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Analysis of flash lamp structure using Monte Carlo photon tracing method
Liefeng ZHAO, Huajun FENG, Zhihai XU
Front Optoelec Chin. 2008, 1 (3-4): 205-209.
https://doi.org/10.1007/s12200-008-0060-y
By analyzing the flash lamp structure, better illumination distributions in the lamp's field of view can be obtained. Instead of geometrical optical approaches, the Monte Carlo photon tracing method was used here to trace the photon tracks in a three-dimensional space. The models of elemental structures in a camera flash lamp, such as the flash tube, reflector and focus lens, were set up by introducing the cosinusoidal random number and other mathematical methods. Initially, the single photon was traced in the flash lamp by using the Monte Carlo method to simulate various photon tracks. A large sum of photons was then generated to simulate the real situation in the flash lamp. Finally, a group of structural parameters was applied to verify the simulative computer program. The output light intensity distributions at different angles of view in the orthogonal directions meet the ISO standards and are very close to the measured ones. Hence, the Monte Carlo photon tracing method in the design of flash lamps has been proven to be applicable and useful.
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Micro Fabry Perot light modulator for flat panel display
Jiyong SUN, Shanglian HUANG, Jie ZHANG, Yi QIN, Xuming SUN
Front Optoelec Chin. 2008, 1 (3-4): 210-214.
https://doi.org/10.1007/s12200-008-0067-4
A new type of Fabry Perot light modulator for displays based on micro-electro-mechanical system technology is proposed. Multiple beam interference theory is used to design the modulator and analyze its characteristics. If Fabry Perot cavity length is one-quarter of the incident wavelength, the transmitted light is blocked by the modulator, and the modulator, which is illuminated from its backside, appears black. If the Fabry Perot cavity length is 0 or one-half of the incident wavelength, light may transmit the Fabry Perot modulator from its backside, and the modulator appears bright. Hence, the modulator may be used for flat panel displays. In this paper one Fabry Perot light modulator based on surface micromachining technology is introduced. The designed modulator has a contrast ratio of 150 and can theoretically be driven by a voltage of 2.4 V.
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2500 km-10 Gbps RZ transmission system based on dispersion compensation CFBGs without electric regenerator
Jihong CAO, Yong CHEN, Ting CHEN, Shuisheng JIAN
Front Optoelec Chin. 2008, 1 (3-4): 219-222.
https://doi.org/10.1007/s12200-008-0003-7
The characteristics of chirped fiber Bragg gratings (CFBGs) are optimized so that the ripple coefficient of the power reflectivity spectrum and group time delay are less than 1 dB and |± 15| ps, group delay is about 2600 ps/nm, polarization module dispersion is very small, PMD < 2 ps, -3 dB bandwidth is about 0.35 nm, and insertion loss is about 4–5 dBm. Using dispersion compensation CFBG, a 2500 km-10 Gbps RZ optical signal transmission system on G.652 fiber was successfully demonstrated without an electric regenerator by optimizing dispersion management and loss management. The RZ optical signal was generated through a two-stage modulation method. At 2081 km, the power penalty of transmission is about 3 dB (conditions: RZ signal, BER = 10-12, PRBS = 1023 - 1); At 2560 km, the power penalty is about 5 dB. It is superior to the system using NRZ under the same conditions.
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Small particle detection method based on laser feedback
Guoqiang SUN, Jihong ZHENG, Gang ZHENG, Songlin ZHUANG
Front Optoelec Chin. 2008, 1 (3-4): 241-246.
https://doi.org/10.1007/s12200-008-0073-6
In order to overcome the shortcomings of traditional particle measurement, a new method for the detection of small and single particles through laser feedback phenomenon is presented. This method is based on the laser feedback caused by radiation scattered back from a moving particle in the external cavity of the laser. The parameters of the single particle, such as the diameter, velocity, and quantity, can be measured and calculated from the change in output laser power. In the experiment, the confocal external cavity composed of a concave reflector and a positive lens is designed. This device is able to obtain the corresponding variety curve of standard particles passing through the confocal area, and then the parameters of the particles can be measured and calculated by combining the experimental data and standard curves. Experimental results show that this method is an easily operated and reliable way for particle detection. The measurement ranges from 0.2 to 2000 μm, resolution is 0.2 μm, and measurement error is within 2%. This device may have wide application in areas such as atmosphere particle detection and calibration of a single particle producer.
