Biological strategies for manipulating light have revealed new concepts in light scattering, inspiring the design of sustainable photonic materials. While iridescent optical systems have been extensively studied, many applications require noniridescent structural colors which are much more difficult to achieve. Photonic glasses, comprising randomly arranged dielectric spheres, offer a promising solution toward such structural colors. However, their intrinsic disorder and particle size polydispersity typically lead to poor color saturation. Here, we identify two strategies employed by certain damselflies to generate unexpectedly vivid, tunable angle-independent colors from a photonic glass. First, doping of transparent pteridine nanospheres with yellow pigments strengthens blue-green reflectance resonances by simultaneously absorbing off-resonant wavelengths and enhancing the refractive-index near the reflectance band. Second, the refractive index of the nanospheres is modulated, via changes in crystallinity, to be almost exactly inversely correlated with nanosphere size. Thus, variations in nanosphere size, that ordinarily broaden reflectance resonances, resulting in poor color saturation, are compensated for by a correlated change in their refractive index. This ensures that even in a polydisperse ensemble, a consistent Mie scattering size parameter is maintained, strengthening short-range correlations and Mie scattering resonances. Finally, we show how damselflies tune these structural colors during maturation by precisely modulating the average size of the nanospheres, which arises naturally during the development of the pigment cells due to the densification and crystallization of the nanospheres. These findings reveal design strategies for overcoming limitations in the saturation of disordered photonic systems.

In lead halide perovskites (APbX3), the effect of the A-site cation on optical and electronic properties has initially been thought to be marginal. Yet, evidence of beneficial effects on solar-cell performance and light emission is accumulating. Here, we report that the A-site cation in soft APbBr3 colloidal quantum dots (QDs) controls the phonon-induced localization of the exciton wavefunction. Insights from ab-initio molecular-dynamics simulations and single-particle fluorescence spectroscopy demonstrate that anharmonic crystal vibrations and the resulting disorder act as an additional confinement potential. Avoiding the trade-off between single-photon purity and optical stability faced by downsizing conventional QDs into the strong confinement regime, dynamical phonon-induced confinement in large organic-inorganic perovskite QDs enables bright (10(6) photons/s), stable ( > 1 h), and pure (> 95%) single-photon emission tunable across a wide spectral range (495-745 nm). Strong electron-phonon interaction in soft perovskite QDs provides an unconventional route toward developing scalable room-temperature quantum-light sources.

We present a continuous-wave (CW) implementation of super-resolution optical fluctuation imaging with image scanning microscopy (SOFISM) using a pixelated single-photon avalanche diode (SPAD) detector camera. In a scanning-based geometry, SOFISM requires fluorescence fluctuations on timescales compatible with the pixel dwell time while maintaining sufficient signal under confocal excitation. Photoswitchable fluorophores in an aqueous switching buffer containing the glucose oxidase-catalase oxygen-scavenging system (GLOXY) and mercaptoethylamine (MEA) were therefore used to promote blinking and reduce photobleaching. Correlation analysis of sparse-emitter measurements showed that Alexa Fluor 647 (AF647) exhibits microsecond-scale fluctuation dynamics suitable for CW SOFISM and guided the choice of imaging conditions for scanned samples. Frame rate and delay accumulation were optimized from detector-pair subset variability using a mean-to-STD criterion. The optimal binning time was 2.5 $μ$s, underscoring the advantage of SPAD-based detection for resolving the relevant fluctuation dynamics. The method was demonstrated on HeLa cell microtubules labeled with AF647, yielding improved spatial resolution in the constructed SOFISM images compared with the corresponding ISM images. Additional super-resolved images from samples labeled with CF568 and Alexa Fluor 555 (AF555) showed the approach is readily generalizable to other fluorophores. These results establish CW SOFISM as a practical fluctuation-based super-resolution method for confocal microscopy.

