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1.
iScience ; 23(1): 100773, 2019 Dec 13.
Artigo em Inglês | MEDLINE | ID: mdl-31887666

RESUMO

Glasses-free three-dimensional (3D) display is considered as a potential disruptive technology for display. The issue of visual fatigue, mainly caused by the inaccurate phase reconstruction in terms of image crosstalk, as well as vergence and accommodation conflict, is the critical obstacle that hinders the real applications of glasses-free 3D display. Here we propose a glasses-free 3D display by adopting metagratings for the pixelated phase modulation to form converged viewpoints. When the viewpoints are closely arranged, the holographic sampling 3D display can approximate a continuous light field. We demonstrate a video rate full-color 3D display prototype without visual fatigue under an LED white light illumination. The metagratings-based holographic sampling 3D display has a thin form factor and is compatible with traditional flat panel and thus has the potential to be used in portable electronics, window display, exhibition display, 3D TV, as well as tabletop display.

2.
Opt Express ; 27(21): 29547-29557, 2019 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-31684214

RESUMO

Flexible electronics, as a futuristic technology, is presenting tremendous impact in areas of wearable displaying, energy saving, and adaptive camouflage. In this work, we constructed a simple triple-layered electrochemical device with high flexibility using the electroplated nickel (Ni) grid electrode and the multifunctional hydrogel. The Ni grid electrode with low resistance (0.5 Ω/sq), high optical transparency (84.8%) and good mechanical flexibility, is beneficial for efficient electron injection, while the transparent lithium chloride hydrogel functions simultaneously for ion storage, ion transportation and counter-conducting. The thin polymer poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS) film is utilized as the electrochromic (EC) material and it also distributes the electrons evenly for uniform coloration. The triple-layered EC architecture not only simplifies the manufacturing procedures but also improves the device performance in terms of optical contrast and mechanical robustness. The device shows fast response for coloration and bleaching with an absolute transmittance contrast of 40% and a contrast retention over 72% after 2500 bending cycles. The ability of the flexible electrochromic device for conformable attaching was also investigated without obvious performance degradation. The electroplated Ni grid electrode and the multifunctional hydrogel are advantageous in constructing flexible electrochromic devices in terms of the response time, the working stability and the bending capability, paving a way for next-generation flexible electronics.

3.
Opt Express ; 27(17): 24194-24206, 2019 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-31510313

RESUMO

A unique freestanding nickel (Ni) metallic mesh-based electromagnetic interference shielding film has been fabricated though the direct-writing technique and a subsequent selective metal electrodeposited process. The structured freestanding Ni mesh film demonstrates a series of advantages, including ultrathin thickness (2.5-6.0 µm) and ultralight weight (0.23 mg cm-2), extraordinary optoelectronic performance (sheet resistance about 0.24-0.7 Ω sq-1 with transparency of 92%-93%), high figure of merit (18000) and outstanding flexibility as it can withstand folding, rolling and crumpling into various shapes while keeping the conductivity constant. Furthermore, by using this high-performance Ni mesh, an ultrathin, lightweight, freestanding and transparent electromagnetic interference shielding (EMI) film with extraordinary optoelectronic properties (shielding effectiveness about 40 dB with transparency of 92%) is demonstrated in X-band, with no performance attenuation observed even in bending state. This freestanding metallic mesh-structured electrode can be further explored or applied in various potential applications, such as conformal microwave antennas, transparent EMI windows, and wearable electronics.

4.
Opt Express ; 27(7): 9570-9577, 2019 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-31045106

RESUMO

This study develops a large-area pixelated filter that can achieve colors covering the entire visible range with a fixed period under normal incidence. Vivid colors as blue, green, and yellow (peak efficiency of ~60%) are experimentally achieved based on a Fano-resonance by altering the overlay's refractive index, which is highly sensitive to the surrounding material. Furthermore, the feasibility of using this device in large-area color printing and index sensors is discussed in detail, wherein a large-area (3 cm × 3 cm) logo and a figure of merit of 254 are achieved. Therefore, this developed structure can be regarded as an alternative to traditional periodic-dependent structure colors, which can also be performed as index sensors with high sensitivity.

