Prism Array Research Articles

Vortex light field microscopy: 3D spectral single-molecule imaging with a twist

3D single-molecule imaging reveals nanoscale structures in cell volumes but is limited by the need for spectrally distinct fluorophores. We address this limitation with vortex light field microscopy (VLFM), a 3D spectral single-molecule localization technique with 25 nm spatial and 3 nm spectral precision over a 4 µm depth of field. By modifying our previous single-molecule light field microscope with an azimuthally oriented prism array, we generated spectral disparity orthogonal to axial disparity, enabling simultaneous spatial and spectral localization on a single detector. We demonstrate VLFM with four-color 3D single-particle tracking and two-color 3D dSTORM imaging in fixed cells, successfully identifying dyes with spectral peaks just 15 nm apart. This shows VLFM’s potential for enhancing spatial biology workflows requiring highly multiplexed imaging.

High-efficiency hard X-ray blazed diffraction via refraction by nanometer-scale prism arrays

X-ray transmission gratings are widely utilized as wavelength dispersion elements in inertial confinement fusion and X-ray astronomy fields due to their high tolerance for alignment errors, light weight and compact size. However, the high transmittance of the grating bars in the hard X-ray range can lead to reduced efficiency of all other diffraction orders except for straight through zeroth order. We propose a novel blazed refraction grating design for the hard X-ray range that combines the advantages of transmission gratings and compound refraction lenses for the first time, demonstrating its superior performance in high broadband efficiency through compound refraction and diffraction from nanometer-scale periodic arrays of silicon prisms using beam propagation method and Fraunhofer diffraction simulation. This research develops blaze methods in gratings design and provides a new solution for compact and sensitive spectrum measurement in hard X-ray range.

Cascaded spectral light field tomography.

We present cascaded spectral light field tomography for multicolor imaging in three dimensions (3D). Building upon light field tomography, our method uses a Dove prism array and a cylindrical lens array to transform a 3D scene into one-dimensional (1D) projections. To further enhance the reconstructed image quality, we incorporate a rotating Dove prism to increase the number of projection angles and a scanning light sheet to sparsify the sample along the depth axis. The resulting 1D projections are then spectrally dispersed for parallel spectral measurements. We demonstrate the effectiveness of our system in both fluorescence and scattering microscopy applications.

Biomimetic Structurally Colored Film for High‐Performance Radiative Cooling

AbstractIn recent years, passive radiative cooling has garnered considerable attention as a sustainable thermal regulation without relying on external energy sources, thus mitigating pollutants generation. However, an intrinsic limitation of these cooling systems lies in the reflective glare, often characterized by an ivory or silvery appearance. This drawback limits their practical application, especially where both functional efficiency and aesthetic appeal are pivotal. Herein, a biomimetic approach inspired by Saharan silver ants' thermoregulatory capabilities is adopted. These ants, equipped with distinctive triangular‐shaped hair, maintain body temperature lower than the ambient air. Leveraging insights from this natural model, a reusable silicon template is employed to fabricate a metasurface structural colored film with a triangular prism array structure using thermoplastic polyurethane (TPU) and the phase separation technique. The film demonstrates an average emissivity of 96% within the atmospheric window and an average solar reflectivity of 93%, leading to a maximum temperature reduction of 8.6 °C during daytime and 5.9 °C at night. Furthermore, the film displays stretchability and mechanical resilience, bolstered by the microscale prismatic structure enhancing superhydrophobicity. This work introduces a biomimetic strategy aimed at augmenting thermal emission while reconciling the challenge of achieving visual appealand high radiative cooling performance.