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Temperature dependence of photoluminescence of QD arrays
Guoliang LIU, Jianghong YAO, Jingjun XU, Zhanguo WANG
Front Optoelec Chin. 2008, 1 (3-4): 258-262.
https://doi.org/10.1007/s12200-008-0050-0
It is essentially important to understand the temperature dependence of the photoluminescence of multimodal quantum dot (QD) arrays for the realization of efficient photonic devices. In this paper, the dynamics processes of different density multimodal QD arrays were fitted by using the rate equation model. It is shown that, in high density QD arrays, the intensity of photoluminescence of different QD families has different temperature dependence, and the intensity of photoluminescence is quenched as the temperature increases in low density QD arrays. In high density QD arrays, as the temperature increases, the carriers will be thermally excited into the wetting layer from QDs, and then some of them will be recaptured by the big scale QDs; carrier coupling takes place between the different QD families, while in low density QD arrays, the carrier transfer between different QD families will be limited. Temperature dependence of the maximum of the ratio of photoluminescence intensity of different QD families strongly depends on the difference of thermal activation energies.
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A portable functional imaging instrument for psychology research based on near-infrared spectroscopy
Xiaohua LV, Yi ZHENG, Ting LI, Zhongxing ZHANG, Hui GONG
Front. Optoelectron.. 2008, 1 (3-4): 279-284.
https://doi.org/10.1007/s12200-008-0057-6
To aid psychology researches on the function of the prefrontal cortex, a 16-channel brain functional imaging instrument based on near-infrared spectroscopy is developed. The probe of the instrument, covering a detection area of 15 cm × 4.4 cm of the prefrontal cortex, is made flexible and is easy to fix to the forehead. By employing multi-wavelength LEDs as light sources, using integrated detectors and choosing a USB-interface-based data acquisition device, the whole system is portable and convenient to use, which is good for psychological experiments. The system software is developed using Visual C++ 6.0, which controls the imaging process, measurement data plotting and storage. The maximal temporal resolution is about 100 ms. Noise and long-term drift test are given. The Valsalva maneuver experiment is used to validate the reliability of the instrument for monitoring hemodynamic changes.
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Synthesis, optical and electroluminescent properties of novel polyfluorene/carbazole-based conjugated polyelectrolytes and their precursors
Wei CAO, Haixing DONG, Fei HUANG, Huilin SHEN, Yong CAO
Front Optoelec Chin. 2008, 1 (3-4): 299-304.
https://doi.org/10.1007/s12200-008-0007-3
A series of novel aminoalkyl-substituted fluorene/carbazole-based main chain copolymers with benzothiadiazole (BTDZ) of different contents: poly[3,6-(N-(2-ethylhexyl)carbazole)-(9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene)-4,7-(2,1,3-benzothiadiazole)] (PCzN-BTDZ) were synthesized by Suzuki coupling reaction. Through a postpolymerization treatment on the precursor polymer, a corresponding quaternized ammonium polyelectrolyte derivatives: poly[3,6-(N-(2-ethylhexyl)carbazole)-(9,9-bis(3′-((N,N-dimethyl)-N- ethylammonium)propyl)-2,7-fluorene)-4,7-(2,1,3-benzothiadiazole)] dibromide (PCzNBr-BTDZ) were obtained. It was found that devices from such polymers with high work-function metal cathode such as Al showed similar device performance to that by using low work-function cathode such as Ba, indicating the excellent electron injection ability of these polymers. The efficient energy transfer from fluorene-carbazole segment to the narrow band gap BTDZ site for both the neutral and the quaternized copolymers was also observed. The addition of BTDZ into the polymer main chain can also improve polymer LED (PLED) device performance. When poly(3,4-ethylenedioxythiophene) (PEDOT)/poly(vinylcarbazole) (PVK) was used as an anode buffer, the external quantum efficiency of the copolymer PCzN-BTDZ1 was 0.99%, which was much higher than the copolymer PCzN without the incorporation of BTDZ in the same device configuration.
