Contents
2005
Volume: 25 Issue 7
28 Article(s)
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Fiber Optics and Optical Communications
Time-Domain Addressing Technique for Fiber Bragg Grating Sensor System with the Function of Real-Time Monitoring
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The emission of light wave from a pulsed broadband source controlled by a clock is injected into a four-element fiber Bragg grating sensor array. A technique of time-domain addressing is introduced to interrogate the gratings spaced 10 m apart by employing a 1×4 analog electrical switches, which is controlled by tThe emission of light wave from a pulsed broadband source controlled by a clock is injected into a four-element fiber Bragg grating sensor array. A technique of time-domain addressing is introduced to interrogate the gratings spaced 10 m apart by employing a 1×4 analog electrical switches, which is controlled by the same clock. The switches allocate the pulses reflected by the sensor elements into corresponding output channels to make the system performing the function of real-time monitoring the measurand. Demodulated with an unbalanced Michelson interferometer, which converts the wavelength shifts to phase changes, the system is demonstrated to be with a sensing sensitivity of 1.658°/με at the wavelength of 1556 nm. It matches the theoretical value of 1.673°/με basically..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 7, 865 (2005)
Effect of Chromatic Dispersion on the Feedback Signal in Polarization Mode Dispersion Compensation
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The effect of chromatic dispersion (CD) on the degree of polarization (DOP) feedback signal in polarization mode dispersion (PMD) compensation is analyzed. Signal suffering from PMD and CD shows a larger DOP than that in the only PMD case, and their DOP deviations relate not only to the polarization splitting ratio or The effect of chromatic dispersion (CD) on the degree of polarization (DOP) feedback signal in polarization mode dispersion (PMD) compensation is analyzed. Signal suffering from PMD and CD shows a larger DOP than that in the only PMD case, and their DOP deviations relate not only to the polarization splitting ratio or relative delay between the signal′s two polarization components, but to the bit error rate and the CD values; But the system performance collapses after a firstly slight improvement with the increasing of CD, as the experiments in 2.5 Gb/s NRZ modulated system and the simulations in 10 Gb/s system show. Therefore DOP can no longer reflect the effect of PMD on system performance in presence of CD. The less the energy difference between two cross-polarization components, or the larger the differential group delay, the greater the signal DOP deviates, and the deviations increase rapidly with the system ratio and CO increase. Modifications to the DOP distortion in PMD compensation are proposed finally, which indicate that CD must be compensated before PMD in actual systems when the effects of PMD and CD simultaneously exist..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 7, 869 (2005)
Development of Optimizing System of Two-Paramenters for Sensing Pressure and Temperature with Dual-Fiber Bragg Grating Sensor
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A new structure of fiber Bragg grating (FBG) sensor based on sticking two FBGs on tubular elastic element is developed. Simultaneous measurement for the pressure and temperature has been experimented by two FBGs producing two wave spike respectively. In the range of 0～20 MPa and 20～150 ℃, the FBG's Bragg wavelengthA new structure of fiber Bragg grating (FBG) sensor based on sticking two FBGs on tubular elastic element is developed. Simultaneous measurement for the pressure and temperature has been experimented by two FBGs producing two wave spike respectively. In the range of 0～20 MPa and 20～150 ℃, the FBG's Bragg wavelength change is linear to the pressure and temperature. The pressure and temperature sensitivities are 0.089 nm/MPa and 0.024 nm/℃ respectively. The experimental value of coefficient matrix of the FBG's wavelength change to pressure and temperature is coincidented with the theoretical value very well, and the relative error is 1.8%. Compared with the standard measurement method, and the accuracies of pressure and temperature are 0.47% and 0.74% respectively. The method can cut the error arising from the temperature cross-sensitivity in pressure, the error of which is about 0.16% as pressure and temperature are at 20 MPa and 150 ℃ respectively..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 7, 875 (2005)
Fourier Optics and Signal Processing
Optical Image Encryption Based on Cascaded Phase Retrieval Algorithm
[in Chinese], and [in Chinese]
