High-performance narrowband thermal emitter based on aperiodic Tamm plasmon structures assisted by inverse design.

Controlling the bandwidth and directionality of thermal emission is important for a broad range of applications, from imaging and sensing to energy harvesting. Here, we propose a new, to the best of our knowledge, type of long-wavelength infrared narrowband thermal emitter that is basically composed of aperiodic Tamm plasmon polariton structures. Compared to the thermal emitter based on periodic structures, more parameters need to be considered. An inverse design algorithm instead of traditional forward methodologies is employed to do the geometric parameter optimization. Both theoretical and experimental results show that the thermal emitter exhibits a narrowband thermal emission peak at the wavelength of 8.6 µm in the normal direction. The angular response of emission properties of the thermal emitter is dependent on the emission angle. We believe that our proposed thermal emitter provides an alternative for low-cost, high-effective narrowband mid-infrared light sources and would have a great potential in many applications.

Narrowband HgCdTe infrared photodetector with integrated plasmonic structure.

The application of plasmonic structure has been demonstrated to improve the performance of infrared photodetectors. However, the successful experimental realization of the incorporation of such optical engineering structure into HgCdTe-based photodetectors has rarely been reported. In this paper, we present a HgCdTe infrared photodetector with integrated plasmonic structure. The experimental results show that the device with plasmonic structure has a distinct narrowband effect with a peak response rate close to 2 A/W, which is nearly 34% higher compared with the reference device. The simulation results are in good agreement with the experiment, and an analysis of the effect of the plasmonic structure is given, demonstrating the crucial role of the plasmonic structure in the enhancement of the device performance.

The interaction between obesity and visceral hypersensitivity.

Obesity has been a worldwide problem associated with numerous chronic diseases such as cardiovascular disease, type 2 diabetes, and metabolic disorders. It may also play a role in visceral hypersensitivity, contributing to irritable bowel syndrome. (i) Adipose tissue secretes various inflammatory mediators, causing intestinal hyperpermeability and nerve endings activation. (ii) Obesity and gastrointestinal microbiota could affect each other, and microbial metabolites can increase sensitivity of the colon. (iii) Vitamin D deficiency contributes to both fat accumulation and disruption of the intestinal mucosal barrier. (iv) Brain-gut axis may be another bridge from obesity to visceral hypersensitivity.

Long-wavelength infrared selective emitter for thermal infrared camouflage under a hot environment.

Thermal infrared camouflage as a kind of counter-surveillance technique has attracted much attention owing to the rapid development of infrared surveillance technology. Various artificial optical structures have been developed for infrared camouflage applications under cold ambient environment (low thermal radiation), but the realization of infrared camouflage under a hot environment (high thermal radiation) is also highly desirable and has been rarely reported. Here, a lithography-free, ultra-thin, high performance long-wavelength infrared (LWIR) selective emitter for thermal infrared camouflage in a high radiation environment is proposed and experimentally demonstrated. Experimental results show that our designed selective emitter exhibits average emissivity higher than 90% over the LWIR range from 8 to 14 µm and low emissivity less than 35% outside this window. Numerical simulations were performed to optimize the geometrical structures and reveal that such a selective emission effect is attributed to the combination of multiple hybrid plasmonic resonances. LWIR thermal images show that the selective emitter can perfectly blend into the high radiation backgrounds. Furthermore, it is found that the sample displays angle-independent emission properties, indicating that our emitter offers great potential for application in evading large-angle detection.

Manipulating the wavefront of light by plasmonic metasurfaces operating in high order modes.

In this work, plasmonic metasurfaces with abrupt phase discontinuities operating in high order modes are investigated for manipulating the wavefront of light. We first design two types of meta-super-cells consisting of V-shaped antennas with the phase shift coverage larger than 2π. And then, we create two linear gradient phased metasurfaces using the designed cells, which exhibit exceptional abilities for light-steering functioned as meta-echelette gratings operating in high order diffraction modes, may be valuable for using in high resolution spectrographs and advantage to achieve high numerical aperture plasmonic lenses. Based on the new designed super cells we further build another two azimuthal gradient phased metasurfaces that are able to generate high order optical vortex beams. Our results could lead to wide applications in photonic research.

