Effects of carrier mobility, energy gap, and excitation size on the performance of single layer organic solar cells

A model of universal single layer organic solar cells in metal-insulator-metal （MIM） representation involving field-depen- dent carrier mobility is set up. The current-voltage characteristics as well as the distribution of electron density, hole density and recombination rate on a set of parameters are simulated. Subsequently, the dependences of the short-circuit current density （Jsc） and open-circuit voltage （Voc） on the electron and hole zero-field mobility, excitation generation rate, energy gap, as well as electron-hole pair distance in an excitation are investigated. It is demonstrated that the enhancement of either the electron mobility or the hole mobility can contribute to the increase of Jsc in the devices. The increase of the hole mobility can lead to the improvement of both Jsc and Voc, and the simultaneous increase of the electron mobility and hole mobility will greatly elevate Jsc but maintain a steady Voc. Additionally, all the increases of the excitation generation rate, energy gap and electron-hole pair distance are beneficial to both the remarkable increases of Jsc and Voc of the devices.     

Radar target recognition based on micro-Doppler effect

Mechanical vibration of target structures will modulate the phase function of radar backscattering, and will induce the frequency modulation of returned signals from the target. It generates a side bands of the target body Doppler frequency shift, which is helpful for target recognition. Based on this, a micro-Doppler atomic storehouse is built for the target recognition, and four kinds of common classifiers are used separately to perform the classified recognition. The simulation experimental results show that this method has high recognition rate above 90%.     

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.     

Laser lift-off technique and the re-utilization of GaN-based LED films grown on sapphire substrate

A thin GaN LED film, grown on 2-inch-diameter sapphire substrates, is separated by laser lift-off. Atom force microscopy （AFM） and the double-crystal X-ray diffraction （XRD） have been employed to characterize the performance of Gan before and after the lift-off process. It is demonstrated that the separation and transfer processes do not alter the crystal quality of the GaN films obviously. InGaN/GaN multi-quantum-wells （MQW＇s） structure is grown on the separated sapphire substrate later and is compared with that grown on the conventional substmte under the same condition by using PL and XRD spectrum.     

Research on immunosensor based on porous silicon

Porous silicon is functionalized using thermal oxidation and silanization. The HYSA antibodies are immobilized to the porous surface in this paper. The changes in the reflection spectrum and photoluminescence spectrum are investigated when BSA are attached to the PS surface. The result shows that the luminescence peak of PS disappears. After the antigen- antibody reaction, the higher light emission is observed and the reflection spectrum also red shifts. Therefore, this research lays a foundation for the development of sensitive label-free optical immunosensor.     

Study of wavelength demultiplexer based on two-dimensional photonic crystals

A wavelength demultiplexer based on two dimensional photonic crystal waveguides is proposed. By using the finite difference time domain （FDTD） method and plane wave extension （PWE） method, the transmission spectra and the distributions of mode field are obtained, and the wavelength demultiplexer has been synthesized. The characteristics of the device are obtained.     

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,     

Combined optical fiber interferometric sensors for the detection of acoustic emission

A type of combined optical fiber interferometric acoustic emission sensor is proposed. The sensor can be independent on the laser source and make light interference by matching the lengths of two arms, so it can be used to monitor the health of large structure. Theoretical analyses indicate that the system can be equivalent to the Michelson interferometer with two optical fiber loop reflectors, and its sensitivity has been remarkably increased because of the decrease of the losses of light energy. PZT is powered by DC regulator to control the operating point of the system, so the system can accurately detect feeble vibration which is generated by ultrasonic waves propagating on the surface of solid. The amplitude and the fre- quency of feeble vibration signal are obtained by detecting the output light intensity of interferometer and using Fourier transform technique. The results indicate that the system can be used to detect the acoustic emission signals by the fre-quency characteristics.     

Studies of the correction for phase diverse speckle

Phase diverse speckle is a novel kind of imaging technique and can be used to overcome image degradation from unknown phase aberrations, such as atmospheric turbulence. The wave-front phase expanded on the Zernike polynomials is esti- mated from a pair of images (in the focal and out of focus planes). In this paper the principle of PDS is analyzed, and genetic algorithm is used as the iterative algorithm to simulate some characteristics, such as the influence of Zernike polynomials’ mode, amplitude of turbulence on the phase estimation. Thus, a new method for recovery of images is explored.     

Theoretical research on light propagation in W-type single-mode fiber

We give the characteristic equation of a W-type fiber by solving Maxwell＇s equations along with boundary conditions at the interfaces. The cutoff condition of the fundamental mode is examined, and a novel W-type fiber working in S-band is designed.     

Research on fault location technology based on BP neural network in DWDM optical network

BP neural network is introduced to the fault location field of DWDM optical network in this paper. The alarm characteristics of the optical network equipments are discussed, and alarm vector and fault vector diagrams are generated by analyzing some typical instances. A 17 × 14 × 18 BP neural network structure is constructed and trained by using MATLAB. By comparing the training performances, the best training algorithm of fault location among the three training algorithms is chosen. Numerical simulation results indicate that the sum squared error （SSE） of fault location is less than 0.01, and the processing time is less than 100 ms. This method not only well deals with the missing alarms or false alarms, but also improves the fault location accuracy and real-time ability.     