5.
Opt Express ; 27(7): 10022-10033, 2019 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-31045149

RESUMO

We propose and demonstrate the versatile fabrication of optical subwavelength microcavities by using imaging holography. As a demonstration, a peculiar square optical microcavity with a periodicity of 400 nm is imaged from a micrometer-scale diffractive optical element, attributing to the interference by the refocusing of the multiple diffractive beams. By spin-coating an active conjugated polymer onto the microcavity, highly directional laser emission with a low pumping threshold of 0.5 kW/cm2 is achieved. The effect of the film thickness on the lasing performance is also investigated. This imaging holography technique can enable convenient and easy fabrication of optical microcavities with subwavelength features, hence providing significant flexibility and richness on engineering the optical response of photonic nanostructures.

6.
Opt Express ; 27(5): 7513-7522, 2019 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-30876314

RESUMO

A compound-eye imaging system based on the phase diffractive microlens array as a compact observation module is proposed. As compared with the refractive microlens in common compound-eye imaging systems, the diffractive microlens is a flat imaging optics featuring high relative aperture, thin component thickness and compatibility with lithography techniques. As an application, a compact fingerprint imaging module was demonstrated using this compound-eye imaging system. The phase Fresnel microlens array with continuous trough morphology was fabricated via the self-developed gray-scale laser direct write equipment. An image reconstruction method is proposed by extracting the effective image information of each Fresnel microlens, removing the complex signal separator layer from the compound-eye imaging system. The illumination optics is further planarized through the waveguide backlighting and the waveguide functions as the touch panel for fingerprint recording. The novel compound-eye imaging device length was only restricted by the focal length of the microlens with a low limit of 4.12f. The applicability of this novel compound-eye imaging system was further demonstrated by recording the human fingerprint texture, paving ways for various applications as a compact imaging system.

7.
Opt Express ; 26(21): 27482-27491, 2018 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-30469814

RESUMO

To date, near-perfect light absorbers at visible frequency are still severely impeded by the complicated architecture design and time-consuming costly fabrication procedures. In this work, we design and fabricate a new cost-effective near-perfect absorber at visible frequency based on homogenous meta-surface nickel (Ni) with a two-dimension cylinder array. The simulated and measured average absorption at normal incidence are beyond 94% and 92% over the entire visible wavelength band from 400 nm to 700 nm, respectively. Additionally, the absorbance property was well retained, and the absorptivity still remained beyond 70% when the incident angles vary from 0° to 60°. Our theoretically and experimentally results indicate that the broadband wide-angular absorption can be ascribed to the Rayleigh-Wood anomaly combined with slot modes induced by excited surface plasmon polaritons. Moreover, the low-cost double-beam interference lithography followed by soft nano-imprinting and electroforming technology, which are directly compatible with the cost-effective and high volume manufacturing requirements, are employed to fabricate the proposed absorber. The proposed approach is simple and inexpensive and the obtained ultrathin homogenous meta-surface nickel absorber can be rolled or folded on the surface of various optoelectronics, such as solar system and radiation thermal devices.

8.
Opt Express ; 26(17): 21479-21489, 2018 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-30130854

RESUMO

We present an omnidirectional broadband metasurface absorber whose dielectric-metal-dielectric layers are modulated by cylinder arrays. The simultaneous excitation of surface plasmon resonance and localized surface plasmon resonance affords an average optical absorption of 0.97 (0.9, experiment), with peak absorption up to 0.99 (0.984, experiment), for the wavelength range of 400-1100 nm, and absorption >0.93 (0.87, experiment) for incident angles up to 60°. The device, which is fabricated by continuously variable spatial frequency photolithography, outperforms previously reported absorbers in cost. Moreover, it exhibits considerably lower emissivity (weak absorption) in the mid-infrared range, which makes it promising for energy harvesting.

9.
Appl Opt ; 57(14): 3674-3678, 2018 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-29791332

RESUMO

A metadielectric nanostructure with narrow cavities is proposed, behaving as a reflective color filter for TM-polarized light while as a broadband reflector for TE-polarized light. By varying the cavity depth or changing the incident light polarization, reflective colors of the proposed structure cover the entire visible spectrum conveniently. In particular, the reflections of this proposed structure show good angular tolerance up to 50° for both polarizations. Furthermore, it can display colors even with two grating slits, which shows high printing resolution up to 70555 dpi, having great potential for applications of a large area color imaging and anticounterfeiting devices.

10.
J Nanosci Nanotechnol ; 18(4): 2965-2970, 2018 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-29442981

RESUMO

In this work, gas sensors based on chemically reduced graphene oxide (rGO) foams were reported for NH3 detection. Polymer foams were used as scaffolds to support rGO, and the resultant soft sensing devices exhibited a high sensitivity, high selectivity, and rapid recovery for NH3 detection at room temperature. The sensor showed more than 0.90% and 3.67% resistance changes respectively, when it's exposed to 1 ppm and 50 ppm NH3. The graphene foam gas sensors (FGS) also showed excellent repeatability. Furthermore, the response of rGO foam gas sensor to NH3 was more than two times higher than that to methanol vapors diluted to 1% of the saturated vapor concentration. Above all, the unique features, such as simple preparation, low cost and energy consumption, as well as excellent sensing performance, endow the sensor a great potential for NH3 detection.

11.
Appl Opt ; 56(22): 6094-6102, 2017 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-29047801

RESUMO

In this paper, we have developed a novel model that is named graph-regularized tensor robust principal component analysis (GTRPCA) for denoising hyperspectral images (HSIs). Incorporating spectral graph regularization into TRPCA makes the model more accurate by preserving local geometric structures embedded in a high-dimensional space. Based on tensor singular value decomposition (t-SVD), we introduce a general tensor-based altering direction method of multipliers (ADMM) algorithm which can solve the proposed model for denoising HSIs. Experiments on both the synthetic and real captured datasets have demonstrated the effectiveness of the proposed method.

12.
Opt Express ; 25(13): 14008-14022, 2017 Jun 26.
Artigo em Inglês | MEDLINE | ID: mdl-28788986

RESUMO

Multispectral light field acquisition is challenging due to the increased dimensionality of the problem. In this paper, inspired by anaglyph theory (i.e. the ability of human eyes to synthesize colored stereo perception from color-complementary (such as red and cyan) views), we propose to capture the multispectral light field using multiple cameras with different wide band filters. A convolutional neural network is used to extract the joint information of different spectral channels and to pair the cross-channel images. In our experiment, results on both synthetic data and real data captured by our prototype system validate the effectiveness and accuracy of proposed method.

13.
Opt Express ; 25(14): 16715-16724, 2017 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-28789173

RESUMO

Broadband metamaterial absorber (MA) in the whole visible regime has attracted an enormous amount of attention for its potential applications in thermophotovoltaic cells, thermal emitters, and other optoelectronic devices. Nonetheless, complicated device configuration is still involved in achieving broadband, polarization-independent MA and it results in a cost-ineffective fabrication process. In this paper, a novel MA composed of a periodic array of dielectric cylinder sandwiched by the non-noble metal of nickel (Ni) film is demonstrated. Experimental results show that the proposed MA exhibits strong absorptive behavior independent of polarization in the whole visible regime (400-700 nm). The absorption still remains 80% when the incident angle is 60°. The proposed fabrication method is well compatible with the conventional soft nano-imprinting lithography technique, thus it is economic and scalable for a large-format substrate. These results provide an alternative method for the realization of high-performance visible light absorber and offer new opportunities for potential applications in related fields.

