Abstract:ZnO quantum dots (QDs)with the sizes of 3.0–5.6 nm are synthesized by solution-phase method at different temperatures. We find that temperature has great influence on the size of ZnO QDs. The growth process is the most sensitive to temperature, and the process is well explained by Lifshitz-Slyozov-Wagner (LSW) model. By photoluminescence (PL) spectra of the quantum dots at different temperatures and reactive time, we come to a conclusion that ultraviolet emission is mainly due to surface defects, and the origination of green visible emission comes from the transition between the bottom of the conduction band and the level of O _i. The work has been supported in part by National Natural Science Foundation of China(Grant No. 60877029), in part by the Tianjin Natural Science Foundation (Grant No. 07JCYBJC06400 06TXTJJC14600), and in part by the Subject of Science and Technology Development Fund at University of Tianjin (Grant No. 20071207)

Abstract:The quantum efficiency and the transient response of the InP semiconductor micro-ring resonant detector are analyzed to get the optimum design parameters. Then the side coupling micro-ring resonant is fabricated using the InP semiconductor material based on the parameters. The micro-ring resonant cavity has the raius of 80 μm, waveguide width of 3 μm and the coupler gap of 1 μm. The test results show that the FSR is 0.75 nm, and the FWHM is 0.5 nm, which are consistent with the theoretical calculation results. The work has been supported by National “973 Program” of China (2003CB314901), the Program for New Century Excellent Talents in University of China (NCET-05-0111), the National “111 Project” (B07005), and the National Program for Changjiang Scholars and Innovative Research Team in University of China (No.IRT0609)

Abstract:Sub-wavelength structures (SWS) were prepared on Ge substrates through photolithography and reactive ion etching (RIE) technology for broadband antireflective purposes in the long wave infrared (LWIR) waveband of 8–12 μm. Topography of the etched patterns was observed using high resolution optical microscope and atomic force microscope (AFM). Infrared transmission performance of the SWS was investigated by Fourier transform infrared (FTIR) spectrometer. Results show that the etched patterns were of high uniformity and fidelity, the SWS exhibited a good broadband antireflective performance with the increment of the average transmittance which is over 8–12 μm up to 8%. This work has been supported by the basic research foundation of Northwestern polytechnical University

Abstract:A novel Cu(I) complex with the formula of [Cu(DPEphos)(Dicnq)]BF₄ (CuDD) was synthesized and characterized by Xray single crystal diffraction method, in which DPEphos and Dicnq denote bis[2-(diphenylphosphino)phenyl]ether and 6, 7-Dicyanodipyrido[2,2-d:2′,3′-f] quinoxaline, respectively. Organic ultraviolet optical sensor based on photovoltaic diode is fabricated by using CuDD as an electron acceptor and 4,4′,4″-tris-(2-methylphenyl phenylamino) triphenylamine (m-MTDATA) as an electron donor. The sensor is sensitive to UV light band from 300 to 400 nm while it has almost no response to the visible light, and under illumination of 365 nm light with power of 1.7 mW/cm², an open circuit voltage of 1.47 V, a short circuit current of 38.9 μA/cm², a fill factor of 0.24, and a power conversion efficiency of 0.8 % are achieved. In addition, the dependence of ultraviolet responsive sensitivity of the sensor on working temperature is also discussed. This work has been supported by the Natural Science Foundation of Jilin Province (No. 20060516), the Doctoral Foundation of Jilin Normal University (No. 2006006 and No. 2007009), and the Subject and Base Construction Foundation of Jilin Normal University (No. 2006041).

Abstract:Coherent beam combination of two W-level fiber amplifiers with multi-dithering technique is demonstrated. In the experiment, the master laser is split into two channels. Multi-dithering technique is used for phase control. One channel is modulated with a 100 kHz sine wave produced by signal generator, and DSP lock-in amplifier is used for electric signal processing in the feedback loop. When the phase control loop is off, the far field interference pattern is blurred and dynamic with 20% fringe contrast. When the feedback loop is closed, the far field interference pattern is clear and stable with 72% fringe contrast, and 75% coherent combination efficiency is achieved.

Abstract:We examine theoretically the performance of an Hg_0.77Cd_0.23Te based p-n photodetector/HFET optical receiver due to its possible application at 10.6 μm free space optical communication system at high bit rate. A rigorous noise model of the receiver has been developed for this purpose. We calculate the total noise and sensitivity of the receiver. The front-end of the receiver exhibits a sensitivity of −45 dBm at a bit rate of 1 Gb/s and −30 dBm at a bit rate of 10 Gb/s, and the total mean-square noise current 〈i _n ²〉 = 5 × 10⁻¹⁵ A² at a bit rate of 1 Gb/s and 〈i _n ²〉 = 10⁻¹² A² at a bit rate of 10 Gb/s, and a 3-dB bandwidth of 10 GHz.