Integrated GaN Prism Array Self‐Powered Photodetector on Si for Ultraviolet Imaging and Communication

AbstractTo realize the advantageous combination of microelectronic integrated circuit technology and photonic technology, the development of high‐speed, low‐power, and chip‐integrated photodetection devices is extremely critical. Here, a large‐scale on‐chip integration photodetector array on a Si wafer consisting of 21×21 GaN p‐n homojunction pixels is prepared. The GaN homojunction subunit has significant photovoltaic performance at a bias voltage of 0 V, including high responsivity of 229.5 mA W−1, outstanding specific detectivity of 2.46×1013 Jones (360 nm, 45.7 µW cm−2), and fast response speed of 240/290 µs. Especially, external quantum efficiency can reach 94% in the faint UV illumination at 0 V bias. The excellent photoresponse is confirmed by finite element analysis, which is resulted from an oversized built‐in potential at the p‐n homojunction interface. For exploring potential practical applicability of the device, the full range of active pixels is statistically analyzed. It is confirmed that the small relative deviation of the GaN array is extremely favorable for obtaining high‐resolution imaging capability. Moreover, the prepared device can be used as an optical data receiver for UV optical communication. With compatibility and integrability to Si‐based optoelectronics platforms, the devices are appealing for sensing, imaging and communications.

360-degree directional micro prism array for tabletop flat-panel light field displays.

Tabletop light field displays are compelling display technologies that offer stereoscopic vision and can present annular viewpoint distributions to multiple viewers around the display device. When employing the lens array to realize the of integral imaging tabletop light field display, there is a critical trade-off between the increase of the angular resolution and the spatial resolution. Moreover, as the viewers are around the device, the central viewing range of the reconstructed 3D images are wasteful. In this paper, we explore what we believe to be a new method for realizing tabletop flat-panel light field displays to improve the efficiency of the pixel utilization and the angular resolution of the tabletop 3D display. A 360-degree directional micro prism array is newly designed to refract the collimated light rays to different viewing positions and form viewpoints, then a uniform 360-degree annular viewpoint distribution can be accurately formed. In the experiment, a micro prism array sample is fabricated to verify the performance of the proposed tabletop flat-panel light field display system. One hundred viewpoints are uniformly distributed in the 360-degree viewing area, providing a full-color, smooth parallax 3D scene.

Mitigation of the Moiré Effect in Overlapped Optical Films by Lateral Buckling of Sharp Edges of Prism Arrays

AbstractThe moiré effect arises from the superposition of periodic structures with differences in periods or angles. Although the moiré effect can be exploited as an intriguing tool to fabricate complex metastructures, reduction of the moiré effect can be an important issue in display technology that uses many optical films with periodic patterns. Because of the superposition, dark and bright regions can be seen by the naked eye, which is a reason for the degradation of the visual quality. In this work, the lateral deformation of shape edges of prism films is harnessed to reduce the moiré effect. After the preparation of a microprism array with hydrogel materials, the hydrogel microprism array is swelled via penetration of water molecules into the hydrogel networks. Due to the compressive stress applied by volume expansion with confinement, only the sharp edges laterally buckle randomly. The swollen hydrogel prism array is replicated by photopolymerization, and prism arrays with laterally buckled edges are obtained. The randomized edges help reduce the moiré effect of the optical film when the prism array is overlapped with other periodic devices, such as other prism arrays or display devices consisting of microscale pixels, without a significant decrease in the optical performance.

Cascade bunch focusing on chip using terahertz pulses to drive prism arrays.

The dielectric laser accelerator (DLA) is a promising candidate for next-generation table-top and even on-chip particle accelerators. Long-range focusing of a tiny-size electron bunch on chip is crucial for the practical applications of DLA, which has been a challenge. Here we propose a bunch focusing scheme, which uses a pair of readily available few-cycle terahertz (THz) pulses to drive an array of millimeter-scale prisms via the inverse Cherenkov effect. The THz pulses are reflected and refracted multiple times through the prism arrays, synchronizing with and periodically focusing the electron bunch along the bunch channel. Cascade bunch-focusing is realized by making the electromagnetic field phase experienced by electrons in each stage of the array, that is, the synchronous phase, in the focusing phase region. The focusing strength can be adjusted via changing the synchronous phase and THz field intensity, optimization of which will sustain the stable bunch transportation in a tiny-size bunch channel on chip. This bunch-focusing scheme sets a base for developing a long-acceleration-range and high-gain DLA.