Tailor the Functionalities of Metasurfaces Based on a Complete Phase Diagram.

Metasurfaces in a metal-insulator-metal configuration have been widely used in photonics, with applications ranging from perfect absorption to phase modulation, but why and when such structures can realize what functionalities are not yet fully understood. Here, we establish a complete phase diagram in which the optical properties of such systems are fully controlled by two simple parameters (i.e., the intrinsic and radiation losses), which are, in turn, dictated by the geometrical or material properties of the underlying structures. Such a phase diagram can greatly facilitate the design of appropriate metasurfaces with tailored functionalities demonstrated by our experiments and simulations in the terahertz regime. In particular, our experiments show that, through appropriate structural or material tuning, the device can be switched across the phase boundaries yielding dramatic changes in optical responses. Our discoveries lay a solid basis for realizing functional and tunable photonic devices with such structures.

Tailor the surface-wave properties of a plasmonic metal by a metamaterial capping.

We show that putting an ultra-thin anisotropic metamaterial layer on a plasmonic surface significantly enriches the surface wave (SW) characteristics of the system, which now supports SWs with transverse-magnetic (TM) and transverse-electric (TE) polarizations simultaneously. In addition, the generated SWs exhibit hybridized polarization characteristics in certain cases, and a SW band gap opens within a particular propagation direction range. We designed and fabricated a realistic structure based on the proposed model, and combined microwave experiments with full-wave simulations to verify the fascinating theoretical predictions. Several potential applications of the proposed system are discussed in the end.

Super broadband mid-infrared absorbers with ultrathin folded highly-lossy films.

Super broadband optical absorbers with ultrathin films have been keenly pursued for a long time. Although highly lossy materials with sharp light attenuation have the potential to become super absorbers, a large percent of light from free space is inevitably reflected back for the distinct impedance mismatch. Here, a simple strategy, of which reducing the thickness of highly-lossy thin films to minish reflectance and simultaneously folding the ultrathin films to make light multiple pass through, is proposed to obtain super broadband mid-infrared absorbers with ultrathin films. Along this line, the absorbers were prepared by depositing Al-doped ZnO film on scaffolds consisted of alumina spherical shells, whose substrates were opaque. When the thickness of Al-doped ZnO is 43 nm and the layer number of scaffolds is three, a maximum average absorptance was achieved as 97.6% over the wavelength range from 3 to 15 µm. Applying this strategy on polished Al foil, excellent infrared camouflage performance on human-body background was demonstrated. Featured by the strong broadband optical absorption with ultrathin films, flexible access to multiple substrates and low-cost procedures, this approach has the potential in widespread applications of infrared thermal emitters and optoelectronic devices.

Bifunctional Manipulation of Terahertz Waves with High-Efficiency Transmissive Dielectric Metasurfaces.

Multifunctional terahertz (THz) devices in transmission mode are highly desired in integration-optics applications, but conventional devices are bulky in size and inefficient. While ultra-thin multifunctional THz devices are recently demonstrated based on reflective metasurfaces, their transmissive counterparts suffer from severe limitations in efficiency and functionality. Here, based on high aspect-ratio silicon micropillars exhibiting wide transmission-phase tuning ranges with high transmission-amplitudes, a set of dielectric metasurfaces is designed and fabricated to achieve efficient spin-multiplexed wavefront controls on THz waves. As a benchmark test, the photonic-spin-Hall-effect is experimentally demonstrated with a record high absolute efficiency of 92% using a dielectric metasurface encoded with geometric phases only. Next, spin-multiplexed controls on circularly polarized THz beams (e.g., anomalous refraction and focusing) are experimentally demonstrated with experimental efficiency reaching 88%, based on a dielectric meta-device encoded with both spin-independent resonant phases and spin-dependent geometric phases. Finally, high-efficiency spin-multiplexed dual holographic images are experimentally realized with the third meta-device encoded with both resonant and geometric phases. Both near-field and far-field measurements are performed to characterize these devices, yielding results in agreement with full-wave simulations. The study paves the way to realize multifunctional, high-performance, and ultra-compact THz devices for applications in biology sensing, communications, and so on.

Uniaxial Strain-Induced Tunable Mid-infrared Light Emission from Thin Film Black Phosphorus.

Strain engineering is a powerful tool that can modulate semiconductor device performance. Here, we demonstrate that the bandgap of thin film (∼40 nm) black phosphorus (bP) can be continuously tuned from 2.9 to 3.9 µm by applying an in-plane uniaxial strain, as evidenced by mid-infrared photoluminescence (PL) spectroscopy. The deduced bandgap strain coefficients are ∼103 meV %-1, which coincide with those obtained in few-layer bP. On the basis of first-principles calculations, the origin of the uniaxial tensile strain-induced PL enhancement is suggested to be due to the increase in both the effective mass ratio (me*/mh*) and the bandgap, leading to the increment of the radiative efficiency. Moreover, the mid-infrared PL emission remains perfectly linear-polarized along the armchair direction regardless of tensile or compressive strain. The highly tunable bandgap of bP in the mid-infrared regime opens up opportunities for the realization of mid-infrared light-emitting diodes and lasers using layered materials.

A spectrally selective visible microbolometer based on planar subwavelength thin films.

In this work, we experimentally demonstrate a new type of compact, low-cost, visible microbolometer based on metal-insulator-metal (MIM) planar subwavelength thin films, which exploits resonant absorption for spectral selectivity without additional filters and has the advantages of compact design, simple structure, cost-efficiency, and large format fabrication. The experimental results show that a proof-of-principle microbolometer exhibits spectrally selective properties in the visible frequency range. At a resonant absorption wavelength of 638 nm, a responsivity of about 10 mV W-1 is achieved at room temperature at a bias current of 0.2 mA, which is about one order of magnitude higher than that of the control device (a bare Au bolometer). Our proposed approach provides a viable solution for the development of compact and inexpensive detectors.

Design of an ultrathin broadband transparent and high-conductive screen using plasmonic nanostructures.

In this Letter, we present a new type of ultrathin antireflection transparent and high-conductive screen based on plasmonic nanostructures that does not suffer from high loss and thickness coating and also can be used as good conductive material due to super electrical conductivity of the component (noble metal). Low reflection and greatly enhanced transmissions over a broad spectral range are observed at optical telecommunication frequencies in arbitrary polarizations. The performance is almost insensitive of the angle of incidence.

Gain-assisted transformation optics.

Loss severely degrades the cloaking effect of the device designed by traditional transformation. In this letter, we propose gain-assisted transformation optics to overcome the loss problem by introducing gain media into a spherical cloak. The gain media, which can amplify the electromagnetic fields, is controlled precisely to compensate the inherent loss in experimental realization of cloaks. We discuss the significance of controlling embedded gain materials in the context of the inverse design mechanism, which allows us to wisely select realizable materials with constant gain and loss along the radius. For practical realizations, isotropic spherical gain-assisted cloak is designed. Full-wave simulations validate the proposed design concept, which can be utilized to alleviate the inevitable loss problem in transformational optical devices.

Photothermal reshaping of gold nanoparticles in a plasmonic absorber.

We experimentally demonstrate that a metamaterial nanostructure can have a localized heating response owing to plasmonic resonances in the near-infrared wavelength range (from 1.5 to 2 µm). With a broadband nanosecond-pulse light, the temperature of composing gold particles in the nanostructure can be easily increased to over 900K within only several nanoseconds, resulting in re-shaping of the particles. The photothermal effect is elaborated with finite-element based numerical simulations. The absorption resonance can in principle be tailored with a great freedom by choosing appropriate metamaterial parameters. The light-induced heating in an artificial metamaterial can be potentially used for all-optical acute temperature tuning in a micro-environment, which may open new frontiers especially in nanotechnology and biotechnology.