Abstract:Fluorescence enhancement of red and blue concurrently emitting Ba₃MgSi₂O₈:Eu²⁺,Mn²⁺ phosphors for plant cultivation has been investigated by Dy³⁺ addition. The Ba₃MgSi₂O₈:Eu²⁺,Mn²⁺,Dy³⁺(BMS-EMD) phosphors have two-color emissions at the wavelength peak values of 437 nm and 620 nm at the excitation of 350 nm. The two emission bands are coincident with the absorption spectrum for photosynthesis of plants. An obvious enhancement effect has been observed upon addition of Dy³⁺ with amount of 0.03 mol%, in which the intensities of both blue and red bands reach a maximum. The origin of red and blue emission bands is analysed. The photochromic parameters of the samples at the nearly UV excitation are tested. This fluoresence enhancement is of great significance for special solid state lighting equipment used in plant cultivation. This work has been supported by National Natural Science Foundation of China (Grant No 50872091) and the Natural Science Foundation of Tianjin, China (06YFJMJC02300, 06TXTJJC14602).

Abstract:Multiple-access interference(MAI) and beat noise(BN) in chip-asynchronous coherent time-spreading OCDMA system are evaluated by the aperiodic cross-correlation function of up-sampled sequence. Relationship between the mean intensity of aperiodic cross-correlation and MAI and BN is deduced, and then the relationship between BER and mean intensity of aperiodic cross-correlation is discussed. For 127-long gold sequence, mean BER performance of chip-asynchronous coherent time-spreading OCDMA is derived and compared with that of the chip-synchronous system. It can be shown that the chip-synchronous assumption provides a performance upper limit. For realistic asynchronous coherent time-spreading OCDMA system, BER will reduce by about one order of magnitude. This work has been supported by the National Natural Science Foundation of China (No. 60772027)

Abstract:Based on the full-vector finite element method, a novel structure of highly negative dispersion photonic crystal fiber with the central index dip in the low germanium doped core is proposed. The highly negative dispersion can be obtained at the wavelength of 1.55 m by adjusting the pitch, the air-hole diameter in the third ring, the germanium doped concentration and the influence of central index dip. This work has been supported by the National Natural Science Foundation of China (Grant No.60877033) and Key Program of Education Ministry of China (Grant No.308002)

Abstract:We propose that nanomaterials are used for fibers. A novel nano-InP doped fiber has been fabricated by the method of modified chemical vapor deposition (MCVD).It has been measured that the doping concentration of phosphorus element is 0.1%. The relationship between refractive index and the wavelength is obtained by fitting experimental data to Sellmeier equation. Dispersion of the fiber has been calculated in the wavelength range of 1.2–1.6 μm. As the wavelength varies from 1.20 μm to 1.60 μm, dispersion parameter D increases but is always negative. It has been found that the dispersion of nano-InP doped fibers is strongly changed compared with standard single-mode fibers, due to the nano-InP dopant which leads to a higher refractive index difference. This work has been supported by the National Natural Science Foundation of China (No. 60871082, 60544002)

Abstract:SNR estimation of communication signals is important to improve demodulation performance and channel quality of communication system, thus it is an important research issue of communication field. According to the core problem of autocorrelation matrix singular value in SNR estimation process, through making use of householder transforming autocorrelation matrix into tridiagonal matrix, and by using the relation of corresponding characteristic equation coefficients and singular value, a numerical algorithm is given to obtain autocorrelation matrix singular value, and the algorithm is used for SNR solving process. Theoretical analysis shows that the algorithm can satisfy the requirements in the aspect of constringency speed and stability. This work has been supported by the National Natural Science Foundation of China (Grant No. 90604031)

Abstract:The analytical expression of bit error probability in a balanced differential phase-shift keying (DPSK) optical receiver considering nonlinear phase noise and EDFA ASE noise is given, which is very useful to estimate the performance of DPSK balanced and unbalanced receiver in optical communication system. Through analysis, if only nonlinear phase noise is considered, both the balance and unbalanced receivers have the same performances. But if adding the ASE noise of EDFA, the balanced receiver is better. This work has been supported by the National Natural Science Foundation of China (No.60772013) and the Fund of Huazhong Uiversity of Science and Technology (2006M041)

Abstract:In order to decrease dispersion penalty and increase the optical bandwidth efficiency, an optical single-side-band modulation (SSBM) scheme in sub-carrier multiplexing (SCM) is proposed. The principle of the SSBM is analytically presented, and a configuration for generating optical SSB signal is proposed using a balanced Mach-Zehnder electro-optic modulator. This work has been supported by Science Foundation for Youthful Teachers of Anhui University (Grant No.2007jql104)

Abstract:A flat-top interleaver, in which a mirror on one arm of the Michelson interferomefer is replaced by a G-T resonator, is proposed. In the interleaver, the parameters including the channel spacing of 50 GHz, ripple less than 0.05 dB, −0.5 dB passband of 43 GHz (86% of the spacing), −30 dB stopband of 42 GHz (84% of the spacing), and a channel isolation higher than 40 dB, are achieved. This work has been supported by the Program for New Century Excellent Talents in Fujian Province of China, (Grant No.X07204), the Key Scientific and Technical Innovation Project of Xiamen University (Grant No.K70007), and the Science and Technology Project of Education Department of Fujian Province of China (Grant No. JA08138).