A new technique of optical image encryption and decryption based on the methodology of virtual optics is proposed. The technique is based on the free space propagation optical system and encodes the target image into two different phase masks (PM) by using cascaded iterative angular spectrum phase retrieval approach (CA new technique of optical image encryption and decryption based on the methodology of virtual optics is proposed. The technique is based on the free space propagation optical system and encodes the target image into two different phase masks (PM) by using cascaded iterative angular spectrum phase retrieval approach (CIASA) and both two phase masks can serve as enciphered texts. The proposed algorithm employs an improved scheme, i.e. modifying the phase distributions of two phase masks synchronously and enlarging the search space, and the time complexity of the algorithm is discussed, too. Computer simulations show that the algorithm generates much faster convergence and better image quality for the decrypted image and key space enlarged. These characters may introduce high security-level that makes the encrypted image much harder to be decrypted by an unauthorized person..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 7, 881 (2005)
Geometric Optics
Exact Calculation of the Lateral Displacement and Optical Path Difference of Savart Polariscopes
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The shearing principle of Savart polariscope in the static polarization interference imaging spectrometer (SPIIS) is presented and the exact expression of the lateral displacement and optical path difference (OPD) are deduced by ray-tracing method and the notion of ray index at random incidence angle. The theoretical aThe shearing principle of Savart polariscope in the static polarization interference imaging spectrometer (SPIIS) is presented and the exact expression of the lateral displacement and optical path difference (OPD) are deduced by ray-tracing method and the notion of ray index at random incidence angle. The theoretical and practical guidance are thereby provided for the study, design, modulation, experiment and engineering of the polarization interference imaging spectrometers..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 7, 885 (2005)
Image Processing
Research on Fusion of Hyperspectral Remote Sensing Image Based on Second Generation Wavelet
[in Chinese], [in Chinese], and [in Chinese]
There are hundreds of bands in hyperspectral remote sensing image and the bands are highly correlative, difficulty of analysis can be reduced by using fusion technology. A novel structure of second generation wavelet weighting fusion algorithm is proposed. Firstly, image is decomposed into two serials, which are predicThere are hundreds of bands in hyperspectral remote sensing image and the bands are highly correlative, difficulty of analysis can be reduced by using fusion technology. A novel structure of second generation wavelet weighting fusion algorithm is proposed. Firstly, image is decomposed into two serials, which are predicted and updated by two-order Neville filter on rectangle and quincunx grid by turns. Secondly, feature level second generation wavelet fusion is carried on the updated serial by using the variance of each band as the feature of fusion. Finally the image is reconstructed by reverse second generation wavelet. In order to test the effect of the new method, hyperspectral remote sensing image of airborne visible and infrared imaging spectrometer is simulated on Pentium IV computer. Compared with typical fusion method such as principal component analysis and discrete wavelet transform, the result of the experiment shows that the proposed method can retain spatial and spectral feature, the entropy is bigger than principal component analysis 0.1949, and bigger than discrete wavelet transform 0.7998..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 7, 891 (2005)
Study on Multispectral Photography with θ Multichannel Modulator
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A multispectral photography of white-light optic/digital image processing with θ-multichannel modulator is brought forward, in which θ-multichannel modulator is used to modulate the several waveband information of the object, and the technique of Fourier transform is employed to decode the modulated image, then wavebanA multispectral photography of white-light optic/digital image processing with θ-multichannel modulator is brought forward, in which θ-multichannel modulator is used to modulate the several waveband information of the object, and the technique of Fourier transform is employed to decode the modulated image, then waveband information of the object is demodulated. Afterwards, a multispectral pseudo-color image can be obtained by means of pseudo-color fusion. A new multispectral system consists of θ-multichannel modulator and a single CCD. And it provest to be feasible to substitute the new system for traditional one composed by several cameras with different bands. Compared with the traditional multispectral photography system, the new one has many advantages, such as small volume and weight, easy operation in pseudo-color fusion..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 7, 897 (2005)
Instrumentation, Measurement and Metrology
Influence Factor Analysis of Sensitivity of Focus Criteria Function
