Showing papers by "Minghui Hong published in 2017"
TL;DR: In this paper, a method to multiplex and demultiplex multiple OAMs, wavelengths, and polarizations channels by a highly integrated off-axis technique on a metasurface is presented.
Abstract: Orbital angular momentum (OAM) has recently gained much interest in high-speed optical communication due to its spatial orthogonality. However, complex spatial phase distributions of OAM make the components difficult for nano-photonic integration. In this work, a method to multiplex and demultiplex multiple OAMs, wavelengths, and polarizations channels by a highly integrated off-axis technique on a metasurface is presented. As a multiplexer, beams without OAM can be transferred into coaxial beams carrying different OAM features by different incident angles; as a demultiplexer, coaxial beams carrying multi-OAMs can be divided into different directions with fundamental modes. Furthermore, the component based on dipole optical antenna metasurface can be used not only as an OAM multiplexer/demultiplexer but also as a multiplexer/demultiplexer to achieve wavelength division multiplexing and polarization-division multiplexing, as both these applications are based on the conservations of momentum and angular momentum. For practical applications, phase-only hologram is analyzed to demonstrate multiple functions of this method.
147 citations
TL;DR: A planar metalens for achieving super-resolution imaging in far-field is proposed, which has a non-sub-wavelength feature size and can be fabricated by conventional laser pattern generator.
Abstract: A planar metalens for achieving super-resolution imaging in far-field is proposed. This metalens, which has a non-sub-wavelength feature size, can be fabricated by conventional laser pattern generator. The imaging process is purely physical and captured in real time, without any pre- and post-processing.
139 citations
TL;DR: A biodegradable flexible SERS film via irreversibly and longitudinally stretching metal deposited biocompatible poly(ε-caprolactone) film is demonstrated and can be conformally attached onto arbitrary nonplanar surfaces for in situ detection of various chemicals.
Abstract: Surface-enhanced Raman scattering (SERS) spectroscopy affords a rapid, highly sensitive, and nondestructive approach for label-free and fingerprint diagnosis of a wide range of chemicals. It is of great significance to develop large-area, uniform, and environmentally friendly SERS substrates for in situ identification of analytes on complex topological surfaces. In this work, we demonstrate a biodegradable flexible SERS film via irreversibly and longitudinally stretching metal deposited biocompatible poly(e-caprolactone) film. This composite film after stretching shows surprising phenomena: three-dimensional and periodic wave-shaped microribbons array embedded with a high density of nanogaps functioning as hot-spots at an average gap size of 20 nm and nanogrooves array along the stretching direction. The stretched polymer surface plasmon resonance film gives rise to more than 10 times signal enhancement in comparison with that of the unstretched composite film. Furthermore, the SERS signals with high uniformity exhibit good temperature stability. The polymer SPR film with excellent flexibility and transparency can be conformally attached onto arbitrary nonplanar surfaces for in situ detection of various chemicals. Our results pave a new way for next-generation flexible SERS detection means, as well as enabling its huge potentials toward green wearable devices for point-of-care diagnostics.
87 citations
TL;DR: This work fabricates a ternary hetero-nanostructured Ag-CuO-ZnO nanotube (NT) composite fabricated via facile and low-temperature chemical and photochemical deposition methods and demonstrates much higher photostability and retains ∼98% of degradation efficiency even after 20 usage cycles.
Abstract: Solar energy represents a robust and natural form of resource for environment remediation via photocatalytic pollutant degradation with minimum associated costs. However, due to the complexity of the photodegradation process, it has been a long-standing challenge to develop reliable photocatalytic systems with low recombination rates, excellent recyclability, and high utilization rates of solar energy, especially in the visible light range. In this work, a ternary hetero-nanostructured Ag–CuO–ZnO nanotube (NT) composite is fabricated via facile and low-temperature chemical and photochemical deposition methods. Under visible light irradiation, the as-synthesized ZnO NT based ternary composite exhibits a greater enhancement (∼300%) of photocatalytic activity than its counterpart, Ag–CuO–ZnO nanorods (NRs), in pollutant degradation. The enhanced photocatalytic capability is primarily attributed to the intensified visible light harvesting, efficient charge carrier separation and much larger surface area. Furthermore, our as-synthesised hybrid ternary Ag–CuO–ZnO NT composite demonstrates much higher photostability and retains ∼98% of degradation efficiency even after 20 usage cycles, which can be mainly ascribed to the more stable polar planes of ZnO NTs than those of ZnO NRs. These results afford a new route to construct ternary heterostructured composites with perdurable performance in sewage treatment and photocorrosion suppression.
