Zhiyuan Zheng

Fast and enhanced broadband photoresponse of a ZnO nanowire array/reduced graphene oxide film hybrid photodetector from the visible to the near-infrared range.

In the present work, a ZnO nanowire array/reduced graphene oxide film hybrid nanostructure was realized, and the photovoltaic responses from the visible to the near-infrared range were investigated. Compared with the pure ZnO nanowire array and rGO thin film, the hybrid composite exhibited a fast and greatly enhanced broadband photovoltaic response that resulted from the formation of interfacial Schottky junctions between ZnO and rGO.

Enhanced photocatalytic capability of zinc ferrite nanotube arrays decorated with gold nanoparticles for visible light-driven photodegradation of rhodamine B

One-dimensional nanostructures grown on substrates are favored for photocatalytic reactions because of their large specific surface areas and well-defined transport paths for charge carriers. In the present paper, zinc ferrite nanotube arrays are synthesized on indium-tin-oxide–glass substrates, and their photocatalytic capabilities are evaluated by degrading an aqueous solution of rhodamine B (RhB) under visible light irradiation. The photocatalytic performance of pure zinc ferrite nanotube arrays is unsatisfactory. To improve their photocatalytic abilities, the surfaces of zinc ferrite nanotube arrays are decorated with Au nanoparticles, significantly enhancing their photocatalytic capabilities for RhB degradation. The drastic improvement in the photocatalytic degradation ability is attributed to the effective separation of photogenerated electron–hole pairs in the Au-decorated zinc ferrite hybrid nanostructure, which facilitates the generation of oxidizing free radicals (i.e., O2• − and OH·) for RhB degradation.

Highly sensitive and ultrafast deep UV photodetector based on a .BETA.-Ga2O3 nanowire network grown by CVD

We investigated a high-performance deep ultraviolet photodetector based on a β-gallium oxide (β-Ga2O3) nanowire network. β-Ga2O3 nanowires were grown at different temperatures by a chemical vapor deposition method. X-ray diffraction, scanning electron microscopy, transmission electron microscopy and energy dispersive spectrum analysis were utilized to characterize the structure and morphology. With increasing the temperature, the nanowires became thicker and their surface appeared more rough with many kinks and branch-like shapes. It is proposed that the growth mechanism is dominated by a combination of vapor–liquid–solid and vapor–solid growth. A photodetector based on the best quality β-Ga2O3 nanowire network was fabricated by a simple and cheap mask method, which exhibited excellent photoelectric performance. The responsive spectrum presented a peak response located at 231 nm with a sharp cutoff at 270 nm. The response rejection ratio of I 231 nm/I 290 nm is more than three orders of magnitude, demonstrating an intrinsic solar-blindness. The full width at half maximum of the response curve is only 1.2 ns under pulsed laser irradiation. The high sensitivity, superior selectivity, ultrafast response speed and simple fabrication technology show that the β-Ga2O3 nanowire network has promising application in solar-blind photodetectors.

Fast photoresponse of zinc ferrite nanotube arrays fabricated by electrodeposition

Although nano-sized zinc ferrite materials exhibit excellent visible light activity, their photoresponse characteristics as photodetectors have rarely been investigated. In this paper, zinc ferrite nanotube arrays were fabricated using electrodeposition with the aid of zinc oxide nanowire arrays as a template. These nanotube arrays showed tens of milliseconds-response photocurrents under the irradiation of a 532 nm solid-state laser, and the magnitudes of the photocurrents were linearly increased with increasing laser power. These features of ZnFe2O4 nanotube arrays revealed their potential applications in high-frequency or high-speed photodevices.

Broadband unidirectional transmission realized by properties of the Dirac cone formed in photonic crystals

An excellent unidirectional transmission device is proposed, which consists of a two-dimensional photonic crystal and a dielectric grating. The photonic crystal is designed to have a Dirac cone at the Γ point which allows the normal incident light to transmit while reflecting the oblique incidence in a broad frequency band. The aim of the dielectric grating is to diffract the normal incident light into other directions. Thus, when the incident light first passes through the grating and then incidents upon the photonic crystal, it will be blocked completely. While when the sequence is reversed it will be transmitted. This sequence selectivity of the transmission makes the photonic crystal/grating structure present an excellent unidirectional transmission effect. The simulation results show that in a broad frequency region, T 1 and T 2, the transmittances in forward and backward directions, satisfy T 1–T 2 > 80%, T 1/T 2 > 1000, and 10 log(1/T 2) > 20 simultaneously.

