Abstract:CdS nanocrystals have been successfully grown on porous silicon (PS) by sol-gel method. The plan-view field emission scanning electron microscopy (FESEM) shows that the pore size of PS is smaller than 5 μm in diameter and the agglomerates of CdS are broadly distributed on the surface of PS substrate. With the increase of annealing time, the CdS nanoparticles grow in both length and diameter along the preferred orientation. The cross-sectional FESEM images of ZnO/PS show that CdS nanocrystals are uniformly penetrated into all PS layers and adhere to them very well. photoluminescence (PL) spectra demonstrate that the intensity of PL peak located at about 425 nm has almost no change after the annealing time increases. The range of emission wavelength of CdS/PS is from 425 nm to 455 nm and the PL intensity is decreasing with the annealing temperature increasing from 100 °C to 200 °C.

Abstract:Cathode samples of nano-diamond by graphitization pretreatment with different temperatures were fabricated by electrophoresis, then the structures and morphologies of the cathode samples were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD), and the field emission tests were conducted. The effects of graphitization pretreatment on the field emission characteristics of nano-diamond cathode surface on titanium substrate are studied. The results indicate that the surface morphologies of nano-diamond cathode samples after graphitization pretreatment change a lot, and the field emission characteristics in low-voltage area are improved obviously. However, in high-voltage area, the curve distortion happens, and it doesn’t conform the mechanism of field emission characteristics.

Abstract:We demonstrate high-brightness blue organic light emitting diodes (OLEDs) using two types of guest-host systems. A series of blue OLEDs were fabricated using three organic emitters of dibenz anthracene (perylene), di(4-fluorophenyl) amino-di (styryl) biphenyl (DSB) and 4,4''-bis[2-(9-ethyl-3-carbazolyl)vinyl]biphenyl (BCzVBi) doped into two hosting materials of 4,4''-bis(9-carbazolyl) biphenyl (CBP) and 2-(4-biphenylyl)-5(4-tert-butyl-phenyl)-1,3,4-oxadiazole (PBD) as blue emitting layers, respectively. We achieve three kinds of devices with colors of deep-blue, pure-blue and sky-blue with the Commission Internationale de L''Eclairage (CIE) coordinates of (0.16, 0.10), (0.15, 0.15) and (0.17, 0.24), respectively, by employing PBD as host material. In addition, we present a microcavity device using the PBD guest-host system and achieve high-purity blue devices with narrowed spectrum.

Abstract:A facile surface plasmon resonance (SPR) chip is developed for small molecule determination and analysis. The SPR chip was prepared based on a self assembling principle, in which the modified bovine serum albumin (BSA) was directly self-assembled onto the bare gold surface. The surface morphology of the chip with the modified BSA was investigated by atomic force microscopy (AFM) and its optical properties were characterized. The surface binding capacity of the bare facile SPR chip with a uniform morphology is 8 times of that of the bare control SPR chip. Based on the experiments of immune reaction between cortisol antibody and cortisol derivative, the sensitivity of the facile SPR chip with the modified BSA is much higher than that of the control SPR chip with the un-modified BSA. The facile SPR chip has been successfully used to detect small molecules. The lowest detection limit is 5 ng/mL with a linear range of 5—100 ng/mL for cortisol analysis. The novel facile SPR chip can also be applied to detect other small molecules.

Abstract:An ultra-wide and flat optical frequency comb (OFC) generation scheme using multiple continuous wave (CW) light sources based on electro-absorption modulator (EAM) and frequency modulator (FM) is proposed. In the scheme, each CW light source is broadened and modulated by the first EAM and FM, respectively. The second EAM is introduced to flatten the ultra-wide OFC lines. By setting the wavelength spacing of light sources equal to the bandwidth of sub-OFC, an ultra-wide OFC can be obtained. Principle analysis and simulation for the scheme are performed. The results show that in the case of a single light source, a tunable and flat OFC is obtained. With the increase of light sources, the bandwidth of the generated ultra-wide OFC expands rapidly. In the case of 28 light sources, a 22 GHz ultra-wide OFC with bandwidth of 16.52 THz can be generated.

Abstract:In this paper, a dynamic optical arbitrary waveform generator (OAWG) based on cross phase modulation (XPM) is proposed. According to the characteristics of XPM, the nonlinear phase shift of signal can be changed along with the pump power. The amplitude of signal can be changed by controlling the phase shift at one arm of a Mach-Zehnder interferometer (MZI) using XPM effect between signal and pump. Therefore, the phase and amplitude of the optical frequency comb (OFC) can be controlled by two pump arrays. As a result, different kinds of waveforms can be synthesized. Due to the ultrafast response of XPM, the generated waveform could be dynamically updated with an ultrafast frequency. The waveform fidelity is affected by the updating frequency.

Abstract:The properties of Al-doped ZnO (AZO) play an important role in the photovoltaic performance of inverted polymer solar cells (PSCs), which is used as electron transport and hole blocking buffer layers. In this work, we study the effects of Al-doping level in AZO on device performance in detail. Results indicate that the device performance intensely depends on the Al-doping level. The AZO thin films with Al-doping atomic percentage of 1.0% possess the best conductivity. The resulting solar cells show the enhanced short current density and the fill factor (FF) simultaneously, and the power conversion efficiency (PCE) is improved by 74%, which are attributed to the reduced carrier recombination and the optimized charge transport and extraction between AZO and the active layer.

Abstract:Organic-inorganic hybrid light emitting diodes (LEDs) were fabricated by incorporating cadmium sulphide (CdS) nanoparticles in hole transporting layer and light emitting materials of a polymer LED. The CdS nanoparticles with size of 10 nm were synthesized by precipitation technique. The LEDs incorporated with the CdS nanoparticles show a reduction in turn on voltage and luminance. When the nanoparticles are incorporated in a suitable fluorene based light emitting polymer, the luminance is increased along with the decrease of turn on voltage.

Abstract:A liquid deformable mirror, which can provide a large stroke deflection more than 100 µm, is proposed for focus control. The deformable mirror utilizes the concept of magnetic fluid deformation shaped with electromagnetic fields to achieve concave or convex surface and to change the optical focus depth of the mirrors. The free surface of the magnetic fluid is coated with a thin layer of metal-liquid-like film (MELLF) prepared from densely packed silver nanoparticles to enhance the reflectance of the deformable mirror. The experimental results on the fabricated prototype magnetic fluid deformable mirror (MFDM) show that the desired concave/convex surface shape can be controlled precisely with a closed-loop adaptive optical system.

Abstract:A single-/dual-wavelength switchable and tunable erbium-doped fiber laser (EDFL) with super-narrow linewidth has been proposed and experimentally demonstrated at room temperature. The fiber laser is based on a compound cavity simply composed of a ring main cavity and a two-ring subring cavity (TR-SC). Regardless of single- or dual-wavelength operation, the EDFL could always work well in single-longitudinal-mode (SLM) state at every oscillating wavelength. In dual-wavelength operation, the spacing could be tuned from 0 nm to 4.83 nm. In single-wavelength operation, the EDFL could lase at a fixed wavelength of 1 543.65 nm or another wavelength with a tunable range of 4.83 nm. The super-narrow linewidths of 550 Hz and 600 Hz for two wavelengths are obtained. The proposed EDFL has potential applications in microwave/terahertz-wave generation and high-precision distributed fiber optical sensing.

Abstract:Micro vapor chamber (MVC) for light emitting diodes (LEDs) can be designed and fabricated to enhance the heat dissipation efficiency and improve the reliability. In this paper, we used photoresist SU-8 and electroforming copper (Cu) to fabricate three kinds of wick structures, which are star, radiation and parallel ones, and the substrate is silicon with thickness of 0.5 mm. Electroforming Cu on silicon to make micro wick structure was a critical step, the ampere-hour factor was used, and accordingly the electroforming time was predicted. The composition of electroforming solution and parameters of electroforming were optimized too. After charging and packaging, thermal behavior tests were carried out to study the heat dissipation performance of MVCs. When the input power was 8 W, the parallel wick structure reached the equivalent temperature of 69.0 °C in 226 s, while the others were higher than that. The experimental results prove that the wick structures have significant influence on the heat transfer capability of MVCs.

Abstract:Nano transparent conducting titanium-zinc oxide (Ti-ZnO) thin films were prepared on glass substrates by radio frequency (RF) magnetron sputtering technique. The deposited films are characterized by X-ray diffraction (XRD), four-probe meter and UV-visible spectrophotometer. The effects of Ti-doping content on the structural, optical and electrical properties of the films are investigated. The XRD results show that the obtained films are polycrystalline with a hexagonal wurtzite structure and preferentially oriented in the (002) crystallographic direction. The structural and optoelectronic characteristics of the deposited films are subjected to the Ti-doping content. The Ti-ZnO sample fabricated with the Ti-doping content of 3% (weight percentage) possesses the best crystallinity and optoelectronic performance, with the highest degree of preferred (002) orientation of 99.87%, the largest crystallite size of 83.2 nm, the minimum lattice strain of 6.263´10-4, the highest average visible transmittance of 88.8%, the lowest resistivity of 1.18×10-3 W∙cm and the maximum figure of merit (FOM) of 7.08×103 W-1∙cm-1. Furthermore, the optical bandgaps of the films are evaluated by extrapolation method and observed to be an increasing tendency with the increase of the Ti-doping content.

Abstract:A novel lower-complexity construction scheme of quasi-cyclic low-density parity-check (QC-LDPC) codes for optical transmission systems is proposed based on the structure of the parity-check matrix for the Richardson-Urbanke (RU) algorithm. Furthermore, a novel irregular QC-LDPC(4 288, 4 020) code with high code-rate of 0.937 is constructed by this novel construction scheme. The simulation analyses show that the net coding gain (NCG) of the novel irregular QC-LDPC(4 288,4 020) code is respectively 2.08 dB, 1.25 dB and 0.29 dB more than those of the classic RS(255, 239) code, the LDPC(32 640, 30 592) code and the irregular QC-LDPC(3 843, 3 603) code at the bit error rate (BER) of 10-6. The irregular QC-LDPC(4 288, 4 020) code has the lower encoding/decoding complexity compared with the LDPC(32 640, 30 592) code and the irregular QC-LDPC(3 843, 3 603) code. The proposed novel QC-LDPC(4 288, 4 020) code can be more suitable for the increasing development requirements of high-speed optical transmission systems.

Abstract:The bending characteristics of dual-hole polarization maintaining photonic crystal fiber (PM-PCF) are demonstrated in this paper. The modal interference is induced by the LP01 mode and LP11 mode propagating in a single PM-PCF with the same polarization direction. Simulation results demonstrate that the bending radius induces the phase difference between LP01 mode and LP11 mode, which leads to the change of light interference intensity on the fiber output facet. The relationship between bending radius and normalized interference intensity with three different bending angles is discussed, where the bending angle is defined as the angle between hole axis and the x axis. The bending sensitivity is obtained to be about -188.78/m around the bending radius of 1.5 cm with the bending angle of 90°. The bending characteristics can contribute for online bending detection in widespread areas.

Abstract:By adopting a distributed feedback laser (DFBL) centered at 1.654 µm, a near-infrared (NIR) methane (CH4) detection system based on tunable diode laser absorption spectroscopy (TDLAS) is experimentally demonstrated. A laser temperature control as well as wavelength modulation module is developed to control the laser’s operation temperature. The laser’s temperature fluctuation can be limited within the range of −0.02—0.02 °C, and the laser’s emitting wavelength varies linearly with the temperature and injection current. An open reflective gas sensing probe is realized to double the absorption optical path length from 0.2 m to 0.4 m. Within the detection range of 0—0.01, gas detection experiments were conducted to derive the relation between harmonic amplitude and gas concentration. Based on the Allan deviation at an integral time of 1 s, the limit of detection (LoD) is decided to be 2.952×10-5 with a path length of 0.4 m, indicating a minimum detectable column density of ~1.2×10-5 m. Compared with our previously reported NIR CH4 detection system, this system exhibits some improvement in both optical and electrical structures, including the analogue temperature controller with less software consumption, simple and reliable open reflective sensing probe.

Abstract:In this paper, a simple aircraft surface ice detection system is proposed based on multi-wavelength imaging. Its feasibility is proved by the experimental results. The influence of color coatings of aircraft surface is investigated. The results show that the ice area can be clearly distinguished from the red, white, gray and blue coatings painted aluminum plates. Due to the strong absorption, not enough signals can be detected for the black coatings. Thus, a deep research is needed. Even though, the results of this paper are helpful to the development of aircraft surface ice detection.

Abstract:With a heralded single photon source (HSPS), a measurement-device-independent quantum key distribution (MDI-QKD) protocol is proposed, combined with a three-intensity decoy-state method. HSPS has the two-mode characteristic, one mode is used as signal mode, and the other is used as heralded mode to reduce the influence of the dark count. The lower bound of the yield and the upper bound of the error rate are deduced and the performance of the MDI-QKD protocol with an HSPS is analyzed. The simulation results show that the MDI-QKD protocol with an HSPS can achieve a key generation rate and a secure transmission distance which are close to the theoretical limits of the protocol with a single photon source (SPS). Moreover, the key generation rate will improve with the raise of the senders’ detection efficiency. The key generation rate of the MDI-QKD protocol with an HSPS is a little less than that of the MDI-QKD protocol with a weak coherent source (WCS) in the close range, but will exceed the latter in the far range. Furthermore, a farther transmission distance is obtained due to the two-mode characteristic of HSPS.

Abstract:A novel no-reference (NR) image quality assessment (IQA) method is proposed for assessing image quality across multifarious distortion categories. The new method transforms distorted images into the shearlet domain using a non-subsample shearlet transform (NSST), and designs the image quality feature vector to describe images utilizing natural scenes statistical features:coefficient distribution, energy distribution and structural correlation (SC) across orientations and scales. The final image quality is achieved from distortion classification and regression models trained by a support vector machine (SVM). The experimental results on the LIVE2 IQA database indicate that the method can assess image quality effectively, and the extracted features are susceptive to the category and severity of distortion. Furthermore, our proposed method is database independent and has a higher correlation rate and lower root mean squared error (RMSE) with human perception than other high performance NR IQA methods.

Abstract:A localized surface plasmon resonance (LSPR) biosensor was prepared with gold nanospheres (AuNSs) coated on the tip face of the optical silica fiber. AuNSs with the sizes of 20 nm and 80 nm were used. The sensitivities of AuNS20 nm and AuNS80 nm modified sensors to bulk refractive index (RI) variation are 82.86 nm/RIU and 218.98 nm/RIU, respectively. The AuNS80 nm modified sensor was used for the detection of 40 bases DNA hybridization and the limit of detection is 50 nmol/L, where the 40-bases DNA probe was covalently linked with AuNS80 nm. The complementary DNA sequence in tris-acetate-EDTA (TAE) buffer solution was detected as the target DNA. This fiber sensor has the advantages of small sample consumption, easy fabrication and high sensitivity.