There is currently significant interest in approaches that combine metaphotonics with back-end algorithms to advance imaging capabilities with less complicated hardware. Here, we combine computational imaging with a low-cost polarimetric encoder to construct a non-line-of-sight full-Stokes polarimetric camera. The polarimetric encoder is a multiscale, solution-processed metagrating composed of conducting-polymer nanofibers. We image the highly corrugated speckle patterns from the metagrating with a polarization-agnostic CCD sensor and achieve full-Stokes imaging from single-image capture with a trained shallow neural network (SNN) model. As SNNs require large amounts of training data, we present an effective method to generate numerous polarimetric scenes that span the full range of the Poincaré sphere. To guide the paired encoder and algorithm design, we also compare the reconstruction performance of SNN to pseudoinverse algorithms with varied sensor sampling size and explore the issues of compressive sensing. Our results provide new guidelines and impressive possibilities with meso-ordered, multiscale, self-assembled materials in future hybrid computing and polarimetric imaging systems.

As a new emerging ecofriendly light-emitting material, carbon dots (CDs) have been a research hotspot in the past decade. However, the synthesis of new types of CDs and the realization of multicolor solid-state emission remains challenging. Herein, we successfully synthesized a new type of N,Cl-doped CDs. The structure, morphology, composition, and optical properties, were well studied. The emission peak of fluorescent CDs solution can be modulated in the range of 512 to 613 nm by varying the concentration of CDs and the solvent type. To obtain a better emission of solid-state CDs, the as-prepared CDs are loaded on silica gel particles. Surprisingly, the solid-state CDs@silica can realize multicolor emission in the region of 521 to 600 nm by adjusting the ratio of CDs and silica. In addition, the single-component solar-simulated white light-emitting diode (WLED) was fabricated by using the CDs@silica particles as phosphor. The high quality of electroluminescence (EL) demonstrated the great potential of the CDs in the next generation of applications.

A myriad of metasurfaces have been demonstrated that manipulate light by spatially structuring thin optical layers. Manipulation of the optical properties of such layers in both space and time can unlock new physical phenomena and enable new optical devices. Examples include photon acceleration and frequency conversion, which modifies Snell’s relation to a more general, nonreciprocal form. Here, we combine theory and experiment to realize wavefront shaping and frequency conversion on subpicosecond time-scales by inducing space-time refractive index gradients in epsilon-near-zero (ENZ) films with femtosecond light pulses. We experimentally tune wavefront steering by controlling the incident angle of the beams and the pump–probe delay without the need for nanostructure fabrication. As a demonstration of this approach, we leverage the ultrafast, high-bandwidth optical response of transparent oxides in their ENZ wavelength range to create large refractive index gradients and new types of nonreciprocal, ultrafast two-dimensional (2D) optics, including an ultrathin transient lens.

Metasurfaces have attracted extensive attention in the micro/nano-optics field depending on their significant ability to modulate optical parameters. However, the current numerical simulation technology cannot meet the demand of the design and analysis of metasurfaces efficiently due to consuming substantial calculating time and memory. Besides, they cannot illustrate the physical mechanism straightforwardly behind the optical responses. Herein, we propose and demonstrate two equivalent circuit models systematically for a bifunctional metasurface with metal–dielectric–metal structural meta-atoms based on polarization multiplexing in the visible band. In the y-polarization state, the equivalent circuit model is established to interpret the phase shift exactly with a high goodness of fit of 0.931, resulting in the beam splitting function from the anomalous reflection phenomenon. The polychromatic light splits from 34 to 69° to produce the grating-type high-saturation structural colors with a large gamut of about 170.07% of the DCI-P3 standard. In the x-polarization state, the metasurface produces the surface lattice resonance that is suitable for the refractive index sensing function due to the high sensitivity to environmental changes. The second equivalent circuit model simulates the linewidth narrowing and red-shift phenomenon with a sensitivity relative error of 7.00%. We introduce a branch with a narrow-band-pass filter and a capacitor in series into the model to mimic the characteristic of Rayleigh anomalies. Both models extend the application of equivalent circuit theory in optics further and provide a crucial approach to enhance the insights into the mechanism of metasurfaces.