14.
ACS Appl Mater Interfaces ; 9(33): 27649-27656, 2017 Aug 23.
Artigo em Inglês | MEDLINE | ID: mdl-28758739

RESUMO

Flexible transparent solid-state supercapacitors have attracted immerse attention for the power supply of next-generation flexible "see-through" or "invisible" electronics. For fabrication of such devices, high-performance flexible transparent current collectors are highly desired. In this paper, the utilization of embedded Ag grid transparent conductive electrodes (TCEs) fabricated by a facile soft ultraviolet imprinting lithography method combined with scrap techniques, as the current collector for flexible transparent solid-state supercapacitors, is demonstrated. The embedded Ag grid TCEs exhibit not only excellent optoelectronic properties (RS ∼ 2.0 Ω sq-1 and T ∼ 89.74%) but also robust mechanical properties, which could meet the conductivity, transparency, and flexibility needs of current collectors for flexible transparent supercapacitors. The obtained supercapacitor exhibits large specific capacitance, long cycling life, high optical transparency (T ∼ 80.58% at 550 nm), high flexibility, and high stability. Owing to the embedded Ag grid TCE structure, the device shows a slight capacitance loss of 2.6% even after 1000 cycles of repetitive bending for a bending radius of up to 2.0 mm. This paves the way for developing high-performance current collectors and thus flexible transparent energy storage devices, and their general applicability opens up opportunities for flexible transparent electronics.

15.
Opt Lett ; 42(10): 1978-1981, 2017 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-28504728

RESUMO

We report the development of a unique scalable Fourier transform 4-f system for instantly structured illumination in lithography. In the 4-f system, coupled with a 1-D grating and a phase retarder, the ±1st order of diffracted light from the grating serve as coherent incident sources for creating interference patterns on the image plane. By adjusting the grating and the phase retarder, the interference fringes with consecutive frequencies, as well as their orientations and phase shifts, can be generated instantly within a constant interference area. We demonstrate that by adapting this scalable Fourier transform system into lithography, the pixelated nano-fringe arrays with arbitrary frequencies and orientations can be dynamically produced in the photoresist with high variation resolution, suggesting its promising application for large-area functional materials based on space-variant nanostructures in lithography.

16.
Opt Express ; 25(2): 1114-1122, 2017 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-28157996

RESUMO

Limited by the refreshable data volume of commercial spatial light modulator (SLM), electronic holography can hardly provide satisfactory 3D live video. Here we propose a holography based multiview 3D display by separating the phase information of a lightfield from the amplitude information. In this paper, the phase information was recorded by a 5.5-inch 4-view phase plate with a full coverage of pixelated nano-grating arrays. Because only amplitude information need to be updated, the refreshing data volume in a 3D video display was significantly reduced. A 5.5 inch TFT-LCD with a pixel size of 95 µm was used to modulate the amplitude information of a lightfield at a rate of 20 frames per second. To avoid crosstalk between viewing points, the spatial frequency and orientation of each nano-grating in the phase plate was fine tuned. As a result, the transmission light converged to the viewing points. The angular divergence was measured to be 1.02 degrees (FWHM) by average, slightly larger than the diffraction limit of 0.94 degrees. By refreshing the LCD, a series of animated sequential 3D images were dynamically presented at 4 viewing points. The resolution of each view was 640 × 360. Images for each viewing point were well separated and no ghost images were observed. The resolution of the image and the refreshing rate in the 3D dynamic display can be easily improved by employing another SLM. The recoded 3D videos showed the great potential of the proposed holographic 3D display to be used in mobile electronics.

17.
Adv Mater ; 28(47): 10353-10380, 2016 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-27976840

RESUMO

Continuous and scalable nanopatterning over flexible substrates is highly desirable for both commercial and scientific interests, but is difficult to realize with traditional photolithographic processes. The recent advancements in nanofabrication methodologies enable light management with photonic structures on flexible materials, providing an increasingly popular strategy to control the light harvesting in the optoelectronic devices of photovoltaics, and in organic and inorganic light-emitting diodes. Here, the current status of nanopatterning technologies for the fabrication of optoelectronic devices is summarized. Scalable nanopatterning technologies for nanomanufacturing on flexible materials are emphasized. Critical challenges in various patterning techniques when considering the resolution, scalability, processing throughput, and the use of masks and resists are addressed. The integration of flexible nanopatterned substrates with light manipulation in organic optoelectronic devices is also discussed; this enables the control of light flux and spectra. Finally, potential development directions are highlighted.

