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Abstract:A 33×33 thermo-optically tunable arrayed-waveguide-grating (AWG) has been fabricated by using the poly (2, 3, 4, 5, 6-pentafluorostyrene-co-glycidylmethacrylate) (PFS-co-GMA). The technological process of the fabrication of the device is described, and the measured results are presented. The measured spacing of the wavelength channel is about 0.81 nm, the 3-dB bandwidth is about 0.35 nm, the crosstalk is about −20 dB, and the insertion loss is between 10.4 dB for the centre port and 11.9 dB for the edge port. The measured thermo — optical tunable shift is about −0.12 nm/K. The measured center wavelength is 1545.21–1551.81 nm in the temperature range from 10°C to 65°C, and the tuning range is 6.6 nm. Supported by National Science Foundation of China (60576045, 60507004)

Abstract:A novel and simple method to generate low timing jitter and discrete tunable dual-wavelength optical pulses at arbitrary repetition rates is demonstrated in this paper. Two multiple quantum wells distributed feedback laser diodes,were used as the external seeding sources to inject the external photons into a gainswitched Fabry-Perot laser diode. The output wavelengths can be tuned discretely to coincide with any two lasing modes in the gain spectra range of the Fabry-Perot Laser diode,and the output side mode suppression ratio was better than 25 dB. Moreover,the timing jitter of optical pulses was reduced from 1.89 ps to 0.83 ps. It was empirically found that the lowest timing jitter operation occurred when the injected light wavelength is 0.2-0.3 nm shorter than the locked mode of the Fabry-Perot laser diode. To our knowledge,this is the first report of using two DFB laser diodes as a seeding source to reduce pulses jitter and select lasing dual-wavelength simultaneously.

Abstract:The rate equations with multipoint boundary conditions are solved by numerical method accurately. A novel method based on genetic algorithm is proposed to optimize distributed pump powers in kilowatt YDDC fiber laser in this paper. The calculated results show that lower operation temperature and better uniformity can be achieved through an optimized pump arrangement.

Abstract:A novel post-treatment method is reported for improving the field emission characteristics of screen-printed carbon nanotubes/nanofibers (CNTs/CNFs) cathodes. After the treatment at the temperature of 500°C in H₂ and C₂H₂ gas for 20 minutes, the CNTs/CNFs cathodes exhibit much better field emission properties than those untreated. The emission current increases from 0.02 mA/cm² to 0.5 mA/cm² at 3.9 V/μm with a decrease in the turn-on field from 2.4 V to 1.8 V, and the emission site density is increased by almost four orders in magnitude. The enhanced field emission of treated CNTs/CNFs cathodes is attributed to the appearance of a large number of exposed CNTs/CNFs caused by heat treatment. This surface morphology is very favorable for the electron field emission. Supported by Funds of Trans-Century Talents Project of State Education Ministry and Shanghai Nanotechnology Promotion Center (0452nm048)

Abstract:Silica-based 71-channle AWGs with 0.4 nm (50 GHz) channel spacing at 1. 5445 μ have been designed and fabricated by using silica-based waveguide. Theoretical simulation and experimental results are given and compared. The test results show that the fiber-to-fiber insertion loss ranges from 3. 5 dB to 7.1 dB for central and peripheral output ports, respectively, the total crosstalk level is better than — 32 dB, 3 dB bandwidth is 25 GHz and polarization dependence loss (PDL) within 3 dB bandwidth is less than 0.5 dB, which agrees well with the simulation results. Supported by National Science Foundation of China (No. 60477035) and National “973” Plan (No. G200003602).

Abstract:To improve the density of information storage,this paper introduces a kind of annular binary filters with super-resolution,Several of these filters have been designed based on the genetic algorithm,the simulations demonstrate that the transverse gain of the filters can reach the value of 1. 37. Thus they can remarkably decrease the recording spot size,which is helpful to improve the density of information storage and to make the depth of focus longer,and therefore they can avoid the mistake caused by the small undulation of the optical disk in the process of recording/reading the information.

Abstract:650 nm AIGalnP/GalnP laser diodes with compressively strained MQW active layer have been successfully fabricated by means of single epitaxy growth. The threshold current is 6.4 mA,at 40 mA CW operation, the fundamental transverse-mode still remains, and the output power and the slope efficiency can reach 34 mW and 1.1 mW/mA respectively. The dead output power in CW operation can reach 66 mW at a saturation current of 88 mA. During 200 h burn in test,the laser diodes show good stabilization with a degradation of less than 8 %.

