Abstract:A silicon-on-insulator 2×2 Mach-Zehnder thermo-optical switch is developed based on strongly guided paired multimode interference couplers. The multimode-interference couplers were etched deeply for improving coupler characteristics such as self-imaging quality, uniformity and fabrication tolerance. The proposed switch achieves good performances, including a low insertion loss of -11 .OdB, a fiber-waveguide coupling loss of -4.3dB and a fast response speed measured to be 3.5 and 8.8 μs for raise and fall switching time, respectively.

Abstract:A dispersion-flattened photonic crystal fiber with normal dispersion is designed for generating flat wideband supercontinuum, and the supercontinuum generation in this fiber is numerically analyzed. The results show that by appropriately designing the photonic crystal fiber, it can achieve flattened dispersion in the normal dispersion region. It is found that a fiber characterized by a flattened dispersion with a small normal dispersion is suitable for a flat wideband supercontinuum generation. In the process of spectral broadening, self-phase modulation effect plays a dominant role. By filtering the supercontinuum, pulses with different central wavelength over a wide spectral range can be obtained. The pulse width is determined by the bandwidth of the filter.

Abstract:We have designed a new structure blue emission device with doped Alq3 of 3% in hole transmission layers of NPB. The CIE coordination of the devices is (0.17,0.19). The maximum electroluminescence efficiency is 4.1 cd/A at 11V, the brightness is 118.8 cd/m2 at 7 V, and the maximum brightness is 10770 cd/m2 at 13V.

Abstract:We present the spectral line narrowing effect in a Λ three-level atomic system where one transition is coupled by a coupling laser and the narrow feature is observed by probing the other transition with a weak laser. As coupling laser detuning increases the electromagnetically induced transparency resonance is observed to evolve into electromagnetically induced absorption resonance with sub-natural linewidth. The linewidth of the narrow spectral feature is studied as a function of coupling laser detuning and the atomic system parameters. The result is explained using density matrix density equation in the dressed-atom picture.

Abstract:We present the properties and potentialities of light emitting devices based on amorphous Si nanoclusters. Amorphous nanostructures may constitute an interesting alternative to Si nanocrystals for the monolithic integration of optical and electrical functions in Si technology. In fact, they exhibit an intense room temperature electroluminescence (EL). The EL properties of these devices have been studied as a function of current and of temperature. Moreover, to improve the extraction efficiency of the light, we have integrated the emitting system with a 2D photonic crystal structure opportunely fabricated by using conventional optical lithography to reduce the total internal reflection of the emitted light. The extraction efficiency in such devices increases by a factor of 4 at a resonance wavelength.

Abstract:Optimiz ed 2×2 switches based on silicon-on-insulator (SOI) were demonstrated. In the design, single mode rib waveguides and multimode interferences (MMIs) are connected by tapered waveguides to reduce the mode coupling loss between the two types of waveguides. The average insertion loss of the switches is about -16.9 dB and the excess loss of one is measured of -1.3 dB. The worst crosstalk is larger than 25 dB. Experimental results indicate that some of the main characteristics of optical switches are improved in the modified design, which is according with theoretic analysis. The novel design can be used to improve the characteristics of optical switch matrixes based on 2×2 switch units.

Abstract:A wavelength division multiplexer based on curved polymer planar waveguide is proposed. According to the coupled mode theory and the waveguide structure, the performance of the curved waveguide coupler (CWC) is analyzed. The results show that CWC can accommodate wider multiplexing bandwidth than parallel straight waveguide coupler (SWC) due to the compensation effect of the effective coupling length. The two variables, curvature radius and minimum spacing, increase the design flexibility of the waveguide device. A 4-channel wavelength division multiplexing (WDM) system based on CWC is designed. The deviation of the center wavelength, due to the errors of curvature radius and minimum spacing during fabrication process, is investigated. The smaller the curvature radius and the minimum spacing are, the larger the central wavelength deviation caused by the error of the curvature radius and the minimum spacing is, which provides some useful theoretical basis for the design and the fabrication of polymer waveguide devices.

Abstract:A silicon-on-insulator 2 × 2 Mach-Zehnder thermo-optical switch is developed based on strongly guided paired multimode interference couplers. The multimode-interference couplers were etched deeply for improving coupler characteristics such as self-imaging quality, uniformity and fabrication tolerance. The proposed switch achieves good performances, including a low insertion loss of −11.0dB, a fiber-waveguide coupling loss of −4.3dB and a fast response speed measured to be 3.5 and 8.8 μs for raise and fall switching time, respectively. Supported in part by the National “973” Plan (No. G2000-03-66 and No.2006CB921702), National Natural Science Foundation of China(NO. 10674185).and the Science Foundation of the Central University for Nationalities (No. CUN07A)

Abstract:PbS quantum dots were prepared in the aqueous medium from readily available precursors. The shape of the particles is approximately spherical, and the average particle size observed from HRTEM image was 7-8 nm. We applied PbS quantum dots and PMMA polymer to fabricate PbS quantum dots-PMMA composites, and investigate the photoluminescence PbS quantum dots in PMMA matrix with different mass ratio. PbS quantum dots in PMMA matrix have broad emission between 900 nm and 1 500 nm and photoluminescence peak at 1 179 nm. Additionally, the photoluminescence intensity increases with increasing the dopant concentration. PbS quantum dots-PMMA polymer composites can be potentially used for polymer optical fiber and electroluminescence (EL) in optical communication.