A transparent metamaterial to manipulate electromagnetic wave polarizations.

We design an anisotropic ultrathin metamaterial to allow perfect transmissions of electromagnetic (EM) waves for two incident polarizations within a common frequency interval. The transparencies are governed by different mechanisms, resulting in significant differences in transmission phase changes for two polarizations. The system can thus manipulate EM wave polarizations efficiently in transmission geometry, including polarization conversion and rotation. Microwave experiments performed on realistic samples are in excellent agreement with numerical simulations.

[Effect of MiR-96 on Cell Invasion and Apoptosis in Pediatric Acute Myeloid Leukemia via Regulating MYB].

OBJECTIVE: To analyze the relationship of the expression of transcription factor MYB targeted regulation by miR-96 to cell invasion and apoptosis in pediatric acute myeloid leukemia (AML). METHODS: A total of 65 children with AML in The 928 Hospital of PLA Joint Logistics Support Forces from January 2017 to November 2019 were selected, including 35 cases diagnosed as primary AML and 30 cases as complete remission AML. Thirty children with immune thrombocytopenia were selected as control group. The clinical characteristics were analyzed and compared between the two groups. The levels of miR-96 and MYB in peripheral blood samples were detected by qRT-PCR and compared between the two groups. The miR-96 mimics and its negative control (NC), inhibitor-miR-96 and its NC transfected HL60 cells induced by liposome (Lipofectamine 2000), respectively, Then the expression levels of MYB were detected with Western blot and compared among four HL60 cell groups. The invasion ability of four HL60 cell groups were detected with Transwell assay. The cell proliferation ability of four HL60 cell groups were detected with MTT at 24 h, 48 h, and 72 h, respectively. The apoptosis rates of four HL60 cell groups were detected with flow cytometry. RESULTS: Compared with control group, the level of miR-96 in AML children were higher, but MYB lower (P<0.05). Compared with complete remission AML, the level of miR-96 in primary AML was higher, but MYB lower (P<0.05). Western blot analysis showed that, the expression level of MYB in the four HL60 cell groups was different (P<0.05), the lowest was in miR-96 mimics group, followed by miR-96 NC group and inhibitor-miR-96 NC group, and the highest in inhibitor-miR-96 group (P<0.05), while there was no difference between miR-96 NC group and inhibitor-miR-96 NC group (P>0.05). The promotion of over-expression level of miR-96 on the invasion ability of HL 60 cells was confirmed by Transwell assay. MTT assay showed that miR-96 could promote the proliferation of HL60 cells, inhibit the apoptosis of HL60 cells, and the effect was time-dependent manner (r=0.804). The inhibition of miR-96 on HL60 cells apoptosis was also confirmed with flow cytometry. CONCLUSION: MiR-96 has significant negative effect on invasion and apoptosis of AML cells by targeting regulation MYB, and it might be a potential novel strategy for pediatric AML treatment.

Self-Assembly of Carbon Black/AAO Templates on Nanoporous Si for Broadband Infrared Absorption.

Broadband absorption in the mid-infrared region is of significance for wide applications, such as photo/thermal detection, infrared stealth, and thermal imaging. Recently, metal-based plasmonic absorbers have been developed in the mid-infrared region. However, the fabrication cost, thickness, and bandwidth of these absorbers applied in aerospace still need to be improved. In this study, we propose and experimentally demonstrate a large-area, rather thin, metal-free absorber with broadband mid-infrared absorption based on a low-cost self-assembly process. The metal-free absorber is fabricated by spraying carbon black nanoparticles onto 5 µm-thick transferrable anodic aluminum oxide (AAO) templates on nanoporous Si graded-index films, which are fabricated by ion irradiation. Experimental results show that the average absorbance can reach 97.5% in the range of 2.5-15.3 µm. Full-wave numerical simulations show that the electromagnetic fields are greatly enhanced into pores, as these random carbon black particles serve as scatter centers and couple light into 5 µm-thick AAO templates, enhancing the interaction of light with carbon black significantly, and reveal that the high-performance broadband absorption is attributed to the light-trapping effect. The significant light absorption combined with a low-cost, high-production self-assembly technique suggests that the absorber can be used in the fields of optoelectronics and integrated photonics.