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The precision of auto-focus system has been affected directly by the sensitivity of focus criteria function. In many researches about performance of focus criteria functions, the sensitivity of each different function is commonly compared, but ignoring that the sensitivity of focus criteria function is not only connectThe precision of auto-focus system has been affected directly by the sensitivity of focus criteria function. In many researches about performance of focus criteria functions, the sensitivity of each different function is commonly compared, but ignoring that the sensitivity of focus criteria function is not only connected with the function itself but also with the parameters, such as area size selected by focus and the spatial frequency of image. Sensitivity of focus criteria function is firstly deduced from the basic function of the imaging theory. Then according to the function, conclusion is drawed near by focus of optical system that the sensitivity of focus criteria function is directly high-order proportional to relation with the spatial frequency of image and linear with the size of focus-area, and inversely proportional to the wavelength of the lighting power and spatial cutoff frequency of optics system. The experiments demonstrated that the theoretical analysis is correct. To some purpose it can provide theoretical guide to the design of auto-focus system and select clearly and control each parameter of focus system to further enhance the precision of autofocus..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 7, 902 (2005)
Study on the Digital Speckle Correlation Method for In-Plane Displacement Measurement in the Case of Slant Optical Axis
[in Chinese], [in Chinese], and [in Chinese]
To resolve the long-range displacement and displacement field measurement by using optical method in engineering environment, the influence of image blurring and image position's change on white light digital speckle correlation method are investigated in the case of slant optical axis, and theoretical formula of tTo resolve the long-range displacement and displacement field measurement by using optical method in engineering environment, the influence of image blurring and image position's change on white light digital speckle correlation method are investigated in the case of slant optical axis, and theoretical formula of the error was given. To weaken the influence of image position's change, the reference measurement technology was introduced and a new high-resolution method of measuring in-plane displacement measurement in the case of slant optical axis was given. The static flexibility measurement of object at distance of 2～50 m is accomplished with the maximal relative error of 1.0%, the technology has a better accuracy both in laboratory environment and engineering environment. It demands no circumstance requirements in common optical axis and is especially effective in flexibility measurement of bridge and cloverleaf junction. It also fits for dynamic displacement measurement when a high-speed image card was used. This technology expands digital speckle correlation method's application field..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 7, 907 (2005)
Extraction of Intrinsic Response of Semiconductor Lasers Using Improved Optical Modulation Technique
[in Chinese], [in Chinese], and [in Chinese]
An improved all-fiber-connected optical modulation setup has been established for the direct measurement of the intrinsic frequency response of semiconductor lasers. The analytical expression of the dynamic response of high-speed semiconductor lasers has been deduced from the rate equations. The measurements have been An improved all-fiber-connected optical modulation setup has been established for the direct measurement of the intrinsic frequency response of semiconductor lasers. The analytical expression of the dynamic response of high-speed semiconductor lasers has been deduced from the rate equations. The measurements have been made with a calibrated vector network analyzer (VNA), and the effects of the pump laser and photodetector have been removed from the measured data using direct-subtracting method and mutual-subtracting method. The accurate intrinsic frequency response of semiconductor lasers can therefore be obtained. The experiment shows that the results obtained using these two methods agree well as expected. It is not only an improvement of extracted data, but also an extension to the range of measurable frequency..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 7, 913 (2005)
Method for Modulation Transfer Function Measurement of Linear Sampled Imaging System Using Random Bar Targets
[in Chinese], and [in Chinese]