The process of vision begins with the absorption of light by retinal, which triggers isomerization around a double bond and, consequently, a large conformational change in the surrounding protein opsin. However, certain organisms evolved different visual systems; for example, deep-sea fishes employ chlorophyll-like antennas capable of capturing red light and sensitizing the nearby retinal molecule via an energy-transfer process. Similar to retinal, most synthetic photochromic molecules, such as azobenzenes and spiropyrans, switch by double-bond isomerization. However, this reaction typically requires shortwavelength (ultraviolet) light, which severely limits the applicability of these molecules. Here, we introduce DisEquilibration by Sensitization under Confinement (DESC) – a supramolecular approach to switch various azoarenes from the E isomer to the metastable Z isomer using visible light of desired color, including red. DESC relies on a combination of a coordination cage and a photosensitizer (PS), which act together to bind and selectively sensitize E-azoarenes. After switching to the Z isomer, the azoarene loses its affinity to—and is expelled from—the cage, which can convert additional copies of E into Z. In this way, the cage⋅PS complex acts as a light-driven supramolecular machine, converting photon energy into chemical energy in the form of out-of-equilibrium photostationary states, including ones that cannot be accessed via direct photoexcitation.

Biology’s strategies for manipulating light offer rich inspiration for the design of sustainable replacements to conventional pigments in paints, coatings, and displays. For these applications, where angle-independent color is required, photonic glasses, composed of random arrangements of dielectric spheres, offer a promising solution. However, their intrinsic disorder, particularly from particle polydispersity, fundamentally limits their color saturation and practical utility. In contrast, insects like damselflies and dragonflies exhibit surprisingly vivid, non-iridescent structural colors, despite relying on disordered photonic structures. Here, we show how damselflies combine compositional and structural dispersion to overcome color saturation limits of photonic glasses. Firstly, doping transparent particles with yellow pigments dramatically enhances blue-green structural resonances by the coupled effects of narrowband absorption and refractive index (material) dispersion. Secondly, the refractive index of the nanospheres varies with their size and crystallinity. This gives rise to a ‘structural dispersion’ which maintains consistent optical path lengths in polydisperse assemblies, preserving high color purity. Finally, we show how damselflies tune their structural colors during maturation by precisely modulating the size of the nanospheres. Remarkably, the tuning of particle size, refractive index and pigment loading, arises naturally during the development of the pigment cells – where the pteridine nanospheres undergo a process of densification, crystallization and metabolic maturation.

How molecular-level understanding of the crystal growth mechanisms and their relation to lattice bonds informs the rational design of crystals with desired shapes and properties has remained elusive. Here we employ theophylline crystals and drive them into classical growth mode, in which the crystals grow molecule-by-molecule and new layers are generated by two-dimensional nucleation. We demonstrate that classical growth allows for controlling the crystal's shape and dimensions. We correlate the anisotropic responses to the supersaturation of the growth rates of crystal layers and crystal faces to the hydrogen and π-π stacking bond chains in the crystal lattice. The obtained insights suggest strategies to direct the crystal shape to either one-dimensional needles or flat sheets. Moreover, we show that crystals that grow by the classical mode of direct monomer incorporation have the potential to regrow and heal once a defect is introduced by mechanical cut or local thermal subliming of crystalline sections.

Lead halide perovskites (HaPs) have gained much attention, especially for use in photovoltaics and optoelectronic devices. However, stability remains the major roadblock to implementing HaP-based devices. Self-healing, the material's intrinsic tendency to recover from damage without any external aid, is observed in HaPs. Yet, understanding of its detailed mechanism is still lacking. Fluorescence recovery after photobleaching and photoluminescence (PL) imaging are used to monitor changes in HaP polycrystalline thin films in both space and time following damage, through the self-recovery path. Changes in PL outside the excitation spot are identified immediately following photodamage for both CsPbI3 (CsPI), showing photo-darkening, and MAPbI3 (MAPI), exhibiting photo-brightening. During self-healing of the directly illuminated spot, MAPI peripheral fluorescence decreases to its initial level, whereas CsPI exhibits photo-brightening to above the original level. This can be correlated with processes occurring on two time scales: rapid electronic defect passivation and slower ion migration. Investigating PL dynamics under intense laser damage demonstrates that changes to PL can be attributed to a combination of charge carrier trapping and trap removal in the early stages and ion migration and redox reactions in later stages. The understanding of spatio-temporal dynamics of damage and self-healing can promote longevity of HaP-based devices.