Studies on Sensing Properties and Mechanism of CuO Nanoparticles to H2S Gas.

In this work, the high crystalline copper oxide (CuO) nanoparticles were fabricated by a hydrothermal method, and their structural properties were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The sensing results show that CuO nanoparticles exhibit enhanced sensitivity and good selectivity for hydrogen sulfide (H2S) gas at a low temperature. There are two working mechanisms involved in the H2S sensing based on CuO nanoparticle sensors. They are the H2S oxidation mechanism and the copper sulphide (CuS) formation mechanism, respectively. The two sensing mechanisms collectively enhance the sensor's response in the H2S sensing process. The Cu-S bonding is stable and cannot break spontaneously at a low temperature. Therefore, the CuS formation inhibits the sensor's recovery process. Such inhibition gradually enhances as the gas concentration increases from 0.2 ppm to 5 ppm, and it becomes weaker as the operating temperature rises from 40 °C to 250 °C. The XPS results confirmed the CuS formation phenomenon, and the micro Raman spectra demonstrated that the formation of CuS bonding and its decomposition can be effectively triggered by a thermal effect. Gas-sensing mechanism analysis supplied abundant cognition for the H2S sensing phenomena based on CuO materials.

Gas Sensing Performance and Mechanism of CuO(p)-WO3(n) Composites to H2S Gas.

In this work, the compositional optimization in copper oxide/tungsten trioxide (CuO/WO3) composites was systematically studied for hydrogen sulfide (H2S) sensing. The response of CuO/WO3 composites changes from p-type to n-type as the CuO content decreases. Furthermore, the p-type response weakens while the n-type response strengthens as the Cu/W molar ratio decreases from 1:0 to 1:10. The optimal Cu/W molar ratio is 1:10, at which the sensor presents the ultrahigh n-type response of 1.19 × 105 to 20 ppm H2S gas at 40 °C. Once the temperature rises from 40 °C to 250 °C, the CuO/WO3 (1:1) sensor presents the p-n response transformation, and the CuO/WO3 (1:1.5) sensor changes from no response to n-type response, because the increased temperature facilitates the Cu-S bonds break and weakens the p-type CuO contribution to the total response, such that the CuS bond decomposition by a thermal effect was verified by a Raman analysis. In addition, with a decrease in CuO content, the CuO is transformed from partly to completely converting to CuS, causing the resistance of CuO to decrease from increasing and, hence, a weakening mode of p-CuO and n-WO3 to the total response turns to a synergistic mode to it.

Flexible Transparent Heat Mirror for Thermal Applications.

Transparent heat mirrors have been attracting a great deal of interest in the last few decades due to their broad applications, which range from solar thermal convection to energy-saving. Here, we present a flexible Polyethylene terephthalate/Ag-doped Indium tin oxide/Polydimethylsiloxane (PAIP) thin film that exhibits high transmittance in visible range and low emissivity in the thermal infrared region. Experimental results show that the temperature of the sample can be as high as 108 °C, which is ~23 °C higher than that of a blackbody control sample under the same solar radiation. Without solar radiation, the temperature of the PAIP thin film is ~6 °C higher than that of ordinary fabric. The versatility of the large-area, low-radiation-loss, highly-transparent and flexible hydrophobic PAIP thin film suggest great potential for practical applications in thermal energy harvesting and manipulation.