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SiC/Mg multilayer reflective mirror for He-II radiation at 30.4 nm and its thermal stability
Jingtao ZHU, Da XU, Shumin ZHANG, Wenjuan WU, Zhong ZHANG, Fengli WANG, Bei WANG, Cunxia LI, Yao XU, Zhanshan WANG, Lingyan CHEN, Hongjun ZHOU, Tonglin HUO
Front Optoelec Chin. 2008, 1 (3-4): 305-308.
https://doi.org/10.1007/s12200-008-0028-y
In applications of solar physics, extreme ultraviolet imaging of solar corona by selecting the He-II (λ = 30.4 nm) emission line requires high reflectivity multilayer mirrors. Some material combinations were studied to design the mirrors working at a wavelength of 30.4 nm, including SiC/Mg, B4C/Mg, C/Mg, C/Al, Mo/Si, B4C/Si, SiC/Si, C/Si, and Sc/Si. Based on optimization of the largest reflectivity and the narrowest width for the multilayer mirror, a SiC/Mg material combination was selected as the mirror and fabricated by a magnetron sputtering system. The layer thicknesses of the SiC/Mg multilayer were measured by an X-ray diffractometer. Reflectivities were then measured on beamline U27 at the National Synchrotron Radiation Laboratory (NSRL) in Hefei, China. At a wavelength of 30.4 nm, the measured reflectivity is as high as 38.0%. Furthermore, a series of annealing experiments were performed to investigate the thermal stability of the SiC/Mg multilayer.
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AlGaAs/GaAs quantum well infrared photodetector focal plane array based on MOCVD technology
Xianjie LI, Yingbin LIU, Zhen FENG, Fan GUO, Yonglin ZHAO, Run ZHAO, Rui ZHOU, Chen LOU, Shizu ZHANG
Front Optoelec Chin. 2008, 1 (3-4): 313-317.
https://doi.org/10.1007/s12200-008-0051-z
128 × 128, 128 × 160 and 256 × 256 AlGaAs/GaAs quantum well infrared photodetector (QWIP) focal plane arrays (FPA) as well as a large area test device are designed and fabricated. The device with n-doped back-illuminated AlGaAs/GaAs quantum structure is achieved by metal organic chemical vapor deposition (MOCVD) epitaxial growth and GaAs integrated circuit processing technology. The test device is valued by its dark current performance and Fourier transform infrared spectroscopy (FTIR) spectra at 77 K. Cut off wavelengths of 9 and 10.9 μm are realized by using different epitaxial structures. The blackbody detectivity DB* is as high as 2.6 × 109 cm?Hz1/2?W-1. The 128 × 128 FPA is flip-chip bonded on a CMOS readout integrated circuit with indium (In) bumps. The infrared thermal images of some targets under room temperature background have been successfully demonstrated at 80 K operating temperature. In addition, the methods to further improve the image quality are discussed.
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Organic electroluminescent characteristics of PS:NPB composite hole transporting layer
Fan SUO, Junsheng YU, Jing DENG, Shuangling LOU, Yadong JIANG
Front Optoelec Chin. 2008, 1 (3-4): 323-328.
https://doi.org/10.1007/s12200-008-0069-2
Green organic light-emitting devices with a structure of indium-tin-oxide (ITO)/polystyrene (PS):N,N′-bis-(3-naphthyl)-N,N′-biphenyl-(1,1′-biphenyl)-4,4′-diamine (NPB)/tris-(8-hydroxyquinoline)-aluminum (Alq3)/Mg:Ag were fabricated. A doping system consisting of small-molecular hole transporting material NPB and polymeric matrix PS was applied as a composite hole transporting layer (HTL), and the thin film preparation was simplified via spin-coating technique. By adjusting the component ratio of the doping system, several devices with different concentration proportion of PS:NPB are constructed. The electroluminescent characteristics of the devices were investigated and discussed. This study demonstrated that the difference of doping concentration of NPB has a remarkable impact on the optoelectronic performance of both HTL and the devices. Optimum device performance can be obtained by choosing a suitable concentration proportion of PS:NPB at 1:1. This study contributes to the construction of composite functional layers of organic light-emitting diode (OLED) devices and to the technical modification.