We demonstarte superresolved coherent anti-Stokes Raman (CARS) microscopy by implementing CARS image scanning microscopy. This requires access to the phase which we obtain using an inline interferometer. Full-text article not available; see video presentation

Semiconductor nanoplatelets present reduced Auger recombination, giving rise to enhanced multiexciton emission. This virtue makes them good candidates to investigate higher-order carrier dynamics, allowing extraction of important excitonic properties, such as biexciton and triexciton binding energies that highly influence applications involving high excitation fluxes. Here, we explore triexciton emission, emanating from single core/shell CdSe/CdS nanoplatelets. We apply heralded postselection of photon triplets using an advanced home-built single-photon spectrometer in order to resolve the triexciton-biexciton-exciton-ground state cascaded relaxation in both time and spectrum, and unambiguously determine the triexciton relaxation route and interaction nature. The results show a characteristic blue shift of the biexciton and triexciton, pointing to repulsive multiexciton interaction in the nanoplatelets under study. The relatively small measured energy shift of the triexciton (5.9 ± 0.7 meV) indicates that it recombines through the 1S bands rather than the 1P bands, in agreement with findings on other colloidal quantum dot systems. Most importantly, the strong correlation between the biexciton and triexciton binding energies, and the ability to tune them via control of the particle dimensions and composition, paves the way for developing emitters of nearly degenerate photon triplets.

Infrared-triggered photon upconversion in porous materials presents intriguing prospects for combined functionalities such as molecular sponge, energy harvesting and conversion functionalities. Metal-organic frameworks (MOFs) are one of the most versatile classes of porous crystals. So far only two-photon upconverting processes have been realized in MOFs both by ligand based triplet-triplet annihilation and directly in lanthanide ions. Here we report on Yb3+/Er3+-trimesate-based MOFs that exhibit photon avalanche (PA) characteristics. The PA process conventionally occurs through cross-relaxation within the lanthanide emitter manifold. In contrast, here PA proceeds in the organic molecule part and relies on a cooperative process, involving multiple emission centers. The IR photons are first absorbed and upconverted into high energy electronic population by the action of the lanthanide ions (Yb3+ and Er3+ are the sensitizer and the activator, respectively). Subsequently, the electrons are funneled into electronically coupled triplet states of the trimesate ligand, enabling accumulation in the organic matrix. This reservoir acts as source for a highly nonlinear spectrally broadband emission, arising mainly from ligand triplet states. The nonlinearity factor is comparable with the well-established PA inorganic nanoparticles. We prove that the PA is strongly related to the degree of crystallinity of the MOF: not well-formed frameworks support only the characteristic Er3+ emission with only linear increase as a function of the excitation power. Our work paves a path towards vastly expanding the range of materials exhibiting PA, well beyond a limited set of lanthanide ions. Moreover, it provides a path for much broader control of the PA emission characteristics.

We demonstrate super-resolved coherent vibrational imaging based on single-pulse Coherent Anti-Stokes Raman Scattering (CARS) combined with Image Scanning Microscopy (ISM), enabling label-free vibrational imaging beyond the diffraction limit. As required for coherent imaging, and unlike conventional ISM applied to fluorescence or spontaneous Raman signals, we perform pixel reassignment on the complex optical field rather than the intensity, accounting for the interference-based nature of coherent imaging. In contrast with previous implementations of coherent ISM, here we do not rely on the use of interferometry with an external reference, but rather utilize the intrinsic nonresonant background as reference, while a programmable pulse shaper enables spectral-phase interferometry between the resonant and nonresonant components of the CARS field. After retrieving both the amplitude and the phase of the resonant CARS signal, we apply coherent ISM to achieve resolution enhancement in chemically specific imaging. This technique opens new avenues for high-speed, label-free super-resolved vibrational microscopy and especially for its extension to the low-frequency spectral range and to an implementation in a backscattering geometry.

