Fabrication and temperature-dependent photoluminescence spectra of Zn–Cu–In–S quaternary nanocrystals

A series of Zn-Cu-In-S nanocrystals （ZCIS NCs） are prepared and the optical properties of the ZCIS NCs are tuned by adjusting the reaction time. It is interesting to observe that the temperature-dependent photoluminescence （PL） spectra of the ZCIS NCs show a redshift with decreasing intensity at low temperature （50-280 K） and a blueshift at high temperature （318--403 K）. The blueshift can be explained by the thermally active phonon-assisted tunneling from the excited states of the low-energy emission band to the excited states of the high-energy emission band.     

Theoretical and experimental analysis of the effects of the series resistance on luminous efficacy in GaN-based light emitting diodes

In this paper, a new equivalent circuit model of GaN-based light emitting diodes （LEDs） is established. The impact of the series resistance to luminous efficacy is simulated using the MATLAB software. GaN-based LEDs with different n- contact electrode materials （LEDs with Ni/Au and LEDs with Cr/Au） are fabricated. By comparing and analyzing the results of performances, we concluded that both the series resistance and the carrier loss could affect the luminous efficacy severely. LEDs with lower series resistance have higher luminous efficacy and its efficiency droop is alleviated simultaneously. To improve luminous efficacy, the fabrication process should be optimized for lower series resistance.     

Improved device reliability in organic light emitting devices by controlling the etching of indium zinc oxide anode

A controllable etching process for indium zinc oxide （IZO） films was developed by using a weak etchant of oxalic acid with a slow etching ratio. With controllable etching time and temperature, a patterned IZO electrode with smoothed surface morphology and slope edge was achieved. For the practical application in organic light emitting devices （OLEDs）, a sup- pression of the leak current in the current-voltage characteristics of OLEDs was observed. It resulted in a 1.6 times longer half lifetime in the IZO-based OLEDs compared to that using an indium tin oxide （ITO） anode etched by a conventional strong etchant of aqua regia.     

Increased performance of an organic light-emitting diode by employing a zinc phthalocyanine based composite hole transport layer

We demonstrate that the electroluminescent performances of organic light-emitting diodes are significantly improved by employing a zinc phthalocyanine （ZnPc）-based composite hole transport layer （c-HTL）. The optimum ris-（8-hydroxyquinoline）aluminum （Alq3）-based organic light-emitting diode with a c-HTL exhibits a lower turn-on voltage of 2.8 V, a higher maximum current efficiency of 3.40 cd/A and a higher maximum power efficiency of 1.91 lm/W, which are superior to those of the conventional device （turn-on voltage of 3.8 V, maximum current efficiency of 2.60 cd/A, and maximum power efficiency of 1.21 lm/W）. We systematically studied the effects of different kinds of N’-diphenyl-N,N’-bis（1-naphthyl）（1,1’-biphenyl）-4,4’diamine （NPB）：ZnPc c-HTL. Meanwhile, we also investigate their mechanisms different from that in the case of using ZnPc as buffer layer. The specific analysis is based on the absorption spectra of the hole transporting material and current density–voltage characteristics of the corresponding hole-only devices.     

Study on the characteristics of linac based THz light source

There are many methods based on linac for THz radiation production. As one of the options for the Beijing Advanced Light, an ERL test facility is proposed for THz radiation. In this test facility, there are 4 kinds of methods to produce THz radiation： coherent synchrotron radiation （CSR）, synchrotron radiation （SR）, low gain FEL oscillator, and high gain SASE FEL. In this paper, we study the characteristics of the 4 kinds of THz light sources.     

Study of the characteristics of a scintillation array and single pixels for nuclear medicine imaging applications

By using a pixelized Nal（T1） crystal array coupled to a R2486 PSPMT, the characteristics of the array and of a single pixel, such as the light output, energy resolution, peak-to-valley ratio （P/V） and imaging performance of the detector were studied. The pixel size of the NaI（TI） scintillation pixel array is 2 mm×2 mm×5 mm. There are in total 484 pixels in a 22×22 matrix. In the pixel spectrum an average peak-to-valley ratio （P/V） of 16 was obtained. In the image of all the pixels, good values for the Peak-to- Valley ratios could be achieved, namely a mean of 17, a maximum of 45 and the average peak FWHM （the average value of intrinsic spatial resolution） of 2.3 mm. However, the PSPMT non-uniform response and the scintillation pixels array inhomogeneities degrade the imaging performance of the detector.     