Abstract:An S band and a C band distributed fiber Raman amplifiers (DFRAs) with flattened gain and compensated dispersion have been studied and implemented with 1 427 nm and 1 455 nm mono-wavelength fiber Raman lasers as the pumped sources respectively. The gain of single-wave pumped S band and C band can reach 10 dB and 15 dB respectively. And a 50 nm gain flattened width was successfully obtained by using a chirp fiber Bragg grating (CFBG) gain flattened filter with gain ripple of 0.6 dB. The C band DFRA has been applied to CDMA wireless communication system successfully.

Abstract:A novel temperature-insensitive strain sensor based on bandwidth demodulation of the reflected light from the tapered fiber grating is presented, which is simple and low-cost and has considerable potential particularly application for strain sensing,and with the development of the interrogation system, it can demodulate both the bandwidth and the center wavelength of the reflected light from TFG to measure strain and temperature simultaneously.

Abstract:A dispersion-flattened photonic crystal fiber with normal dispersion is designed for generating flat wideband supercontanuum, and the supercontinuum generation in this fiber is numerically analyzed. The results show that by appropriately designing the photonic crystal fiber, it can achieve flattened dispersion in the normal dispersion region. It is found that a fiber characterized by a flattened dispersion with a small normal dispersion is suitable for a flat wideband supercontinuum generation. In the process of spectral broadening, self-phase modulation effect plays a dominant role. By filtering the supercontinuum, pulses with different central wavelength over a wide spectral range can be obtained. The pulse width is determined by the bandwidth of the filter.

Abstract:A novel structure for efficient side-coupling of high power double-cladding fiber lasers is presented. The maximum coupling efficiency of this structure is more than 90% for TM-polarization in the 1 and -1 order but is only 40% for TE-polarization. Thus, a multi-layer stair-structure is introduced and optimized by combining transmission algorithm and genetic algorithm to obtain higher coupling efficiency η for TE-polarization and the maximum coupling efficiency almost reaches to 70%.

Abstract:We have designed a new structure blue emission device with doped Alq₃ of 3% in hole transmission layers of NPB. The CIE coordination of the devices is (0.17,0.19). The maximum electroluminescence efficiency is 4.1 cd/A at 11V, the brightness is 118.8 cd/m² at 7 V, and the maximum brightness is 10770 cd/m² at 13 V. Supported by the National Natural Science Foundation of China (Grant No 60207003 and No.60376028), the Special Funds for Major State Basic Research Project of China under Grant No 2003BC314703.

Abstract:We report the design of benzocyclobutene microring resonator of symmetric coupling made of a readily available polymer with a higher isolation of 43.8 dB, a finesse of 34, and a Q value of 1.5 × 10s. The FDTD method predicts a drop efficiencyof almost 80% for a gap of 0.55μm.

Abstract:A remnant dispersion monitoring method based on spectral-shift of SOA in high speed optical communication system with CSRZ format and single channel speed of 40 Gbit/s is proposed. The system performance can be optimized by careful choosing bandwidth and center wavelength of the optical fiber grating filter. The dynamical monitoring range is ±60 ps/nm and the monitoring precision is about 5 ps/nm. This method can be suitable for the application in dynamical dispersion compensation of high speed optical communication systems.

Abstract:Chaotic synchronization of injected multiple-quantum-well lasers of optical fiber system and a theoretical model of optical fiber chaotic secure communication system are presented by coupling a chaotic multiple-quantum-well laser synchronization system and a fiber channel. A new chaotic encoding method of chaos phase shift keying On/Off is proposed for optical fiber secure communications. Chaotic synchronization is achieved numerically in long-haul fiber system at wavelength 1.55μm. The effect of the nonlinear-phase of fiber is analyzed on chaotic signal and synchronization. A sinusoidal signal of 0.2 GHz frequency is simulated numerically with chaos masking in long-haul fiber analog communication at wavelength 1.55μm while a digital signal of 0.5 Gbit/s bit rate is simulated numerically with c1 haos masking and a rate of 0.05 Gbit/s are also simulated numerically with chaos shift keying and chaos phase shift keying On/Off in long-haul fiber digital communications at wavelength 1.55μm

Abstract:We proposed a scheme of fiber Bragg grating (FBG) sensor interrogation system based on all fiber Mach-Zehnder Interferometer (MZI) edge filter and tunable-FBG. The equal power signals from FBG sensor and tunable FBG are coupled into port 1 and port 2 of MZI respectively. The experimental results show that the interrogation precision of the proposed system is 0.02 nm in a range of Inm. Furthermore, the precision can be improved by adjusting the two interference arms of the filter.