Investigation of luminescence from SiC nano-granule films on porous glass substrate

SiC granule films were fabricated onto porous glass substrate by RF-magnetron sputtering. Photoluminescence （PL） measurements show that there are light emissions at three different wavelengths. Ultraviolet emission peaked at 360 nm originated from the band-band transmission of SiC nanoparticles with relatively small size. The 370 nm light emission was due to the luminescence of the nano-skeletons of porous glass that was formed during the etching of the glass substrate. The blue emission at about 460 nm was associated with the recombination of the excited electron and O-deficient defects appeared at the interface between SiC nanoparticles and the porous glass. Furthermore, the optimal PL performance was obtained when SiC deposited time was I h and the glass substrate was etched for 20 min in the annealing sample （450 ℃）.     

Study of a displacement sensor based on transmission varied-line-space phase grating

A displacement sensor based on transmission varied-line-space （VLS） phase gratings is proposed. The relationship be-tween the properties of the sensor and the parameters of VLS is discussed. Compared with the displacement sensor manu- factured by the reflective VLS grating, this type of sensor contains a grating with simpler structure and high diffraction efficiency. It also has good stability with the change of temperature.     

A morphology screen coding anti-counterfeiting method based on visual characteristics

A paper information anti-fake and tamper-proofing method based on human visual characteristics and morphology screen coding technology is proposed. Through controlling the distribution of mathematical morphology of screen dot-matrix, warning mark and information are hidden in the background texture. Because of the differences between human vision and the duplicate characteristics of copy machine, warning mark which can not be discriminated by human eyes will emerge after copy. Tampered or fake certificates can be verified by comparing embedded information which is extracted from scanned image of certificate with plain text printed on the certificate： This method is applied in many bills and certificates. Experimental results show that the identifica- tion accuracy is above 98%.     

Influence of stress birefringence on the performance of a FBG pressure sensor

No matter designing and manufacturing a FBG pres-sure sensor ,or monitoringthe strain on material surfaceby using FBGas a pressure sensor ,the difficult technicalproblems to be solved are as follows :first ,howto effec-tively couple and propagatethe external stresstothe ax-ial direction of FBGthrough the underlay material ;sec-ond,howto make the FBGpressure sensor achieving aneffect of enhancing sensitivity;third,how to ensure alinear relationship between FBG′s reflection wavelengthand t…     

Low voltage n-type OFET based on double insulators

A top contact n-type organic field-effect transistor with low operating voltage was fabricated by employing Ta2O5/PMMA as the double insulators and PTCDI-Cl2 as the semiconductor active layer. The Ta2O5 layer was prepared by using simple economical anodization technique and the PMMA layer was prepared by using the spin-coating method. Compared with the OFET with single Ta2O5 insulator, the device with double insulators shows obviously better electrical performance. It has a field effect electron mobility of 0.063 cm^2/Vs, an on/off ratio of 1.7 × 10^4 and a threshold voltage of 2.3 V.     

Quality improvement of the dual-wavelength signals in DLOB via power equalization

The data packet buffeting can be implemented in dual loop optical buffer （DLOB） through cross-phase modulation （XPM） between the control signal and the data packets. However, the output equality of dual wavelength signals will degrade due to the unbalanced gain and phase shift. This problem can be resolved by power oqualizafion using the saturation characteristics of SOA. The data packets with 2.5 Gb/s can be buffered in DLOB for 16 cycles corresponding to 16.5 μs.The extinction ratio of the output packet is 8 dB while the S/N is 8.1 dB.     

The optimal time-frequency atom search based on a modified ant colony algorithm

this paper, a new optimal time-frequency atom search method based on a modified ant colony algorithm is proposed to improve the precision of the traditional methods. First, the discretization formula of finite length time-frequency atom is inferred at length. Second; a modified ant colony algorithm in continuous space is proposed. Finally, the optimal time- frequency atom search algorithm based on the modified ant colony algorithm is described in detail and the simulation experiment is carried on. The result indicates that the developed algorithm is valid and stable, and the precision of the method is higher than that of the traditional method.     

Analysis on characteristics of 1-D apodized and chirped photonic crystals containing negative refractive materials

Using transfer matrix method, the optical transmission properties of 1-D photonic crystals composed partially of negative refraction media are analyzed. The transmission spectra of periodic photonic crystal, chirped photonic crystal and apodized photonic crystal are numerically simulated respectively. By contrast with optical transmission properties of ordinary photo- nic crystals made of positive refraction media, the transmission spectra of apodized photonic crystal become unregular, the Bragg flat-headed area recurs but the peak of transmission does not change significantly. Futhermore, the band gap range of chirped photonic crystal diminishes gradually.     

Teleportation of an arbitrary unknown N -qubit entangled state under the controlling of M controllers

A new quantum protocol to teleport an arbitrary unknown N-qubit entangled state from a sender to a fixed receiver under M controllers（M 〈 N） is proposed. The quantum resources required are M non-maximally entangled Greenberger-Home- Zeilinger （GHZ） state and N-M non-maximally entangled Einstein-Podolsky-Rosen （EPR） pairs. The sender performs N generalized Bell-state measurements on the 2N particles. Controllers take M single-particle measurement along x-axis, and the receiver needs to introduce one auxiliary two-level particle to extract quantum information probabilistically with the fidelity unit if controllers cooperate with it.