80 citations
TL;DR: This conceptual design deviates from the conventional by deliberately employing back-reflecting NIR to enable waste heat reutilization/recuperation to enhance pyroelectric generation, avoiding excessive solar heat uptake and also retaining high visual transparency of the device.
Abstract: At present, there are various limitations to harvesting ambient waste heat which include the lack of economically viable material and innovative design features that can efficiently recover low grade heat for useful energy conversion. In this work, a thermal nanophotonic-pyroelectric (TNPh-pyro) scheme consisting of a metamaterial multilayer and pyroelectric material, which performs synergistic waste heat rejection and photothermal heat-to-electricity conversion, is presented. Unlike any other pyroelectric configuration, this conceptual design deviates from the conventional by deliberately employing back-reflecting NIR to enable waste heat reutilization/recuperation to enhance pyroelectric generation, avoiding excessive solar heat uptake and also retaining high visual transparency of the device. Passive solar reflective cooling up to 4.1 °C is demonstrated. Meanwhile, the photothermal pyroelectric performance capitalizing on the back-reflecting effect shows an open circuit voltage (Voc) and short circuit ...
64 citations
TL;DR: In this paper, a broadband acoustic metamaterial comprising a space coiling structure was proposed and demonstrated by introducing an impedance-matching layer between air and the metammaterial, which is achieved by especially designing the parameters of the space-coiling structure to form a gradient index.
Abstract: Narrowband transmission of some acoustic metamaterials limits their device applications. Here, we propose and demonstrate a broadband acoustic metamaterial comprising a space coiling structure by introducing an impedance-matching layer between air and the metamaterial. The impedance-matching layer is achieved by especially designing the parameters of the space coiling structure to form a gradient index. It is found that the metamaterial with the impedance matching layers substantially improves energy transmission in the frequency range of 2–6 kHz. We also show the capability of such a metamaterial to modulate the phase of acoustic waves with high energy transmission up to at least 60%.
46 citations
26 Oct 2017
TL;DR: In this paper, the authors present a highly sensitive microfluidic sensing technique for the terahertz (THz) region of the electromagnetic spectrum based on spoof surface plasmon polaritons (SPPs).
Abstract: We present a highly sensitive microfluidic sensing technique for the terahertz (THz) region of the electromagnetic spectrum based on spoof surface plasmon polaritons (SPPs). By integrating a microfluidic channel in a spoof SPP waveguide, we take advantage of these highly confined electromagnetic modes to create a platform for dielectric sensing of liquids. Our design consists of a domino waveguide, that is, a series of periodically arranged rectangular metal blocks on top of a metal surface that supports the propagation of spoof SPPs. Through numerical simulations, we demonstrate that the transmission of spoof SPPs along the waveguide is extremely sensitive to the refractive index of a liquid flowing through a microfluidic channel crossing the waveguide to give an interaction volume on the nanoliter scale. Furthermore, by taking advantage of the insensitivity of the domino waveguide’s fundamental spoof SPP mode to the lateral width of the metal blocks, we design a tapered waveguide able to achieve further...
31 citations
TL;DR: In this paper, a submicron periodic nanostructure called Periodic upright nanopyramids (PuNPs) is fabricated by an integrated process of laser interference lithography and anisotropic etching of silicon in an alkaline solution.
