Light-sheet microscopy has attracted considerable attention because it is a fluorescence imaging technique with rapid optical sectioning capability for transparent samples. In this study, we report a new application based on light-sheet microscopy for exploratory investigation of three-dimensional surface topography of opaque objects. Instead of using inelastic scattering fluorescent signals, our method utilizes the elastic scattering of light from the surface of opaque samples, which are illuminated by a light sheet generated by a cylindrical lens. Through a simple structural modification by removing the fluorescent filter, the orthogonal imaging module can capture the elastically-scattered image. As the opaque object is scanned by a motorized stage, the light-sheet microscope acquires a series of sectional images, which can be stitched into a three-dimensional surface topography image. This method also offers the opportunity to visualize a 3D fingerprint at micron-level resolution. Therefore, this technique may be used in industry and the biomedical field for the measurement of surface microstructure. To our best knowledge, this is the first time a light-sheet microscopy is utilized to perform surface topography measurement.

We report multifunctional optical imaging using dye-coated gold nanorods. Three types of useful information, namely, Raman, fluorescence signals, and absorption contrast, can be obtained from a phantom experiment. These three kinds of information are detected in a nanoparticle-doped-phantom using diffuse optical imaging. Our novel nanoparticle could be used as a multimodality marker for future bioimaging applications.

Dopant-free carrier-selective contacts are emerging in the field of crystalline silicon (c-Si) photovoltaic solar cells, which are potential to further improve the power conversion efficiency (PCE) and lower the cost of c-Si solar cells. Here, we demonstrate tens of microns thin c-Si heterojunction solar cells with substochiometric MoOx and LiFx as dopant-free hole- and electron-selective contacts, respectively. Chemical thinning of 200-mu m thick c-Si wafers enables the production of proof of concept devices with good flexibility and strong performance. When the wafer thickness is reduced to 49.4 mu m (24.7% of the initial thickness), the power conversion efficiency (PCE) of the solar cell still maintains 88.2% of the initial value for the 200-mu m thick cell. When the wafer thickness becomes less than 10% (or even 3.4%) of the initial value, 61.2% and 39.2% of the initial PCEs are still achieved for the 14.8- and 6.8-mu m thick cells, respectively. Passivating and carrier-selective effects of the MoOx and LiFx films allow for the maintenance of performance. An oxide interlayer at the MoOx/c-Si interface passivates the dangling bonds of the c-Si surface and improves the minority carrier lifetime. Field-effect passivation and carrier-selective effects induced by the band bending near the MoOx/c-Si interface and the Al/LiFx/c-Si interface play an important role in maintaining high open-circuit voltage and high fill factor. To the best of our knowledge, this is the first time that <100-mu m thin c-Si heterojunction solar cells are reported with undoped contacts. Our solar cells have been fabricated on thin c-Si wafers with low-temperature processes and without additional doping, and thus our work provides a promising cost-effective means in the field of thin and flexible c-Si solar cells.

Liquid Crystals are extraordinary materials for the organization of fluids and nanoparticles. The director field wraps around colloidal inclusions and inevitably forms topological defects to meet far-field boundary conditions. Droplets of isotropic fluids which promote planar anchoring form boojums in the surrounding LC which cause bulk quadrupolar distortions. At an air-LC interface the droplets directly contact the air and one boojum can disappear leaving a solitary boojum pointing down. As the liquid crystal layer becomes thinner, the hybrid anchoring of the LC layer causes the boojum to tilt enabling the formation of dipolar chains. As the layer becomes thinner still, the bottom planar alignment forces the second boojum to reappear recovering the quadrupolar alignment. The elastocapillary force associated with droplets at an air-LC interface is a surprising many body force which can distort the layer thickness by up to 1 micron leading to the formation of rounded superstructures containing thousands of droplets. Polydisperse droplets can enable the formation of branched structures where a mix of dipolar and quadrupolar interaction allows for the formation of y-branches. The self-assembly properties of LC enable the formation of interesting emulsions and switchable hybrid materials.

Topological waveguides with arbitrary pathway are desirable for many applications. In this paper we construct a triangular compound lattice consisting of magnetic dielectric rods. By breaking the space symmetry and the time-reversal symmetry, the structure generates topological edge states (TESs) from the hybrid quantum Hall effects and valley Hall effects. This topological edge waveguide pathway can be arbitrary arranged just by the external magnetic field. The hybrid topological phase provides a new and ultraflexible way to the reconfiguration of the TESs.