Label-free detection of single biomolecules in solution has been achieved using a variety of experimental approaches over the past decade. Yet, our understanding of the magnitude of the optical contrast and its relationship with the underlying atomic structure as well as the achievable measurement sensitivity and precision remain poorly defined. Here, we use a Fourier optics approach combined with an atomic structure-based molecular polarizability model to simulate mass photometry experiments from first principles. We find excellent agreement between several key experimentally determined parameters such as optical contrast-to-mass conversion, achievable mass accuracy, and molecular shape and orientation dependence. This allows us to determine detection sensitivity and measurement precision mostly independent of the optical detection approach chosen, resulting in a general framework for light-based single-molecule detection and quantification.

Dielectric metasurfaces provide a unique platform for efficient harmonic generation and optical wavefront manipulation at the nanoscale. Tailoring phase and amplitude of a nonlinearly generated wave with a high emission efficiency using resonance-based metasurfaces is a challenging task that often requires state-of-the-art numerical methods. Here, we propose a simple yet effective approach combining a sampling method with a Monte Carlo approach to design the third-harmonic wavefront generated by all-dielectric metasurfaces composed of elliptical silicon nanodisks. Using this approach, we theoretically demonstrate the full nonlinear 2π phase control with a uniform and highest possible amplitude in the considered parameter space, allowing us to design metasurfaces operating as third harmonic beam deflectors capable of steering light into a desired direction with high emission efficiency. The TH beam deflection with a record calculated average conversion efficiency of 1.2 × 10–1 W–2 is achieved. We anticipate that the proposed approach will be widely applied as alternative to commonly used optimization algorithms with higher complexity and implementation effort for the design of metasurfaces with other holographic functionalities.

Ultra-broadband detection and imaging devices with high speed, high bandwidth, and high sensitivity are in great demand for a variety of technological applications. An ultra-broadband high-speed device is realized based on a p-GaAs homojunction interfacial work function internal photoemission detector-photodiode device (HIWIP-photodiode). The ultrabroad dual-band response from terahertz (THz) to short-wavelength-infrared (SWIR) (4.2–150 THz) and visible/near-infrared (VIS/NIR) (330–450 THz) regions is realized by intentionally constructing two kinds of contact structures as well as utilizing various absorption mechanisms simultaneously. In addition, the HIWIP-photodiode could be used as a high-resolution ultra-broadband pixelless imaging device for THz to SWIR regions. The pixelless imaging of the mid-infrared spot is further demonstrated. These unique characteristics of an ultrabroad response range, bi-functional operating mode, mature growth/fabrication process, and high-speed response make the HIWIP-photodiode a strong contender for miniaturized and monolithic optoelectronic systems, paving the way for application of the interfacial work function internal photoemission (IWIP)-photodiode, which provides an alternative strategy for photon-type ultra-broadband detection.

Fascination with nature’s color palette has propelled mankind’s efforts to imitate and surpass it. Apart from the traditional interests in brighter and more fade-resistant colors, the present time adds the need for doing so without impacting the environment based on nontoxic materials. Although most commercial colorants are based on chemical pigments that absorb wavelengths of light matching their electronic and molecular transitions, the development of nanofabrication techniques in the last decades has spurred researchers to study structural colors, where color can be made out of colorless materials by carefully designed micrometer and nanoscale inclusions. Although, a myriad of such configurations have been reported for the production of color, in most cases, they suffer from angle or polarization dependence or require expensive materials or impractical fabrication techniques that are incompatible with large-scale production. Recently, some approaches have been proposed for the use of random media to mitigate these effects. Here, we demonstrate an approach based on colorless mirrors and transparent lossless dielectrics and show how this can be harnessed to produce a full color palette by using a subwavelength bilayer structure composed of thin films of titanium and its oxide for the production of inexpensive structural color. Furthermore, we introduce an additive manufacturing process that creates 58 different hues from 4 primaries in only three sequential evaporations. Based on this color palette, we reproduce Van Gogh’s self-portrait on a 1 sq in. area providing proof of the applicability of the platform for large-scale, low-cost, and environmentally friendly production of structural colors.

Coupling between light and material excitations underlies a wide range of optical phenomena. Polaritons are eigenstates of a coupled system with a hybridized wave function. Owing to their hybrid composition, polaritons exhibit at the same time properties typical for photonic and electronic excitations, thus offering new ways for controlling electronic transport and even chemical kinetics. While most theoretical and experimental efforts have been focused on polaritons with electric-dipole coupling between light and matter, in chiral quantum emitters, electronic transitions are characterized by simultaneously nonzero electric and magnetic dipole moments. Thus, it is natural to wonder what kinds of novel effects chirality may enable in the realm of strong light–matter coupling. Right now, this field located at the intersection of nanophotonics, quantum optics, and chemistry is in its infancy. In this Perspective, we offer our view toward chiral polaritons. We review basic physical concepts underlying chirality of matter and electromagnetic field, discuss the main theoretical and experimental challenges that need to be solved, and consider novel effects that could be enabled by strong coupling between chiral light and matter.

Organic materials have drawn significant interest for next-generation advanced optoelectronic devices or systems owing to their extraordinary light absorption, intrinsic flexibility, and low-temperature, large-scale processability. While for high-performance organic photodetectors, their restricted carrier mobility, limited diffusion length, and high binding energy of Frenkel excitons have long been regarded as the major challenges. In this paper, we report a sensitive organic rubrene crystal/graphene heterostructure photodetector. Especially, using an asymmetrical van der Waals stacking configuration, we realized self-powered photon detection in such a graphene-based organic heterostructure device. Long-range exciton diffusion of the rubrene single crystal, the efficient exciton dissociation, and the ultrafast charge transfer near the heterointerface enabled several commendable performances, including the great responsivity of 8 × 105 A/W, specific detectivity of >1012 Jones, and a fast response speed (ca. 20/70 μs). Encouragingly, the device exhibits excellent mechanical flexibility, remaining good conductivity, and stable light detection, even under harsh strain and after hundreds of cycles. Utilizing their outstanding photoresponse, we demonstrate fast-speed imaging applications on rigid and flexible substrates. Our work offers a practical strategy for developing high-performance, self-powered organic photodetectors for future wireless photon detection and high-speed imaging applications.

Using a single emissive layer, color tuning within a wide visible light range (from blue to red) is achieved in organic light emitting transistors. In the fabricated devices, both the gate and drain electrodes are made of aluminum (acting as an optical resonator), and the emissive layer thickness is adjusted to vary the distance between them. Remarkably, layer thickness variation, which is responsible for color tuning, does not affect the optical turn-on voltages, in contrast to organic light emitting diode devices. Significantly enhanced external quantum efficiencies are also observed for thick emissive layer devices. Optical simulations that accurately match experimental results indicate that the wide range of color tunability is mainly due to an outcoupling effect through the Fabry–Perot cavity. Our study presents a simpler and more flexible alternative for display technology design.

We propose and demonstrate an improved method for transfer printing that allows for the accurate docking of a photonic crystal nanobeam (NB) laser onto a SiNx waveguide. Our proposed method enables achieving much smaller transfer printing misalignments compared to the conventional approach based on visual alignment in experiments. We tested our method by docking a modified NB laser design with a theoretical unidirectional coupling efficiency of 64% to the SiNx waveguide. The results show a mean rotational misalignment of only 0.08° and a mean displacement misalignment of 26 nm for 48 NB lasers docked at the SiNx waveguides, demonstrating the high accuracy and excellent transfer printing reproducibility of our proposed method. Additionally, measurements indicated that over 97% of these highly accurate docked NB lasers exhibited uniform unidirectional coupling to specific waveguide output facets. We believe that the improved transfer printing steps presented in this study, along with the corresponding hybrid integration of docking NB lasers at the SiNx waveguide, provide a highly promising method for accurately integrating nanowire-based light sources into silicon-based photonic integrated circuits.