Abstract: Motivated by the primary benefit of reduced material cost, the thickness of crystalline silicon solar cells has been continuously reduced. Laboratory and industrial studies have explored ultrathin crystalline silicon solar cells below 50 μ m with ambitious endeavors toward thicknesses of only a few micrometers. Ultrathin crystalline silicon solar cells require compatible small-scale surface textures to enhance the optical absorption. For this purpose, a novel submicron periodic nanostructure—periodic upright nanopyramids (PuNPs)—is fabricated by an integrated process of laser interference lithography and anisotropic etching of silicon in an alkaline solution. By simulation and measurements, we demonstrate that PuNPs are able to reduce front surface reflectance more effectively than conventional micron-scale pyramid textures and previously investigated periodic inverted nanopyramids (PiNPs). With a silicon nitride antireflection coating, we predict that PuNPs reduce the front surface reflectance to below 1% at an angle of incidence of 8°, which is comparable to black silicon. The superior antireflective property of PuNPs contributes to an absorbed photocurrent density of 40.8 mA/cm2 for a 40 μ m silicon absorber layer, which is 0.7 mA/cm2 higher than PiNPs, 0.8 mA/cm2 higher than inverted pyramids and 1 mA/cm2 higher than upright pyramids.
28 citations
TL;DR: By changing the design of the engineered microspheres, the relative contribution of the longitudinal and radial components of a radially polarized incident beam to the photonic nanojet can be modified efficiently, leading to a sharp spot size which exceeds the optical diffraction limit.
Abstract: Dielectric microspheres exhibit the ability to focus an incident beam to a subwavelength spot with strong localized field intensity. In this Letter, a high beam quality of a longitudinally polarized electromagnetic component is created by decorating the surface of the microsphere with engineered structures. By changing the design of the engineered microspheres, the relative contribution of the longitudinal and radial components of a radially polarized incident beam to the photonic nanojet can be modified efficiently, leading to a sharp spot size which exceeds the optical diffraction limit. More importantly, a high conversion efficiency of 0.89 is achieved. At a wavelength of 633 nm, a focal spot of 266 nm (0.42λ) is achieved numerically by illuminating the engineered microsphere with a focusing beam at a numerical aperture of 0.7.
28 citations
TL;DR: In this paper, a tailored inorganic transition metal cavity that boosts optically controlled reversible and repeatable chromism driven by a photocatalytic reaction is presented, which is a solution-processable TiO2/CuO nanocomposite with a mesoporous cavity that is highly adept at performing selfregulating reversible photochromism under solar irradiation.
Abstract: Over the years, the exploration of inorganic chromogenic materials commonly interfaced with expensive noble metals has been limited, while the study of organic photochromic materials has proliferated. The key challenge lies in the optimization of inorganic materials’ constituents and structural design to achieve enhanced light–matter interaction chromism with performance commensurate with that of their organic counterparts. Here, we demonstrate a tailored inorganic transition metal cavity that boosts optically controlled reversible and repeatable chromism driven by a photocatalytic reaction. The solution-processable TiO2/CuO nanocomposite is endowed with a mesoporous cavity that is highly adept at performing self-regulating reversible photochromism under solar irradiation. The improved photoreactive chromism stems from the tailored critical structural parameters of the highly accessible mesoporous shell, reduced charge carrier diffusion length thin shell, and cavity enhanced optical field for photon–matter interactions. Consequently, the nanocomposite exhibits dual-functional photoregulated effects, i.e. photochromism mediated light transmittance modulation and rewritable printing/patterning. The nanocomposite offers high sensitivity, resulting in a short response time due to the efficient charge transfer, and such chromism effects are stable in the ambient environment. Furthermore, controlled switching of the chromism effects may be obtained simply by low-temperature heating. The concerted combination of inexpensive materials/production, low toxicity and a highly transparent noble metal-free inorganic nanocomposite renders chromogenic properties that will trigger a renewed interest in smart light-stimulus integrated technology.
23 citations
TL;DR: In this article, a femtosecond laser (fs-laser) micromachining system in a Pr:LiYF4 (Pr:YLF) crystal was reported.
Abstract: We report on the fabrication of channel waveguide by a femtosecond laser (fs-laser) micromachining system in a Pr:LiYF4 (Pr:YLF) crystal. The micro Raman (μ-Raman) spectra and scanning confocal fluorescence imaging investigations of the depressed cladding structure indicated that slight changes (with respect to widths of the emission lines and spectral positions) have been generated in the laser-modification region. In the meantime, the possible relation of these changes with the waveguide formation was analyzed. The microphotoluminescence (μ-PL) experiment manifests an excellent preservation of the fluorescence properties of the Pr3+ ions in the guiding area. π-polarized waveguide lasers at wavelengths of 605 nm and 720 nm were achieved with a pumping laser at a wavelength of 444.5 nm. The maximum output power of the lasers achieved was 66 mW and 47 mW with slope efficiencies of 9.5% and 6.3%.