Transparent conductive electrodes (TCEs) are experimentally demonstrated using patterned few nanometer-thick silver films on zinc oxide-coated rigid and flexible substrates. The grid lines are completely continuous, but only 8.4 nm thick. This is the thinnest metallic grid we are aware of. Owing to the high transparency of both the grid lines and spacing, our TCE with an opening ratio (OR) as small as 36% achieves an average optical transmittance up to similar to 90% in the visible regime, breaking the optical limits of both the unpatterned film counterpart and the thick grid counterpart (whose optical transmittance is determined by the OR). The small OR enables a low sheet resistance of similar to 21.5 omega sq(-1). The figure of merit up to similar to 17 k omega(-1) is superior to those of the unpatterned film counterpart, our fabricated 180 nm thick ITO, as well as most reported thick metal grid TCEs. Our ultrathin TCE, firmly attached to the substrate, is mechanically more flexible and more stable than the film counterpart and ITO. As a flexible transparent film heater, it achieves comparable or even superior heating performances with previously-reported heaters and performs well in a thermochromic test.

We propose and experimentally demonstrate a distinct visible-blind and flexible metal-semiconductor-metal ultraviolet (UV) photodetector (PD) based on sub-10-nm thick silver interdigital electrodes. The transparent PD with 7-nm thick electrodes shows enhanced visible transmittance (80%) in average and achieves greatly improved responsivity (60.5 mA/W), and detectivity (1.75 x 10(10) Jones) at 5 V under 380-nm illumination, compared with its opaque counterpart. It is as fast as the opaquePDwith short rise and fall times (22.4 and 11.5 ms) and shows good flexibility. All the properties are comparable or superior to many reported transparent UV PDs, mainly attributed to the broad high UV-visible transmittance and the high conductivity of the ultrathin silver film.

A secure P2P optical fiber communication scheme based on ultra-dense optical spectral phase coding (UD-SPC) is proposed. The multi-code interference is suppressed by increasing the memory of the multilevel BCJR equalizer as shown by simulations.

Compared to natural materials, artificial subwavelength structures can enhance chiroptical effects in a stronger way, and the requirement of low material loss and wideband operation is desired in many situations. Here, we propose an all-dielectric chiral metasurface as a periodic array of centrosymmetric staggered silicon cuboid pairs to achieve strong circular dichroism in a wide band. As a demonstration, the designed chiral metasurface may strongly reflect the chosen circularly polarized light with the spin preserved in the operating wavelength range of 1.51 ti 1.60 mu m while highly transmit (with an efficiency greater than 95%) the opposite circularly polarized light with the spin flipped. Then, two application cases are given for the designed chiral metasurface. A flat chiral meta-lens is constructed to produce wideband focusing in the transmission/reflection side while the disturbing from the opposite circular polarization is well blocked by high reflection/transmission. A chiral Fabry-Perot cavity is also constructed, which has an extremely high quality factor (2.1E4). The proposed method provides an efficient way to produce strong chiroptical effects and has a promising potential for various applications such as signal processing, sensing, radiation and detection.

A vertical slot LiNbO3 waveguide with an Ag nanowire and 3L MoS2 embedded in the low-refractive index slot region is proposed for the purpose of improving light confinement. We find that the proposed waveguide has a novel dielectric based plasmonic mode, where local light field is enhanced by the Ag nanowire. The mode exhibits an extremely large figure of merit (FoM) of 6.5x10(6), one order of magnitude larger than that the largest FoM of any plasmonic waveguide reported in the literature to date. The waveguide also has an extremely long propagation length of 84 cm in the visible wavelength at 680 nm. Furthermore, the waveguide has a low sub-micro bending loss and can be directly connected to all-dielectric waveguides with an extremely low coupling loss. The proposed vertical slot LiNbO3 waveguide is a promising candidate for the realization of ultrahigh integration density tunable circuits in the visible spectral range.

A suspended thin-film lithium-niobate-on-insulator nano-waveguide (NanoLN) is designed, and tunable mid-infrared dispersivewave generation of high-efficiency and broadband is numerically studied on this designed platform. By hollowing out the silicon dioxide substrate between the NanoLN core and silicon wafer, the loss issue induced by mode leaking at mid-infrared region is eliminated. The second zero-dispersion wavelength of the suspended NanoLN is tailored to locate around 2 mu m wavelength, so that mode-locked fiber laser pump sources in this waveband can be conveniently leveraged to generate dispersive wave beyond 3 mu mwavelength. We show that dispersive wave at 3.16 mu m with high conversion efficiency up to 36.26% and bandwidth (at 10 dB level) of similar to 471 nm can be achieved at the pump pulse energy of 0.23 nJ. The central wavelength of the dispersive wave can be flexibly tuned up to 5 mu m with a maximum 10 dB bandwidth of similar to 2 mu m by lithographic control of the waveguide geometry, which is naturally at the expense of degraded conversion efficiency. Our results show the suspended NanoLN can provide a versatile chip-scale platform for cost-effective mid-infrared targetable, broadband, and coherent sources generation. Using fiber laser pump sources gives the advantages of compactness, free-maintenance, and long-term stability, which suit field applications.

