White organic light-emitting diodes based on emission from DPVBi-doped 4,48-bis (2,28-diphenylvinyl)-1, 18-biphenyl

Organiclight-emitting diodes (OLEDs) have beenin-vestigated for many years on account of their highlumi-nance,low driven voltages ,wide visual range,flexiblesubstratesinflat-panel ,full color displays and backlightapplications .For high brightness and eff…     

Differences of silicon photodiode spectral reflectance among the same batch

Photodiode＇s reflectance plays an important role regarding the relation between responsivity and the incident flux. In this work we analyze how the spectral reflectance changes among photodiodes from the same manufacturer and batch and how the reflectance of three standard photodiodes has drifted during six years. The results show that the reflectance changes from diode to diode within the same batch and also show that the reflectance ofphotodiodes changes on time. This ageing is spectraUy dependent.     

Design for SOP AMOLED display panel

A novel full color SOP（system on panel） AMOLED display based on the MIUC polycrystalline silicon TFT technique, and a new control circuit for the panel, which can deal with both VGA and DVI input signals have been developed. To realize gray-scale a sub-frame technique has been designed and im- plemented by FPGA device, in which an 120 module has been inserted. Through actual circuit, the whole design has been proven and the advantages of the SOP AMOLED display panel have been confirmed.     

GaAs/AlGaAs quantum well infrared photodetector with low noise

A novel kind of multi-quantum well infrared photodetector（QWlP） is presented. In the new structure device,a p-type contact layer has been grown on the top of the conventional structure of QWlP,then a small tunneling current is instead of the large compensatory current,which made the device low dark current and low noise characteristics. The measured result of dark current is consistent with the calculated result, and the noise of the new structure QWIP is decreased to one third of the conventional QWlP.     

InAs/InAsSb Avalanche Photodiode （APD） for applicaions in long-wavelength infrared region

A generic numerical model of a long-wavelength Avalanche Photodiode （APD） based on narrow bandgap semiconductor InAsSb on InAs substrate is reported for the first time. This model has been applied for theoretical characterization of a proposed N^＋ InAS/P-InAsSb avalanche photodiode structure for possible application in 2-5 μm wavelength region. The parameters such as gain, excess noise factor and their trade-off with variation of doping concentration and bias voltage have been estimated for the APD taking into account history-dependent theory of avalanche multiplication process, The LWIR APD is expected to fred application in optical gas sensor and in future generation of optical communication system.     

Mechanism of negative capacitance in LEDs

In order to explain the phenomenon of negative capacitance（NC） in light emitting diodes LEDs, we present a new model based on local strong recombination in active region and firstly deduce the analytic expression of NO from continuity equation. The theoretical result indicates that the NC effect becomes stronger when the carrier recombination rate increases in a certain range,which is consistent with the experimental result. Accordingly,we confirm that the NO is caused by carrier recombination in active reaion instead of by other exterior factors.     

Numerical analysis on heat transfer of laser diode module by equivalent electrical network method

Because it is complex and inconvenient to use the common temperature field calculating method and experiment method, for arialyzing heat transfer properties of laser diode module （LDM）, an equivalent electrical network method is presented in this paper. Simulation results show that the temperature stability is closely related to ambient temperature, heat sink, LDM current and TEC current. Ambient temperature and TEC controller are the dominant terms effecting on temperature control in practice,     

Fabrication of flexible organic light-emitting diodes with Alq3 as emitting layer

Fabrication of flexible organic light-emitting diodes（FOLEDs） with ITO/PVK ：TPD/Alq3/Al configuration prepared on PET substrates is reported. Alq3 is used as the light-emitting material. The curves of the current density vs. voltage,optical current vs. voltage and quantum efficiency vs. current density of the devices are investigated. Compared the devices with the ones that have the same configuration and are fabricated under the same conditions but on glass substrates,the characteristics of the two kinds of devices are very similar except that the threshold voltage of the flexible FOLEDs is a little higher. Under the driving voltage of 20V,the corresponding brightness and the external quantum efficiency are 1000 cd/m^2 and 0. 27%, respectively. In addition, the anti-bend ability of the devices is tested and the reasons of failure of the devices are analyzed.     

Design of violet InGaN light-emitting diode with staggered quantum well structure

The staggered InGaN quantum well (QW) structure and the conventional InGaN QW structure for the emission at a particu-lar wavelength of 400 nm are designed and theoretically investigated,including the distribution of the carriers’ concentration,the radiative recombination rate,the Shockley-Read-Hall (SRH) recombination rate as well as the output performance and the internal quantum efficiency. The theoretical result indicates that the staggered QW structure offers significant improve-ment of carriers’ concentration in the QW,especially the hole concentration. The output power and the internal quantum efficiency also show 32.6 % and 32.5 % enhancement,respectively,in comparison with that of the conventional InGaN QW structure. The reduction of the electron overflow can be the main factor for the improvement of the optical perfor-mance for novel staggered InGaN QW structure.     

Effect of BCP ultrathin layer on the performance of organic light-emitting devices

Based on conventional double layer device, triple layer organic light-emitting diodes （OLEDs） with two heterostructures of indium-tin oxide （ITO）/N,N＇-diphenyl-N,N＇-bis（1-naphthyl）（1,1 ＇-biphenyl）-4,4＇-diamine（NPB）/2,9-dimethyl-4,7-diphenyl- 1,10-phenanthroline （BCP）/8-Hydroxyquinoline aluminum （Alq3）/Mg：Ag USing vacuum deposition method have been fabricated. The influence of different film thickness of BCP layer on the performance of OLEDs has been investigated. The results showed that when the thickness of the BCP layer film gradually varied from 0.1 nm to 4.0 nm, the electroluminescence （EL） spectra of the OLEDs shifted from green to greenish-blue to blue, and the BCP layer acted as the recombination region of charge carriers related to EL spectrum, enhancing the brightness and power efficiency. The power efficiency of OLEDs reached as high as 7.3 lm/W.     