We report on the coupling of a reconfigurable high Q fiber micro-cavity to an organic color center grafted to a carbon nanotube for telecom wavelength emission of single photons in the Purcell regime. Using three complementary approaches, we assess various figures of merit of this tunable single photon source and of the cavity quantum electrodynamical effects: the brightening of the emitter is obtained by comparison of the count rates of the very same emitter in free-space and cavity coupled regimes. We demonstrate a fiber coupled single-photon output rate up to 20 MHz at 1275 nm. Using time-resolved and saturation measurements, we determine independently the radiative quantum yield and the Purcell factor of the system with values up to 30 for the smallest mode volumes. Finally, we take advantage of the tuning capability of the cavity to measure the spectral profile of the brightness of the source which gives access to the vacuum Rabi splitting g with values up to 25 μeV.

As solution-processed hybrid quantum dot light-emitting diodes (QLEDs), they may undergo a positive ageing process to improve their performance. It is highly desirable to investigate the ageing treatment and further use this positive effect to regulate the performance of the device. Under different ageing periods, we analyze how CdSe/ZnxCd1–xSe/ZnSeyS1–y core/shell quantum dot (QD)–ZnMgO interface and possible interface reactions between the QD, ZnMgO, and the Al electrode can affect device performance via positive ageing. The Kelvin probe measurements indicate a reduction in the energy level difference between ZnMgO and Al, leading to a relatively large built-in potential. By simply adjusting the annealing temperature of ZnMgO, the degree of positive ageing can be adjusted to optimize the device performance. By comparing the work function change of ZnMgO at different annealing temperatures, the change of surface electron affinity becomes more obvious, which may affect the degree of positive ageing. With an about 22 times improvement in operational lifetime, the peak external quantum efficiency of aged QLEDs can be optimized from 14.7 to 26.7%. This work presents an entirely new perspective on positive ageing and can serve as an important scientific guideline to further improve device performance.

Luminescent solar concentrators (LSCs) are able to concentrate both direct and diffuse solar radiation, and this ability has led to great interest in using them to improve solar energy capture when coupled to traditional photovoltaics (PV). In principle, a large-area LSC could concentrate light onto a much smaller area of PV, thus reducing costs or enabling new architectures. However, LSCs suffer from various optical losses which are hard to quantify using simple measurements of power conversion efficiency. Here, we show that spatially resolved photoluminescence quantum efficiency measurements on large-area LSCs can be used to resolve various loss processes such as out-coupling, self-absorption via emitters, and self-absorption from the LSC matrix. Further, these measurements allow for the extrapolation of device performance to arbitrarily large LSCs. Our results provide insight into the optimization of optical properties and guide the design of future LSCs for improved solar energy capture.

Luminescent solar concentrators (LSCs) are waveguiding devices that collect solar light to supplement photovoltaic devices. Scattering in waveguides is critical to the LSC performance, but it is challenging to quantify its contribution, severely hindering the development of LSCs. In this work, we developed an analytical approach to quantify the Mie scattering coefficient (αs) and anisotropy factor (g) in LSCs. By using the αs and g, we conduct theoretical calculation and Monte Carlo ray-tracing simulation to estimate the optical properties and optical efficiency of LSCs based on Gd1.5Y1.5Al5O12:Ce3+ phosphors. In all cases, both the calculated and simulated results agree well with the experimental observations, evidencing the feasibility of this approach. According to our model, scattering in the waveguide improves LSC performance by rerouting incident photons propagation to the edges but degrades LSC performance by redirecting radiated photons into the escape cone. We demonstrate that the enhancement of scattering increases both the scattering gain and loss as well as improves the absorption of LSCs. Finally, an external quantum efficiency (ηext) of 4.2% for a 20 × 20 cm2 LSC is achieved by optimizing the scattering. This work provides quantitative guidelines for estimating the scattering in LSCs, which will guide future research on LSC designs.

