiation detectors are essential in high-energy physics, nuclear physics, and photonics. While conventional silicon detectors are constrained in high-energy X-ray detection by their low atomic number, emerging perovskite detectors face limitations in high-frequency signal detection due to low carrier mobility. Here, we introduce a perovskite-sensitized silicon detector with a tunnel oxide passivated contact (TOPCON) structure that merges the wide-energy-range X-ray detection efficiency of perovskites with the high carrier mobility and effective passivation of silicon TOPCON. The perovskite layer reverses the energy-dependent sensitivity of silicon from decreasing to increasing in the 40 – 80 kV_p range. Moreover, the TOPCON design reduces the dark current density to 797.4 nA cm^–2 at 100 V (from 1.4 μA cm^–2) and shortens rise and fall times to 1.4 and 1.3 ms under 80 kV_p X-rays. Most importantly, the device demonstrates the first polycrystalline perovskite-based α-particle spectroscopy (²⁴¹Am, 5.49 MeV) with 4.1% energy resolution and a response time of ∼250 ns, thereby challenging the conventional requirement for high-quality single crystals in such measurements.

Recent advancements in near-infrared (NIR) spectroscopy have significantly contributed to the field of biomedical imaging and diagnosis, highlighting the critical importance of near-infrared detection. In this work, we report on the successful implementation of high-performance NIR detection based on the lateral photovoltaic effect (LPE) in a graphene/porous silicon (PS)/Si structure. The detector achieves exceptional linearity and active area at a modest penalty in sensitivity, mitigating the conventional trade-off between sensitivity and active area. The enhanced performance is attributed to a synergistic combination of factors within the unique architecture, including improved NIR absorption of porosity, superior carrier mobility of graphene, and carrier dynamics based on dual-junction regulation at the interfaces of graphene/PS and PS/Si. Building on these characteristics, the device transcends the typical constraints of LPE-based detectors, namely restricted active area and inefficient energy utilization. The study advances the development of the LPE in NIR detection, holding great promise for routes toward scalable and high-quality position-sensitive detectors.

Addressing the substantial energy consumption from building heating and cooling is critical for climate change mitigation. Passive daytime radiative cooling (PDRC) offers a highly promising zero-energy strategy to mitigate global warming; however, it encounters several key limitations, including susceptibility to overcooling, constrained environmental adaptability, and challenges in manufacturability. Herein, we develop a trimode multicolor thermochromic canopy with distinct microsphere-rich and pore-rich zones in orthogonal polytetrafluoroethylene (PTFE) fibrous membranes. This design achieves programmable multitemperature spectral responses, including high mid-infrared emissivity (0.94) in the atmospheric transparency window, competitive near-infrared reflectance (93.7%), and visible light modulation capability of 30.44% via polychromic thermochromic microcapsules (TMs). Promisingly, our PTFE/TM composite enables three autonomous operational modes, yielding a maximum subambient daytime cooling of 7.6 °C in hot conditions, heating of 5.4 °C in cold conditions, and a stable intermediate state at comfortable temperatures. The composite also exhibited excellent durability and superhydrophobicity. EnergyPlus simulations confirm the significant global potential, showing substantial annual energy savings and CO₂ emission reductions across diverse climates, outperforming static cooling materials by effectively avoiding overcooling penalties. This work provides a viable zero-energy pathway for mitigating urban heat island effects and promoting climate-resilient building thermal regulation.