The measurement of modulation transfer function (MTF) of the sampled imaging opto-electronic system is rather complex and irrepeatable for their shift-variant characteristics. Based on the theory of statistical optics and stochastic process, the correlation relationship of spatially discrete random signal pattern and iThe measurement of modulation transfer function (MTF) of the sampled imaging opto-electronic system is rather complex and irrepeatable for their shift-variant characteristics. Based on the theory of statistical optics and stochastic process, the correlation relationship of spatially discrete random signal pattern and its correspoding image through a linear optical imaging system are analyzed. A method using random bar pattern for modulation transfer function measurement is proposed, and the emulational experimental result is demonstrated. The random bar pattern test method reduces the effect of sample-scene phasing of sampled imaging device in statistical sense. This method is also adapted to the MTF measurement of commonly shift-invariant optical system and is expected to greatly improve the flexibilities and automation degree of MTF testing..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 7, 918 (2005)
Study on the Autofocus Evaluation Function in Ellipsometric Imaging System
[in Chinese], [in Chinese], and [in Chinese]
Auto focusing is key technique in ellipsometric imaging system. The process is studied by use of several autofocus' evaluation functions. FIB on Si wafer and multi-channel proteinchip has been used in experiment. The change of functions value has been studied. The effect of noise and selected area used for auto focAuto focusing is key technique in ellipsometric imaging system. The process is studied by use of several autofocus' evaluation functions. FIB on Si wafer and multi-channel proteinchip has been used in experiment. The change of functions value has been studied. The effect of noise and selected area used for auto focusing are evaluated. The experiment shows that Laplacian function and Sobel function are suitable for this system. By using several frames to get average result, the effect of noise has reduced to good level when the number of frame more than 9. Along the same sharp edge, selecting different areas for autofocus, it has no influence on result. Using autofocus evaluation function to get the focus image of tilting plane, and the result agrees with the theoretical plane of image. It has been confirmed that autofocus evaluation function can be used in ellipsometric imaging system..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 7, 923 (2005)
Lasers and Laser Optics
Joule Level XeF Laser Operating in the Blue-Green Region
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The design of XeF(C-A) laser and measuremant of the pumping source radiation ability are given. The results of experimental study on XeF(C-A) laser properties under different conditions of initial XeF2 concentration, output transmissivity and gas components are reported and analyzed in detail. The area of discharge cirThe design of XeF(C-A) laser and measuremant of the pumping source radiation ability are given. The results of experimental study on XeF(C-A) laser properties under different conditions of initial XeF2 concentration, output transmissivity and gas components are reported and analyzed in detail. The area of discharge circuit is reduced efficiently by using the compact pumping source, and the equivalent inductance of discharge circuit is decreased to about 330 nH, so that the deposited efficiency is up to 74% and the average deposited power density of the pumping source is about 12 MW/cm. Radiative intensity of pumping source is diagnosed by calculating XeF2 photodissociation wave evolvement which is photographed by framing camera. The photon flux in the wavelength of 140～170 nm is about 5×1023 s-1cm-2 of which the radiative brightness temperature is more than 25 kK. The effective gain length of laser is 80 cm and a plane-spherical stable resonator is used. A laser energy output in joule level is stably obtained. The maximum output energy is 2.5 J with the total conversion efficiency of 0.1%, and the laser pulse width is about 700 ns..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 7, 930 (2005)
Experimental Analysis of Spectral Properties of (Tm,Ho)∶YLF Laser Pumped by a Laser Diode
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The tunability and high gain amplification of (Tm,Ho)∶YLF crystal with wide spectral band in the range from 2047～2070 nm are studied in theory and experiment. The crystal length and (Tm,Ho) doped concentration are optimized for room operation and high gain amplification. The microchip Tm(fraction of number of atoms 0.0The tunability and high gain amplification of (Tm,Ho)∶YLF crystal with wide spectral band in the range from 2047～2070 nm are studied in theory and experiment. The crystal length and (Tm,Ho) doped concentration are optimized for room operation and high gain amplification. The microchip Tm(fraction of number of atoms 0.06),Ho(fraction of number of atoms 0.004)∶YLF laser is tunable from 2.0656～2.0671 μm under pumping power of 1.88 W at 792 nm. The 2.048 μm radiation from (Tm,Ho)∶GdVO4 laser is amplified by cryogenic Tm(8%), Ho(1.4%)∶YLF amplifier dual-end pumped by two 15 W fiber-coupled laser diodes, an amplification factor of 2.5 is achieved. The blue-green upconversion fluorescence spectral from (Tm,Ho)∶YLF laser under strong pumping condition are measured within the radiation range of 480～492 nm and 530～550 nm..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 7, 935 (2005)
