Contents
2004
Volume: 24 Issue 9
30 Article(s)
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Fiber Optics and Optical Communications
Study of the Reverse Dispersion Fiber with Depressed-Core Index Profile
[in Chinese], and [in Chinese]
Reverse dispersion fiber (RDF) with depressed-core index profile is fabricated successfully by using plasma-activated chemical vapor phase deposition. The fabricated RDF has a core-effective-area of 45 μm2, dispersion of -19.65 ps/(nm?km) and dispersion slope of -0.132 ps/(nm2?km) while maintaining the low bending induReverse dispersion fiber (RDF) with depressed-core index profile is fabricated successfully by using plasma-activated chemical vapor phase deposition. The fabricated RDF has a core-effective-area of 45 μm2, dispersion of -19.65 ps/(nm?km) and dispersion slope of -0.132 ps/(nm2?km) while maintaining the low bending induced attenuation and low PMD value. Furthermore, the hydrogen induced attenuation at 1530 nm decreases to the value of less than 0.01 dB/km by optimizing the dopant concentration of different core layer. The dispersion managed pairs, consisting of RDF and non-zero dispersion shifted fiber with ultra large effective-core-area (ULAF), have the ultra low dispersion slope of less than 0.006 ps/(nm2·km) at the wavelength range from 1530 nm to 1625 nm, and the largest dispersion value is lower than 0.2 ps/(nm?km). Moreover, the attenuation characteristic also shows a remarkable flatness over the broad-band wavelength, and the attenuation at 1550 nm is as low as 0.224 dB/km. The dispersion managed pairs are applicable for large capacity, high bit-rate long-haul wavelength division multiplexing (WDM) transmission system without using dispersion compensation mode..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 24, Issue 9, 1181 (2004)
Study on Characteristics of Two High-Birefringence Fiber Loops Mirror Filter
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Birefringence fiber loop mirror has filtering characteristics. By cascading two loops, the transmission performance can be improved and become more flexible compared with that of the single-stage one. Such a simple cascading scheme which can improve filtering characteristics of loop mirror, is proposed. The transmissioBirefringence fiber loop mirror has filtering characteristics. By cascading two loops, the transmission performance can be improved and become more flexible compared with that of the single-stage one. Such a simple cascading scheme which can improve filtering characteristics of loop mirror, is proposed. The transmission characteristics of the loop mirror filter constituted by birefringence fiber and Sagnac loop have been analyzed in detail. The filtering characteristics of two cascaded birefringence fiber loop mirror are discussed. By numerical simulation, explicit expression of the transmission spectrum for the cascaded mirrors with the high-birefringence fiber (HBF) length ratio of 1∶2 is obtained. Compared with its single-stage counterpart, the 3 dB bandwidth of the two-stage filter is compressed to approximately 7 nm and its quality factor reaches about 4.5. Experimental results conform well with the theoretical calculation, thus proving the validity of this theory..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 24, Issue 9, 1185 (2004)
Analysis and Fabrication of Tunable Edge Fiber Bragg Grating Filters
[in Chinese], [in Chinese], and [in Chinese]
The index modulation function of edge fiber Bragg grating (EFBG) is acquired using genetic algorithms synthesizing, and a method for fabricating tunable EFBG by changing the diameter of the fiber along its axis and applying tension to the fiber grating is proposed and testified. The influence of physical parameters of The index modulation function of edge fiber Bragg grating (EFBG) is acquired using genetic algorithms synthesizing, and a method for fabricating tunable EFBG by changing the diameter of the fiber along its axis and applying tension to the fiber grating is proposed and testified. The influence of physical parameters of the device on the edge filter's reflection spectrum is analyzed. An EFBG with a bandwidth of 0.7 nm at shorter wavelength side and a peak reflectivity of 96% is fabricated by ultraviolet laser-scanning. The edge bandwidth of the fiber Bragg grating may be adjusted by tension and the edge bandwidth at shorter wavelength side increases from 0.7 nm to 2.3 nm as the tension increased from 0 to 1.715 N..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 24, Issue 9, 1189 (2004)
Transmission Properties of Elliptical-Hole Photonic Crystal Fiber with a Central Defect Hole in the Core Region
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Based on the supercell overlapping method developed before by authors, the full vector is adopted to model transmission properties of elliptical-hole photonic crystal fiber (EHPCF) with a central smaller elliptical-hole core. It is concentrated on the influence of the smaller central elliptical hole on modal field, modBased on the supercell overlapping method developed before by authors, the full vector is adopted to model transmission properties of elliptical-hole photonic crystal fiber (EHPCF) with a central smaller elliptical-hole core. It is concentrated on the influence of the smaller central elliptical hole on modal field, modal birefringence and dispersion. It was found that this EHPCF has a larger birefringence than the solid core EHPCF does because of the introduction of the smaller central hole. The transmission properties strongly depend on wavelength and the structure parameter of the EHPCF. The birefringence will increase due to an increase in the wavelength and the central smaller elliptical-hole core. The magnitude of birefringence can attain the level of 10-3. The broadband flat dispersion or anomalous dispersion can be obtained through changing the structure parameter of this EHPCF. The numerical results show that there is 400 nm flat dispersion region near the wavelength 1.55 μm in this EHPCF with the central small holes dc=0.4D..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 24, Issue 9, 1193 (2004)