Abstract:Wavelength modulation technique (WMT) and active intra-cavity technique (ACIT) are first introduced in this paper, which are used to realize the concentration detection of methane and acetylene respectively. When ACIT is combined with wavelength sweep technique (WST), the detection sensitivity of acetylene can be enhanced sharply. When ACIT is combined with WST and WMT, the detection sensitivity of acetylene can be enhanced further. This work has been supported by the National Natural Science foundation of China (contact No. 60577013), and the New Century Support Program for Talented Young Teachers in Universities, Ministry of Education of China.

Abstract:A new method is proposed to implement an optical S-R flip-flop by polarization encoded light signal, necessary optical nonlinear material and half-wave plate. In this system the real time speed of operation can be achieved, and at the time of transmission the average power of a byte remains constant. This polarization encoded flip-flop can act as a memory cell.

Abstract:A novel image stabilization system is presented, which consists of a global feature point tracking based motion estimation, a Kalman filtering based motion smoothing and an image mosaic based panoramic compensation. The global motion is estimated using feature point matching and iteration with the least-square method. Then, the Kalman filter is applied to smooth the original motion vectors to effectively alleviate unwanted camera vibrations and follow the intentional camera scan. Lastly, the loss information of image boundary due to the motion compensation is reconstructed with image mosaic to improve the visual quality. The experimental results show that this system can smooth unwanted translation or rotation of the video sequences and realize a panoramic stabilization at real-time speed. This work has been supported by the National “863 Program” on High Technology Research and Development of China (Grant No. 2006AA01Z127)

Abstract:Grey self-organizing map (GSOM) model is proposed and applied in the detection of intrusion. Through the improvement of the weight adjustment using the GRC (grey relational coefficient), the training results of SOM get better. In the detection of deny of service (DOS) attacks, this model can consider the relativity of the data set of DOS attacks. Finally, the experiments on the DOS data set confirm their validities and feasibilities over this GSOM model. This work has been supported by the Tianjin Key Subject Fund, and the Higher Education Science and Technology Development Fund of Tianjin Municipal Education Commission (No. 2006BA19).

Abstract:This paper proposed a fuzzify functor as an extension of the concept of fuzzy sets. The fuzzify functor and the first-order operated fuzzy set are defined. From the theory analysis, it can be observed that when the fuzzify functor acts on a simple crisp set, we get the first order fuzzy set or type-1 fuzzy set. By operating the fuzzify functor on fuzzy sets, we get the higher order fuzzy sets or higher type fuzzy sets and their membership functions. Using the fuzzify functor we can exactly describe the type-1 fuzzy sets, type-2 fuzzy sets and higher type or higher order fuzzy sets. The fuzzify functor makes type-1, type-2 and any fuzzy sets much more accessible to all readers. This work has been supported in part by the Project of Tianjin Key Laboratory of Control Theory & Applications in Complicated Systems and the Key Project of Tianjin Natural Science Foundation (Grant No. 06YFJMJC01)

Abstract:We present a study of electromagnetically induced transparency (EIT) under the excitation of a 100% amplitude-modulated (AM) coupling field. The EIT feature is associated with a Λ type three-level configuration where a coupling and probe field couples two separate optical transitions and it is well-known that the spectrum of the swept probe field gives a simple single transparency feature induced by the single mode coupling field. It is shown that when a 100% AM coupling field is applied, there is an EIT doublet and the separation of the EIT doublet can be controlled by the modulation frequency of the coupling field. Our result implies a new way of manipulating EIT resonance and opening more than one EIT windows. This project has been supported by the Natural Science Foundation of Hebei Province (Grant No.A2005000091) and the Natural Science Foundation of Education Office of Hebei Province (Grant No.2004103).

Abstract:The generation and propagation of partially coherent vortex beams have been investigated experimentally. It is found that a vortex beam with more uniform intensity distribution can be obtained by decreasing the coherence of the beam. We find that the beam shape of a completely coherent beam will keep hollow profile invariant during its propagation in free space. However, the center of the beam turns to be blurred for a partially coherent vortex beam on propagation. It is also found that the beam spreads more rapidly for the vortex beam with lower coherence, and this influence can be decreased by increasing the topological charge of the vortex beam. This work has been supported by the Key Project of Science and Technology (2007H0027) of Fujin Province and the Natural Science Founation of Fujin Province (A0810012)