La3Ga5SiO14 as Active Electrooptic Q-Switch in a Pulsed Nd∶LiYF Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A Nd∶LiYF(Nd∶LYF) laser actively Q-switched with an electrooptic La3Ga5SiO14 (LGS) single crystal was designed. Each end of the Nd∶LiYF rod was cut at Brewster′s angle and the orientation of the two surfaces with respect to the crystal′s optic axis was such as to ensure operation at 1.053 μm, which saved the use of a pA Nd∶LiYF(Nd∶LYF) laser actively Q-switched with an electrooptic La3Ga5SiO14 (LGS) single crystal was designed. Each end of the Nd∶LiYF rod was cut at Brewster′s angle and the orientation of the two surfaces with respect to the crystal′s optic axis was such as to ensure operation at 1.053 μm, which saved the use of a polarizer. LGS Q-switch has the advantages of small insertion loss (2%), high damage threshold (950 MW/cm2) and non-deliquescence. When the pump energy was 120 J and the repetition rate was 3 Hz, the energy of single pulse was 275 mJ, pulse width was 8 ns, dynamic to static ratio was 76%, pulse fluctuation was smaller than 3%, polarization degree was more than 99%, and beam divergence was 0.7 mrad. The polarization characteristics of the laser, the design of the unstable cavity, the characteristics of the thermal effect of LiYF and its compensation were discussed. The principle, characteristics and problems of the LGS E-O Q-switch were also investigated..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 7, 939 (2005)
Machine Vision
Study on Single Camera Simulating Stereo Vision Measurement Technology
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Based on the three-dimensional binocular vision sensor measurement model, a kind of low cost single camera model used to measure coordinates in space was established. By using optical imaging, the single camera was imaged as two virtual cameras. Two parallax images which screened by the same object can be collected in Based on the three-dimensional binocular vision sensor measurement model, a kind of low cost single camera model used to measure coordinates in space was established. By using optical imaging, the single camera was imaged as two virtual cameras. Two parallax images which screened by the same object can be collected in the same charge coupled device (CCD) image surface. Then the three-dimensional information of the measured points can be retrieved. The principle of measuring coordinates in space by single camera sensor was discussed, and the single camera sensor model was constructed. This method overcame some disadvantages in double cameras system, such as high system cost, reduction of the measurement speed when switching the image of two cameras, and provided an economical, rapid, useful measuring approach. Experiment showed that the sensor can attain relative accuracy about 0.8％ which indicated the rationality and effectivity of this method..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 7, 943 (2005)
Materials
Research of the Morphologies and Structure of γ-LiAlO2 Annealed in Various Atmospheres
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
(001) γ-LiAlO2 plates grown by temperature gradient technique (TGT) have been annealed in Li-rich and O2 atmosphere at 1100 ℃/70 h. The surface structure, morphology and absorption spectra were investigated through scanning electron microscopy, X-ray diffraction, spectrophotometer at room temperature. Compared to the p(001) γ-LiAlO2 plates grown by temperature gradient technique (TGT) have been annealed in Li-rich and O2 atmosphere at 1100 ℃/70 h. The surface structure, morphology and absorption spectra were investigated through scanning electron microscopy, X-ray diffraction, spectrophotometer at room temperature. Compared to the plate annealed in Li-rich atmosphere, the surface of the plate annealed in O2-atmosphere became coarse and grew Li-poor polycrystalline (LiAl5O8). With the all spectral analysis, it is confirmed that the 196 nm absorption peak is probably caused by Li vacancies in the plate..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 7, 949 (2005)
Research on Performance of Tb3＋-Doped Silicate Luminescent Glass for High-Energy X-Ray Application
[in Chinese], [in Chinese], and [in Chinese]
X-ray to light convertor in a real time radiography image formation system plays an important role. A new type of Tb3＋-doped silicate luminescent glass has been developed recently. It can take the place of traditional rare earth fluorescent screen in high energy radiography applications because of no visible light dispX-ray to light convertor in a real time radiography image formation system plays an important role. A new type of Tb3＋-doped silicate luminescent glass has been developed recently. It can take the place of traditional rare earth fluorescent screen in high energy radiography applications because of no visible light dispersion in it. For its spatial resolution will not greatly reduce when its thickness increases within a certain range, a thicker glass can be used in order to reach a higher DQE. The luminescent glass can be used in a radiography image formation system which adopt a high energy X-ray source up to 30 MeV. The spatial resolution is about the same as 301 type luminescent glass excited by 100 keV X-ray and the spatial resolution may not be less than 1.5 lp/mm when excited by 12 MeV X-ray. Its luminescence intensity is about 3 times of 301 type. Some effects on its characters of main ingredient materials (BaO, Cs2O, Tb2O3, Gd2O3, Ce2O3) are also researched in the way of changing the mass percentage and appropriate ingredient configuration for high performance is derived. Optical performances are tested and results are given out..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 7, 953 (2005)