Theoretical and Experimental Research on Voltage Sensing Based on Attenuated-Total-Reflection
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A new type of voltage sensor which uses the prism and symmetrical metal-cladding polymer waveguide configuration has been proposed. The structure consists of a coupling prism and 3-layer film that prepared on the bottom of prism in proper order. The 3-layer films are metal layer, poled polymer, bottom electrode. Owing A new type of voltage sensor which uses the prism and symmetrical metal-cladding polymer waveguide configuration has been proposed. The structure consists of a coupling prism and 3-layer film that prepared on the bottom of prism in proper order. The 3-layer films are metal layer, poled polymer, bottom electrode. Owing to the electrooptical effect of the poled polymer, and the sensitive feature of its refractive index to the resonance obsorption peak of the guided mode, the voltage change can be determined through the measurement of the light intensity when applying voltage on the poled polymer. The measurement range of voltage is from -140 V to 140 V in the experiment. The linearity is 0.991. The resolution of voltage measurement is 0.1 V-1. The sensitivity coefficients is about 0.0011 V-1. The experimental results show the fine linearity and the high sensitivity of the proposed voltage sensor..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 24, Issue 9, 1199 (2004)
Optical Power Distribution in Multimode Polymer Optical Fiber under Offset Launching
[in Chinese], [in Chinese], and [in Chinese]
Numerical and experimental studies of cross sectional optical power distribution (OPD) in polymer optical fiber under offset launch are given. The OPD of fibers with various lengths and under various launch offsets are numerically simulated by using ray tracing method and measured by two-dimensional CMOS image detectorNumerical and experimental studies of cross sectional optical power distribution (OPD) in polymer optical fiber under offset launch are given. The OPD of fibers with various lengths and under various launch offsets are numerically simulated by using ray tracing method and measured by two-dimensional CMOS image detector array. Results show that the OPD shifts gradually away from axis center and forms ring with increasing of launch offset and the circular uniformity increases with the length of fiber. OPD measurements are taken on bend fibers under center launch. It is indicated that the OPD shift gradually away from axis to outer radii with the decrease of curvature radii when curvature radii are far greater than critical radius of curvature. When curvature radii decrease to critical radius, the OPD is significantly broaden under mode coupling effect..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 24, Issue 9, 1259 (2004)
The Research of Coarse Wavelength Division Multiplexer Based on Array Waveguide Grating with Broadened Pass-Band and Low Crosstalk
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A CWDM with a 20 nm spacing and 8 channels based on AWG is successfully fabricated on 4-inch Si wafer using 0.75%-Δ silica-based waveguides by planar lightwave circuit (PLC) technology. Both simulations and measured results show that broadened pass-band (1 dB bandwidth is above 10 nm)and low crosstalk (no less than 24 A CWDM with a 20 nm spacing and 8 channels based on AWG is successfully fabricated on 4-inch Si wafer using 0.75%-Δ silica-based waveguides by planar lightwave circuit (PLC) technology. Both simulations and measured results show that broadened pass-band (1 dB bandwidth is above 10 nm)and low crosstalk (no less than 24 dB) are realized by applying a short multimode interference (MMI) structure at the end of input waveguide. The design and fabrication process are introduced, and the simulations and measured results are discussed..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 24, Issue 9, 1265 (2004)
An Optimized Design of Interleaver Filter Based on Planar Lightwave Circuit-Type Lattice Structure
[in Chinese], [in Chinese], and [in Chinese]