Temporal photon correlations have been a crucial resource for quantum and quantum-enabled optical science for over half a century. However, attaining non-classical information through these correlations has typically been limited to a single point (or, at best, a few points) at a time. Here, we perform a massively multiplexed wide-field photon correlation measurement using a large 500 x 500 single-photon avalanche diode array, the SwissSPAD3. We demonstrate the performance of this apparatus by acquiring wide-field photon correlation measurements of single-photon emitters and illustrate two applications of the attained quantum information: wide-field emitter counting and quantum-enabled super-resolution imaging (by a factor of root 2). The considerations and limitations of applying this technique in a practical context are discussed. Ultimately, the realization of massively multiplexed wide-field photon correlation measurements can accelerate quantum sensing protocols and quantum-enabled imaging techniques by orders of magnitude. (c) 2025 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Recent years have seen significant interest in photovoltaic conversion systems tailored not for solar insolation but for particular laser frequencies operating in transmission windows as a means to deliver energy remotely to a consumer. The recent advent of lead halide perovskite-based photovoltaics, calls for the exploration of their use also in such applications. Here, we present perovskite laser cells (PLCs) with significantly enhanced performance by hybridizing the CsPbBr3 with CoOx nanocrystals for optimizing the active layer and its interface with the cathode. The CoOx composite can accelerate solute consumption and guarantee low-density nucleation in the precursor for improving the crystalline grains size. We present a laser-electric photovoltaic generator with an active absorber layer of CoOx-CsPbBr3 under conditions of atmospheric (420 nm) and underwater (505 nm) transmission windows, whose performance significantly exceeds that of the reference CsPbBr3 one. The champion device obtained an ultrahigh PCE of 62.77 % under laser irradiation with a wavelength of 505 nm and power intensity of 80 mW & sdot;cm- 2. This study not only provides a hybridization engineering strategy technique with the synergy of gradient engineering and surface optimization for improving the absorber film and its interface with the cathode, but also provides opportunities for multiple scenarios of remote power transmission applications.

Multiexcitons (MXs) in quantum dots (QDs) manifest many body interactions under quantum confinement. Beyond this fundamental interest, MXs are of importance in numerous optoelectronic applications including QD lasing, light emitting diodes and photocatalysis. Yet, the strong interactions between MXs leading to rapid non-radiative decay introduce challenges for their characterization. While so far, the measurement techniques rely either on indirect methods or on single particle studies, herein we introduce a new method to study MXs in QD ensembles utilizing spectrally resolved time-gated heralded spectroscopy. With this approach we extract the biexciton binding energies in a series of CdSe/CdS QD ensembles of several core/shell sizes, manifesting a transition between attractive and repulsive exciton-exciton interactions. Additionally, for triexcitons, which involve occupation of two excitons in the 1s energy levels, as well as one exciton in the 1p energy levels, we address the open issues of isolating the spectra of the two triexciton pathways from one another and from high-order MXs, and extract the MX lifetimes. The measurements on ensembles provide high photon counts and low noise levels, and alongside the time-gated heralded approach thus enable the observation of MX characteristics that are difficult to resolve in single particle studies. The approach can be further implemented in the characterization of the energies and lifetimes of MXs in other QD systems to enable rapid characterization and understanding of the MX properties. Such insight bears relevance to optoelectronic applications ranging from lasing to electroluminescent devices to quantum light sources.

Multiexcitons in quantum dots (QDs) manifest many-body interactions under quantum confinement and are significant in numerous optoelectronic and quantum applications. Yet, the strong interactions between multiexcitons leading to rapid non-radiative Auger decay introduce challenges for their characterization. While so far, the measurement techniques rely either on indirect methods or on single particle studies, herein a new method is introduced to study multiexcitons in QD ensembles utilizing spectrally resolved time-gated heralded spectroscopy. With this approach, the biexciton binding energies is extracted in CdSe/CdS QD ensembles of several core/shell sizes, manifesting a transition between attractive to repulsive exciton-exciton interactions. Additionally, for triexcitons, involving occupation of two excitons in the 1s energy levels and one exciton in the 1p energy levels, the open issues of extracting the lifetime, the spectra of the two triexciton pathways and their branching ratio are resolved. The ensemble measurements provide high photon counts and low noise levels, and alongside the time-gated heralded approach, thus enable the observation of multiexciton characteristics that are often obscured in single particle studies. The approach can be further implemented in the characterization of the energies and lifetimes of multiexcitons in other QD systems to enable rapid characterization and understanding.

Super-resolution imaging is a powerful tool in modern biological research, allowing for the optical observation of subcellular structures with great detail. In this paper, we present a deep learning approach for image fusion of intensity and super-resolution optical fluctuation imaging (SOFI) microscopy images. We construct a network that can successfully combine the advantages of these two imaging methods, producing a fused image with a resolution comparable to that of SOFI and an SNR comparable to that of the intensity image. We also demonstrate the effectiveness of our approach experimentally, specifically on cell samples where microtubules were stained with ATTO647N and imaged using a confocal microscope with a single photon fiber bundle camera, allowing for the simultaneous acquisition of an image scanning microscopy (ISM) image and a SOFISM (ISM and SOFI) image. Our network is designed as a self-supervised network and shows the ability to train on a single pair of images and to generalize to other image pairs without the need for additional training. Our approach offers a flexible and efficient way to combine the strengths of correlation based imaging techniques along with traditional intensity based microscopy, and can be readily applied to other fluctuation based imaging modalities.