Optical Design and Fabrication
Programmable Lens and Lenslet Array by Operating a Liquid Crystal Device
[in Chinese], [in Chinese], and [in Chinese]
The property of the computer programmable optical devices is investigated. The programmable lenses have been performed by operating an electrically addressable liquid crystal spatial light modulator (LC-SLM) in amplitude mode, binary phase mode, and continuous phase mode. The programmable lenslet arrays have also been The property of the computer programmable optical devices is investigated. The programmable lenses have been performed by operating an electrically addressable liquid crystal spatial light modulator (LC-SLM) in amplitude mode, binary phase mode, and continuous phase mode. The programmable lenslet arrays have also been carried out experimentally. Both the experimental and calculating results show that the continuous phase mode provides the best results in terms of both light efficiency and focus quality. The advantage of the programmable lenslet array over the conventional one is that each lenslet in the array can be controlled individually. An 8×8 array mode without the central 4×4 light spot array generator has been demonstrated experimentally. The programmable lens was also implemented as a convenient way of investigating the aberration of the lenses experimentally. Although the computer programmable LC-SLM device has its great flexibility, its finite pixel size limits its fineness and, therefore, limits its applications..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 7, 959 (2005)
Tentative Fabrication Test for Large Aperture Thin Astronomical Mirror
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A tentative fabrication test for thin astronomical mirror has been done. In the test, the active support system is used. The mirror is a meniscus spherical mirror and its parameters are as follows: the diameter is 1035 mm, radius of curvature is 3220 mm, and aspect ratio is close to 40. During the processing, the mirrA tentative fabrication test for thin astronomical mirror has been done. In the test, the active support system is used. The mirror is a meniscus spherical mirror and its parameters are as follows: the diameter is 1035 mm, radius of curvature is 3220 mm, and aspect ratio is close to 40. During the processing, the mirror was supported by 55 supporting points in its back surface. The positions of supporting points and the magnitude of supporting force supplied by force actuators were analyzed by using finite element analysis software. In all of 55 supporting points, 3 points are fixed and the rest are active support which is linked with force actuator. The low-frequency error on the mirror can be corrected when the forces of actuators were adjusted. Finally root mean square (RMS) of surface accuracy error is less than 0.0465λ, RMS of high-frequency error is less than 0.0435λ. It is demonstrated that the technique is suited for fabrication of astronomical thin mirror..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 7, 965 (2005)
Optical Devices
Characteristic Analysis of Multi-Cavities Fabry-Pérot Filters with Attenuation
[in Chinese], [in Chinese], and [in Chinese]
Multi-cavities Fabry-Pérot filter is a key device used in optical fiber communication system. To improve the transmission spectrum, the influence of attenuation on the device is discussed here. A matrix treatment is presented by two different methods based on multi-mirror theory to calculate the transmission charaMulti-cavities Fabry-Pérot filter is a key device used in optical fiber communication system. To improve the transmission spectrum, the influence of attenuation on the device is discussed here. A matrix treatment is presented by two different methods based on multi-mirror theory to calculate the transmission characteristics of the multi-cavities Fabry-Pérot filters with attenuation. As an example, the transmission of a three-cavities Fabry-Pérot filter with different attenuation is obtained. The comparison of simulated results indicated that the multi-mirror Fabry-Pérot filter with attenuation could suppress the crosstalk of intra-avities effectively, improves the transmission of the signal in the passband, and increase the utilization of the signal consequently. The relation of transmission with different attenuation is discussed primary, and also discussing the relationship of the value of peak transmission and the secondary peak transmission. Simulating by TFC approved the result. At last the method of increasing the reflection of mirrors to reduce attenuation is put forward for the sake of reducing the cost of the system. And the feasibility of the method is demonstrated by matrix calculation..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 7, 970 (2005)