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Monolithically integrated long wavelength photoreceiver OEIC based on InP/InGaAs HBT technology
Xianjie LI, Yonglin ZHAO, Daomin CAI, Qingming ZENG, Yunzhang PU, Yana GUO, Zhigong WANG, Rong WANG, Ming QI, Xiaojie CHEN, Anhuai XU
Front Optoelec Chin. 2008, 1 (3-4): 336-340.
https://doi.org/10.1007/s12200-008-0059-4
The epitaxial structure and growth, circuit design, fabrication process and characterization are described for the photoreceiver opto-electronic integrated circuit (OEIC) based on the InP/InGaAs HBT/PIN photodetector integration scheme. A 1.55 μm wavelength monolithically integrated photoreceiver OEIC is demonstrated with self-aligned InP/InGaAs heterojunction bipolar transistor (HBT) process. The InP/InGaAs HBT with a 2 μm × 8 μm emitter showed a DC gain of 40, a DC gain cutoff frequency of 45 GHz and a maximum frequency of oscillation of 54 GHz. The integrated InGaAs photodetector exhibited a responsivity of 0.45 A/W at λ = 1.55 μm, a dark current less than 10 nA at a bias of -5 V and a -3 dB bandwidth of 10.6 GHz. Clear and opening eye diagrams were obtained for an NRZ 223-1 pseudorandom code at both 2.5 and 3.0 Gbit/s. The sensitivity for a bit error ratio of 10-9 at 2.5 Gbit/s is less than -15.2 dBm.
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Optical properties of InN films grown by MOCVD
Jieying KONG, Bin LIU, Rong ZHANG, Zili XIE, Yong ZHANG, Xiangqian XIU, Youdou ZHENG
Front Optoelec Chin. 2008, 1 (3-4): 341-344.
https://doi.org/10.1007/s12200-008-0038-9
By means of optical absorption, photoluminescence (PL), Raman scattering and ellipsometry, optical properties of indium nitride (InN) films grown by metal organic chemical vapor deposition (MOCVD) are investigated. Through absorption and PL measurements, it is proven that the band gap of high quality InN is 0.68 eV, which agrees with the recently reported value, 0.7 eV. By analysis of the Raman scattering spectrum, the comparatively low background concentration of electron results in a smaller band gap value. The transition energy of wurtzite InN at critical point is determined by ellipsometric spectra. In addition, the complex refractive index of InN at energy ranging from 0.65 to 4.0 eV is obtained for the first time.
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Fringe-contoured-window sine/cosine filter for saw-tooth phase maps in ESPI
Sihua FU, Xuejun LONG, Hui LIN, Qifeng YU
Front Optoelec Chin. 2008, 1 (3-4): 345-351.
https://doi.org/10.1007/s12200-008-0044-y
In electronic speckle pattern interferometry (ESPI), because saw-tooth phase map obtained by phase-shifting is inherently full of speckle noise, noise reduction should be carried out to suppress high-level noise before it is unwrapped. In accordance with the feature of the saw-tooth phase map, an adaptive filter method combining the classical sine/cosine filter and the fringe orientation information of the phase map is developed. A fringe orientation map is first generated from the saw-tooth phase map, and then a fringe-contoured window is derived accordingly. Finally, filtering is carried out within the window. Compared with existing filters, it has a better performance on phase jump information preservation without any blurring effect on phase distribution provided that filtering is implemented on the equal-phase window. Moreover, its capability for noise reduction is more powerful. The effectiveness and advantages of the novel filter have been also verified by both simulated and real saw-tooth phase maps.
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