On the basis of analyzing the principles of interleaver filters of the interference of polarized light and planar lightwave circuit-type lattice structure, the equivalent mathematical representation of the spectral transmittance of the two kinds of interlearers is revealed. The equivalent relationships of the structuraOn the basis of analyzing the principles of interleaver filters of the interference of polarized light and planar lightwave circuit-type lattice structure, the equivalent mathematical representation of the spectral transmittance of the two kinds of interlearers is revealed. The equivalent relationships of the structural parameters of them are given. The interleaver filter baged on planar lightwave circuit-type lattice structure can be designed through directly utlizing the structure parameters of crystal obtained by the method of companing Fourier series. A two-stage lattice structural interleaver filter is designed by the use of the method. Compared with only one group of structural parameters obtained using a lattice theory proposed recently, the designing method is more simple and efficient for isolation to be increased by 5 dB and many groups of structural parameters to be obtained..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 24, Issue 9, 1269 (2004)
Effect of The Fiber Dispersion Parameter on the Performance of Average-Soliton Transmission System
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The effect of optical fiber dispersion parameter on the performance of average-soliton transmission system using PSA as in-line amplifiers has been analyzed theoretically by computer simulation. The simulation results show that because of the phase-sensitive nature of PSA′s gain, fiber dispersion will cause soliton pulThe effect of optical fiber dispersion parameter on the performance of average-soliton transmission system using PSA as in-line amplifiers has been analyzed theoretically by computer simulation. The simulation results show that because of the phase-sensitive nature of PSA′s gain, fiber dispersion will cause soliton pulse amplitude descending and its width broadening. Moreover it will result in pulse wings presenting. The larger the fiber dispersion is, the more significant the pulse amplitude descending and its width broadening are, as well as the higher the wing′s amplitude is and the wider its width is, after long distance transmission. So for this system, in order to realize long distance transmission, the optical fiber dispersion coefficient must be small..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 24, Issue 9, 1274 (2004)
Fourier Optics and Signal Processing
Diffraction Characteristics of Local Volume Holographic Gratings
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Based on the three- dimensional coupled wave theory, the theory of diffraction of local volume holographic gratings recorded with arbitrary polarization plane waves is studied. Simple analytical expression for the amplitude profiles of the main component and cross component of transmitted and diffracted waves are obtaiBased on the three- dimensional coupled wave theory, the theory of diffraction of local volume holographic gratings recorded with arbitrary polarization plane waves is studied. Simple analytical expression for the amplitude profiles of the main component and cross component of transmitted and diffracted waves are obtained. The influence of the polarized azimuths of the incident wave during recording and reconstruction on the amplitude of the transmitted and diffracted waves is discussed. It is demonstrated that the conversion is seen to proceed more quickly for reducing the polarized azimuth at recording, but the output beam deviates more and more from the uniform amplitude distribution. It is also shown that owing to the different coupling values of between the diffracted and incident beams inside the grating from different directions of the electric vector, the amplitude profiles of the main component and cross component of the output beam are different from each other when the polarized azimuth at reconstruction is different..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 24, Issue 9, 1203 (2004)
Analysis of the Characteristics about the Digital Holography of the Spherical Reference Wave
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Based on some detailed theoretic analysis about the recording sampling and reconstructing separation requirement for the digital holography of the spherical reference wave, the relationship fulfilling above requirement for the lateral size of the object and CCD, the distance between the object, CCD and the reference waBased on some detailed theoretic analysis about the recording sampling and reconstructing separation requirement for the digital holography of the spherical reference wave, the relationship fulfilling above requirement for the lateral size of the object and CCD, the distance between the object, CCD and the reference wave point source are deduced. In the recorded plane, it is proved that the superposed complex amplitude of the scattering object is equivalent to that of a point source. The theoretic analysis and experimental results show.
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 24, Issue 9, 1209 (2004)
Image Fusion Based on Non-Separable Orthogonal Compact Supported Wavelet
[in Chinese], and [in Chinese]
Image fusion method based on non-separable orthogonal compact supported wavelet is presented. First a non-separable wavelet 4-channels filter bank using the theory of non-separable wavelets is constructed. The images involing the fusion are decomposed by the filter bank. We use the fusion algorithm as followImage fusion method based on non-separable orthogonal compact supported wavelet is presented. First a non-separable wavelet 4-channels filter bank using the theory of non-separable wavelets is constructed. The images involing the fusion are decomposed by the filter bank. We use the fusion algorithm as follow.