Unidirectional emissions from dielectric photonic circuits decorated with plasmonic phased antenna arrays

Thanks to resonant characteristics of metallic nanoparticles, optical waves scattered from plasmonic nanoantennae can be well tailored in both amplitude and phase. We numerically demonstrate that, by varying the lengths and the lateral positions of gold nanorods in vicinity of a silicon waveguide, unidirectional emissions with typical forward-backward contrast ratio of 15 dB and directivity of 12 dB can be acquired in a plasmonic phased antenna array with sub-wavelength device length. The properties, i.e., the emission directionality and the size compactness, can be employed to control the far-field radiation pattern from a dielectric photonic circuit. Moreover, by altering the orientations of the dielectric waveguides decorated with plasmonic phased antenna arrays, we propose wireless light transportations in a layered photonic infrastructure, which may have applications in high-density photonic integrations.     

Improved light extraction of organic light emitting diodes with a nanopillar pattering structure

We have investigated the properties of organic light emitting diodes(OLEDs)with a nanopillar patterning structure at organic–metal or organic–organic interfaces.The results demonstrate that the introduction of a nanopillar structure can improve the light extraction efficiency greatly.We also find that the number,height,and position of nanopillars all affect the light extraction of OLEDs.The maximum power efficiency of a device with an optimized nanopillar patterning mode can be improved to 2.47 times that of the reference device.This enhancement in light extraction originates from the improved injected carriers,the broadened charge recombination zone,and the intensified wave guiding effects.     

Nonlinear effect of the structured light profilometry in the phase-shifting method and error correction

Digital structured light （SL） profilometry is increasingly used in three-dimensional （3D） measurement technology. However, the nonlinearity of the off-the-shelf projectors and cameras seriously reduces the measurement accuracy. In this paper, first, we review the nonlinear effects of the projector-camera system in the phase-shifting structured light depth measurement method. We show that high order harmonic wave components lead to phase error in the phase-shifting method. Then a practical method based on frequency domain filtering is proposed for nonlinear error reduction. By using this method, the nonlinear calibration of the SL system is not required. Moreover, both the nonlinear effects of the projector and the camera can be effectively reduced. The simulations and experiments have verified our nonlinear correction method.     

Post-post-Newtonian deflection of light ray multiple systems with PPN parameters

The post-Newtonian scheme in multiple systems with post-Newtonian parameters presented by Klioner and Soffel is extended to the post-post-Newtonian （PPN） order for light propagation problem in the solar system. Under considering the solar system experiment requirement, a new parameter ε is introduced. This extension does not change the virtue of the scheme on the linear partial differential equations of the potential and vector potential mentioned in previous work. Furthermore, this extension is based on the former work done by Richter and Matzner in one global system theory. As an application, we also consider the deflection of light ray in the global coordinates. And the deflection angle of light ray is obtained with post-Newtonian parameters.     

Nature of light scalars through photon-photon collisions

The surprising thing is that arising almost 50 years ago from the linear sigma model （LSM） with spontaneously broken chiral symmetry, the light scalar meson problem has become central in the nonperturbative quantum chromodynamics （QCD） for it has been made clear that LSM could be the low energy realization of QCD. First we review briefly signs of four-quark nature of light scalars. Then we show that the light scalars are produced in the two photon collisions via four-quark transitions in contrast to the classic P wave tensor qq mesons that are produced via two-quark transitions γγ→qq. Thus we get new evidence of the four-quark nature of these states.     

Measurements of the light output functions of plastic scintillator using 9Be（d,n）10B reaction neutron source

The light output functions for protons of ST-401 and BC-408 plastic scintillators were measured using white neutron source produced by the 9Be（d,n） 10B reaction at the HI-13 Tandem Accelerator at China Institute of Atomic Energy（CIAE）.The LOFs of plastic scintillators for protons in the energy range of 0.5-16.5 MeV were obtained by the time-of-flight（TOF） technique and an iterative procedure.Two parameters（kB and C） were deduced by fitting the experimental data.     

Comment on ＇The scale-transformation of electromagnetic theory and its applications＇, ＇Distribution characteristic of scattering field for an ellipsoidal target irradiated by an electromagnetic wave from an arbitrary direction＇ and ＇Electric fields inside and outside an anisotropic dielectric sphere＇

It is shown that the ＇scale-transformation＇ method proposed by Li Ying-Le et al. is not applicable to the Maxwell theory.     