The role of slow photons in enhancing photochemical processes within photonic crystals has been widely proposed but remains experimentally elusive due to confounding effects from the intrinsic photoactivity of constituent materials. Here, we present a chemical strategy to directly probe slow photon effects using SiO₂ opal photonic crystals constructed from non-photoabsorbing and chemically inert building blocks. Our approach notably employs a chromogenic molecule as a sensitive probe whose photobleaching behavior serves as an indicator of local light intensity, enabling the direct interrogation of light–matter interactions within the photonic crystal. By tuning the photonic bandgap via controlled structural periodicity, we demonstrate that photobleaching efficiency and reaction kinetics are enhanced by up to 1.4-fold and 1.8-fold for substrate-supported and three-dimensional opals, respectively, when their photonic bandgap aligns with the molecule’s absorption band. Control experiments with disordered SiO₂ assemblies and off-resonant opals confirm that the enhancement originates from slow photon generation rather than from molecular surface adsorption or other light-scattering effects. This study provides the first chemical evidence that slow photons can amplify local optical fields and promote molecular transformations. Our findings deepen the understanding of light trapping via slow photon generation, offering valuable insights for enhancing light-to-chemical conversion in sustainable photochemistry and photocatalysis.

Tunable optical filters are essential for dynamic holography, spectral imaging, optical storage and reconfigurable displays. Yet achieving full-color coverage with continuous grayscale control remains an exceptional challenge. Phase-change materials introduce the prospect of nonvolatile optical modulation, pushing these systems beyond conventional limits. Here we present a Fabry–Pérot bandpass filter integrating dual distributed Bragg reflectors with phase change material. Electrical and laser-driven modulation of the optical constants enables narrowband filtering with high spectral selectivity, spanning the visible-to-NIR range. Structural optimization of the cavity thickness enables wide-gamut spectral coverage by design, while active phase-change control enables continuous multilevel grayscale intensity modulation. Materials screening and structural optimization enable wide-gamut color tuning and multilevel grayscale modulation. This lithography-free multilayer structure supports scalable pixel-level programming, with gradual crystallization of the phase change layers enabling multilevel encoding. We implement pixelated full-color and grayscale holography, exploiting both wavelength- and intensity-dependent responses. This compact and energy-efficient reconfigurable photonic platform provides a scalable route to dynamic photonic devices, holographic displays, optical information processing, and adaptive metasurfaces.

Brillouin scattering in optical fibers has been widely studied over the last few decades and has given rise to numerous significant applications in optical sensing, laser technology, and optical communications. However, most Brillouin studies to date have focused on the fundamental modes; explorations of Brillouin scattering involving cylindrical vector modes, which possess diverse spatial information and polarization states, and have found applications in optical trapping, particle acceleration, and laser machining, still remain limited. Here, we report Brillouin scattering (including spontaneous and stimulated cases) of cylindrical vector modes in annular-core photonic crystal fiber and show robust nonreciprocal interaction between them via Brillouin-enhanced four-wave mixing, where two distinct Brillouin interactions involving different optical modes are coherently coupled through a common acoustic wave. Extending this principle to a resonant Brillouin laser cavity, we further demonstrate coherent oscillations of both optical and acoustic modes, leading to the stable emission of cylindrically vector beams with line widths of several kHz. These results pave the way for vector-mode Brillouin photonics, opening up opportunities for narrow-line-width structured light sources, reconfigurable nonreciprocal devices, and precision metrology.

Technological advances in the fabrication of nanophotonic circuits have driven the scientific community to increasingly focus on the precise tailoring of their key optical properties, over a broadband spectral domain. In this context, modulation of the local refractive index can be exploited to customize an effective reflectivity by the use of distributed Bragg mirrors, enabling the on-chip integration of Fabry–Pérot resonators. The resulting cavity length is strongly wavelength-dependent, offering practical solutions to the growing demand for dispersion engineering. Owing to their typically high core-to-cladding refractive index contrast, III–V semiconductor platforms enable the fabrication of strong Bragg reflectors. In addition, their intrinsically high nonlinear optical coefficients make these materials particularly attractive for nonlinear optics applications. In this work, we discuss the first experimental demonstration of a systematic, shape-constrained inverse design technique that tailors a prescribed dispersion profile, showing a strong agreement between simulations and measurements. In perspective, the proposed approach offers an efficient and general response to the challenge of dispersion engineering in integrated optical circuits.