Efficient enhancement of photoluminescence and second-harmonic generation of few-layer InSe coupled with surface-plasmonic Ag prism array

Efficient enhancement of photoluminescence and second-harmonic generation of few-layer InSe coupled with surface-plasmonic Ag prism array

Multi-objective optimization of custom compound prism arrays for multiplexed optical imaging.

Compound prism arrays are a powerful, yet underutilized, solution for producing high transmission and customized chromatic dispersion profiles over broad bandwidths, the quality of which is unobtainable with commercially available prisms or diffraction gratings. However, the computational complexity associated with designing these prism arrays presents a barrier to the widespread adoption of their use. Here we introduce customizable prism designer software that facilitates high-speed optimization of compound arrays guided by target specifications for chromatic dispersion linearity and detector geometry. Information theory is utilized such that target parameters can be easily modified through user input to efficiently simulate a broad range of possible prism array designs. We demonstrate the capabilities of the designer software to simulate new prism array designs for multiplexed, hyperspectral microscopy that achieve chromatic dispersion linearity and a 70-90% light transmission over a significant portion of the visible wavelength range (500-820 nm). The designer software is applicable to many optical spectroscopy and spectral microscopy applications-with varying requirements for spectral resolution, light ray deviation, and physical size-that are photon-starved and for which the enhanced transmission of refraction versus diffraction warrants custom optical designs.

Adaptive aberration correction using an electrowetting array.

We demonstrate a method that permits wavefront aberration correction using an array of electrowetting prisms. A fixed high fill factor microlens array followed by a lower fill factor adaptive electrowetting prism array is used to correct wavefront aberration. The design and simulation of such aberration correction mechanism is described. Our results show significant improvement to the Strehl ratio by using our aberration correction scheme which results in diffraction limited performance. Compactness and effectiveness of our design can be implemented in many applications that require aberration correction, such as microscopy and consumer electronics.

Flange-type liquid-level sensor based on laser light reflection

We report a liquid-level sensor composed of a laser, prism, and photodiode array. The sensor does not require components, such as a sensor head, inside the container that stores liquid. The sensor detects the liquid level based on the difference between the intensities of laser light reflected at the liquid/glass and air/glass interfaces. As the detected liquid level shows a shift from the correct liquid level owing to surface tension and the broadening of the laser light, we correct the shift through calculations. The sensor can be attached to a flange-type glass viewport, providing compatibility with broad-ranging containers for industrial use. The sensor can accurately detect the liquid level with a maximum error of 0.3875 ​mm. We demonstrate the implementation and operation of the liquid-level sensor using a wireless system comprising a sensor head and wireless voltmeter. The reported sensor allows accurate measurement of the liquid level in a tank inside which foreign objects such as sensor heads cannot be installed.

Reflection-mode nanostructured GaAlAs photocathode with narrow-band response to 532 nm

The underwater photoelectric detection equipment mainly uses 532 nm laser as the light source, but the corresponding photocathodes like Na2KSbCs, GaAs and GaAsP have a wide spectral response region and are easily affected by other signals. Thereby, GaAlAs are materials worth developing because of their adjustable band gap, which usually is used as a window layer of GaAs-based photocathode. In this paper, the finite difference time domain (FDTD) method is used to carry out nanostructure design simulations. The results show that GaAlAs with Al component of 0.63 can obtain the cutoff wavelength near 532 nm, which is an excellent photocathode material to meet the requirement of narrow-band spectral response of 532 nm laser. Furthermore, the light absorptance can be improved effectively by the quadrangular prism or cylinder nanostructured array prepared on the Ga[Formula: see text]Al[Formula: see text]As emission layer surface, and the maximum light absorptance can reach 96.2% at 532 nm for the cylinder nanostructure array with a height of 900 nm and a base width of 100 nm. Nevertheless, the reflection-mode Ga[Formula: see text]Al[Formula: see text]As photocathode with the quadrangular prism nanostructured array can be slightly influenced with incident angle of light.

Protein Crystallization-Mediated Self-Strengthening of High-Performance Printable Conducting Organohydrogels.