We present super-resolved coherent anti-Stokes Raman scattering (CARS) microscopy by implementing phase-resolved image scanning microscopy (ISM), achieving up to two-fold resolution increase as compared with a conventional CARS microscope. Phase-sensitivity is required for the standard pixel-reassignment procedure since the scattered field is coherent, thus the point-spread function (PSF) is well-defined only for the field amplitude. We resolve the complex field by a simple add-on to the CARS setup enabling inline interferometry. Phase-sensitivity offers additional contrast which informs the spatial distribution of both resonant and nonresonant scatterers. As compared with alternative super-resolution schemes in coherent nonlinear microscopy, the proposed method is simple, requires only low-intensity excitation, and is compatible with any conventional forward-detected CARS imaging setup.

Self-healing (SH) of (opto)electronic material damage can have a huge impact on resource sustainability. The rising interest in halide perovskite (HaP) compounds over the past decade is due to their excellent semiconducting properties for crystals and films, even if made by low-temperature solution-based processing. Direct proof of self-healing in Pb-based HaPs is demonstrated through photoluminescence recovery from photodamage, fracture healing and their use as high-energy radiation and particle detectors. Here, the question of how to find additional semiconducting materials exhibiting SH, in particular lead-free ones is addressed. Applying a data-mining approach to identify semiconductors with favorable mechanical and thermal properties, for which Pb HaPs are clear outliers, it is found that the Cs2AuIAuIIIX6, (X = I, Br, Cl) family, which is synthesized and tested for SH. This is the first demonstration of self-healing of Pb-free inorganic HaP thin films, by photoluminescence recovery. A data-mining approach is used to find self-healing materials for photovoltaic applications. Target ranges of material property combinations are found for candidate materials that can self-heal from damage. Cs2AuIAuIIICl6 and Cs2AuIAuIIIBr6 are successfully synthesized and tested to support the general finding.image

Regulating strain in perovskite films via utilizing the crystal structure relationship between solid-phase materials (SPMs) and perovskite is an effective method to achieve high-performance perovskite solar cells. It is crucial to investigate and manipulate the heterointerfaces between perovskites and SPMs since the mismatched crystal structure and energy band structure of SPMs will bring recombination sites to the heterointerfaces. In this work, CdS-modified PbS nanosheets (CPS) were prepared through cation exchange with (200)-preferred PbS nanosheets. The wide-band gap CdS charge-blocking layer of CPS nanosheets distributed at the grain boundaries effectively passivates the heterointerfaces in FAPbI3-CPS heterostructures (FAPI-CPS). Further, it potentially blocks carrier transportation and suppresses carrier recombination at grain boundaries and in FAPbI3-PbS nanosheet heterointerfaces. Attributed to the CdS layer, the FAPI-CPS devices achieve an enhanced power conversion efficiency. CPS nanosheets with an interplanar spacing slightly smaller than that of α-FAPbI3 could provide compressive strain to FAPbI3 at the FAPI-CPS heterointerfaces, leading to significantly improved device stability. The unencapsulated FAPI-CPS solar cells maintained 92% of their initial PCE after being stored at 20 ± 5 °C, 20 ± 5% RH for 2500 h.

We present super-resolved coherent anti-Stokes Raman scattering (CARS) microscopy by implementing phase-resolved image scanning microscopy, achieving up to two-fold resolution increase as compared with a conventional CARS microscope. Phase-sensitivity is required for the standard pixel-reassignment procedure since the scattered field is coherent, thus the point-spread function is well-defined only for the field amplitude. We resolve the complex field by a simple add-on to the CARS setup enabling inline interferometry. Phase-sensitivity offers additional contrast which informs the spatial distribution of both resonant and nonresonant scatterers. As compared with alternative super-resolution schemes in coherent nonlinear microscopy, the proposed method is simple, requires only low-intensity excitation, and is compatible with any conventional forward-detected CARS imaging setup. The authors present super-resolved CARS microscopy using phase-sensitive image scanning, achieving nearly twice the resolution of conventional CARS. This method requires low excitation laser power and integrates easily into existing systems.