TL;DR: A novel multifunctional nanoagent AuNRs@SiO2-IR795 was developed to realize the integrated photothermal/photodynamic therapy (PTT/PDT) and FLI at a very low dosage of IR795 based on metal-enhanced fluorescence (MEF) effects to highlight the applications of multimodal diagnostics and therapy in tumors based on MEF.
Abstract: Near-infrared (NIR) triggered cyanine dyes have attracted considerable attention in multimodal tumor theranostics. However, NIR cyanine dyes used in tumor treatment often suffer from low fluorescence intensity and weak singlet oxygen generation efficiency, resulting in inadequate diagnostic and therapy efficacy for tumors. It is still a great challenge to improve both the photodynamic therapy (PDT) and fluorescent imaging (FLI) efficacy of cyanine dyes in tumor applications. Herein, a novel multifunctional nanoagent AuNRs@SiO2-IR795 was developed to realize the integrated photothermal/photodynamic therapy (PTT/PDT) and FLI at a very low dosage of IR795 (0.4 μM) based on metal-enhanced fluorescence (MEF) effects. In our design, both the fluorescence intensity and reactive oxygen species of AuNRs@SiO2-IR795 nanocomposites were significantly enhanced up to 51.7 and 6.3 folds compared with free IR795, owing to the localized surface plasmon resonance band of AuNRs overlapping with the absorption or fluorescence emission band of the IR795 dye. Under NIR laser irradiation, the cancer cell inhibition efficiency in vitro with synergetic PDT/PTT was up to 82.3%, compared with 10.3% for free IR795. Moreover, the enhanced fluorescence intensity of our designed nanocomposites was helpful to track their behavior in tumor cells. Therefore, our designed nanoagents highlight the applications of multimodal diagnostics and therapy in tumors based on MEF.
TL;DR: In this article, laser ablation technique is proposed as a substituting method to remove paint from steel structure for shipyards of marine and offshore engineering, and excellent adhesion strength of 20 MPa between repainted coating and the substrate is achieved.
Abstract: Paint removal from steel structure is executed for shipyards of marine and offshore engineering. Due to environmental unfriendliness and unhealthy drawbacks of sand blasting technique, laser ablation technique is proposed as a substituting method. By absorbing high energy of the 1064 nm pulsed laser, the paint is vaporized quickly. The ablated debris is then collected by using a suction pump. Initial metal surface of the steel is exposed when laser beam irradiates perpendicularly and scans over it. The cleaned surface fulfills the requirements of surface preparation standards ISO 8501 of SA2. The adhesion is further characterized with pull-off test after carrying out painting with Jotamastic 87 aluminum paint. The repainting can be embedded onto the laser cleaned surface to bond much more tightly. The excellent adhesion strength of 20 MPa between repainted coating and the substrate is achieved, which is higher than what is required by shipyards applications.
TL;DR: In this article, periodical silicon nanowires (SiNWs) integrated with metal-insulator-metal (MIM) layers are employed as SERS substrates.
Abstract: Surface enhanced Raman scattering (SERS) is an efficient technique to detect low concentration molecules. In this work, periodical silicon nanowires (SiNWs) integrated with metal-insulator-metal (MIM) layers are employed as SERS substrates. Laser interference lithography (LIL) combined with reactive ion etching (RIE) is used to fabricate large-area periodic nanostructures, followed by decorating the MIM layers. Compared to MIM disks array on Si surface, the SERS enhancement factor (EF) of the MIM structures on the SiNWs array can be increased up to 5 times, which is attributed to the enhanced electric field at the boundary of the MIM disks. Fur-thermore, high density of nanoparticles and nanogaps serving as hot spots on sidewall surfaces also contribute to the enhanced SERS signals. Via changing the thickness of the insulator layer, the plasmonic resonance can be tuned, which provides a new localized surface plasmon resonance (LSPR) characteristic for SERS applications.
TL;DR: In this paper, a hybrid method was proposed to modify the mechanical strength and light trapping efficiency of the photoresist, which transferred the photoreformer into the micro-concretes.