An aberration-free line scanning confocal Raman imager (named AFLSCRI) is developed to achieve rapid Raman imaging. As an application example, various types and sizes of MPs are identified through Raman imaging combined with a machine learning algorithm. The system has excellent performance with a spatial resolution of 2 µm and spectral resolution of 4 cm−1. Compared to traditional point-scanning Raman imaging systems, the detection speed is improved by 2 orders of magnitude. The pervasive nature of MPs results in their infiltration into the food chain, raising concerns for human health due to the potential for chemical leaching and the introduction of persistent organic pollutants. We conducted a series of experiments on various types and sizes of MPs. The system can give a classification accuracy of 98% for seven different types of plastics, and Raman imaging and species identification for MPs as small as 1 µm in diameter were achieved. We also identified toxic and harmful substances remaining in plastics, such as Dioctyl Phthalate (DOP) residues. This demonstrates a strong performance in microplastic species identification, size recognition and identification of hazardous substance contamination in microplastics.

A three-dimensional (3D) finite-element mode-propagation analysis is presented to give an accurate and efficient simulation for silicon-nanowire- based multimode interference (MMI) couplers. For the presented numerical method, a finite-element method mode solver is used to calculate the mode profiles and the propagation constants in a multimode section. The comparison between the presented method and some other numerical methods [e.g., finite-difference time-domain (FDTD) method, beam propagation methods, etc.] is also shown. It is shown that the presented numerical method gives simulation results very close to those from the 3D FDTD (with a deviation less than 1%). Therefore, it is very convenient for the design of Si-nanowire-based MMI couplers.

A broadband transparent and flexible silver (Ag) mesh is presented experimentally for the first time for both efficient electromagnetic interference (EMI) shielding in the X band and high-quality free-space optical (FSO) communication. High transmission is achieved in a broad wavelength range of 0.4-2.0 mu m. The transmittance of the Ag mesh relative to the substrate is around 92% and the sheet resistance is as low as 7.12 ohm/sq. The Ag mesh/polyethylene (PE) achieves a high average EMI shielding effectiveness (SE) of 28.8 dB in the X band with an overall transmittance of 80.9% at 550 nm. High-quality FSO communication with small power penalty is attributed to the high optical transmittance and the low haze at 1550 nm, superior to those of the Ag NW networks. With a polydimethylsiloxane (PDMS) coating, the average EMI SE is still up to 26.2 dB and the overall transmittance is increased to 84.5% at 550 nm due to antireflection. The FSO communication does not change much due to the nearly unchanged optical property at 1550 nm. Both the EMI shielding performance and the FSO communication function maintain after 2-hour chemical corrosions as well as after 1000 bending cycles and twisting. Our PDMS/Ag mesh/PE sandwiched film can be self-cleaned, suitable for outdoor applications.

Greatly enhanced hole collection of MoOx is demonstrated experimentally with a top sub-10 nm thick Ag film, allowing for an efficient dopant-free contacted crystalline silicon (c-Si) heterojunction solar cell without a front grid electrode. With the removal of shadows induced by the front grid electrode, the gridless solar cell with the MoOx/Ag hole-selective contact (HSC) shows an increment of similar to 8% in its power conversion efficiency (PCE) due to the greatly improved short-circuit current density (J(sc)) as well as the almost undiminished fill factor (FF) and open-circuit voltage (V-oc), while the gridless solar cells with the conventional MoOx/ITO and pure MoOx HSCs exhibit similar to 20% and similar to 43% degradations in PCE due to the overwhelming decrease in their FF and J(sc), respectively. Through systematic characterizations and analyses, it is found that the ultrathin Ag film (more conductive than ITO) provides an additional channel for photogenerated holes to transport on MoOx, contributing to the great enhancement in the hole collection and the great suppression of the shunt loss in the gridless solar cells. A 50 mu m thick gridless c-Si heterojunction solar cell with the MoOx/Ag HSC is 75% thinner but is 86% efficient compared to its 200 mu m thick counterpart (while the 50 mu m thick gridless solar cell with the MoOx/ITO HSC is much less efficient). It is over 82% efficient after being bent to a curvature radius as small as 4 mm, also showing superior mechanical flexibility to its counterpart with the MoOx/ITO HSC. Our MoOx/Ag double-layer HSC can be easily fabricated through thermal evaporation without breaking the vacuum, saving both the time and cost of the fabrication of the whole device. Therefore, this work provides a guide for the design of efficient HSCs for high-efficiency, low-cost, and flexible solar cells.

