Abstract:To achieve uniform distribution of silver nano clusters (SNCs) on substrate and reveal its effect on the performance of organic light-emitting diode (OLED), the SNCs incorporated OLED was fabricated and SNCs were coated by multi-step spin coating. Compared with the device without SNCs film, the brightness and current efficiency of the OLED devices with SNCs film were highly raised. The enhancement is attributed to SNCs induced local surface plasmon (LSP) oscillation, which can increase the radiative rate of excitons on Alq3 molecules.

Abstract:The self-heterodyne detection Brillouin optical time domain reflectometer (BOTDR) system using broad-band laser is proposed to reduce coherent Rayleigh noise and improve the system performance. Compared with the system with narrow-band laser, the stimulated Brillouin scattering (SBS) threshold can be improved by about 3 dB. The experimental results of the narrow-band laser measurements for three times independently and the broad-band laser measurement for one time are compared. The root-mean-square (RMS) errors of Brillouin linewidth for two systems with narrow-band laser and broad-band laser are 6.9 MHz and 2.7 MHz, respectively, and the RMS errors of temperature for the heated fiber are about 1.3 °C and 0.7 °C. With the broad-band laser, signal-to-noise ratio (SNR) of the unheated fiber is approximately equivalent to that of the integrated three independent Brillouin signals for the narrow-band laser, and the results are believed to be beneficial for performance improvement and measurement time reduction.

Abstract:We numerically demonstrate that whispering-gallery modes (WGMs) in a microsphere resonator with three layers of high, low and high refractive index (RI) are analyzed by using the finite difference time domain (FDTD) method. To make the light couple in and out of the microsphere, a phase matched waveguide is used to overlap the WGMs evanescent radiation field. By changing the gap between the microsphere and waveguide, the WGMs of two high-RI layers are efficiently excited. The stored energy and the mode volume are optimized for sensing applications. The coupling structure reveals a good sensitivity of 38.29 nm/RIU (RI unit).

Abstract:A graded-index mode division multiplexer with low loss and low crosstalk is proposed. The transmission channel adopts a pure silica core with large effective area to achieve low attenuation, which effectively reduces the splicing loss with pure silica core few-mode transmission fiber. Low differential mode group delay is realized by using graded-index distribution. Also the effective index difference of the modes is greater than 0.5×10-3 to ensure low crosstalk between modes. The performance of the mode division multiplexer is investigated using the beam propagation method and full-vector finite element method. The result shows that the coupling efficiency of multiplexer is better than −0.479 dB, and the extinction ratio is higher than 31.2 dB in the wavelength of 1 400—1 700 nm. In C band, the average coupling efficiency of all mode channels of multiplexer is better than that of −0.140 dB, which shows flatness. The proposed scheme is an effective way to implement a multiplexer with low crosstalk, low loss, low fusion loss, high coupling efficiency, high extinction ratio and wide operating band.

Abstract:A 1 550 nm long-wavelength vertical cavity surface emitting laser (VCSEL) on InP substrate is designed and fabricated. The transfer matrix is used to compute reflectivity spectrum of the designed epitaxial layers. The epitaxial layers mainly consist of 40 pairs of n-AlxGayIn(1-x-y)As/InP, and 6 strain compensated AlxGayIn(1-x-y)As/InP quantum wells on n-InP substrate, respectively. The top distributed Bragg reflection (DBR) mirror system has been formed by fabricating 4.5 pairs of SiO2/Si. The designed cavity mode is around 1 536 nm. The dip of the fabricated cavity mode is around 1 530 nm. The threshold current is 30 mA and the maximum output power is around 270 μW under CW operation at room temperature.

Abstract:A real-time label-free DNA biosensor based on thin-core fiber (TCF) interferometer is demonstrated experimentally. The proposed biosensor is constructed by splicing a TCF between two segments of single mode fibers (SMFs) and integrated into a microfluidic channel. By modifying the TCF surface with monolayer poly-l-lysine (PLL) and single-stranded deoxyribonucleic acid (ssDNA) probes, the target DNA molecules can be captured in the microfluidic channel. The transmission spectra of the biosensor are measured and theoretically analyzed under different biosensing reaction processes. The results show that the wavelength has a blue-shift with the process of the DNA hybridization. Due to the advantages of low cost, simple operation as well as good detection effect on DNA molecules hybridization, the proposed biosensor has great application prospects in the fields of gene sequencing, medical diagnosis, cancer detection and environmental engineering.