Abstract: Arbitrary micro-scale three-dimensional (3D) structures fabrication is a dream to achieve many exciting goals that have been pursued for a long time. Among all these applications, the direct 3D printing to fabricate human organs and integrated photonic circuits are extraordinary attractive as they can promote the current technology to a new level. Among all the 3D printing methods available, two-photon polymerization (2PP) is very competitive as it is the unique method to achieve sub-micron resolution to make any desired tiny structures. For the conventional 2PP, the building block is the photoresist. However, the requirement for the building block is different for different purposes. It is very necessary to investigate and improve the photoresist properties according to different requirements. In this paper, we presented one hybrid method to modify the mechanical strength and light trapping efficiency of the photoresist, which transfers the photoresist into the micro-concretes. The micro-concrete structure can achieve ±22% strength modification via a silica nano-particles doping. The structures doped with gold nano-particles show tunable plasmonic absorption. Dye doped hybrid structure shows great potential to fabricate 3D micro-chip laser.
TL;DR: Wang et al. as discussed by the authors used scanning electron microscopy and surface contact angle measurement to characterize the surface morphology and wettability behavior of the textured brass surfaces, and demonstrated that after low-temperature heating, the low adhesive force between the water droplet and the sample surface is demonstrated.
Abstract: Superhydrophobic surfaces have attracted extensive interests and researches into their fundamentals and potential applications. Laser texturing provides the convenience to fabricate the hierarchical micro/nanostructures for superhydrophobicity. However, after laser texturing, long wettability transition time from superhydrophilicity to superhydrophobicity is a barrier to mass production and practical industrial applications. External stimuli have been applied to change the surface composition and/or the surface morphology to reduce wettability transition time. Herein, by temperature tuning, wettability transition of laser textured brass surfaces is investigated. Scanning electron microscopy and surface contact angle measurement are employed to characterize the surface morphology and wettability behavior of the textured brass surfaces. By low-temperature heating (100 ℃~150 ℃), partial deoxidation of the top CuO layer occurs to form hydrophobic Cu2O. Therefore, superhydrophobicity without any chemical coating and surface modification could be achieved in a short time. Furthermore, after low-temperature heating, the low adhesive force between the water droplet and the sample surface is demonstrated for the laser textured brass surface. This study provides a simple method to fabricate the micro/nanostructure surfaces with controllable wettability for the potential applications.
TL;DR: In this article, the authors proposed a new design of metasurface with just one single layer dielectric structure to tune the reflection of an interface by destructive interference in a subwavelength scale.
Abstract: Reflection engineering plays an important role in optics. For conventional approaches, the reflection tuning is quite challenging in a loss-free component. Therefore, a simple approach to tune the reflection is highly desired in plenty of applications. In this paper, we propose a new design of metasurface with just one single layer die-lectric structure to tune the reflection of an interface by destructive interference in a subwavelength scale. By ar-ranging the orientation of nano-antennas, the reflectivity tuning from 20% to 90% can be achieved at the wavelength of 1550 nm. Moreover, such reflectivity tuning of the designed metasurface works at the tunable wavelength from 1500 nm to 1600 nm. This ultra-thin solution can achieve similar performance as the traditional bulky components without diffraction orders, while the design and fabrication are much simple and flexible. The ultra-thin and tunable properties indicate the great potentials of this method to be applied in laser fabrication, optical communication and optical integration.
01 Feb 2017
TL;DR: In this paper, the physics behind laser interaction with materials and its applications in precision engineering are mainly introduced, and several case studies are introduced, which have great potential and high impact applications, such as ultrafast laser direct writing, laser micro-lens lithography, laser nanofabrication to break through the optical diffraction limit and hybrid micro/nanostructures with unique functionality fabricated by laser.
Abstract: In this paper, laser interaction with materials and its applications
in precision engineering are mainly introduced. To further explore
the physics behind laser interaction with materials, it is of much
significance to investigate the mechanisms in the process. First of
all, it is desired to understand the characteristics and principle
of laser. Laser is generated by stimulated radiation, and has excellent
physical properties, such as high monochromaticity, high brightness,
high directivity and high coherence. Meanwhile, it benefits much to
study the dynamic process of interactions and its mechanisms. There
exist both photo-chemical and photo-thermal processes when laser and
materials interact. Furthermore, developing laser application in nanomaterial
synthesis is also an unique area. It is worth further studying the
design and fabrication of nanostructured materials. Last but not least,
it is interesting to explore the specific process and characteristics
of laser processing, which play an important role in advanced manufacturing.