Abstract:The retardation of wave plate has the sensitivity to the incident angle. We design a new kind of tunable Lyot filter based on the sensitivity. The method of tuning is rotating the wave plate by the axial direction parallel to the optical axis. It is proved that this kind of tunable Lyot filter has the properties of favorable tenability,wide tunable range.

Abstract:A widely tunable quasi-phase-matched optical parametric generator pumped by a 1064 nm acousto-opticallyQ-switched diode-end-pumped Nd: YAG laser based on a MgO-doped periodically poled LiNbO₃ crystal with a multigrating structure (29.2–30.4 μm) is reported. A broad continuous signal spectrum 1513–1731 nm is obtained by changing the crystal grating periods from 29.2 μ to 30.4 μ and by tuning simultaneously the crystal temperature from 60°C to 150°C. When the average pump power is 1.82 W with about 120 ns pulse duration operating at a repetition rate of 10 KHz, the maximum total output power of the PPMgLN OPG is about 323.58 mW consisting of 210 mW of 1.639 μm signal radiation and 113.58 mW of 3.02 μm idler radiation.

Abstract:An equivalent electrical network method is presented in this paper to analyze the cooling characteristics of a laser diode module (LDM). And a modified equivalent model of a thermoelectric cooler (TEC) with an adjunctive thermal resistance and a contact resistance is proposed. The performance of a commercial TEC has been simulated. The thermal analysis of a LDM incorporated with a TEC has been performed by using an equivalent circuit model of the LDM. In the analysis the change of LD current, TEC current, and the ambient temperature are all considered. It shows that the equivalent circuit approach is an offective tool for the qualitative analysis of TEC and LDM.

Abstract:A wavefront method of measuring the thermal lensing of solid-state lasers is proposed. This method is easy to implement and has a high spatial resolution for diagnosing thermal lensing. By this method,the thermal lensing of Nd,YAG laser is studied in detail. And this work provides a means for studying the thermal effects of laser medium and many instructional parameters for optimizing the design of the laser cavity.

Abstract:The GaN thin film is successfully grown on the sample of ZnO/Si by dual ion beams deposition (DIBD) system. The thin film GaN/ZnO/Si is characterized by the in-situ X-ray photoelectron spectroscopy (XPS). It is shown that after a thin GaN film grown on the Zn/Si, the peaks of the Zn and O are not observed. This indicates that the GaN film can be successfully grown on the ZnO/Si by the dual ion beam deposition (DIBD) system associated with the pulsed laser deposition (PLD) method. Supported by the National “863” Program (No. 863-715-001-0162) and by the Science and Technology Foundation of China University of Geosciences (Beijing) (No. 200524).

Abstract:Influence of molecular composition in hemicyanine Langmuir-Blodgett (LB) films, on the aggregation features was investigated by using steady state and time-resolved photoluminescence spectroscopy. It was found that a lower degree of H-aggregation (smaller aggregate size) could be realized in hemicyanine LB films with larger donor groups, leading to a smaller photoluminescence peak blue shift with respect to their solution spectra and longer aggregate lifetime.

Abstract:Preparation of Nd³⁺: Gd₃ Ga₅ O₁₂ polycrystalline material by sol-gel method was preparated in this paper. The structure and the pattern of the sample were analyzed by thermogravimetric analysis and differential thermal analysis (TG-DTA), Infrared spectrum, XRD, TEM and electron spectrum, which indicated that the powder with good characteristics of 70–100 nm can be obtained by sintering at 1 000°C. It was shown that the chemical composition of the sample was agreed with experimental requirements by electron spectrum analysis.

Abstract:In this letter, the effects of Bragg-mirror quasi-periodicity on the shifts and quality factor in defect modes of photonic crystals are studied by using the transfer matrix method. Furthermore the influence of the quasi-periodicity on electric field enhancement effect inside the defect layer is studied,which is similar to that on the quality factor.