Abstract:A series of single-unit and tandem blue phosphorescent organic light-emitting diodes (OLEDs) were prepared by adjusting the concentration of dopant based on the structure of ITO/NPB/EL unit/Alq3/Cs2CO3/Al. The results show that tandem device with doping concentration of 10 wt% has appropriate energy transfer, which achieves the best performance with a maximum current efficiency of 3.4 cd.A-1. Further study found that current efficiency and power efficiency of the tandem OLED adding BCP as hole blocking layer (HBL) can achieve 7.85 cd.A-1 and 0.72 lm.W-1, respectively. It is 2.88 times and 1.57 times larger than those of sing-unit devices, and green peak is restrained effectively.

Abstract:The growth of Na5Lu9F32 single crystals doped with Cr3+ ions in 0.1 mol%, 0.2 mol% and 0.5 mol% concentrations by Bridgman method was reported. The optical absorption and luminescence spectra decisively demonstrate that the Cr dopant enters Na5Lu9F32 as Cr3+. Fluorescence emission at wavelengths of 418 nm, 444 nm, 653 nm and 678 nm can be observed under the excitation of 372 nm and the fluorescence lifetime at 418 nm was measured to be ~10.31 μs. The possible crystal sites for Cr3+ ions in Na5Lu9F32 single crystal were discussed, and the lattice parameter Dq, Racach parameters B and C were estimated.

Abstract:The UV photorefractive properties of near-stoichiometric LiNbO3 single crystal are found to be significantly enhanced compared with the congruent one at 325 nm. The temperature dependence of the band edge of near-stoichiometric LiNbO3 crystal is investigated. Significant thermal-induced spectral shift in band gap which obeys the Bose-Einstein expression is observed, and the fundamental band gap at zero absolute temperature is found to be much larger than the congruent one. New absorption bands near the UV band edge which are much stronger in the near-stoichiometric LiNbO3 than those in the congruent LiNbO3 crystal show up at temperatures lower than ~400 K. Note that the UV photorefractivity is enhanced in SLN, which has exactly the same tendency as the absorption strength.

Abstract:With reducing the absorber layer thickness and processing temperature, the recombination at the back interface is severe, which both can result in the decrease of open-circuit voltage and fill factor. In this paper, we prepare Al2O3 by atomic layer deposition (ALD), and investigate the effect of its thickness on the performance of Cu(In,Ga)Se2 (CIGS) solar cell. The device recombination activation energy (EA) is increased from 1.04 eV to 1.11 eV when the thickness of Al2O3 is varied from 0 nm to 1 nm, and the height of back barrier is decreased from 48.54 meV to 38.05 meV. An efficiency of 11.57 % is achieved with 0.88-μm-thick CIGS absorber layer.

Abstract:We theoretically study the evolution of dark solitons in the biased photorefractive-photovoltaic crystal by using beam propagation method (BPM). We find that when the absolute value of the extra bias field is less than the photovoltaic field, the dark screening-photovoltaic (SP) solitons can be observed. The initial width of the dark notch at the entrance face of the crystal is a key parameter for generating an sequence of dark coherent solitons. If the initial width of the dark notch is small, only a fundamental soliton or Y-junction soliton pair is generated. When the initial width of the dark notch is increased, the dark notch tends to split into an odd (or even) number of multiple dark solitons, which realizes a progressive transition from the low-order solitons to a sequence of higher-order solitons.

Abstract:Coherent optical fiber communications for data rates of 100 Gbit/s and beyond have recently been studied extensively because high sensitivity of coherent receivers could extend the transmission distance. Spectrally efficient modulation techniques such as M-ary phase shift keying (PSK) can be employed for coherent optical links. The integration of multi-level modulation formats based on coherent technologies with wavelength-division multiplexed (WDM) systems is vital to meet the aggregate bandwidth demand. This paper reviews coherent quadrature PSK (QPSK) systems to scale the network capacity and maximum reach of coherent optical communicationsystems to accommodate traffic growth.