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 24, Issue 9, 1214 (2004)
Caustic Phenomena in Holographic Interferometry and Its Relation with the Interference Fringes
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In the experiments of real-time holographic interferometry, some dark shadow areas appear among the interference fringes. The dark shadow areas play a very important role in the fracture process. When the applied force increases near to the fracture stress, these dark areas extend in an accelerative manner and quickly In the experiments of real-time holographic interferometry, some dark shadow areas appear among the interference fringes. The dark shadow areas play a very important role in the fracture process. When the applied force increases near to the fracture stress, these dark areas extend in an accelerative manner and quickly leads to total rupture of the specimen. In fact, the appearing of these dark shadow areas are the phenomena of caustic in geometry optics. The shadow area is so-called shadow spot and the factor of stress intensity can be calculated by measuring the size of corresponding length of the shadow spot according to fracture mechanics theory. The research works on the relationship between interference fringes and the factor of stress intensity are introduced. The quantitative expression of this relationship has been found and introduced. It provides a basic foundation for calculating the results of the experiment in real-time holographic interferometry combine with caustic method..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 24, Issue 9, 1219 (2004)
Color Difference Weight Computer Color Matching Based Linear Dadabase
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Computer color matching is widely applied in industry such as textile printing and dyeing, paint, plastic and building material. The fundamental theory of computer color matching is the linear relationship between Kubelka-Munk function and concentration of dye. But in fact, Kubelka-Munk function is nonlinear with the cComputer color matching is widely applied in industry such as textile printing and dyeing, paint, plastic and building material. The fundamental theory of computer color matching is the linear relationship between Kubelka-Munk function and concentration of dye. But in fact, Kubelka-Munk function is nonlinear with the concentration of dye, which limits the wide appliation of computer color matching in China. Therefore, a kind of mathematical method is put forward and a linear dye database is set up accordingly. Spectrophotometric color matching is an important method for computer color matching. But the change of reflectivity of coordinative spectrum at each wavelength can cause different degree color difference for the object, and the change is sharp at some wavelength while it is lazier at others. So the different degree color difference weight factor at each wavelength is given for spectrophotometric color matching according to colorimetry, and provided with linear dye database. The result show that the linearity of the database is increased obviously and the use of color difference weight factor could improve the spectrophotometric color matching distinctly..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 24, Issue 9, 1224 (2004)
Geometric Optics
Design of 3-Zone Amplitude-Type Superresolution Pupil Filters
[in Chinese], [in Chinese], and [in Chinese]
At the special Strehl ratio( the ratio of the maximum intensity of the central core of the superresolving pattern to the Airy pattern) 3-zone amplitude-type pupil filters are designed by nonlinear programming and goal programming,which can let the imaging system resolutions of transverse,axial and 3-D reach the maximumAt the special Strehl ratio( the ratio of the maximum intensity of the central core of the superresolving pattern to the Airy pattern) 3-zone amplitude-type pupil filters are designed by nonlinear programming and goal programming,which can let the imaging system resolutions of transverse,axial and 3-D reach the maximum. Some superresolution optimization design models and examples are presented with figures testification. To suppress the sidelobe intensity which is concomitant with the increase of the resolutions, these filters are used in confocal scanning microscopic system, as a result, higher signal-to-noise and good image contrasts are achieved. The strategie can also be applied to designing phase-only or more than 3-zone amplitude-type superresolution filters, which gives some references for the design of superresolution filters..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 24, Issue 9, 1177 (2004)
Lasers and Laser Optics
Self-Mixing Speckle Interference Generated in Laser Diode