In precision engineering, the tool of laser has also been more applicable
considering its great advantages in microprocessing and nanofabrication.
Several case studies are introduced, which have great potential and
high impact applications, such as ultrafast laser direct writing,
laser micro-lens lithography, laser nanofabrication to break through
optical diffraction limit and hybrid micro/nanostructures with unique
functions fabricated by laser. These studies have triggered intensive
research interests due to their great application prospect.
TL;DR: Development of a prototype of a portable optical sensing system is presented for fast detecting of samples’ fluorescence spectra by integrating a small spectrometer, a microcontroller, a Universal Serial Bus Host Shield, a network module, and a web server.
Abstract: Development of a prototype of a portable optical sensing system is presented for fast detecting of samples’ fluorescence spectra. A compact configuration is achieved by integrating a small spectrometer, a microcontroller, a Universal Serial Bus (USB) Host Shield, a network module, and a web server. The fluorescence spectra of a tested sample can be obtained. Then the test data are sent through network communication to our Cloud Server which can store the data for further analyses. With this configuration, test results can be revealed in a short time and downloaded by users to their laptops, tablets or cellphones anytime and anywhere.
TL;DR: These biosensors can detect cardiac troponin in serum with a high sensitivity, at a limit of detection (LOD) of 0.55 ng/mL, which is clinically relevant, and show low chip-to-chip variance (due to the high quality of the fabrication process).
Abstract: For a biosensing platform to have clinical relevance in point-of-care (POC) settings, assay sensitivity, reproducibility, and ability to reliably monitor analytes against the background of human serum are crucial.
Nanoimprinting lithography (NIL) was used to fabricate, at a low cost, sensing areas as large as 1.5 mm x 1.5 mm. The sensing surface was made of high-fidelity arrays of nanoholes, each with an area of about 140 nm2. The great reproducibility of NIL made it possible to employ a one-chip, one-measurement strategy on 12 individually manufactured surfaces, with minimal chip-to-chip variation. These nanoimprinted localized surface plasmon resonance (LSPR) chips were extensively tested on their ability to reliably measure a bioanalyte at concentrations varying from 2.5 to 75 ng/mL amidst the background of a complex biofluid-in this case, human serum. The high fidelity of NIL enables the generation of large sensing areas, which in turn eliminates the need for a microscope, as this biosensor can be easily interfaced with a commonly available laboratory light source. These biosensors can detect cardiac troponin in serum with a high sensitivity, at a limit of detection (LOD) of 0.55 ng/mL, which is clinically relevant. They also show low chip-to-chip variance (due to the high quality of the fabrication process). The results are commensurable with widely used enzyme-linked immunosorbent assay (ELISA)-based assays, but the technique retains the advantages of an LSPR-based sensing platform (i.e., amenability to miniaturization and multiplexing, making it more feasible for POC applications).
TL;DR: In this paper, the authors briefly introduce the field modulation mechanism and design principle of planar metalens, and discuss the research advances of the super-oscillatory lens and super-critical lens, as well as their applications in far-field label-free super-resolution imaging.
Abstract: Super-oscillatory lens (SOL) and super-critical lens (SCL) are the typical representatives of planar metalens which could achieve sub-diffractive focusing and imaging in far field by means of light field modulation. Through precisely modulating the interference effect of each diffractive unit, the electromagnetic wave could be oscillated faster than its maximum frequency components in a certain region of the target plane, and then the focal spot size is controllable in lateral and longitudinal directions. Compared with the traditional optical lens, the planar metalens is much more attractive in the fields of diffractive optics and nanophotonics due to its distinct advantages of powerful focusing capabilities, compact configuration, higher design freedom and the integratable properties, etc. In this review, we briefly introduce the field modulation mechanism and design principle of planar metalens. The research advances of the super-oscillatory lens and super-critical lens, as well as their applications in far-field label-free super-resolution imaging, are discussed in detail. In addition, a perspective about the future outlook of planar metalens is summarized. Since the planar metalens has powerful capability in manipulating the light field, the rapid development in various applications would be gradually realized in the near future.