Xinghua Yang

A Toothbrush-shaped Patch Antenna for Millimeter-wave Communication

A printed toothbrush-shaped antenna is proposed for millimeter wave communication. The designed antenna features with a compact size is 7 × 10 mm2, and satisfies the VSWR requirement less than 2.0 in the frequency band from 32 GHz to more than 38 GHz. Simulated and measured results for main parameters such as return loss, impedance bandwidth, and radiation patterns are also discussed herein. The study shows that modeling of such antennas, with simplicity in designing and feeding, can well meet millimeter-wave wireless communication.

Compact CPW-fed ultra-wide band antenna with dual band notched characteristics

A CPW-fed ultra-wideband antenna with dual band-notch characteristics is realized experimentally and numerically. Two notched frequency bands are obtained by utilizing a tuning stub between the fork-like radiation element and a rectangle slot in the CPW ground plane. The two notched bands can be controlled by adjusting the length of the tuning stub and the length of the rectangle slot. Experimental and numerical antenna shows that the proposed antenna, with compact size of 21×28mm2, has an impedance bandwidth ranging from 3.1GHz to 10.6GHz for voltage standing-wave ratio less than 2, expect two notch band frequency 5GHz-6GHz for WLAN and 7.7GHz-8.5GHz for X-band for satellite and military applications.

Single-fiber tweezers applied for dye lasing in a fluid droplet

We report on the first demonstration of a single-fiber optical tweezer that is utilized to stabilize and control the liquid droplet for dye lasing. In order to trap a liquid droplet with a diameter of 15-30 μm, an annular core micro-structured optical fiber is adopted. By using wavelength division multiplexing technology, we couple a trapping light source (980 nm) and a pumping light source (532 nm) into the annular core of the fiber to realize the trapping, controlling, and pumping of the oil droplet. We show that the laser emission spectrum tunes along the same size as the oil droplet. The lasing threshold of the oil droplet with the diameter of 24 μm is 0.7 μJ. The presented fiber-based optical manipulation of liquid droplet micro-lasers can be easily combined with the micro-fluidic chip technology and also may extend the application of optical fiber tweezers for micro-droplet lasing technology in the biological field.

Dual-truncated-cone structure for quasi-distributed multichannel fiber surface plasmon resonance sensor.

We propose and demonstrate an effective method to adjust the dynamic range of a fiber surface plasmon resonance (SPR) sensor by introducing a multimode fiber-sensing probe with a dual-truncated-cone (DTC) structure. When the grind angle of the DTC structure increases, the dynamic range redshifts. Based on this result, we fabricate a quasi-distributed two-channel multimode fiber SPR sensor by cascaded-connecting a DTC-sensing probe of 14° grind angle and a traditional transmitted multimode fiber (TMF)-sensing probe in the same fiber. The corresponding sensitivities of two sensing probes are 3423.08 nm/RIU and 2288.46 nm/RIU. By using this quasi-distributed multichannel fiber SPR-sensing approach, we may improve the detecting accuracy by extracting, calibrating, and compensating for the signals caused by the nonspecific bindings, other physical absorptions, and temperature changes in detecting samples, truly achieving dynamic detection in real-time. The excellence of this multichannel fiber SPR sensor is that the sensitivity of each subchannel-sensing probe stays unreduced after it is cascaded-connected in the main-channel fiber; the sensor is based on the multimode fiber, which is inexpensive, accessible, and convenient to be universalized in applications.

Unipolar nonvolatile memory devices based on the composites of poly(9-vinylcarbazole) and zinc oxide nanoparticles

The application of poly(9-vinylcarbazole) (PVK) to make a composite with zinc oxide (ZnO) as the active layer has been reported. Unipolar resistive switching behaviors were observed from ITO/PVKu2009+u2009ZnO/Al memory devices. The reset voltages were higher than the set voltages. These devices present a low resistance state (LRS)/high resistance state (HRS) current ratio of 104 when read at −0.5xa0V, retaining the information for a time of 105xa0s. The bistable resistive switching behaviors were entirely steady within 104 cycles. The fitted results of I–V curves shown that the dominant conduction mechanisms in LRS and HRS were Ohmic conductive behavior and space-charge-limited current mechanism, respectively.

Fiber-Based Helical Channels Refractive Index Sensor Available for Microfluidic Chip

We propose and demonstrate a refractive index (RI) sensor based on a dual-hole elliptical core fiber (DHECF), which is available for microfluidic chips. By using the heating-twisting technology, we fabricate a helical long period grating (HLPG) structure in the DHECF. This sensor is convenient for microfluidic chips because of the dual-hole structure in the fiber, which is the natural microfluidic channels. The heating-twisting technology ensures that the fabrication of the gratings sensor is easy and low-cost. In addition, the dual-hole structure contributes to one internal sensing channel which contains two sensing routes (two holes), and one external sensing channel. Experimental results indicate that the testing sensitivity of the internal sensing channel can be 584 nm/RIU (RI range 1.385–1.405), and the sensitivity of the external sensing channel can be 1108.8 nm/RIU (RI range 1.385–1.405).

Microparticle collection for water purification based on laser-induced convection

Water purification is required for environmental protection. In this paper, we propose and demonstrate a rapid, effective and low-cost approach to collect numerous impurities (microparticles) in water on the basis of laser-induced thermal convection. We introduce a heat source by using a fiber tip, which is fabricated into a non-adiabatic-tapered shape. In order to improve the laser power absorption efficiency, we coat a gold film with a thickness of 300 nm on the fiber tip. Due to absorption, the laser power transferred from the fiber to the water results in thermal convection. The forces generated from the thermal convection drive the microparticles to move towards the fiber tip, thereby performing microparticle collection and achieving water purification. Laser-induced thermal convection provides a simple, high-efficiency and low-cost method of collecting microparticles, which is a suitable and convenient for local water purification.

Optical trapping and axial shifting for strongly absorbing particle with single focused TEM00 Gaussian beam

We propose and demonstrate a stable three-dimensional trap and manipulation of a micron-sized strongly absorbing particle in pure liquid glycerol by using a single tight focused TEM00 Gaussian beam. We employ a bottom-side bidirectional view observation system to observe the trapped particle. We use the light at 980u2009nm to trap the absorbing particle and the light at 532u2009nm to indicate the distribution of the temperature field around the trapped particle. The trapping position of the absorbing particle is related to the incident laser power; the lower the incident laser power, the longer the particle shift distance. Our approach provides full control over trapped absorbing particles and expands optical manipulation of strong absorbing particles into a liquid media.

Microparticles controllable accumulation, arrangement, and spatial shaping performed by tapered-fiber-based laser-induced convection flow

The ability to arrange cells and/or microparticles into the desired pattern is critical in biological, chemical, and metamaterial studies and other applications. Researchers have developed a variety of patterning techniques, which either have a limited capacity to simultaneously trap massive particles or lack the spatial resolution necessary to manipulate individual particle. Several approaches have been proposed that combine both high spatial selectivity and high throughput simultaneously. However, those methods are complex and difficult to fabricate. In this article, we propose and demonstrate a simple method that combines the laser-induced convection flow and fiber-based optical trapping methods to perform both regular and special spatial shaping arrangement. Essentially, we combine a light field with a large optical intensity gradient distribution and a thermal field with a large temperature gradient distribution to perform the microparticles shaping arrangement. The tapered-fiber-based laser-induced convection flow provides not only the batch manipulation of massive particles, but also the finer manipulation of special one or several particles, which break out the limit of single-fiber-based massive/individual particles photothermal manipulation. The combination technique allows for microparticles quick accumulation, single-layer and multilayer arrangement; special spatial shaping arrangement/adjustment, and microparticles sorting.

Optofluidic in-fiber interferometer based on hollow optical fiber with two cores

We demonstrate a novel integrated optical fiber interferometer for in-fiber optofluidic detection. It is composed of a specially designed hollow optical fiber with a micro-channel and two cores. One core on the inner surface of the micro-channel is served as sensing arm and the other core in the annular cladding is served as reference arm. Fusion-and-tapering method is employed to couple light from a single mode fiber to the hollow optical fiber in this device. Sampling is realized by side opening a microhole on the surface of the hollow optical fiber. Under differential pressure between the end of the hollow fiber and the microhole, the liquids can form steady microflows in the micro-channel. Simultaneously, the interference spectrum of the interferometer device shifts with the variation of the concentration of the microfluid in the channel. The optofluidic in-fiber interferometer has a sensitivity of refractive index around 2508 nm/RIU for NaCl. For medicine concentration detection, its sensitivity is 0.076 nm/mmolL-1 for ascorbic acid. Significantly, this work presents a compact microfluidic in-fiber interferometer with a micro-channel which can be integrated with chip devices without spatial optical coupling and without complex manufacturing procedure of the waveguide on the chips.