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Based on the theory of the speckle and the self-mixing interference in laser diode (LD), Fabry-Perot (F-P) cavity model is given. The dynamics solution of a laser diode is obtained in the case of a rough surface after studying and analyzing the self-mixing speckle interference (SMSI). The Gaussian correlation random suBased on the theory of the speckle and the self-mixing interference in laser diode (LD), Fabry-Perot (F-P) cavity model is given. The dynamics solution of a laser diode is obtained in the case of a rough surface after studying and analyzing the self-mixing speckle interference (SMSI). The Gaussian correlation random surface and its speckle field on the Fraunhofer plane as well as superposition of speckle filds and interference field are simulated, and theiry statistical characteristics of the optical intensity are also analyzed. Compared with the known experiment, the results of simulation agree with the known statistical properties. The output gain variation of a LD and its probability density function are obtained when the rough surface is moving across the light beam. The effects of illumination width and external cavity length on the changes of output gain of a LD are discussed. The experimental results agree with the simulation calculation..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 24, Issue 9, 1229 (2004)
High-Power Ytterbium-Doped Fiber Laser Based on Fiber Grating
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A double-clad Yb3+ doped fiber laser is made when choosing fiber grating as resonator and pumped by LD fiber-coupled modules, with tapered fiber to get all-fiber structure. Fusion is often adopted to incorporate the fiber grating with the double-clad fiber, and the inner-cladding shape of double-clad fiber (DCF) is quaA double-clad Yb3+ doped fiber laser is made when choosing fiber grating as resonator and pumped by LD fiber-coupled modules, with tapered fiber to get all-fiber structure. Fusion is often adopted to incorporate the fiber grating with the double-clad fiber, and the inner-cladding shape of double-clad fiber (DCF) is quasi-circular shape of Yb3+-doped silica fiber with 970 nm center wavelength of fiber output modules as pump source. When the current of pump source is 2.4 A, the single-tranverse-mode output with max output power of 10.8 W is obtained with FWHM of 0.54 nm at output wavelength of 1100.5 nm, and the slope efficiency of 59% is observed..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 24, Issue 9, 1237 (2004)
Side-Pumped Yb-Doped Double-Clad Fiber Laser
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Side-pumped Yb-doped double-clad fiber laser is studied with a novel technology of fiber-angle-polished side-coupler. In experiments, multimode fibers with small polished-angle end by advanced technics are acquired and the precision mechanical adjustments is used to aim the polished-angle multimode fiber end at the douSide-pumped Yb-doped double-clad fiber laser is studied with a novel technology of fiber-angle-polished side-coupler. In experiments, multimode fibers with small polished-angle end by advanced technics are acquired and the precision mechanical adjustments is used to aim the polished-angle multimode fiber end at the double-clad fiber side accurately. Several kinds of index-matching materials are adopted for research to find that the index-matching materials are critical to launching power and coupling efficiency in this kind of side-couplers. The fiber-angle-polished side-coupled technology is adopted to inject maximal pumping power of 1.12 W into double-clad fiber, and the highest coupling efficiency acquired is even near 80%. Using the side-coupled to pump a CW side-pumped Yb-doped double-clad fiber laser, maximum output power of 282 mW and slope efficiency of 55.5% are obtained by one pigtail laser diode pumping source. The experimental results demonstrate fiber-angle-polished side-coupling technology is a simple and efficient pumping way for Yb-doped double-clad fiber laser..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 24, Issue 9, 1240 (2004)
Materials
Research on the Deposition of Thick Silica on Silicon Substrate by Flame Hydrolysis Deposition
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Thick SiO2 and B2O3-P2O5-SiO2 cladding materials for waveguide are fabricated on single crystal silicon substrate by flame hydrolysis deposition and high-temperature consolidation. The micro-morphologies and phase structures of the samples are observed by scanning electron microscope (SEM) and X-ray diffraction (XRD). Thick SiO2 and B2O3-P2O5-SiO2 cladding materials for waveguide are fabricated on single crystal silicon substrate by flame hydrolysis deposition and high-temperature consolidation. The micro-morphologies and phase structures of the samples are observed by scanning electron microscope (SEM) and X-ray diffraction (XRD). The main research focuses on the cracking and crystallizing of the thick silica film deposited on silicon substrate. It can be seen from the SEM photo that the silica particles are porous and like a honeycomb. These particles have very high ratio surface area, which make it consolidated to form glass easily. The XRD spectrum indicates that these particles are completely non-crystal. But after consolidation, it can be seen obviously from the SEM photo that cracks appears on the silica film on the silicon substrate. And the XRD result shows a little of silica crystallized. However, the above-mentioned cracks and crystallization disappeared thoroughly by doping with small amount of B2O3 and P2O5 into SiO2. The silica waveguide cladding material fabricated by this procedure has a thickness above 20 micrometers. It has smooth and crack free surface and non-crystal phase structure. This B2O3-P2O5-SiO2 cladding material is very fit for fabricating all kinds of silica-on-silicon waveguide devices..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 24, Issue 9, 1279 (2004)