Abstract:This paper devoted to report the design and the achievement of an optical communication subsystem with 12 parallel channels in one chip. The system is capable of transmitting 10 Gbps bidirectional date over hundreds of meters. It can provide error detection and correction by using 8B/10B encoding and Cyclical Redundancy Checking (CRC) encoding when only single-channel fails. The design scheme has already passed the simulation in FPGA. This technique is useful to enhance the capability and the reliability of the very short reach (VSR) transmission systems. This work is supported by the National Nature Science Foundation of China (No. 60502005) and the National “863” Project of China (No. 2005AA311030)

Abstract:An ion mobility spectrometer equipped with a laser ionization source is used for the sensitive detection of benzene. Mobility spectra of the benzene are presented. We also discussed the mobility spectra at various concentrations and drift voltages. Detection limits are determined to be in the upper ppbv range. In the end,the advantages and possibilities of this technique are briefly discussed.

Abstract:Log-polar mapping has been proposed as a very appropriate space-variant imaging model in active vision applications. There is no doubt about the importance of translation estimation in active visual tracking. In this paper an approach is presented,and its performances are evaluated. The approach uses a gradient descent for minimizing a dissimilarity measure. The experimental results reveal that this method is efficient for approaching active image translations.

Abstract:In digital holographic microscopy, when the object is placed near the COD, the Fresnel approximation is no longer valid and the convolution approach has to be applied. With this approach, the sampling spacing of the reconstructed image plane is equal to the pixel size of the CCD. If the lateral resolution of the reconstructed image is higher than that of the CCD, Nyquist sampling criterion is violated and aliasing errors will be introduced. In this Letter, a new method is proposed to solve this problem by investigating convolution reconstruction of holograms. By appending enough zeros to the angular spectrum between the two FFT's in convolution reconstruction of digital holograms, the displayed resolution of the reconstructed image can be improved. Experimental results show a good agreement with theoretical analysis. Supported by the Science Foundation of Aeronautics of China (No 02153075) and the Doctorate Foundation of Northwestern Polytechnical University (No CX200421)

Abstract:Phase unwrapping is so important in interierometry that it determines the veraclty of the absolute phase value. Goldsteins branch-cut algorithm performs path-independent algorithm that uses a nearest neighbor heuristic to link and balance the residues based on identifying the residues. A modified nearest neighbor algorithm is presented based on the principle, the mathematic formula of the Goldsteins algorithm and indepth analysis of the key problem of phase unwrapping. It not only holds the advantage of the Goldsteins algorithm but also solves the problem that the Goldsteins algorithm is incapable to be used at high residue densities. Therefore, it extends the application of the Goldsteins algorithm and enhances the precision of phase unwrapping. Supported by Spaceflight Support Technology Fund Project (04 1. 3 JW05)

Abstract:Based on the maximum fuzzy entropy principle,the edge image with low contrast is optimally classified into two classes adaptively,under the condition of probability partition and fuzzy partition. The optimal threshold is used as the classified threshold value, and a local parametric gray-level transformation is applied to the obtained classes. By means of two parameters representing,the homogeneity of the regions in edge image is improved. The excellent performance of the proposed technique is exercisable through simulation results on a set of test images. It is shown how the extracted and enhanced edges provide an efficient edge-representation of images. It is shown that the proposed technique possesses excellent performance in homogeneity through simulations on a set of test images,and the extracted and enhanced edges provide an efficient edge-representation of images.

Abstract:The luminescent properties of terbium complex (terbium citrate) by binding to silver nanopartilces in the solution have been reported in this paper. The enhanced luminescence of the complex containing silver nanoparticies was observed at a limited particle concentration region. The nanoparticle concentration dependence of the luminescent intensity was regarded as the result of a delicate balance between an enhancing and a quenching effect of the silver nanoparticles. Furthermore, silver nanoparticles also affected the asymmetric ratio (AS) value of terbium luminescence. We discuss the luminescent properties of the terbium complex in terms of the local electromagnectic field, refractive index, and the ligand field around terbium ion. Supported by National 973-project (2002CB61306) and National Natural Science Foundation of China (50425204 and 50572043).

Abstract:It is shown that in an open lambda type atomic system, the gain and dispersion of the probe field are quit sensitive to variation of spontaneously generally coherence (SGC). The value of the parameterp reflects whether SGC effect exists and the size of SGC effect. Under certain condition, whenp=0.002 electromagnetically induced transparency occurs; whenp≠0.002, lasing without inversion can be realized; whenp=0.95, high index of the refraction with zero absorption can be obtained. This work was supported by Natural Science Foundation of Shandong Province (No. Y2001A07)

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Abstract:Optoelectronics Letters is the companion journal to Journal of Optoelectronics Laser (the core journal in Chinese) . The purpose of Optoelectronics Letters is reporting the new important results in the fields of optoelectronics ,/photonics in English to …