Characteristics of droplets ejected from liquid glycerol doped with carbon in laser ablation propulsion

The characteristics of droplets ejected from liquid glycerol doped with carbon are investigated in laser ablation propulsion. Results show that carbon content has an effect on both the coupling coefficient and the specific impulse. The doped-carbon moves the laser focal position from the glycerol interior to the surface. This results in a less consumed glycerol and a high specific impulse. An optimal propulsion can be realized by varying carbon content in glycerol.

Tunable dual-band nearly perfect absorption based on a compound metallic grating

ABSTRACT Traditional metallic gratings and novel metamaterials are two basic kinds of candidates for perfect absorption. Comparatively speaking, metallic grating is the preferred choice for the same absorption effect because it is structurally simpler and more convenient to fabricate. However, to date, most of the perfect absorption effects achieved based on metamaterials are also available using an metallic grating except the tunable dual(multi)-band perfect absorption. To fill this gap, in this paper, by adding subgrooves on the rear surface as well as inside the grating slits to a free-standing metallic grating, tunable dual-band perfect absorption is also obtained for the first time. The grooves inside the slits is to tune the frequency of the Cavity Mode(CM) resonance which enhances the transmission and suppresses the reflectance simultaneously. The grooves on the rear surface give rise to the phase resonance which not only suppresses the transmission but also reinforces the reflectance depression effect. Thus, when the phase resonance and the frequency tunable CM resonance occur together, transmission and reflection can be suppressed simultaneously, dual-band nearly perfect absorption with tunable frequencies is obtained. To our knowledge, this perfect absorption phenomenon is achieved for the first time in a designed metallic grating structure.

Target micro-displacement measurement by a “comb” structure of intensity distribution in laser plasma propulsion

A “comb” structure of beam intensity distribution is designed and achieved to measure a target displacement of micrometer level in laser plasma propulsion. Base on the “comb” structure, the target displacement generated by nanosecond laser ablation solid target is measured and discussed. It is found that the “comb” structure is more suitable for a thin film target with a velocity lower than tens of millimeters per second. Combing with a light-electric monitor, the ‘comb’ structure can be used to measure a large range velocity.

Application of delrin in laser plasma micro-propulsion

The interaction between polymer of Delrin with nano-second pulse laser is investigated in laser plasma micro-propulsion. The coupling coefficient and specific impulse are measured respectively. The coupling coefficient about 42 dyne/W and specific impulse up to 646 s have been obtained. Moreover, the surface images after ablation have been observed. It is found that Delrin has less debris on ablation surface. This indicates that Delrin is a potential polymer material in laser plasma propulsion.

The numerical calculation and analysis for designing a polarization beam splitter based on a rectangular phase grating

A new method based on the combination of Finite-Difference Time-Domain (FDTD) algorithm and Fourier transform was proposed to analyze the Fraunhofer vector diffraction of gratings in this paper. The interaction of a grating with the incident linearly polarized light was simulated using FDTD algorithm, the complex amplitude distribution on the rear plane of the grating was extracted, and then the Fraunhofer diffraction pattern was obtained by performing Fourier transform of the complex amplitude. It was found that for the rectangular phase grating if the period of the grating is comparable to the wavelength of the incident wave, the propagation speeds of the TE and TM waves in the dielectric of the grating are different, which makes the diffraction of the grating is polarization dependent. Besides, the relative phase retardations of TE and TM waves formed on the rear plane of the grating are different and both of them can be controlled by changing the thickness of the grating, which makes it be realized that the intensities of TE and TM waves concentrate onto the 0th order and 1st order separately by selecting a suitable grating thickness. Therefore a polarization beam splitter based on a rectangular dielectric grating can be easily designed.