Theoretical calculation of kerma coefficients for n+16O reaction below 30 MeV

On the basis of the light nuclear reaction model, a new kerma coefficient formula has been developed. In terms of the analysis for n＋^16O reactions below 30 MeV, the average energies of all kinds of the emitted particles are presented. The calculated partial kerma coefficients agree well with the existing experimental data. The discrepancies of the total kerma coefficients between the calculation and the measurement are analyzed in detail.     

Surveying post-saddle nuclear dissipation with protons and α particles as probes

Using a Langevin model, we calculate post-saddle proton and α-particle multiplicities as a function of the post-saddle dissipation strength （β） for the heavy systems 234Cf, 240Cf, 246Cf and 240U. We find that, with increasing isospin of the system, the sensitivity of post-saddle light charged-particle multiplicities to β decreases considerably and, moreover, for 240U the charged-particle multiplicities are no longer sensitive to β. These results suggest that in order to determine the post-saddle friction strength more accurately by measuring the multiplicities of pre-scission protons and α particles, it is best to populate those heavy compound systems with low isospin.     

具有T宇称的最小Higgs模型与LHC上Higgs波色子与弱规范波色子的联合产生

Considering the process pp→VH ＋X（V = W or Z） is a significant channel for searching for a light Higgs boson, we calculate the contributions of the littlest Higgs model with T-parity （called LHT model） to its production cross section. We find that, in most of the parameter space, the value of the relative correction parameter R is very small. However, with reasonable values of the free parameters, its value can be significantly larger.     

Theoretical Model Calculation for d ＋^8Li Reaction

Based on the theoretical models for light nuclei, the calculations of reaction cross sections and the angular distributions for d ＋^8Li reaction are performed. Since all of the particle emissions are from the compound nucleus to the discrete levels, the angular momentum coupling effect in pre-equilibrium mechanism is taken into account. The three- body break-up process and the recoil effect are involved. The theoretical calculated results are compared to existing experimental data.     

Theoretical Analysis of Neutron Double-Differential Cross Sections of n ＋^9Be Reactions

By using the nuclear reaction model for light nuclei, the calculations of the double-differential cross sections of outgoing neutrons from n ＋^9Be reactions are performed. The total outgoing neutrons are only come from the （n, 2n）2a reaction channel. The （n, 2n）2a reaction channel is achieved through six different reaction approach, which are illustrated in this paper. The calculated results agree very well with the measured data at En = 7.1, 8.09, 8.17, 9.09, 9.97 and 10.26 MeV, because the updated level schemes related to the n ＋ ^9Be reactions have been employed in this calculations.     

A new kind of superimposing morphology for enhancing the light scattering in thin film silicon solar cells:Combining random and periodic structure

In this article, a new type of superimposing morphology comprised of a periodic nanostructure and a random structure is proposed for the first time to enhance the light scattering in silicon-based thin film solar cells. According to the framework of the Reyleigh-Sommerfeld diffraction algorithm and the experimental results of random morphologies, we analyze the light-scattering properties of four superimposing morphologies and compare them with the individual morphologies in detail. The results indicate that the superimposing morphology can offer a better light trapping capacity, owing to the coexistence of the random scattering mechanism and the periodic scattering mechanism. Its scattering property will be dominated by the individual nanostructures whose geometrical features play the leading role.     

A novel yellow phosphor for white light emitting diodes

This paper reports that a novel yellow phosphor, LiSrBO₃:Eusup>2+, was synthesized by the solid-state reaction. The excitation and emission spectra indicate that this phosphor can be effectively excited by ultraviolet (360 and 400~nm) and blue (425 and 460~nm) light, and exhibits a satisfactory yellow performance (565~nm). The role of concentration of Eusup>2+ on the emission intensity in LiSrBO₃ is studied, and it is found that the critical concentration is 3 mol\%, and the concentration self-quenching mechanism is the dipole--dipole interaction according to the Dexter theory. White light emitting diodes were generated by using an InGaN chip (460~nm or 400~nm) with LiSrBO₃:Eusup>2+ phosphor, the CIE chromaticity is (x=0.341, y=0.321) and (x=0.324, y=0.318), respectively. Therefore, LiSrBO₃:Eusup>2+ is a promising yellow phosphor for white light emitting diodes.