Explore the vast range of titles available.

Metasurfaces, composed of artificial meta-atoms of subwavelength size, can support strong light–matter interaction based on multipolar resonances and plasmonics, hence offering the great capability of empowering nonlinear generation. Recently, owing to their ability to manipulate the amplitude and phase of the nonlinear emission in the subwavelength scale, metasurfaces have been recognized as ultra-compact, flat optical components for a vast range of applications, including nonlinear imaging, quantum light sources, and ultrasensitive sensing. This review focuses on the recent progress on nonlinear metasurfaces for those applications. The principles and advances of metasurfaces-based techniques for image generation, including image encoding, holography, and metalens, are investigated and presented. Additionally, the overview and development of spontaneous photon pair generation from metasurfaces are demonstrated and discussed, focusing on the aspects of photon pair generation rate and entanglement of photon pairs. The recent blossoming of the nonlinear metasurfaces field has triggered growing interest to explore its ability to efficiently up-convert infrared images of arbitrary objects to visible images and achieve spontaneous parametric down-conversion. This recently emerged direction holds promising potential for the next-generation technology in night-vision, quantum computing, and biosensing fields.

Statistical distributions of the analog readings of an antenna-coupled THz superconducting bolometer were measured and analyzed under a special type of irradiation by low-energy fluxes of THz photons with Poisson photon statistics and controllable mean photon numbers. The photons were generated via low-gain parametric down-conversion in pulse-pumped Mg:LiNbO3 crystal placed to a cooled cryostat together with the bolometer NbN film. Results of theoretical approximation of experimental histograms reveal the discrete nature of THz detection by superconducting bolometers and open a way for studying their quantum characteristics. It is shown that bolometer readings per pulse consist of discrete counts (“single charges”), with the mean number linearly dependent on the number of input photons. Contributions of single counts to a total analog reading are statistically distributed according to the normal law, with average values slightly depending on the number of counts in each reading. A general formula is proposed to describe the relationship between continuous statistical distribution of the bolometer readings and discrete quantum statistics of the incident photons.

Most of the present‐day down‐conversion white light‐emitting devices (WLEDs) utilize rare‐earth elements, which are expensive and facing the problem of shortage in supply. WLEDs based on the combination of orange and blue emitting copper nanoclusters are introduced, which are easy to produce and low in cost. Orange emitting Cu nanoclusters (NCs) are synthesized using glutathione as both the reduction agent and stabilizer, followed by solvent induced aggregation leading to the emission enhancement. Photoluminescence quantum yields (PL QY) of 24% and 43% in solution and solid state are achieved, respectively. Blue emitting Cu nanoclusters are synthesized by reduction of polyvinylpyrrolidone supported Cu(II) ions using ascorbic acid, followed by surface treatment with sodium citrate which improves both the emission intensity and stability of the clusters, resulting in the PL QY of 14% both in solution and solid state. All‐copper nanocluster based down‐conversion WLEDs are fabricated by integrating powdered orange and blue emitting Cu NC samples on a commercial GaN LED chip providing 370 nm excitation. They show favorable white light characteristics with Commission Internationale de l'Eclairage color coordinates, color rendering index, and correlated color temperature of (0.36, 0.31), 92, and 4163 K, respectively. Photoluminescence of blue and orange emitting Cu nanoclusters (NCs) is enhanced by surface treatment with sodium citrate and the solvent induced aggregation, respectively, resulting in high quantum yields of 14% and 43% in the solid state. White light emitting diodes are fabricated using powdered Cu NCs as phosphors, with a high color rendering index of 92 and low correlated color temperature of 4163 K.

Oxyfluoride transparent glass‐ceramics (GC) are widely used as the matrix for rare‐earth (RE) ions due to their unique properties such as low phonon energy, high transmittance, and high solubility for RE ions. Tb3+ doped oxyfluoride glasses exhibit a large absorption cross section for ultraviolet (UV) excitation, high stability, high photoluminescence quantum efficiency, and sensitive spectral conversion characteristics, making them promising candidate materials for use as the spectral converter in UV photodetectors. Herein, a Tb3+ doped oxyfluoride GC is developed by using the melt‐quenching method, and the microstructure and optical properties of the GC sample are carefully investigated. By combining with a Si‐based photo‐resistor,a solar‐blind UV detector is fabricated, which exhibits a significant photoelectric response with a broad detection range from 188 to 400 nm. The results indicate that the designed UV photodetector is of great significance for the development of solar‐blind UV detectors. A Tb3+ ion doped glass‐ceramic (GC) obtained by the traditional melt‐quenching method, is employed as the converter to combine with a silicon photo‐resistor for the development of a solar‐blind UV detector. Due to the efficient conversion of broadband solar‐blind UV light (188–400 nm) into visible light by the GC, the device exhibits meaningful photovoltage response at a low bias voltage. The research results of this work are of great significance for the development of efficient broadband solar‐blind UV detectors at a low cost.

Entangled photons are a cornerstone of quantum technologies, enabling applications from secure communication to quantum computing. A longstanding challenge is to develop a compact source that would generate polarization‐entangled photons with tunable quantum state on demand. The promising materials for such sources are ferroelectric nematic liquid crystals (FNLCs), due to their nonlinear optical properties and easily controllable configuration. In this work, it is demonstrated that the polarization state and the degree of entanglement of photon pairs generated within FNLCs can be changed in a controllable and reversible manner. First, tuning of the entanglement is demonstrated via sample geometry with twisted FNLC configurations in a sample of varying thickness. Secondly, by applying an electric field, the degree of entanglement can be tuned in real time. In both scenarios, the degree of entanglement can be adjusted from nearly entirely separate photons to fully entangled. These findings represent a significant step toward tunable quantum sources that can produce any desired polarization state on demand. In the future, by adding more electrodes, different parts of the sample could be controlled individually, allowing for the creation of pixelated quantum light sources. By exploiting the strong nonlinear optical response and controllable molecular ordering of ferroelectric nematic liquid crystals (FNLCs), these materials can serve as tunable sources of polarization‐entangled photons. Adjusting the sample geometry or applying an external electric field enables continuous control of the entanglement degree, advancing the development of on‐demand, pixelated quantum light sources for emerging quantum technologies.

In recent years, there has been a growing interest in optical simulation of lattice spin models for applications in unconventional computing. Here, we propose optical implementation of a three-state Potts spin model by using networks of coupled parametric oscillators with phase tristability. We first show that the cubic nonlinear process of spontaneous three-photon down-conversion is accompanied by a tristability in the phase of the subharmonic signal between three states with 2 /3 phase contrast. The phase of such a parametric oscillator behaves like a three-state spin system. Next, we show that a network of dissipatively coupled three-photon down-conversion oscillators emulates the three-state planar Potts model. We discuss potential applications of the proposed system for all-optical optimization of combinatorial problems such as graph 3-COL and MAX 3-CUT.

Stimulated parametric down-conversion is a nonlinear optical process that can be used for phase conjugation and frequency conversion of an optical field. A precise description of the outgoing stimulated field has been developed for the case where the input pump and seed fields are coherent. However, partially coherent beams can have interesting and important characteristics that are absent in coherent beams. One example is the twist phase, a novel optical phase that can appear in partially coherent Gaussian beams and gives rise to a nonzero orbital angular momentum. Here, we consider stimulated down-conversion for partially coherent input fields. As a case study, we use twisted Gaussian Schell-Model beams as the seed and pump beams in stimulated parametric down-conversion. It is shown both theoretically and experimentally that the stimulated idler beam can be written as a twisted Gaussian Schell-Model beam, where the beam parameters are determined entirely by the seed and pump. When the pump beam is coherent, the twist phase of the idler is the conjugate of that of the seed. These results could be useful for the correction of wavefront distortion such as in atmospheric turbulence in optical communication channels, and synthesis of partially coherent beams.

Inorganic fluoride‐based compounds are present today as decisive components in many advanced technologies, including energy storage and conversion, dye‐sensitized solar cell, microphotonics, medicine, pharmaceuticals, etc. Most of these outstanding behaviors can be correlated to the exceptional electronic properties of the element fluorine: “F2.” The role of fluorinated rare‐earth (RE)‐based nanoparticles (NPs), mostly deriving from the fluorite structure, is also crucial in medicine and biotechnologies, where doped photoluminescent rare‐earth fluoride nanoparticles (REFNPs), exhibiting high responsivity, can be used as bi‐ or multi‐modal agents in theranostics, integrating both imaging probes and therapeutics; these materials can thus carry out both diagnosis and therapy within the same nano‐object. Relevant nanotherapeutics also include fluorine‐labeling of NPs, in vivo 19F magnetic resonance imaging, photodynamic therapy, up‐ and down‐conversion luminescence, ultrafast upconversion superfluorescence, luminescent thermometry, photoacoustic imaging, radiotracers for positron emission tomography. Finally, research aimed at better understanding the toxicity risks of these NPs as well as better knowledge of the type of formulations of the used nano‐sensors should make it possible to improve the correlations between the selected REFNPs and the expected responses. Rare‐earth fluoride nanocrystals (REFNCs) exhibit high responsivity and can be used as multi‐modal agents in medicine and theranostics. This review summarizes recent advances in REFNCs, covering their synthesis, structures, luminescent properties, and applications in multi‐modal imaging and photodynamic therapy, highlighting their theranostic potential and safety challenges.

The development of novel optical self‐healing materials holds significant importance for applications in anticounterfeiting and information encryption, but remains a formidable challenge. This study presents a fluorescent self‐healing material designed for 2D/3D printing anticounterfeiting applications, exhibiting outstanding properties such as high transmittance, excellent mechanical strength, and remarkable self‐healing efficiency. The triple dynamic bond networks provide robust mechanical and self‐healing capabilities, with the polymer demonstrating a tensile strength of 26.9 MPa, an elongation at break of 1400%, toughness of 149.4 MJ m−3, and a self‐healing efficiency of 97%. When incorporated with core–shell nanoparticles, the polymer forms a fluorescent elastomer capable of triple‐mode up/down conversion fluorescence emission. This material can be easily customized via 2D/3D printing to create the desired shapes, and its self‐healing property allows for the combination of various configurations, thereby facilitating the encryption of multiple information applications. This study presents an effective protocol for synthesizing fluorescent self‐healing materials, further advancing their potentials for use in information encryption and fluorescence‐based anti‐counterfeiting. A self‐healing elastomer with triple dynamic bonds and 2D/3D printing capability is prepared in this work, and synthesized triple‐mode core–shell fluorescent nanoparticles are introduced to enable bright fluorescence under 254, 808, and 980 nm laser irradiation. 2D/3D printing is found to efficiently and conveniently customize patterns or shapes to fabricate information encryption and anticounterfeiting devices.

Efficient generation of high-quality photon pairs is essential for modern quantum technologies. Micro-ring resonator is an ideal platform for studying on-chip photon sources due to strong nonlinear effect, resonant-enhanced optical fields, and high integration. Thin-film lithium niobate (TFLN) micro-ring resonators with periodically poled quasi-phase matching have shown high-quality photon pair generation. However, periodic poling technology remains expensive and requires complex fabrication hindering its scalability and capability for practical application in nonlinear photonic devices. To address this, we propose a scalable approach using TFLN micro-ring resonators based on modal phase matching to achieve cost-effective, efficient high-quality photon pair generation, significantly simplifying fabrication. We achieved pair generation rates up to 40.2 MHz/mW through spontaneous parametric down-conversion, with coincidence-to-accidental ratios exceeding 1,200. By combining micro-ring resonance enhancement with modal phase matching, our approach reduces device size and fabrication cost while maintaining high nonlinear efficiency. These results advance the development of compact, efficient on-chip photon sources for next-generation nonlinear and quantum photonic applications.