Organic Optoelectronic Device with Switchable Character
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A new type of organic electro-optic device combining an organic light emitting diode with an organic photovoltaic cell is studied. The structure is ITO/NPB/Alq3/CuPc/C60/NPB/Alq3/LiF/Al. NPB/Alq3 functions as the light-emitting layer; meanwhile CuPc/C60 functions as a photonic/electric energy transfer cell. The device A new type of organic electro-optic device combining an organic light emitting diode with an organic photovoltaic cell is studied. The structure is ITO/NPB/Alq3/CuPc/C60/NPB/Alq3/LiF/Al. NPB/Alq3 functions as the light-emitting layer; meanwhile CuPc/C60 functions as a photonic/electric energy transfer cell. The device presents different current density-voltage and power density-voltage curves when in the forward voltage scan then in the backward voltage scan. These transition from a high (ON) to low (OFF) luminance renders a prototype to realize a switchable organic electroluminescence. The conversion efficiency of the optioelectric layer is 0.153%. Several methods to improve the conversion efficiency are also discussed..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 7, 976 (2005)
New Design of High Precision Achromatic Phase Retarder
[in Chinese], [in Chinese], and [in Chinese]
Achromatic retarder is such a device that can be used in wide spectrum in optical phase retardation. Based on the total-reflection phase transformation theory of the phase retardation, the principle of achromatic phase retardation with oblique incident angle is expounded. And based on the detailed design of Fresnel rhoAchromatic retarder is such a device that can be used in wide spectrum in optical phase retardation. Based on the total-reflection phase transformation theory of the phase retardation, the principle of achromatic phase retardation with oblique incident angle is expounded. And based on the detailed design of Fresnel rhomb, the parameters which induced the change of phase retardation are analyzed. The new achromatic retarder with the specific incident angle and high precision is designed by choosing suitable material in this papaer. It is shown at the achromatic property curve within the range of 365 nm to 1150 nm theoretically that the retardation error is smaller than 0.4°, which is nearly one-fifth of the ordinary Fresnel rhomb phase retardation. So the new design retarder can be used in wide spectrum, at the same time it has the characteristic of small retardation error and high precision..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 7, 980 (2005)
OPTOELECTRONICS
The Study of the Defect Modes and Coupling Characteristics of Photonic Crystals
[in Chinese]
The defect modes in two-dimensional square dielectric photonic crystals have been calculated, and the coupling characteristics of the defect modes of point defects have been simulated systematicly when the numbers of defects, the distance between two defects and the direction of coupling vary respectively, which is basThe defect modes in two-dimensional square dielectric photonic crystals have been calculated, and the coupling characteristics of the defect modes of point defects have been simulated systematicly when the numbers of defects, the distance between two defects and the direction of coupling vary respectively, which is based on the results of the calculation performed by solving Maxwell's equations using the supercell plane-waves expansion method. The results show that, split photon states change according to the distance between localized photons. When the defect separation becomes large, the interaction between localized modes becomes small, and the parity of the defect mode alternates as the inter-defect distance varies. The defect modes form a defect band in a photonic band gap when the number of coupled point defects increases. The parallel propagating plane waves can excite both the even and odd defect modes. However, the perpendicularly propagating plane waves can excite only the even mode. The defect modes of point defects can be decoupled along diagonal directions where the defect mode decays rapidly, each single micro-cavity is not coupled to its neighbor, and the eigenfrequency is independent of the wavevector..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 7, 984 (2005)
The Characteristic Studies in Photonic Crystal with Chirped and Apodized Structures