A high-performance polarization beam splitter(PBS) is proposed and experimentally demonstrated on the220-nm silicon-on-insulator (SOI) platform. The proposed PBSconsists of a sub-wavelength grating (SWG) assisted adiabaticdirectional coupler (ADC) and a simple filter at the throughport of the ADC. The SWG structures embedded in the ADCcan suppress and enhance the optical field evolutions of thefundamental TE and TM modes (referred to as TE and TMmodes in short), respectively, thus enhancing the separation ofthese two modes. The simple filter composed of four Euler bendsis used to further improve the polarization extinction ratio (PER)of the TM mode while maintaining low insertion loss (IL) forthe TE mode. The simulated results show that our proposedPBS possesses the high performance of IL<0.3 dB and PER>30 dB for both the TE and TM modes over the bandwidthof 1.46-1.625 mu m, which covers the most important S, C, and,L bands for optical communications. The experimental resultsshow that the fabricated PBS has excellent performance of IL<0.8 dB and PER>24.5 dB over the bandwidth of 1.53-1.61 mu m

In this work, we demonstrate the bulk self-alignment of gold nanorods (GNRs) dispersed in lyotropic nematic liquid crystals (LCs) with high optical absorption coefficient at the surface plasmon resonant wavelength. The polymer-coated GNRs which show spontaneous long-range orientational ordering along the director of LC host exhibit long-term stability as well as high concentration. External magnetic field and shearing allow for alignment and realignment of the orientation of gold nanorods by changing the director of the liquid crystal matrix. This results in a switchable polarization-sensitive surface plasmon resonance exhibiting stark differences from that of the same nanorods in isotropic fluids. The devise-scale bulk nanoparticle alignment may enable optical metamaterial mass production and control of surface plasmon resonance of nanoparticles.

In geometrical optical design, we only need to choose a suitable combination of lenses, prims, and mirrors to design an optical path. It is a simple and classic method for engineers. However, people cannot design fantastical optical devices such as invisibility cloaks, optical wormholes, etc. by geometrical optics. Transformation optics has paved the way for these complicated designs. However, controlling the propagation of light by transformation optics is not a direct design process like geometrical optics. In this study, a novel mixed method for optical design is proposed which has both the simplicity of classic geometrical optics and the flexibility of transformation optics. This mixed method overcomes the limitations of classic optical design; at the same time, it gives intuitive guidance for optical design by transformation optics. Three novel optical devices with fantastic functions have been designed using this mixed method, including asymmetrical transmissions, bidirectional focusing, and bidirectional cloaking. These optical devices cannot be implemented by classic optics alone and are also too complicated to be designed by pure transformation optics. Numerical simulations based on both the ray tracing method and full-wave simulation method are carried out to verify the performance of these three optical devices.

By using transformation thermodynamics, an open, adaptive thermal buffer shell (TBS) is designed and experimentally implemented with natural materials (layered copper and expanded polystyrene [EPS]). The TBS can store excessive heat flux quickly in the shell and release it slowly when it is needed, which also has some distinctive features: first it is a buffer shell that can avoid external extremes in temperature (either high or low) and also provide a relatively stable temperature for the interior of the shell when the temperature outside the shell has some fluctuations; second the TBS is not thermally insulated (with holes connected to the outside world) and the buffering effect of the TBS originates from the heat recycling mechanics, not thermal insulation; third the TBS has a short response time and the temperature inside the shell can be quickly adjusted according to the average temperature outside the shell; fourth the TBS is a passive device. Unlike traditional air conditioning, the TBS can work without an external power supply. The TBS will have many applications in energy recycling systems, smart heat controlling systems, and passive heat self-adaptation systems. Numerical simulations and experimental demonstrations are given to verify the function of the TBS.

A slow-wave half-mode substrate integrated waveguide with a spoof surface plasmon polariton (SW-HMSIW-SSPP) transmission line structure is proposed, analyzed, and demonstrated. Results show longitudinal and lateral size reductions of more than 80% and 73%, respectively, as compared with an equivalent SIW at the same cutoff frequency while maintaining a low attenuation constant of 0.02 dB/mm. By altering the geometric parameters of the SW-HMSIW-SSPP the dispersion curve can be tailored. The dispersion and electromagnetic (EM) field distribution characteristics of the proposed SW-HMSIW-SSPP unit cell and overall structure are analyzed by HFSS simulations and an equivalent circuit, and pertinent performance parameters are compared to those of SW-HMSIW and HMSIW-SSPP structures. A proof-of-concept PCB SW-HMSIW-SSPP sample was fabricated, and measurement results showing a band-pass of 4.8-11.5 GHz are found consistent with simulation results. The SW-HMSIW-SSPP structure has applications in the design of miniaturized microwave circuits.

We demonstrate experimentally a flexible crystalline silicon (c-Si) solar cell (SC) based on dopant-free interdigitated back contacts (IBCs) with thickness of merely 50 µm for, to the best of our knowledge, the first time. A MoO_x thin film is proposed to cover the front surface and the power conversion efficiency (PCE) is boosted to over triple that of the uncoated SC. Compared with the four-time thicker SC, our thin SC is still over 77% efficient. Systematic studies show the front MoO_x film functions for both antireflection and passivation, contributing to the excellent performance. A double-interlayer (instead of a previously-reported single interlayer) is identified at the MoO_x/c-Si interface, leading to efficient chemical passivation. Meanwhile, due to the large workfunction difference, underneath the interface a strong built-in electric field is generated, which intensifies the electric field over the entire c-Si active layer, especially in the 50-µm thick layer. Photocarriers are expelled quickly to the back contacts with less recombined and more extracted. Besides, our thin IBC SC is highly flexible. When bent to a radius of 6 mm, its PCE is still 76.6% of that of the unbent cell. Fabricated with low-temperature and doping-free processes, our thin SCs are promising as cost-effective, light-weight and flexible power sources.

optically transparent and flexible coplanar waveguide (CPW)-fed wideband antenna is proposed and demonstrated experimentally based on sub-micron thick micro-metallic meshes (mu-MMs). Due to the high visible transmittance (83.1%) and low sheet resistance (1.75 & OHM;/sq) of the silver mu-MM with thickness of only 190 nm, the transparent CPW has very low insertion loss and provides a good feed to the high-performance transparent antenna. The measured S11 spectrum of our antenna matches well with that of the opaque counterpart. The measured fractional bandwidth is 22% from 3.4 to 4.25 GHz. Based on numerical modeling, whose accuracy is experimentally verified, the radiation efficiency and peak gain of our transparent antenna at 3.45 GHz are calculated to be 89.7% and 3.03 dBi, respectively. Besides the good optical and electromagnetic properties, our transparent antenna is also highly flexible. Despite the sub-micron thick mu-MMs, the transparency, radiation efficiency, and mechanical properties of our transparent antenna are obviously superior to those of the transparent antennas reported previously, and the overall size and radiation gain are also comparable. Therefore, our transparent antenna has an excellent comprehensive performance, showing great potential for practical applications as well as the emerging applications in the field of flexible and wearable electronics.

A low-profile radio frequency identification (RFID) tag antenna is proposed with a compact size of 45 × 45~mm2 and circular polarization (CP) for metallic surfaces. A star-shaped slot is etched onto the antenna for the CP and antenna size reduction. A terminal-grounded L-shaped feedline is embedded in the etched slot to efficiently excite the wideband CP mode, complexly match the tag-antenna impedance, and further reduce the antenna size. The embedded feed structure also helps achieve a relatively higher gain, resulting in a longer reading range. The proposed antenna can cover the impedance bandwidth of 60 MHz (from 880 to 940 MHz) as well as the 3-dB CP bandwidth of 12 MHz (from 905 to 917 MHz). Further results demonstrate that the proposed tag antenna provides a stable reading range when mounted on metal plates of various sizes.

A perfect mid-infrared dual-band absorber based on a very simple lithography-free polar dielectric/metal double-layer nanostructure is demonstrated experimentally. Silicon dioxide (SiO2) is chosen as the top polar dielectric, which is deposited through room-temperature plasma enhanced chemical vapor deposition to protect the bottom metal layer. A nearly 100% absorption is obtained at the wavelength of similar to 10 mu m due to the constructive interference resonance, which is related to the SiO2 thickness but insensitive to the light polarization or incident angle. Another enhanced absorption is observed experimentally at similar to 8 mu m under oblique incidence. Both numerical simulation and analytical calculation show that such absorption enhancement is induced by the excitation of the Berreman mode, where the refracted light propagates almost horizontally within the SiO2 layer. Different from the interference-induced absorption, the Berreman mode induced absorption exists even for a very thin absorber and is sensitive to the light polarization and incident angle.

Energy spectrum of a multiphoton-transition Jaynes-Cummings model with supersymmetry breaking and some relevant topics such as multiphoton dark state (photon-atom dark-state polariton) and multiphoton coherent population trapping are considered in this paper. We show that for a moving atom, because of Doppler effect and the relativistic electromagnetic induction for the incident optical field, there appears supersymmetric gauge potentials induced by the multiphoton transition and then this can lead to some interesting physical effects such as supersymmetric "spin" Hall effect and supersymmetric Aharonov-Bohm effect of atoms. Both supersymmetric vectorial gauge potential and scalar gauge potential can drive the population transition in the supersymmetric "isospin" doublet states in this Jaynes-Cummings model. As an illustrative example, we address the quantum collapse and revival in atomic population inversion driven by squeezed vacuum states and displaced squeezed vacuum states in such a multiphoton-transition Jaynes-Cummings model. It can be found that different from a coherent state that drives the Jaynes-Cummings model, where quantum collapse-revival effect in atomic level population inversion can be exhibited, a squeezed vacuum state, which excites the Jaynes-Cummings model, cannot give rise to the quantum collapse and revival because there is no Fock-state probability peak in the distribution function in the squeezed vacuum state. If, however, the Jaynes-Cummings model with multiphoton transition is driven by a displaced squeezed vacuum state, it can exhibit the effect of collapse and revival in the energy-level population inversion. In addition, we shall consider the interaction among atom paths (spatial wavefunctions), atomic internal levels and the photon field. Such a coupling leads to an atomic path-level-photon entangled state, and the traditional atomic-level quantum Rabi oscillation and quantum collapse-revival effect that occurred in time domain would be exhibited in the atom spatial wavefunctions (or in atomic paths).

Quantum-dot-molecular phase coherence (and the relevant quantum-interference-switchable optical response) can be utilized to control electromagnetic wave propagation via a gate voltage, since quantum-dot molecules can exhibit an effect of quantum coherence (phase coherence) when quantum-dot-molecular discrete multilevel transitions are driven by an electromagnetic wave. Interdot tunneling of carriers (electrons and holes) controlled by the gate voltage can lead to destructive quantum interference in a quantum-dot molecule that is coupled to an incident electromagnetic wave, and gives rise to a quantum coherence effect (e.g., electromagnetically induced transparency, EIT) in a quantum-dot-molecule dielectric film. The tunable on- and off-resonance tunneling effect of an incident electromagnetic wave (probe field) through such a quantum-coherent quantum-dot-molecule dielectric film is investigated. It is found that a high gate voltage can lead to the EIT phenomenon of the quantum-dot-molecular systems. Under the condition of on-resonance light tunneling through the present quantum-dot-molecule dielectric film, the probe field should propagate without loss if the probe frequency detuning is zero. Such an effect caused by both EIT and resonant tunneling, which is sensitive to the gate voltage, can be utilized for designing devices such as photonic switching, transistors, and logic gates.

Red-emitting carbonized polymer dots (CPDs) was prepared from p-phenylenediamine (p-PD) aqueous solution with the assistance of sulfuric acid (H2SO4), and the optical properties and bio-imaging application were studied in this paper. Compared with other strong acids-assisted systems, SA-CPDs (prepared from H2SO4-assisted system, average diameter is similar to 5 nm) is the brightest. The photoluminescence Quantum Yields (QYs) is 21.4% (in water), and the product yield is 16.5%. SA-CPDs aqueous solution emits at 600 nm when excited by the light from 300 to 580 nm. The emission wavelength is independent on the excitation wavelength. Formation energies of CPDs in two ways were calculated to show that longitudinal growth (forming polymers) is difficult, and the transverse growth (forming CPDs) is easy. In addition, the two-photon photoluminescence properties (emitting at 602 nm when excited by 850 nm femtosecond pulse laser) of SA-CPDs were also utilized in the experiments for HeLa cells staining and shown to have potential applications in bio-imaging.

Metal-free polymer daytime radiative cooling coatings with hierarchical eye-like air pores are proposed and fabricated with a super-large-scale film-stretching method. The hierarchically porous film (HPF) can be further coated with polymethyl methacrylate (PMMA) micro-hemispheres, forming coated HPF (cHPF), which do not dramatically change the optical or thermal properties. The cHPF is slightly better with a lower solar absorptivity (2.4%) and a higher thermal emissivity over the atmospheric transparency window (90.1%). The low solar absorptivity is due to the strong scattering of the hierarchical eye-like air pores, while the molecular vibrations and the focusing effect of the PMMA micro-hemispheres contribute to the high emissivity. An average mid-day temperature reduction of 7.92 °C is achieved relative to the air temperature, and the average cooling power reaches 116.0 W m−2, which are much better than the cooling performances of the commercial cooling cushion. During the day, the cHPF-covered simulated building is up to 6.47 and 4.84 °C cooler than the ambient and the white painted counterpart, respectively. The film is durable and resistant to chemical etching, and very promising to use globally, especially in warm and tropical regions. 

A compact photoacoustic spectroscopy system integrated with a non-coaxial multi-pass cell was developed for improving the instrument performance in the measurement of methane. The multi-pass cell with compact light spot mode was proposed for concentrating the light radiation within a limited space, which effectively reduces the instrument dimension. A distributed feedback (DFB) laser with a central wavelength of 1653 nm was employed to excite the photoacoustic signal of methane. A total of 21 round trips of reflection were achieved in an acoustic resonant cavity with a radius of 4 mm and a length of 36 mm. Four microphones were installed around the cavity to collect the signal. An 11-fold enhancement of the photoacoustic signal was achieved through the multi-pass cell, compared to a single-pass cell with dimension of 10 cm. The system was used to measure different concentrations of methane, which showed good linearity. The continuous detection of 10 ppm methane gas was carried out for 6000 s. The Allan standard deviation analysis indicates that the limit of detection of the system was 5.7 ppb with an optimum integration time of 300 s.

Morphological differentiation between myeloblasts and monoblasts is pivotal for the majority of acute myeloid leukemia (AML) diagnosis in clinical settings. Manual morphology-based classification of blasts encounters challenges due to the limited differentiation of these bone marrow cells (BMC) of early stages. Hence, the utilization of artificial intelligence is essential to assist in the classification of these cells. 4001 single-cell images of monoblasts and myeloblasts were collected from Taizhou Hospital to form the BMC-1 dataset. The main novelties and features of the proposed method are as follows: 1) A maximum connected domain extraction method grounded in the watershed algorithm is introduced to efficiently eliminate stained impurity cells from single cell images. 2) A dynamic focal loss is introduced to gradually focus on difficult-to-classify samples as the training progresses. 3) A dual-channel convolutional block attention network (DCCBANet) is introduced to enhance feature extraction. It employs attention mechanisms to focus on key features, utilizing ordinary convolution for local feature extraction, dilated convolution for global feature extraction, and a decreasing dilation rate sequence to preserve detailed information. A macro F1-score (macro_F) of 96.8% is achieved on the BMC-1 validation dataset. Additionally, the presence of multiple differentiation types of granulocytes pose difficulties in granulocytes distinction. To further validate the efficacy of our proposed method on multi-classification tasks, we collected 6626 granulocyte single-cell images from Taizhou Hospital. Augmenting the dataset with 2441 granulocyte single-cell images from the public dataset BM_cytomorphology addressed sample shortages, forming the BMC-2 dataset. We applied our model to the BMC-2 dataset for experiments and ultimately achieved a macro_F of 87.49%. Our proposed method effectively distinguishes monoblasts and myeloblasts and excels in the classification of granulocytes.

Here, we report an all-fiber tunable ultrafast Raman laser synchronously pumped by a home-made 1.6 pm dissipative soliton (DS) picosecond (ps) laser, which produces Stokes light beyond 1.7 pm. The Raman gain medium is a segment of highly germanium-doped (Ge-doped) fiber offering a high Raman gain coefficient at the target wavelength. Once the Raman conversion cavity is synchronized with the pump light, a stable 1.7 pm Raman laser (the first Stokes light) can be obtained at a low pump threshold. The maximum output power of the 1.7 pm Raman laser can reach similar to 22.62 mW. The wavelength tuning operation is independent of tunable pump source and intra-cavity filter. By adjusting the intra-cavity delay line simply, the different spectral component within the broad Raman gain bandwidth can be selectively synchronized with the pump light so that the Raman laser wavelength can be tuned continuously from 1702.6 nm similar to 1728.84 nm. This tunable 1.7 pm waveband ultrafast laser will have potential applications in multiphoton microscopy for e.g. deep bio-imaging.