Design of low-confinement-loss and highly birefringent index-guiding photonic crystal fibers

We present a systematic scheme to achieve both high birefringence and low confinement loss in index-guiding photonic crystal fibers （PCFs）, using a structurally-simple PCF with finite number of air holes in the cladding region. By increasing the size of the outermost-ring air holes in the cladding region, highly birefringent PCFs with low confinement loss can be successfully achieved. The design strategy is based on the fact that the modal birefringence of PCFs is dominated by the inner-ring air holes in PCF, which is verified by a full-vector finite element method with anisotropic perfectly matched layers. Numerical results show that modal birefringence in the order of 10-3 and confinement loss less than 0.1 dB/km can be easily realized in the proposed PCF with only four rings of air holes in the cladding region. We expect that such fibers will be much easier to be fabvicated than those with more air holes in the cladding region.     

Design of a multi-channel free space optical interconnection component

A multi-channel free space optical interconnection component, fiber optic rotary joint, was designed using a Dove prism. When the Dove prism is rotated an angle of at around the longitudinal axis, the image rotates an angle of 2 at. The optical interconnection component consists of the signal transmission system, Dove prim and driving mechanism. The planetary gears are used to achieve the speed ratio of 2：l between the total optical interconnection component and the Dove prism. The Clenses are employed to couple different optical signals in the signal transmission system. The coupling loss between the receiving fiber of stationary part and the transmitting fiber of rotary part is measured.     

Multi-active region laser diode with a narrow beam divergence angle

A novel large optical cavity laser diode, which consists of multi-active regions cascaded together through tunnel junctions, is proposed. After growing the epi-layers with LP-MOCVD system on GaAs substrate, the ridge waveguide laser structure is fabricated, and it shows a transverse divergence angle as low as 14.4°. This work was supported by special foundations for major state basic research project of China(G20000683-02)     

High power collimated diode laser stack

Compared with other kinds of lasers ,high power di-odelaser has many advantages suchas highelectro-opti-cal efficiency,compact structure,longlifeti me andso on.As alaser source,diode laser is sufficient for many dif-ferent applications suchas pumping of s…     

Passive mode locked diode-pumped Nd:GdYVO4 laser with a GaAs absorber

A passively Q-switched mode-locked Nd：GdYVO4 laser is successfully demonstrated by using a piece of GaAs crystal grown at low temperature as the passively saturated absorber and the output coupler. Fundamental properties of the Nd： GdYVO4 laser are investigated. The maximum average output power of 3.5 W is obtained by using plainsphere when the incident pumping power is 10 W, which corresponds to an optical-optical coversion efficiency of 35%. The threshold power for the Q-switching mode-locked is 1.2 W. The maximum average output power of 1.72 W is obtained by using GaAs when the incident pumping power is 10 W, mode-locked pulse train with a repetition rate of - 113 MHz is achieved. At the incident laser pumping power of 7 W, the modulation depth is 100%.     

High stable power control of a laser diode

For a high precise sensing and measuring system,theerror of measurement resulting fromthe fluctuation ofthe light source must be considered[1-3].The main noisesources include fluctuation of current source,self-heat ,aging and theintrinsic noises of a lase…     

Study of a high-temperature and high-pressure FBG sensor with Al2O3 thin-wall tube substrate

A fiber Bragg grating （FBG） high-temperature and high pressure sensor has been designed and fabricated by using the Al2O3 thin-wall tube as a substrate. The test results show that the sensor can withstand a pressure range of 0-45 MPa and a temperature range of-10-300 ℃, and has a pressure sensitivity of 0.0426 nm/MPa and a temperature sensitivity of 0.0112 nm/℃     

Design of buffer structure at core nodes in optical burst switching

DrivenbybothpromptincreaseofIPserviceandvast bandwidthofWDM,conventionalopticalnetworksareevolvingintothenextgenerationopticalInternet(NGOI).Somefunctionsofconfiguration,performance andfaultmanagement,executedinelectronicdomainatpresent,willbeshiftedintoo…     

Reconstruction of strain distribution in fiber Bragg gratings with differential evolution algorithm

Differential evolution algorithm is used to solve the inverse problem of strain distribution in fiber Bragg grating （FBG）. Linear and nonlinear strain profiles are reconstructed based on the reflection spectra. An approximate solution could be obtained within only 50 rounds of evolutions. Numerical examples show good agreements between target strain profiles and reconstructed ones. Online performance analysis illuminates the efficiency and practicality of differential evolution algorithm in solving the inverse problem of FBG.     

Diode-end-pumped Nd:YVO4/LBO lasers with 4.2W continuous-wave output at 457 nm

A continuous-wave （CW） 457 nm blue laser operating at the power of 4.2 W is demonstrated by using a fiber coupled laser diode module pumped Nd： YVO4 and using LBO as the intra-cavity SHG crystal. With the optimization of laser cavity and crystal parameters, the laser operates at a very high efficiency. When the pumping power is about 31 W, the output at 457 nm reaches 4.2 W, and the optical to optical conversion efficiency is about 13.5% accordingly. The stability of the output power is better than 1.2% for 8 h continuously working.