Abstract:According to the common Glan-Taylor prism's design feature, Fresnel formulae and Brewster's law, a novel Glan -Taylor prism was designed and fabricated. In the new prism, the structure angles of second half were modified to proper values so that extraordinary ray is incident on with Brewster angle. In order to minimize the deviation angle of the new prism, an additional angle was designed. Theory and experiments have confirmed that the transmittance of the new prism is higher than that of a common one in a wide wavelength range and the interference effect will not occur in the new prism. Experimentally, its deviation angle is smaller than 3' in the wavelength range of 540-670 nm.

Abstract:In original Zernike moments subpixel edge operator, ideal step edge model is chosen for calculating four parameters of a pixel point, and therefore principle deviation is caused by edge model. In order to discuss the effect of principle deviation on edge location, sampled edge model is chosen for calculating edge parameters, principle deviation of edge translation l is derived based on Zernike moments edge detection theory, and modified formula of l is given for Zernike moments operator with masks of 5×5 size. Both theory analysis and testing result demonstrate that principle deviation is zero when edge translation l is limited in central pixel of a sampled window. In another case, the modification of l should be considered, which results in edge location accuracy of non-subpixel level for this subpixel edge operator.

Abstract:The autofocusing technique based on contourlet transform is discussed in this paper and an autofocusing method is proposed for images with much information in certain directions. The experimental results show that theproposed method can focus accurately and the sensitivity ratio is higher than that of the other autofocusing methods based on conventional image processing

Abstract:According to the design method of laser resonator cavity, we optimized the primary parameters of resonator and utilized LD arrays symmetrically pumping manner to implementing output of the high-brightness laser in our laser cutter, then which was applied to precisely cutting the conductive film of CuInSe2 solar cells, the buried contact silicon solar cells' electrode groove, and perforating in wafer which is used to the emitter wrap through silicon solar cells. Laser processing precision was less than 40μm, the results have met solar cell's fabrication technology, and made finally the buried cells' conversion efficiency be improved from 18% to 21% .

Abstract:We present the spectral line narrowing effect in a A threeAevel atomic system where one transition is coupled by a coupling laser and the narrow feature is observed by probing the other transition with a weak laser. As coupling laser detuning increases the electromagnetically induced transparency resonance is observed to evolve into electromagnetically induced absorption resonance with sub-natural linewidth. The linewidth of the narrow spectral feature is studied as a function of coupling laser detuning and the atomic system parameters. The result is explained using density matrix density equation in the dressed-atom picture.

Abstract:It is shown that in an open Λ-type system with spontaneously generated coherence, the transient evolution rule of the gain of lasing without inversion (LWI) is very sensitive to variation of the relative phase ϕ between the probe and driving fields; the variety of the atomic exit rate γ₀ and the ratio C of the atomic injection rates also have a considerable effect on the phase-dependent transient evolution rule of LWI gain. We find that when ϕ =0, the transient and stationary LWI gain increases with C increasing but decreases with γ₀ increasing; when ϕ ≠ 0, the effect of C and γ₀ on LWI gain is just opposite to that when ϕ=0; in order to get the largest transient and stationary LWI gain, we need selecting suitable values of ϕ, γ₀ and C. Supported by the National Natural Science Foundation of China (Grant No. 10675076)and the Natural Science Foundation of Shandong Province (Grant No. Y2006A21).

Abstract:The time evolution process of the plasma generated by laser pulse interaction with solid target in air is observed by optical shadowgraph imaging technique. The ablation pressure of the shock wave generated with the plasma is calculated analytically.It is found that plasma expansion in perpendicular and lateral directions are both proportional to t2/5 with t as delay time, and the ablation pressure reaches 108 Pa.

Abstract:To perceive the epithelial dysplasia from the light scattering spectroscopy (LSS) is an inverse problem, which can be transformed into the inversion of the size distribution of epithelial-cell nuclei. Based on the simulation of single polarized LSS for epithelial-cell nuclei, Chahine algorithm is adopted to retrieve the size distribution. Numerical results show that Chahine algorithm has high inversion precision for both single-peaked and bimodal models, which implies the potential to increase diagnostic resolution of LSS.

Abstract: