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Electro-optic modulation has been first demonstrated using a poled electro-optic polymer films, placed in a Fabry-Perot cavity. In our configuration, incorporating an electro-optic material in the spacer layer of a Fabry-Perot device creates such a structure whose optical transmission characteristics depend on the applied voltage. And the longitudinal electro- optic modulation, in which the direction of the poling electric field, the applied electric field and the light traveling are parallel with one another and perpendicular to the surface of the polymer film, is applied. According to the electro-optic tensor of a poled polymer film, there is no birefringence effect and only phase modulation of the light is produced. Considering the interferometric nature of the Fabry- Perot cavity, the phase modulation can be converted to the amplitude modulation. The cavity used had a finesse of about 20. The thickness of film is about 1 micrometers . The modulation depth achieved was about 0.07% for a low ac field of 1V/micrometers . The results are promising for the study of array modulation and optical interconnection.
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We present a novel, non-destructive technique which the low- frequency terminal electrical noise (TEN) is used to study facet stability of semiconductor lasers. We do different treatments for the facet and measure the changes of TEN before and after treatments. The results indicate that TEN level at low injection shows facet stability and can be used to predict facet stability of the device.
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We use a new impedance graded line that is backland coplanar wave-guide to design transmission line. During the permission of measurement scope on project, we can perform arbitrarily matching for 5(Omega) approximately 75(Omega) , calculated in the method of quasi-static analysis, using the microwave matching network and high-frequency encapsulation, we can improve our work frequency and effective power effectively.
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A novel class of NLO polyimide was obtained by modified a backbone polyimide, consisting of promellitic dianhydride (PMDA) and succinamide, with a functional based on biphenyl. The resulting polymer shows exceptional thermal stability higher than the polyimide skeleton. Moreover, high electro- optical activity of the corona poled polymeric film is determined, and the phase separation which usually occur in the side-chain system is effectively minimized. Successful reactions were confirmed by 1H NMR and FT-IR spectra and the weight of the polymer was determined by gel permeation chromatography analysis. From DSC and TGA thermograms the glass transition temperatures up to 320 degree(s)C and initial decomposition temperature up to 480 degree(s)C. The polymer solution in DMF could be spin coated on the indium-tin-oxide (ITO) glass or other substrates to form optical quality thin films. In our experiments the in situ poling and temperature ramping technique was used to select the optimal temperature (Topt) in order to get the largest second-order NLO response. The electro-optic coefficient ((gamma) 33) at the wavelength of 830 nm for polymer thin film poled around Topt was up to 42 pm/V, and the value remained well at elevated temperatures for move than 120 hours in the air.
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Measurements of low-frequency electrical noise (LFN) in quantum-well (QW) semiconductor lasers have been conducted using index guided AlGaInP lasers. To investigate location and origin of the LFN in QW lasers, temperature dependence of the LFN is investigated over a wide range of injected current from 10-7 to 6 X 10-2 A, at temperatures between 0 degree(s)C and 65 degree(s)C. The effects of a short duration of burn-in process on the LFN have been investigated by measuring the LFN in the virginal device and the device after 20 hours stress (current I equals 45 mA, temperature T equals 40 degree(s)C). We find, (1) there are different noise mechanisms associated to the observed terminal current noise when laser diodes operate above and below threshold current; (2) it is much more clear to see the effects of the stress on the LFN versus injected current (SI - ID) than in current versus voltage (ID - V) and optical-power versus injected current (PO - ID); (3) over the wide range of injected current, we did not observe the temperature dependence of the 1/f, though different g-r components appear in the spectra of the LFN measured at different temperatures. We have qualitatively analyzed the noise mechanisms and their location. We will also demonstrate that the noise measurement can be used as a diagnostic tool for the reliability of QW laser diodes.
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Photoelectronic characteristics of the fabricated InxGa1-xAs/AlyGa1- yAs/AlzGa1-zAs asymmetric step quantum-well middle wavelength (3 to approximately 5 micrometers ) infrared detectors are studied. The components display photovoltaic-type photocurrent response as well as the bias- controlled modulation of the peak wavelength of the main response, which is ascribed to the Stark shifts of the intersubband transitions from the local ground states to the extended first excited states in the quantum wells, at the 3 to approximately 5.3 micrometers infrared atmospheric transmission window. The blackbody detectivity (Dbb*) of the detectors reaches to about 1.0 X 1010 cm(DOT)Hz1/2/W at 77 K under bias of +/- 7 V. By expanding the electron wave function in terms of normalized plane wave basis withn the framwork of the effective-mass envelope-function theory, the linear Stark effects of the intersubband tansitions between the ground and first excited states in the asymmetric step well are calculated. The obtained results agree well with the corresponding experimental measurements.
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This paper reports on the design, fabrication and performance of some novel MEMS (Micro-electro-mechanical system) optical switches. We have developed a new kind of MEMS electromagnetic micro actuator, which can drive mirrors enter or leave the optical path of switch. The 1 X 2, 2 X 2, 1 X 4 and 1 X 8 single mode optic-fiber switches have been fabricated. The switching voltage is less than 8 V and the switching time is no more than 5 ms. Using optic-fiber collimator for light coupling, we obtain small insertion loss (> -0.8 dB), considering the length of the light path is 40 mm. The cross-talk is less than -60 dB, extinction ratio is -60 dB.
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This research has focused on modeling of optically triggered, high gain nonlinear GaAs switches. A complete model with dynamics of deep level trap, carries, direct band-gap recombination radiation and heat involved has been constructed. The various generation and recombination mechanism have been discussed and presented. Photo-ionization, thermal emission of deep level traps, intrinsic impact ionization, standard Shockley-Read-Hall recombination, direct band-gap recombination and Auger recombination have been considered.
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The model is written using Pspice8.0 soft, such that it can be directly integrated with the normal Pspice components used to simulate drive circuitry. The equivalent circuit model is based on a set of rate equations of vertical-cavity surface- emitting lasers (VCSEL's). To confirm that our model is valid, we present samples simulations that demonstrate its ability to replicate typical dc, small-signal, temperature-dependent light-current curves, transient operation, and modulation responses. Characteristics of the extracted quantum well models are discussed in detail. The predictive capability of the extracted models is demonstrated by good agreement between modeled and measured transient response pulse shapes.
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Photoacoustic measurement techniques can be used to determine thermal properties on and below the sample's surface, thus subsurface thermal inhomogeneities, such as continuous distributions of thermal parameters, become measurable by photoacoustic methods. In this paper, a numerical reconstruction treatment of thermal conductivity depth distribution is provided. Some simulation examples show that the method can be used in inverse computation of thermal conductivity by surface modulated photoreflectance signals.
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Low-cost optical switch is one of the most important components for fiber-based local area networks. In this paper electrostatic driven self-aligned optical switch was developed for the application in optical networks. A convenient wet etching by KOH solution was used to fabricate the structure in (100) silicon wafer in the optical switch. The cantilever, vertical mirror and V-grooves were formed in the bulk silicon directly, which makes the batch process and assembly simpler and more operable. A displacement of 30 microns of the mirror was achieved by the electrostatic force between the silicon block and the aluminum pad. An obvious advantage of the electrostatic driven way is that the operation has no power consumption. Operating frequency of 200 Hz was accepted as the working frequency, which indicated that the switching time can be less than 5 ms. Coupling alignment demonstrated that the insertion losses can be less than 2 dB in the ON-OFF positions.
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Innovative Waveguide Materials, Devices, and Sensors
Planar lightwave circuits based on silicon are playing important roles in integrated optical systems. Integrated waveguide turning mirror (IWTM) is essential component for the compactness of optical devices. We design an integrated waveguide turning mirror with a 90 degree(s) directional change in SOI, which diminishes the primary loss from the displacement of waveguide and mirror and has very low mirror surface roughness. In this paper, the theory, design and fabrication of this IWTM are introduced. A beam splitter using the structure is fabricated to test the performances, and expected results are obtained.
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Because of high resolution, infinite depth of focus and the usefulness over a broadfrequency spectra which range from visible light to x-ray and (gamma) -ray, the mask with periodic apertures image system is adopted very widely and play the part of leading role in the modern technology, such as pinhole camera, coded image system and optical information processing et al. While masks with periodic apertures investigated in the literatures are only limited to far-field diffraction, it did not take the shift of apertures within the mask into consideration. Therefore the derivation of far-field diffraction for single aperture can not be applied to mask with periodic apertures. The modified formula of far-field diffraction for multi-aperture mask has been proposed in the past, the analysis is still too complex to offer some practical rules for mask design. In order to develop an easier interpretation, this paper studies the circular mask with periodic rectangular apertures. First, we calculate the near- field diffraction intensity of circular aperture by means of Lommel's function. After the convolution of circular mask diffraction with periodic rectangular apertures together, we present a simple mathematical tool to analyze the mask including the distribution of intensity, aberration of blurring and the criterion of defining the far- or near-field diffraction. This concept can also be expanded to analyze the different type of mask with the arbitrary shape apertures.
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The microcavity light emitting devices were fabricated based on ladder-type poly (p-phenyline) (LPPP) and doped tris (8- hydroxyquinoline aluminum Alq3) heterojunction structure. The light emitting layers we LPPP with hole transportation and Alq3 as electron transporter. ITO and AL were the hole and electron injecting. Experimental results showed that the microcavity effect has been achieved simply by adjusting thickness of the organic light emitting layers between the ITO and AL electrodes. The stability of the microcavity devices with the heterojunction structure based on LPPP and doped- Alq3 was greatly improved. This can be ascribed to that the ladder-type structure of LPPP exhibited a higher thermal and chemical stability, and the intermolecular hydrogen bonding between the depant molecules was eliminated, led to decreasing nonvadiative centers.
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The diamond-based photodetectors were investigated. The diamond films were synthesized by microwave plasma assisted chemical vapor deposition. The films were characterized by scanning electron microscopy and Raman spectroscopy etc. The photodiode structures were fabricated on the free standing diamond films. The experimental results showed that the devices exhibited a strong UV photoresponse. It was found that the structures of the diamond films have a significant effect on the performance of the devices. The photoconductive gain of heteroepitaxial diamond films was greater than that of polycrystalline diamond films.
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We propose a novel wavelength-selective photodetector with two subcavities, for obtaining a flat-top and steep-edge spectral response and a high quantum efficiency simultaneously. Simulated nearly rectangular response curves can be obtained by insert an absorption layer into the latter subcavity. We discuss the effects of key factors on the response curve of this kind of photodetector. Such devices are promising for wavelength division multiplexing (WDM) applications.
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Innovative Waveguide Materials, Devices, and Sensors
The ZnS0.06Se0.94 epilayer is obtained by metallorganic chemical vapor deposition (MOCVD) with Se on-off modulation. The activation energy of as grown ZnSxSe1- x layer is lower than that by conventional growth method. From the 77 K photoluminescence spectra, high quality of as grown layer is obtained as the composition of ZnSxSe1- x reaches x equals 0.06 with which the lattice of ZnS0.06Se0.94 matches that of GaAs substrate. The 77K near band edge emission peak of as grown ZnS0.06Se0.94 is observed at 441.5 nm and the full width at half maximum of 12.7 meV is obtained.
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In this communication we present a NOT XOR gate using the cross-polarization modulation (XPolM) effect in a semiconductor optical amplifier (SOA). The gate utilizes only a SOA and it needs neither an inversion stage nor an additional synchronized clock. We demonstrate that the XPolM effect can rotate 73.5C the polarization-state of a CW beam when the power of a control beam changes from 0 to 300 (mu) W. The control and CW beams are introduced into the amplifier with a linear-polarization near to the unperturbed amplifier TM axis where the waveguide eigenmodes modification has a strong participation on the XPolM effect.
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In this paper, we propose a new technique to suppress the non- linearity of multiple quantum well (MQW) electro-absorption (EA) modulator, mainly due to an exponential-like transmission characteristics of EA modulator and non-linearity of quantum confined stark effect (QCSE), by intermixing MQW absorption region. Optical properties and its dependence on applied bias voltages of intermixed InGaAs/InGaAsP MQW absorption region, such as transition energy and gain (or absorption) spectrum have been calculated by solving Luttinger-Kohn Hamiltonian. It has been shown that the transfer function of a MQW-EA modulator can be tailored by introducing differently intermixed regions along the waveguide direction. It has been also shown that proposed technique can suppress IMD2 (2nd order intermodulation distortion) by 39.6 dB and enhance spurious free dynamic range (SFDR) by a 3.6 dB by choosing proper combination of interdiffusion lengths and waveguide lengths.
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Innovative Waveguide Materials, Devices, and Sensors
Here we report a simulation of bending loss of a photonic wire ring resonator. The ring resonator and waveguide core are composed of InGaAs/InGaAsP, which is isolated by an InP spacer. The waveguide core below the ring resonator could be used as a bus waveguide. The dependence of coupling coefficient on the thickness of InP spacer is calculated.
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In this work InGaAs/InGaAsP/InP microcylinder lasers with diameter of 10 micrometers were fabricated by wet chemical etching. At liquid nitrogen temperature the lasers show lasing at 1.55 micrometers when electrically pumped with pulse width 300 ns and cycle of 200 microsecond(s) . The threshold current is about 3 mA.
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Innovative Waveguide Materials, Devices, and Sensors
Silicon-based photonic wire waveguide was designed. The waveguide was consisted of a sandwiched structure with a nanocrystalline silicon film embedded between two low index silicon oxide films. The conformal transformation method was used in the simulation to obtain the basic coupling characteristics. The results showed that the coupling coefficient was strongly dependent on the gap spacing and the radius of the ring waveguide. A coupling efficiency of 10% could be obtained when the gap spacing was about 0.3 micrometers .
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The farfield characteristics of a InGaAs/GaAs quantum dots laser was investigated. It was found that the farfield picture on the screen in front of the laser was composed of two straight lines due to the side modes of the junction. And the straight lines consisted of three bright spots, which we believe were presumably originated from the feedback of the substrate and the capping layer.
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We have found that the optical power of a laser diode does not change with the injected light intensity that is modulated when its injection current is at some specified values. The amplitude of optical power change of the LD varies periodically with the increase of the injection current. It is made clear through the theoretical analysis that these phenomena are caused by gain compression and interband carrier absorption of the LD that depend on the longitudinal mode competition, bandgap-shrinkage effects, thermal conduction, and so on. Our experimental results make it get easy to eliminate optical power change of LDs. We only need to choose a proper value of the injection current.
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In this paper, some new results of the study on the bistability and the instability of semiconductor optical amplifier are presented, which may be expected to be available to a class of excitonic optical bistable and amplifying systems. For these systems, both saturation and increasing absorptive bistability will product, depending on the competition among the interactions in the medium, especially the nonlinear couplings, and the lasing conditions. Particularly, the output curve appears a novel feature of optical hysteresis, with amplifying effect as well. On the other hand, the instability of the stationary states is investigated by linear stability analyzing. Some new phenomena of 'critical slowing down' are discovered near the relevant critical points, in the dynamic responding course.
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Innovative Waveguide Materials, Devices, and Sensors
Currently, a number of techniques are used to access cell deformability. We study a novel silicon microchannels device for use in red blood cell deformability. The channels are produced in silicon substrate using microengineering technology. The microgrooves formed in the surface of a single-crystal silicon substrate. They were converted to channels by tightly covering them with an optical flat glass plate. An array of flow channels (number 950 in parallel) have typical dimensions of 5 micrometers width X 5.5 Xm depth, and 30 micrometers length. There the RBC's are forced to pass through channels. Thus, the microchannels are used to simulate human blood capillaries. It provides a specific measurement of individual cell in terms of both flow velocity profile and an index of cell volume while the cell flow through the channels. It dominates the complex cellular flow behavior, such as, the viscosity of whole blood is a nonlinear function of shear rate, index of filtration, etc.
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The design and integration of a fully embedded Si-CMOS process-compatible optical interconnects are presented. The transmitting and receiving functions will be incorporated within the embedded optoelectronic interconnection layers of 3-D integrated multilayer boards and ASICs. All elements including waveguide, coupler, detector and laser for the fully embedded board-level optical interconnection system are developed. The propagation loss of waveguide is 0.58 dB/cm at 632.8 nm and 0.21 dB/cm at 850 nm. The 45-degree TIR (total internal reflection) micro-mirror couplers with high coupling efficiencies are formed by reactive ion etching. The MSM (metal-semiconductor-metal) photo-detector array is fabricated on a GaAs wafer by a CMOS compatible technique. The external quantum efficiency of 0.4 A/W and 3 dB bandwidth of the integrated MSM photo-detector of 2.648 GHz are experimentally confirmed. The VCSEL array with a sacrificial layer for the epitaxial liftoff of VCSEL from the GaAs substrate is designed and manufactured. A 1 X 12 array of VCSELs, MSM photo- detectors and polyimide channel waveguides via 45-degree TIR micro-couplers are integrated on Si wafer. The experimental performances of the highly integrated system are given.
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The uniformization of Gaussian beam intensity is necessary in many applications. In active night-vision, monitoring targets especially requires this. IR semiconductor laser is widely used in the area because of its low power-consumption and small size. But the effects of the product are restrained due to system output Gaussian beam of ununiform intensity. The essay discusses a former system design and then gives an improved experimental scheme with some exciting results. The previous structure was as follows. High power SQW-LD beam was coupled to a plastic optical fiber (POF) directly, and then output through a lens. With its angle varied, targets ranged from 60 to 100 meters can be monitored. But unfortunately there were interference speckles folded on the target. An experimental system based on the thoughts of fiber transmission and complex filter was designed to improve the distribution of Gaussian beam intensity, with the result that the relatively well-distributed beam was got. Laser wavefront propagated through a very small pinhole whose diameter was 20 micrometers or so. The pinhole acted as an amplitude filter. Then the beam was coupled directly into a multi-mode quartz fiber whose core/cladding layer diameter parameter was 50/125micrometers . It conveyed laser beam about 200 mm. At the end of the fiber, several phase plates stood. Laser beam transmitted through the fiber was then phase-filtered and at last beam-expanded by a lens to illuminate the target. The more plates you used, the more uniform the illuminated picture was on condition the beam intensity was so strong that the CCD device could respond to.
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In this paper, we studied the spatial distribution of atomic hydrogen in diamond deposition. The number of hydrogen dissociation as a function of the ratio of electric field to gas pressure is given. And the number of hydrogen dissociation as a function of distance from the hot filament is also given here. These results are of great importance to the study of diamond deposited by EACVD.
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One of the earth observing instruments on HY-1 Satellite which will be launched in 2001, the multi-spectral CCD camera system, is developed by Beijing Institute of Space Mechanics & Electricity (BISME), Chinese Academy of Space Technology (CAST). In 798 km orbit, the system can provide images with 250 m ground resolution and a swath of 500 km. It is mainly used for coast zone dynamic mapping and oceanic watercolor monitoring, which include the pollution of offshore and coast zone, plant cover, watercolor, ice, terrain underwater, suspended sediment, mudflat, soil and vapor gross. The multi- spectral camera system is composed of four monocolor CCD cameras, which are line array-based, 'push-broom' scanning cameras, and responding for four spectral bands. The camera system adapts view field registration; that is, each camera scans the same region at the same moment. Each of them contains optics, focal plane assembly, electrical circuit, installation structure, calibration system, thermal control and so on. The primary features on the camera system are: (1) Offset of the central wavelength is better than 5 nm; (2) Degree of polarization is less than 0.5%; (3) Signal-to-noise ratio is about 1000; (4) Dynamic range is better than 2000:1; (5) Registration precision is better than 0.3 pixel; (6) Quantization value is 12 bit.
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Histogram Modification is a simple but effective method to enhance an infrared image. There are several methods to equalize an infrared image's histogram due to the different characteristics of the different infrared images, such as the traditional HE (Histogram Equalization) method, and the improved HP (Histogram Projection) and PE (Plateau Equalization) method and so on. If to realize these methods in a single system, the system must have a mass of memory and extremely fast speed. In our system, we introduce a DSP + FPGA based real-time procession technology to do these things together. FPGA is used to realize the common part of these methods while DSP is to do the different part. The choice of methods and the parameter can be input by a keyboard or a computer. By this means, the function of the system is powerful while it is easy to operate and maintain. In this article, we give out the diagram of the system and the soft flow chart of the methods. And at the end of it, we give out the infrared image and its histogram before and after the process of HE method.
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Optical bistability with 100 ps switching time has been observed in ZnS/ZnSe stratified grating filter at room temperature for the first time. We think that the optical bistability results from the band-filling effect caused by the nonlinear absorption of the material and reflection occurred among the multilayer films. When the light intensity is larger enough. The refractive index change will be larger and the transmitted light intensity increases remarkably owing to the third order nonlinear effect of ZnS/ZnSe, so ZnS/ZnSe stratified grating is of optical bistability.
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In night vision applications, because the light reflected by a target is very weak, the image captured by the Low-Light- Level camera has a great deal of noise attached on it. To remove such noise, the image must be processed in time. In this paper a real-time image processing system with a high- speed DSP device embedded in is constructed. The system employs an Analog Front End (AFE) device as the analog video digitalizer, and a DA converter with video synthesizing function in the analog video output channel. The whole processing board is small in size, and easy in use.
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Under the condition of zero net strain, the effect of high temperature on the optical gain and threshold characteristics and the dependence of the characteristic temperature on the cavity length are analyzed theoretically for InGaAs/InGaAsP strain-compensated multiple quantum well (SCMQW) lasers lattice-matched to InP around 1.55 micrometers wavelength emission. The computed results show that as the temperature increases, both the threshold carrier density and the threshold current density increase. As the cavity length increases, the characteristic temperature increases and the temperature dependence becomes better. The characteristic temperature of a SCMQW laser is higher than that of a strain-compensated single quantum well (SCSQW) laser. Therefore, the temperature dependence of the SCMQW laser is better than that of the SCSQW laser. In addition, we find that in order to always keep 1.55 micrometers wavelength emission, certain relations exist among the well width, cavity length and temperature.
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A MIM thin film diode (TFD) with Ta-Ta2O5-Ta symmetrical structure for active-matrix liquid crystal display (AM-LCD) was prepared. The Ta2O5 insulator layer as a key to the MIM thin film diode was got by anodizing sputtered tantalum oxide film (sputtering/anodization two-step process), and was heat-treated by vacuum/atmosphere two-step heat- treatment with different process parameter. The microstructure of tantalum oxide film was analyzed by Atomic Force Microscope (AFM) and Transmitting Electron Microscope (TEM), respectively. The I-V characteristics of the MIM thin film diode were also measured. The influence of heat-treatment on microstructure of Ta2O5 insulator film and the I-V characteristics of the MIM thin film diode were investigated. The relationship between the I-V characteristics of the MIM thin film diode and microstructure of Ta2O5 film was also indicated. The results showed that the Ta2O5 film sample with vacuum/330 degree(s)C atmosphere two-step heat- treatment had uniform and dense amorphous microstructure, and had a good stability, a high switching-on/off ratio (105), and excellent symmetric I-V characteristics with the positive and negative threshold voltages 7V and 6.6V, respectively, and little relative errors (< 6%). The properties of this MIM- TFD can meet the needs of AM-LCD.
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The network disorder of a-Si1-xCx:H films containing carbon concentrations below 20at.% has been studied by means of Raman spectroscopy and photoluminescence measurements (PL). Two different radiations were employed to excite these materials, one is nearly the same as the optical gaps of these materials and weakly absorbed (647.1 nm), another is higher than the optical gaps of these materials and strongly absorbed (488 nm). The variations in probed depth together with the significant differences observed in the Raman spectra and PL spectra indicate the existence of two kinds of spatially inhomogeneities: a highly disordered thin layer near free surface and gap fluctuations due to spatial variations of compositions in the bulk. When excited with strongly absorbed radiation, the frequency and width of TO mode have a large redshift and broadening relatively to the weakly absorbed radiation, while the position and width of PL peak have a blue shift and broadening. The above results indicate that different radiations may lead to different Raman and PL results.
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A 160-channel DWDM system integrating a 1 X 4 25-GHz nonlinear Fourier Filter Flat-top (F3T) interleaver with four 1 X 40 100-GHz AWGs was investigated for 10 Gb/S PRBS laser and DWDM detuning transmission experiments and OC-192 network applications. Telcordia GR-1221 testing results were also discussed in this work.
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Crystalline carbon nitride thin films are synthesized by pulsed XeCl excimer laser deposition technique following by a high temperature annealing or accompanying a pulsed glow discharge plasma assistance. The composition, the structure and the binding state of the deposited films are analyzed by several techniques such as Scanning electron microscopy, Energy-disperse X-ray (EDX), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Experiment results show that the crystalline carbon nitride films preferentially formed at high temperature companying with the nitrogen content reduction and the films graphitization, combining high substrate temperature and nitrogen activation through pulsed discharge is favorable for the formation of (alpha) -C3N4 crystallites.
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Pulse laser ablating graphite is adopted to deposit SiC films on Si(111) under different laser fluence and substrate temperature. Experiment results show that the deposited films present different morphology and X-ray diffraction characteristics. Single crystalline SiC is obtained when the laser fluence is 10J/cm2 and the deposition temperature is 900 degree(s)C. At lower laser fluence or lower substrate temperature, a carbon overlayer is formed. Meanwhile the surface roughness of the films becomes relative smooth and the deposition rate increase with laser fluence. The stress accumulation during film growth releases gradually as the substrate temperature increase. The mechanism of the crystalline SiC formation in the initial stage that the energetic carbon species penetrate several layers below the silicon surface by subplantation and transversely migration in silicon substrate is discussed. All the results suggest that the energy of incident atom play an important role in growth silicon carbon at low substrate temperature.
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Photon Scanning Tunneling Microscope (PSTM) is a newly developed technique. As a near-field optical microscope, it has the high resolution breaking through the diffraction limit and the advantage for easy to prepare the samples. PSTM is a useful tool in the inspection for many kinds of material film as the image containing the sample's information of topography and refractive index. We have developed a PSTM with resolution 5 to approximately 10 nm and scanning range 6 X 6 micrometer. By making use of two lasers, the false image caused by inclination of sample surface can be reduced. This PSTM is engaged in the inspection of Al2O3 optical waveguide film made using ion-beam-enhanced-deposition (IBED) technique at different substrate temperature. The PSTM images of the optical waveguide film are obtained and analyzed. The PSTM images show that as the increasing of the substrate temperature during the deposition, the sample images of refractive index and topography tend to smooth and even, consequently the scattering loss can be decreased. The conclusion is that by properly increasing the temperature of the substrate during the deposition period, the scattering loss can be decreased and the property of Al2O3 optical waveguide can be improved.
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The mechanical reliability of electronic packaging is a topic of concern. Characterization of the thermo-mechanical behavior including the thermal stress/strain of electronic packages is critical for this topic. In this paper, current principal experimental methods used for this purpose are reviewed, their advantages and disadvantages are analyzed, also their newest applications are introduced. The hybrid method that takes the advantage of experimental methods and finite elemental method -- FEM is pointed out to be the best investigation method and represents a developing direction.
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Phase change optical recording disks using have been found to demonstrate long stability of the amorphous recording marks. Structural analysis of the material were studied by X Ray Diffraction (XRD), Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) respectively. The films were studied for both the cases: before and after annealing and it was concluded that the alloy (Ag-Sb-Te) could be used as a phase change optical memory material.
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In this paper, we want to optimize photo-resist coating recipe by using orthogonal experiment and statistical regression analysis. We combined two major factors influenced coating performance -- 'wafer coating time' & 'wafer spinning speed' in TRACK unit with IDITM pump dispense recipe. Eventually, IDITM pump dispense recipe contained of four steps dispense time and dispense pressure. By using orthogonal experiment and statistical regression method we obtained set of process parameters which have good predicted performance values. Based on those data, we could apply it on different viscosity type resist to get good coating performance as decreasing resist dispense volume from 3 cc/pcs to 1.6 cc/pcs. Results showed the performance of CD (Critical Dimension) and CP (Chip Probe) yield was comparable to original 3 cc/pcs coating recipe condition. Actually, we could optimize coating recipe to reach resist usage decreasing purpose.
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As one application experiment of the synchrotron radiation, the soft X-ray lithography beam line is an important instrumentation producing a super integrate circuit exposure area that is a large scale. As principle part of the system, shutter and mirror sweep system affect quality of the lithography directly. A convenient and smart control and measuring system for lithography soft X-ray beam line at Hefei National Synchrotron Laboratory had been developed soon after successful storage ring commission. The process control system was composed of monitoring, interlock, data processing, and control. It has been operated so safety and reliability. The measuring and control system is still reliable, noise reduced and very convenient after several years operation. It is the time that the new technology is rapid developed. A site survey of developing computer science, control and measurement method in the world, we need to spend some time to consider old system existed, I think. What are the main questions of the old system in new concept? For putting oneself ahead of thinking how to solve the questions above, We have taken a long time looking for some suitable methods. As we know, the equipment on beam line and station are not changed in general after manufacture. An electronics processing and control method is developed in original system, and system software is advanced, such as new linear drive sub program by using dynamic complete method, noise reduce, on line data processing, and so on.
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It is a new technology to use synchrotron radiation lithography for making large scale integral circuit. Synchrotron radiation lithography System is composed of lithography beam line and exposure chamber. A scanning mirror system is making the largest linear exposure area for integrate circuit. By means of increasing control fineness and optimizing scanning frequency in on-line control system, the uniformity of exposure grating is improved quite well. It is opening good idea for every scientist and technician to continue study. It is shown that inspect and control system is still reliable, noise reduced and very convenient after several years operation. It shows operating status of each equipment and vacuum figures on beam line and station, mirror scanning linearity, exposure time, beam current, and so on. Some successful soft X-ray lithography sub-micrometer results are achieved by different users in this system, they are showing very good resolution, more clear leakage and enough depth for example. A convenient and smart optimum analysis system will be developed soon. It is easy to find very good oscillation frequency for mirror vibrating, and the strong interference from current monitor in synchrotron radiation storage ring is reduced very well. Convenient, compact, reliability and safety are the basic but important idea of system design, and what is higher level consideration for getting fine result of micro lithography. There will have enough database space for a different kind user to storage on- line test datum in system.
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In this paper, an approach to linear feature extraction for infrared image is presented, which consists of three major modules: image preprocessing by using fuzzy feature transformation and fuzzy enhancement, edge strength map and direction map generation by using low pass filter and multi- dimension edge detector and linear feature extraction by using gradient profile maximum method. Comparison with some other edge detection methods, accuracy and robust experiments are done to testify its better position accuracy and reliability. Computational simulation and experiment results show that the proposed algorithm can solve the linear feature extraction problem for infrared image.
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Fuzzy feature extraction and image information analysis for the infrared image and optical image are studied firstly, and fuzzy gradient profile direction detection processing is presented in this paper. Then the relationship between infrared image and optical image is described. Through analyzing the images, a description-based fuzzy feature matching algorithm is proposed. Computational simulation and experiment results using infrared image and optical image are presented finally.
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This paper highlights a set of high data rate, small size and low power dissipation time delay integration charge couple device (TDICCD) focal plane assemblies (FPAs), which has good demand for higher resolution capability (GRD equals 0.5 m) and has many good specifications: (1) TDICCD-FPA has high data rate of 16 MHz. (2) The size of TDICCD-FPA is 190*180*100 mm3. (3) The weight of TDICCD-FPA is 6 kg. (4) TDICCD-FPA working temperature is 0 degree(s)C - 10 degree(s)C. (5) Low power dissipation is 25 W. (6) A/D is 10 bit. (7) Dynamic range is 3000:1. Also, from the angle of the design of space TDICCD cameras, it introduces how to design focal plane assemblies (FPAs) -- including TDICCD field butt, FPAs machine design, electronic focal plane assemblies (EFPAs) video electronic- signal processing unit (SPU), TDICCD FPAs temperature control. Two dynamic TDICCD imaging instruments are manufactured using the 'push-broom' imaging principle, and their confident performances are also achieved.
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In this paper, digital navigation concept is introduced to the application of aircraft navigation parameter estimation firstly and an estimation method for navigation parameter using digital camera is presented, where navigation parameters represent the position and attitude information of a helicopter for autonomous navigation. The proposed method is composed of relative position estimation, absolute position estimation and integrated position estimation. Multi-image space orientation is introduced and real-time aerial scene (i.e., sequence image) matching is processed in relative position estimation. Digital image reference map and digital elevation reference map are employed and multi-source matching is processed in absolute position estimation. Integrated position estimation is proposed to perform the estimation of helicopter navigation parameters. Computational simulation and experiment results show that our proposed navigation parameter estimation is feasible for helicopter navigation.
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Two-photon absorption coefficients and the corresponding absorption cross sections of 5-(9-anthryl)-3-(4-nitrophenyl)- 1-phenyl-2-pyrazoline (ANPP) are obtained from intensity dependent transmission measurements. The linear and nonlinear fluorescence spectra of ANPP have been studied. The linear florescence spectrum of ANPP has two emission bands originating from the anthryl and pyrazoline moieties of ANPP on excitation at 355-nm, respectively. The nonlinear two- photon and three-photon fluorescence from these two moieties are observed simultaneously when ANPP is excited at 1064-nm due to the proximity of the absorption bands of these two moieties to (lambda) /3 and (lambda) /2 of the exciting wavelength. The similar spectra structure indicates that the nonlinear and linear fluorescence originates from the same relaxation process.
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Using dual-galvanometer optical scanning head as the reflecting type optic-fiber confocal scanning microscope's planar scanning outfit can achieve the fast scanning to plane image, but there are distortion and vignetting. In the paper, the basic principle of reflecting type fiber-optical confocal scanning microscope is described briefly. The distortion caused by using the common eyepiece as scanning lens, the inherent distortion and vignetting for pre-eyepiece dual galvanometer scanning system have been analyzed in theory, and the according high-speed scanning electronic control system that has the function of distortion correction and image processing has been discussed.
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In the pH-ISFET (ion sensitive field effect transistor) applications, the temperature is one of the important factors for the stability. The hydrogenated amorphous carbon (a-C:H) films is used for the sensitive layer of the pH-ISFET. The a- C:H pH-ISFET device is prepared by the plasma-enhanced low pressure chemical vapor deposition (PE-LPCVD). The thickness of the a-C:H was 2000 Angstrom, and the a-C:H gate pH-ISFET was encapsulated by epoxy. The Keithley 236 instrument was used to measure the IDS - VGS curves of the a-C:H gate pH-ISFET in the various pH buffer solutions at 15 degree(s)C - 55 degree(s)C. According to the experimental results, we found the sensitivity of the a-C:H gate pH-ISFET is increased with the temperature. Finally, the TCS (temperature coefficient of sensitivity) can also be calculated.
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The temperature effect is an important factor for the deviation of the pH-ISFET (ion sensitive field effect transistor). In this paper, we use the SnO2 as the pH sensing membrane to investigate the temperature characteristics of the pH-ISFET. The SnO2 membrane was prepared by the sol-gel technology. We use the tin (II) chloride dihydrate (SnCl2(DOT)2H2O) and ethanol to synthesize the sol of the SnO2 thin film. For the sol-gel prepared SnO2, the cost is lower than other methods.The Keithley 236 instrument was used to measure the IDS - VG curves of the SnO2 gate pH-ISFET for different pH buffer solutions form ranging temperature 15 degree(s)C - 45 degree(s)C. According to the experimental results we can obtain the sensitivities for different operation temperatures. The sensitivity is increased with increasing temperature. The TCS (temperature coefficient of the sensitivity) is also calculated.
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The thin transparent and conductive ITO layers have been deposited onto the both surface of the glass of dimensions 0.2 X 16 X 16 mm using the DC ion sputtering method. In order to study the electron emission the voltage has been applied between the both ITO layers. One of the layer was 1 micrometer thick (field electrode) and another one (10 divided by 200 nm) at opposites surface of the glass surface was treated as the electron emitter. The negative biasing voltage has been applied to the field electrode. The studies has been carried out in vacuum (10-7 hPa). The multichannel analyzer of amplitude of voltage pulses created by the electron multiplier has been used in order to record the electron emission yield. The pulses are recorded in channels of the pulse analyzer according to their height creating so-called voltage pulse amplitude spectrum. Aside of the effects the studies concerning the result of UV illumination on the photoemission monitored by field has been examined. With increasing of biasing voltage (0 divided by -2 kV) and after illumination the count frequency of pulses grows monotonically. The shape of obtained curves of the spectral dependence of the photoelectron emission yield was found to be independent of the excitation wavelength. However, the surface under the experimental curves were found to be different and the maximal one appeared to be for the wavelength corresponding approximately for the value of the energy gap of ITO (3.5 eV).
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In the process of precision cutting machining, in order to obtain smooth surface, the tool wear is an important factor besides the optimizing the cutting parameters. When the tool was worn to a certain degree, the machined surface quality would be very difference after cutting with the tool wear. So in the process of precision cutting, the measuring of the tool wear is a very important problem. In the paper, A simple and reliable monitoring method based on laser-CCD trigonometric measurement is proposed for tool wear sensing on-line in the automation of precision cutting processes. With laser-CCD trigonometric measurement, the tool wear is measured. When the tool wear is to a certain degree, the measurement system give the alarm and the tool must be replaced, and then go on to cut work-pieces with new tool. Much experimental studies of the precision cutting are carried out with the measuring system and the experimental result is given. The results show that the measurement accuracy of the measurement system is +/- 0.1 micrometers , it can be used very well in the on-line measurement and workplace's surface quality is guaranteed.
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In accordance with the disadvantages of focus depth decrease caused by the large enough numerical aperture of the project photolithography imaging system and larger optical energy loss of amplitude filtering, the improvements in imaging resolution, focus depth and the availability of optical energy by means of amplitude phase compound filtering are studied in detail. The fact that corresponding optimal compound filters should be designed according to the different mask pattern designs has been proposed. The calculation analysis and experimental results show that amplitude phase compound filtering can improve the imaging resolution and focus depth of project photolithography by a big margin. At the same time the availability of optical energy can be improved and this is good for the improvement of production efficiency.
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Based on the reflective principle, a new kind of laser and fiber optic sensor system was proposed and designed based on the formidable on-site operation conditions with the temperature over 700 degree(s)C, the abominable electromagnetic interference and the hard mounting problems. The optical fiber sensor is a total fiber fabric which has the high performance for high-temperature, very good insulating property. It is particularly suitable for those special accessions and conditions that conventional sensors are difficult to apply. Because of the superiorities of this kind of sensor such as simple structure, convenient to use, and the high measurement accuracy, there is an attractive application foreground on the turbine and other complex measurement problems. The measurement principle of the optical fiber sensor and its structure was described. The compensation technique for the thermal radiation and variation of the light power was proposed. The preliminary experimental results showed that the measurement range of the gap can reach 5 mm and the measurement resolution was better 0.01 mm. The operating temperature was about 700 - 10 degree(s)C, and rotational speed was 3,600 turn per minute.
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Silver halide emulsion is an important component of image materials. It can develop permanent image through the absorption of light. It is widely used in many kinds of fields and has a very prosperous prospect. Now many scientists study the properties of image material, but they mainly focus on experimental methods. Computer simulation method opens up a brand-new way in the study of optoelectronic behavior in image materials. Compared with traditional experimental ways, this method is more economical and convenient and has a shorter research period. So it is a very practical method to exploit new type of image materials and perfect photosensitive theory. In this paper, Nucleation & Growth model and Monte Carlo method were adopted to simulate the optoelectronic behavior in image materials and results with different input parameters will be given.
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The optoelectron lifetimes in imaging process are directly related to photographic efficiency of silver halide emulsion. The lifetime of the free electrons and shallow trapped electrons decide the sensitivity and other efficiency of silver halide emulsion. Modern emulsion technology uses the incorporation of well-defined phase boundaries in emulsion crystals to reduce the recombination rate of optoelectrons and optoholes after actinic exposure. This process leads to an enhanced photographic efficiency due to the increasing optoelectron lifetime. Microwave absorption and dielectric spectrum detection technology is a powerful tool that could quickly detect the change of dielectric function of emulsion film. This technology enables contactless measurement of the optoelectron lifetime. YAG super-fast pulse laser (355 nm, 35 ps) is used as an exposure source. Signals of the free optoelectrons and shallow trapped electrons are the decay curve versus the time. The concentration of the optoelectrons depends on the maximum concentration and decay rate constant. The reciprocal of the slop of this straight line is the lifetime of the optoelectrons. The lifetime and decay curve of the free optoelectrons and shallow trapped electrons of different emulsion samples have been measured and analyzed.
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A novel micromachined uncooled infrared (IR) detector based on hydrogened amorphous silicon (a-Si:H) thin film transistor (TFT) as thermosensitive element is proposed for the first time. It utilizes the high temperature dependence of the drain current induced by the influences of temperature variation on the effective carrier mobility in channel and on the threshold voltage. An IR resonance cavity between absorber and the gate electrode improving the IR absorptivity and a microbridge providing a low thermal conductance are designed. The differential amplifier whose input pair is two identical TFTs, of which one is shielded to the IR while the other is unshielded, can not only amplify the voltage signal that is equivalent to the drain current variation but also simultaneously compensate the self-heating effect. Using PSPICE simulator, the responsivity calculated is about 4.1 mV/K at room temperature.
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