Meter-scale transparent conductive circuits based on silver nanowire (AgNW) networks are fabricated for transparent light-emitting diode (LED) screens on both rigid and flexible substrates. A 25-cm long AgNW transparent conductive strip is fabricated with a strip resistivity of 9.95 Omega/cm. A high uniformity is achieved in terms of film optical transmission (up to 84.5% in average) and sheet resistance (as low as 4.7 Omega/sq in average), superior to ITO. A transparent LED screen based on a 1.2-m ultralong AgNW circuit is demonstrated with LEDs emitting bright red, green and blue lights under different biases. The AgNW strip on a polyethylene terephthalate substrate shows mechanical flexibility and stable performance in bending tests. Based on this, a flexible transparent LED screen is proposed and presented. It works well when dynamically bent to a radius as small as similar to 15 mm. Therefore, the AgNW transparent conductive circuits are very promising as a replacement to ITO circuits for such smart screens, to be integrated into modern glass architectures and display videos in various public places.

A dual-mode hyperspectral imager using field of view scanning needs no moving macro parts. It could work in dual-mode (macro imaging and micro imaging) and is equipped with a conjugated camera for quick object-selection and focusing. By adjusting the imaging lens and achieving the image clarity on the conjugated camera, we could find the correct location and focusing of the ROIs simultaneously instead of inefficiently checking the hyperspectral image after the whole scanning process. The whole system was applied to the study of spectral characteristics of blood oxygen in human hands and the microscopic identification of algae, showing a great potential of clinical and marine applications of our system.

We propose a novel multi-photon evanescent wave (MPEW) excitation modality for upconverting nanoparticles (UCNPs) based microscopy. Experimental results show this new imaging method for UCNPs is nonscanning, ultrahigh contrast and high spatiotemporal resolution.

In this paper we present a resolution-enhanced system for digital micromirror device (DMD) projected images by utilizing time multiplexing and birefringence in order to achieve this with static components only. This provides a less expensive solution than reducing the size of the hardware pixels and can also be applied to higher resolution displays, as and when, these become available. Birefringent materials have different refractive indices for linearly polarized light with orthogonal polarization directions. A high-resolution projected image can be observed by overlapping two or three native resolution images at shifts of one half or one third of a DMD pixel diagonal respectively on successive frames. The optical components comprise a custom-made quartz plate as the birefringent component and an off-the-shelf twisted nematic liquid crystal display (TN-LCD) screen as a polarization rotator that is synchronized with the DMD frame rate. This paper covers the principle of operation and the system design. The functioning of the display is verified using enlarged images of the letter 'R' and a checkerboard pattern that are formed from a small number of DMD pixels.

Despite enormous breakthroughs in lab-on-a-chip techniques, light-driven manipulation faces two long-standing challenges: the ability to achieve both multiform manipulation and tunable manipulation range and the means to avoid potential thermal damage to the targets. By harnessing the optical heating of hybrid photothermal waveguides (HPW), we develop a hybrid optofluidic technique involving buoyancy and thermocapillary convection to achieve fluid transport with controllable modes and tunable strength. Switching of the optofluidic mode from buoyancy to thermocapillary convection, namely, from vertical to horizontal vortices, is employed for three-dimensional manipulation. The strong confinement and torque in the vortices are capable of trapping and rotating/spinning particles at the vortex centers rather than the HPW. Buoyancy convection provides a trapping circle to achieve collective trapping and vertical rotation/spin, while thermocapillary convection offers a trapping lattice to achieve distributed trapping and horizontal rotation/spin. By integrating micro/nanoparticles with various properties and sizes, further investigations of the optofluidic arrangement, mixing, and synthesis will broaden the potential applications of the hybrid optofluidic technique in the fields of lab-on-a-chip, materials science, chemical synthesis and analysis, photonics, and nanoscience.

We demonstrate a substantial enhancement of gas Raman scattering using a bidirectional multi-pass cavity CERS system, which incorporates a polarization beam-splitting optical path. The system design allows the laser light to traverse the multi-pass cavity for four specific trips, satisfying the need for quick detection of various gas components. Our gas detection experiments using multi-pass cavities with different times of reflection indicate that the addition of polarization beam-splitting optical path gives 1.5 to 1.68 times enhancement of Raman signal compared with that of the system without polarization beam-splitting. For the detection of CH4, a limit of detection of 1.66 ppm was achieved with our system using a multi-pass cell with 41 times of reflection and an integration time of 30s. Our proposed design, which integrates a bidirectional multi-pass cavity with polarization beam-splitting optical path, gives an economical multicomponent gas detection system and a valuable tool for guiding the design and precise alignment of these cavities. This system shows significant promise for applications in e.g. human breath and environmental monitoring.