Conductive polymers have many advanced applications, but there is still an important target in developing a general and straightforward strategy for printable, mechanically stable, and durable organohydrogels with typical conducting polymers of, for example, polypyrrole, polyaniline, or poly(3,4-ethylenedioxythiophene). Here we report a protein crystallization-mediated self-strengthening strategy to fabricate printable conducting organohydrogels with the combination of rational photochemistry design. Such organohydrogels are one-step prepared via rapidly and orthogonally controllable photopolymerizations of pyrroles and gelatin protein in tens of seconds. As-prepared conducting organohydrogels are patterned and printed to complicated structures via shadow-mask lithography and 3D extrusion technology. The mild photocatalytic system gives the transition metal carbide/nitride (MXene) component high stability during the oxidative preparation process and storage. Controlling water evaporation promotes gelatin crystallization in the as-prepared organohydrogels that significantly self-strengthens their mechanical property and stability in a broad temperature range and durability against continuous friction treatment without introducing guest functional materials. Also, these organohydrogels have commercially electromagnetic shielding, thermal conducting properties, and temperature- and light-responsibility. To further demonstrate the merits of this simple strategy and as-prepared organohydrogels, prism arrays, as proofs-of-concept, are printed and applied to make wearable triboelectric nanogenerators. This self-strengthening process and 3D-printability can greatly improve their voltage, charge, and current output performances compared to the undried and flat samples.

Integrated Solar‐Driven Device with a Front Surface Semitransparent Catalysts for Unassisted CO2 Reduction

AbstractMonolithic integrated photovoltaic‐driven electrochemical (PV‐EC) artificial photosynthesis is reported for unassisted CO2 reduction. The PV‐EC structures employ triple junction photoelectrodes with a front mounted semitransparent catalyst layer as a photocathode. The catalyst layer is comprised of an array of microscale triangular metallic prisms that redirect incoming light toward open areas of the photoelectrode to reduce shadow losses. Full wave electromagnetic simulations of the prism array (PA) structure guide optimization of geometries and length scales. An integrated device is constructed with Ag catalyst prisms covering 35% of the surface area. The experimental device has close to 80% of the transmittance with a catalytic surface area equivalent 144% of the glass substrate area. Experimentally this photocathode demonstrates a direct solar‐to‐CO conversion efficiency of 5.9% with 50 h stability. Selective electrodeposition of Cu catalysts onto the surface of the Ag triangular prisms allows CO2 conversion to higher value products enabling demonstration of a solar‐to‐C2+ product efficiency of 3.1%. This design featuring structures that have a semitransparent catalyst layer on a PV‐EC cell is a general solution to light loss by shadowing for front surface mounted metal catalysts, and opens a route for the development of artificial photosynthesis based on this scalable design approach.

Hybrid non-sequential modeling of an image mapping spectrometer.

An image mapping spectrometer (IMS) is a kind of snapshot imaging spectrometer characterized by containing several array components including the image mapper, prism array, and reimaging lens array. We propose a hybrid non-sequential modeling method of IMS and present the complete optical model of the system built in Zemax. This method utilizes the spatial periodicity of the array components and requires only a small number of input parameters. Moreover, we design a collimating lens of a large relative aperture, sufficient working distance, and low aberration to meet the requirements of an IMS with good optical performance and compact volume. The designed lens is quantitatively evaluated in the entire IMS model, and the results demonstrate that the lens has excellent optical performance. The evaluation on the collimating lens also demonstrates the capability of the proposed modeling method in the design and optimization of systems such as the IMS that contain multiple array components. The designed collimating lens is manufactured and assembled in the experimental setup of the IMS. The proposed modeling method is verified by experimental results.