Room-temperature strong coupling between plasmonic nanocavities and monolayer semiconductors is a prominent path toward efficient, integrated devices. However, designing such systems is challenging due to the nontrivial dependence of the strong coupling on the properties of both the cavity and the emitter, as well as the subwavelength scale of interaction. In this work, we develop a general methodology for obtaining strongly coupled hybrid metasurfaces consisting of plasmonic nanocavities coupled to atomically thin semiconductor layers, exhibiting extreme values of Rabi splitting, by inverse design of the near-field plasmonic response. We experimentally demonstrate large values of Rabi splitting in a nanoantenna design while providing theoretically optimal configurations for additional types of nanostructures. Our results open a path to maximizing light–matter interactions in integrated platforms for classical and quantum-optical applications.

Paramagnetic ions and radicals play essential roles in biology and medicine, but detecting them requires highly sensitive and ambient-operable sensors. Optically addressable spin color centers in 3D semiconductors are useful for detecting paramagnetic spins due to their sensitivity to spin magnetic noise. However, creating high-quality spin defects near the surface of 3D materials is challenging. Here, we show that spin qubits in hexagonal boron nitride (hBN), a layered van der Waals (vdW) material, can efficiently detect paramagnetic spins in liquids at nanoscales. We create shallow spin defects near the hBN surface, which maintain high-contrast optically detected magnetic resonance (ODMR) in liquids. Then, we detect paramagnetic ions in water using spin relaxation measurements, with a sensitivity of about 10–18 mol/ for Gd3+ ions. Finally, we show that paramagnetic ions reduce the contrast of spin-dependent fluorescence, enabling efficient detection by continuous wave ODMR. Our results demonstrate the potential of ultrathin hBN quantum sensors for chemical and biological applications.

Label-free, bond-selective imaging offers new opportunities for fundamental and applied studies in chemistry, biology, and materials science. Preventing its broader application to investigating spatially- congested specimens are issues related to low sensitivity as well as low spatial and temporal resolution. Here, we demonstrate a widefield, mid-infrared (MIR) photothermal imaging technique, called widefield Infrared Photothermal Heterodyne imaging (wIR-PHI), that massively parallelizes acquisition of MIR absorption data through use of a high-speed complementary metal-oxide-semiconductor camera. wIR-PHI possesses notable features that include: spatial resolution significantly below the MIR diffraction limit, hyperspectral imaging capabilities, high sensitivity, and ∼100 ns temporal resolution. The first two features are highlighted by hyperspectral imaging of proximally close poly(methyl methacrylate) (PMMA) and polystyrene (PS) nanoparticles where clear, bond-specific imaging of nanoparticles, separated by less than the MIR diffraction limit, is demonstrated. Sensitivity is highlighted by imaging individual PMMA and PS nanoparticles with radii between r = 97–556 nm. This leads to a current, peak absorption cross-section limit-of-detection of σabs = 1.9 × 10–16 cm2. wIR-PHI’s 100 ns temporal resolution is simultaneously demonstrated by observing the decay of photothermal contrast on individual nanoparticles on a ∼200–6200 ns timescale. In whole, wIR-PHI’s dramatic increase in acquisition speed opens opportunities for future MIR kinetic imaging and spectroscopic studies of important chemical, biological, and material processes.

We study lateral light scattering on fiber Bragg gratings (FBG) with the goal of creating an optical fiber-based linear light source with controllable emission angles. The scattering from two FBGs was measured for polar angles (measured from the fiber axis) in the range θ = 27.1–152.9° and for all azimuth angles around the fiber. The observed light emission is strongly concentrated in one or more scattering cones around the fiber axis, showing four intensity peaks on opposite sides. These scattering phenomena are described and explained using the volume current method. This method shows a novel and simple way to understand the side scattering on FBGs as a combined effect of the grating’s longitudinal period, the grating harmonics, and its transversal shape. Further, this work contributes to a better understanding of the azimuth FBG-scattering caused by an interplay of the transversal grating shape and the fiber modes. The presented method can generate tailored side emissions for fiber light source applications, create light power sensors, or suppress unwanted scattering on FBGs for low optical loss applications.