18.
Opt Express ; 24(22): 25774-25784, 2016 Oct 31.
Artigo em Inglês | MEDLINE | ID: mdl-27828512

RESUMO

An embedded Ag mesh transparent conductive electrode (TCE) on flexible substrate, which is suitable for polymer dispersed liquid crystal (PDLC) device, is demonstrated. With the combination of soft ultra-violet nanoimprinting lithography and scrape technique, it offers parallel processing with high resolution (10000dpi), as well as remarkable simplicity and fully controllable flexibility to tailor the transmittance and sheet resistance. While being able to achieve maximum transmittance 60% in the on state and the minimum 0.1% in the off state, the PDLC smart window displays low sheet resistance (5.58 Ω/sq.) under low driven voltage (30V) safe for human. The main advantage of adoption of PDLC as an optically scattering element lies in the fact that there needs no mechanical part for in situ tunability. An enhancement factor of 50 of the diffraction intensity is observed experimentally. The embedded Ag mesh TCE for PDLC device has an environmentally-friendly additive manufacturing process inherently. Compared to existing solutions, the fabricated sample shows superior performance in both optoelectronic and mechanic characteristics. We envision that the embedded Ag mesh TCE will enable economically widen application of PDLC devices on flexible substrate.

19.
Sci Rep ; 6: 28319, 2016 06 22.
Artigo em Inglês | MEDLINE | ID: mdl-27328713

RESUMO

Diffractive optical elements suffer from large chromatic aberration due to the strong wavelength-dependent nature in diffraction phenomena, and therefore, diffractive elements can work only at a single designed wavelength, which significantly limits the applications of diffractive elements in imaging. Here, we report on a demonstration of a wavefront coded broadband achromatic imaging with diffractive photon sieves. The broadband diffraction imaging is implemented with a wavefront coded pinhole pattern that generates equal focusing power for a wide range of operating wavelength in a single thin-film element without complicated auxiliary optical system. Experimental validation was performed using an UV-lithography fabricated wavefront coded photon sieves. Results show that the working bandwidth of the wavefront coded photon sieves reaches 28 nm compared with 0.32 nm of the conventional one. Further demonstration of the achromatic imaging with a bandwidth of 300 nm is also performed with a wavefront coded photon sieves integrated with a refractive element.

20.
Opt Express ; 24(6): 6203-12, 2016 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-27136814

RESUMO

Without any special glasses, multiview 3D displays based on the diffractive optics can present high resolution, full-parallax 3D images in an ultra-wide viewing angle. The enabling optical component, namely the phase plate, can produce arbitrarily distributed view zones by carefully designing the orientation and the period of each nano-grating pixel. However, such 3D display screen is restricted to a limited size due to the time-consuming fabricating process of nano-gratings on the phase plate. In this paper, we proposed and developed a lithography system that can fabricate the phase plate efficiently. Here we made two phase plates with full nano-grating pixel coverage at a speed of 20 mm2/mins, a 500 fold increment in the efficiency when compared to the method of E-beam lithography. One 2.5-inch phase plate generated 9-view 3D images with horizontal-parallax, while the other 6-inch phase plate produced 64-view 3D images with full-parallax. The angular divergence in horizontal axis and vertical axis was 1.5 degrees, and 1.25 degrees, respectively, slightly larger than the simulated value of 1.2 degrees by Finite Difference Time Domain (FDTD). The intensity variation was less than 10% for each viewpoint, in consistency with the simulation results. On top of each phase plate, a high-resolution binary masking pattern containing amplitude information of all viewing zone was well aligned. We achieved a resolution of 400 pixels/inch and a viewing angle of 40 degrees for 9-view 3D images with horizontal parallax. In another prototype, the resolution of each view was 160 pixels/inch and the view angle was 50 degrees for 64-view 3D images with full parallax. As demonstrated in the experiments, the homemade lithography system provided the key fabricating technology for multiview 3D holographic display.

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