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The chirped photonic crystal and the apodized photonic crystal are constructed, and the characteristics of them are studied by finite-difference-time-domain (FDTD) method and perfectly matched layer (PML) technology. The different photonic crystal structures with different chirped coefficients, and with different apodiThe chirped photonic crystal and the apodized photonic crystal are constructed, and the characteristics of them are studied by finite-difference-time-domain (FDTD) method and perfectly matched layer (PML) technology. The different photonic crystal structures with different chirped coefficients, and with different apodized functions are compared. The result shows that the width of the bandgap in chirped photonic crystal is larger than the one of ordinary photonic crystal, and the center frequency of the bandgap is moved to the lower frequency. When the chirp coefficient increases as 0.002 in the range of 0 to 0.01, the width of the band becomes wider and the center frequency of the band is lower. The apodized function has analogic effect to the center frequency and the width of the bandgap..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 7, 990 (2005)
Thin Films
Studies on the Micro-Structure and Laser Damage Threshold of ZrO2 Thin Films Deposited at Different Parameters
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
ZrO2 is an important material used in high laser damage coatings. Influence on the microstructure of ZrO2 thin films deposited at different O2 partial pressure and substrate temperature was analysed by X-ray diffraction (XRD) technique, the surface roughness and laser damage threshold also were measured. The results shZrO2 is an important material used in high laser damage coatings. Influence on the microstructure of ZrO2 thin films deposited at different O2 partial pressure and substrate temperature was analysed by X-ray diffraction (XRD) technique, the surface roughness and laser damage threshold also were measured. The results showed that morphology transition from polycrystalline to amorphism occurred with O2 pressure increaed while from amorphism to polycrystalline occurred with substrate temperature increased. Simultaneously, it was found that the grain size was reduced with the increased O2 pressure but increased with the increasing substrate temperature. The surface roughness was improved with increasing O2 pressure but has little change with substrate temperature increased. The change of grain size have some relationship with the surface roughness. The damage results indicated that O2 pressure and substrate temperature can influence the laser damage threshold of ZrO2 thin films..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 7, 994 (2005)
Orientation-Enhanced Photorefractive Effect and Holographic Storage in Novel Azobenzene Doped Polymer Films
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A novel type of azobenzene molecule (Azo-diphenylamine) (ADPA) doped in poly (N-vinylcarbazole) (PVK), Poly-butylacrylate (PBA) and 2,4,7-trinitro-9-fluorenone (TNF) was synthesized and studied. The experimental results showed that the polymer film possesses strong photo-induced orientation-enhanced photorefractive effA novel type of azobenzene molecule (Azo-diphenylamine) (ADPA) doped in poly (N-vinylcarbazole) (PVK), Poly-butylacrylate (PBA) and 2,4,7-trinitro-9-fluorenone (TNF) was synthesized and studied. The experimental results showed that the polymer film possesses strong photo-induced orientation-enhanced photorefractive effect. The change value of photo-induced refractive index Δn surpasses 1.3×10-3. When irradiated by two-beams, the sample can set up refractive index grating with the diffraction efficiency over 30%. The optical holographic storage was achieved. The factors that influenced refractive index were discussed and the analysis to optical holographic storage was given..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 7, 999 (2005)
Determination of the Extinction Coefficient of TiO2 and Effect of Preparation Parameters
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Based on measurement of peak transmittance of narrow band filter, the extinction coefficient of a weakly absorbing thin film can directly be calculated. This is a new method used for determination of the extinction coefficients of weakly absorbing thin films with ease to do and very high precision. The principle of meaBased on measurement of peak transmittance of narrow band filter, the extinction coefficient of a weakly absorbing thin film can directly be calculated. This is a new method used for determination of the extinction coefficients of weakly absorbing thin films with ease to do and very high precision. The principle of measurement is illustrated and the precision of this method is analyzed. The effect of preparation parameters on the extinction coefficients of TiO2 films deposited by ion-beam-sputtering is discussed. The experiment shows that the deposition rate and ratio of Ar∶O2 during the deposition are important factors. When the rate reduces from 0.35 nm/s to 0.23 nm/s, the extinction coefficient of TiO2 film falls from 3.9×10-5 to 2.1×10-5; and when the ratio of Ar∶O changes from 1∶2 to 1∶4, the extinction coefficient of TiO2 film falls from 5.6×10-5 to 2.3×10-5. In addition, the optical loss increases with substrate temperature rising. It is proved that the determination of the extinction coefficient of weakly absorbing thin films, by means of measured peak transmittance of narrow band filter, is a successful method..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 7, 1005 (2005)
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