Simultaneous solar rejection and infrared emission switching using an integrated dielectrics-on-VO2 metasurface

Passive infrared emittance switching can be achieved with a metal-to-insulating phase transition material vanadium dioxide (VO2), but its non-transitioning bandgap results in high absorptance in the visible wavelength range. To achieve a half-order reduction of absorptance in the visible to near-infrared region, we design integrated dielectric photonic metasurface structures on monolithic VO2 coatings. This combination of nano/micro-patterned dielectric diffractive and resonant gratings with a multilayer VO2 structure preserves the terrestrial thermal wavelength emission switching capabilities. We demonstrate a periodic microscale diffractive prism array, comparing the reflectance provided by either infrared-transparent germanium (Ge) or silicon (Si). Despite the advantage of total internal reflection in the broad near-infrared region, some bandgap absorption limits the performance in the visible wavelengths. A better theoretical means to reflect broadband light via waveguide-like Fabry–Pérot resonance are near-wavelength 1D and 2D High Contrast Grating (HCG) high-index metasurface structures surrounded by a low-index host medium. This HCG metasurface allows broadband high-quality reflection within the dual-mode (or tri-mode) region from 1.0 to 2.2 µm wavelengths for HCG with a refractive index of 4.0, which corresponds to Ge. This study investigates the advantages and disadvantages along with the thermal performance of these metasurface augments aimed to enable thermally switchable passive radiative cooling—thermal emission exceeding solar absorption—of solar cells, terrestrial buildings, and energy storage devices.

Enhanced lighting on the road surface with TIR-PA optical element on tunnel sidewall.

Both the lighting quality and driving safety inside the tunnel have been quite a concern around the world. In this study, a plate with prism array of total internal reflection (TIR-PA) has been designed to enhance the lighting on the road surface inside the tunnel in adherence to traffic safety as well as energy savings. Such optical elements, above the tunnel sidewall, can redirect the rays emitted from both the headlight and lighting devices to the road surface, which supports higher flux on the road. Simultaneously, the simulation is conducted with consideration of practical factors based on the mathematical model and edge-ray principle to attain the effect of the TIR-PA plates. On the one hand, for the rays from the lighting devices, the enhancement rate of illuminance has reached 12.60%-16.58%, which is attributed to TIR-PA plates above the different sidewalls of the Lambertian scattering property. TIR-PA can be suitable for various sidewall materials due to the small effect of illumination reduction. On the other hand, 30.2%-32.2% rays of the headlight source received by the sidewall, due to the effect of TIR-PA plates, are redirected to the driving distance for 27.3-71.9 m, which makes 15.9-31.1m2 of road surface brighter. It makes contributions to the improvement of illuminance distribution and drivers' pre-judgment. In the future, broader applications regarding the TIR-PA plates will be explored widely in tunnel lighting systems due to the low production cost.

Field-of-view enhanced integral imaging with dual prism arrays based on perspective-dependent pixel mapping.

A field-of-view (FOV)-enhanced integral imaging system is proposed by the combined use of micro-lens array (MLA) and dual-prism array (DPA). The MLA coupled with a DPA virtually function as a new type of the MLA whose FOV is much more increased than that of the original MLA, which enables the capturing of perspective-expanded elemental image arrays (EIAs) of input 3-D scenes and the FOV-enhanced reconstruction of them. For its practical operation, a two-step digital process called perspective-dependent pixel-mapping (PDPM) is also presented. With this PDPM method, picked-up EIAs with a couple of MLAs and DPAs are remapped into the new forms of EIAs to be properly reconstructed in the conventional integral imaging system. Operational performances of the proposed system are ray-optically analyzed. In addition, the feasibility of the proposed system is also confirmed from the computational and optical experiments with test 3-D objects on the implemented prototype. Experimental results finally show a two-times increase of the FOV range of the proposed system when it is compared with that of the conventional system.

Overlapping-free dual-view integral imaging display

In this paper, an overlapping-free dual-view integral imaging (II) display system was proposed. The light rays emitted from the left and right parts of the compound element images were deflected into opposite directions by using a prism array, thus the left and right viewing zones were completely separated. In addition, a compound elemental image array generation method was also proposed, in which a non-uniform camera array was built up according to the viewpoints distribution of the proposed system. Compared with previous dual-view II displays, our proposed system avoided the overlapping images between two viewing zones, and the crosstalk was removed. In the experiment, we designed and developed a prototype whose left and right viewing zones were spatially separated. The left and right viewing angles were both 28°, and the angular spacing between them was 54°. Both viewing zones presented vivid three-dimensional display performances. Our proposed dual-view II display system is eminently suitable for the vehicle display.