Abstract:In this paper, a novel vertical cavity surface emitting laser (VCSEL) polarization modulation technique based on polarization switching due to thermal heating in a single transverse mode class 10 G VCSEL at 1 310 nm is demonstrated experimentally. The inherent orthogonal polarization switching of the VCSEL carrier with changing bias is exploited in the transmission of pulse-per-second (PPS) timing clock signal. Experimental results show that PPS pulse widths of 9.97 µs and 9.98 µs are measured for back-to-back analysis and over 3.21 km of G 652 urban fibre transmission, respectively. This work provides a novel alternative for adoption in optical frequency and time transfer applications.

Abstract:In this paper, a new method for the rapid, economical and convenient detection of cyclic adenosine monophosphate (cAMP) in jujube is proposed and verified. Based on near-infrared (NIR) fiber spectroscopy combined with stoichiometric analysis, the cAMP content in red jujube can be quickly detected. 68 red jujube samples were used for the NIR spectroscopy data acquisition and the corresponding chemical values were determined. The sample set was adjusted based on the joint XY distance (SPXY) to select the correction sample set. After different preprocessing on the spectra, the partial least squares (PLS) method was used to establish the model, and the smoothed and normalized PLS model result was obtained better. The model's correction correlation coefficient (Rc), correction set mean square error (RMSEC), prediction correlation coefficient (Rp), and prediction and mean square error (RMSEP) are 0.951 5, 25.793 7, 0.910 8 and 28.228 0, respectively. The results show that NIR combined with specific chemometric methods can achieve rapid detection of cAMP in red jujube.

Abstract:This paper designs an energy-quality multilevel framework for the coding and transmission of aerial images, and then introduces a scaling-based intra encoder with flexible sampling factor (SF) and quantization parameter (QP). By experimentally investigating how different coding configurations affect the complexity-rate-quality characteristics of aerial images, this paper derives a configuration estimation model between energy-quality level and appropriate (SF, QP) configuration. By utilizing the model, a bivariate control scheme is proposed so as to progressively adjust sender's energy consumption under quality constraints. The experimental results show that the proposed scheme can achieve better energy-quality tradeoff with a wider quality range, and reduce the energy consumption above a certain quality.

Abstract:The resolution and quality of the depth map captured by depth cameras are limited due to sensor hardware limitations, which becomes a roadblock for further computer vision applications. In order to solve this problem, we propose a new method to enhance low-resolution depth maps using high-resolution color images. The structural-aware term is introduced because of the availability of structural information in color images and the assumption of identical structural features within local neighborhoods of color images and depth images captured from the same scene. We integrate the structural-aware term with color similarity and depth similarity within local neighborhoods to design a local weighting filter based on structural features. To use non-local self-similarity of images, the local weighting filter is combined with the concept of non-local means, and then a non-local weighting filter based on structural features is designed. Some experimental results show that super-resolution depth image can be reconstructed well by the process of the non-local filter and the local filter based on structural features. The proposed method can reconstruct much better high-resolution depth images compared with previously reported methods.

Abstract:Determining the light absorption distribution (LAD) of uterine tissue helps the detection of endometrial carcinoma. In this work, a 3-dimensional optical model of the human uterus is proposed and examined. The model is filled with strong scattering medium (undiluted raw and homogenized milk, URHM) or air at 630 nm and 800 nm wavelengths. Monte Carlo simulations are used to find the absorption profiles of photons by transcervical laser illumination, with a cylindrically diffused light source (CDLS) or spherically diffused light source (SDLS). The results show that 800 nm is a good laser wavelength value for the detection of endometrial carcinoma by photoacoustic imaging (PAI). At the same time, the shape of the light source becomes less important in a relatively large cavity. The impacts of different scattering coefficients of CDLS on the irradiated area are demonstrated. Strong scattering medium is helpful to the illumination of the uterus cavity.