Large Size and High Quality BIBO Crystal Growth and Blue Laser Output
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A type Ⅰ SHG element with the length of 5 mm was fabricated from a high quality BIBO crystal grown with TSSG method. From the element 216 mW blue laser was obtained in a quasi-CW Nd∶YAG laser. The conversion efficiency is twice of that of LBO in the same condition.A type Ⅰ SHG element with the length of 5 mm was fabricated from a high quality BIBO crystal grown with TSSG method. From the element 216 mW blue laser was obtained in a quasi-CW Nd∶YAG laser. The conversion efficiency is twice of that of LBO in the same condition..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 24, Issue 9, 1283 (2004)
Nonlinear Optics
Second Harmonic Generation in AlN Film
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The crystal structure of AlN film deposited on a (100) surface of a sapphire by a DC reactive magnetron sputtering is studied by a X-ray diffraction, the diagram of the X-xay diffraction shows that the film made by this way is a single crystal film; using a Nd∶YAG laser with a repetition rate of 10 Hz,a pulse width of The crystal structure of AlN film deposited on a (100) surface of a sapphire by a DC reactive magnetron sputtering is studied by a X-ray diffraction, the diagram of the X-xay diffraction shows that the film made by this way is a single crystal film; using a Nd∶YAG laser with a repetition rate of 10 Hz,a pulse width of 10 ns, a maximum average power of 20 W and a maximum energy per pulse of 2 J as a pump. Its second harmonic generation is studied, some conclusions were analysed, and the results indicate that the AlN film deposited on a (100) surface of a sapphire can generate an effective second harmonic wave in a large range of incidence angle, and the generated power of the second harmonic wave is symmetric to the normal of the surface of the AlN film. This proves that the normal of the surface of the AlN film is the axis of the AlN..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 24, Issue 9, 1245 (2004)
Pulse Expanded and Delaying Effect of Second Harmonic Wave in CsLiB6O10 by Group Velocity Mismatching and Dispersion
[in Chinese], and [in Chinese]
Group velocity mismatching and group velocity dispersion of fs laser pulse in CsLiB6O10 crystal are analyzed. The coupled equations of ultra-short pulse SHG are deduced by Fourier transform. The second harmonic pumped by 532 nm, 50 fs fundamental wave through CLBO is simulated numerically. The results show that the groGroup velocity mismatching and group velocity dispersion of fs laser pulse in CsLiB6O10 crystal are analyzed. The coupled equations of ultra-short pulse SHG are deduced by Fourier transform. The second harmonic pumped by 532 nm, 50 fs fundamental wave through CLBO is simulated numerically. The results show that the group velocity delay of second harmonic is about 100 fs at 266 nm through 0.5 mm lengths CsLiB6O10 and the second harmonic shape is widened linearly with the increase of crystal length. The group velocity mismatching Δβ(2)1=226.243 fs/mm, and lowness and second order group velocity dispersion β(2)2=210.120 fs2/mm, β(3)2=65.587 fs3/mm are reported for second harmonic on CsLiB6O10 crystal. The results indicate that group velocity mismatching and group velocity dispersion lead to the widening and defomation of the harmonic..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 24, Issue 9, 1249 (2004)
Amplification and Compression of Ultrashort Optical Solitons in an Erbium-Doped Nonlinear Amplifying Fiber Loop Mirror Ⅱ Effects of the Loop Mirror and Input Pulse Characteristics
[in Chinese], and [in Chinese]
Recent work has shown that amplification and compression of ultrashort fundamental solitons in an erbium-doped nonlinear amplifying fiber loop mirror not only can avoid soliton distortion caused by nonlinear effects such as self-phase modulation etc., but also overcome the difficulty of adiabatic amplification that theRecent work has shown that amplification and compression of ultrashort fundamental solitons in an erbium-doped nonlinear amplifying fiber loop mirror not only can avoid soliton distortion caused by nonlinear effects such as self-phase modulation etc., but also overcome the difficulty of adiabatic amplification that the amplifier length must increase exponentially with the input pulse width. In this paper, the effects of loop and input pulse characteristics on the device performance are investigated. Numerical simulation has shown that, for given input pulses, the device performance is fairly insensitive to variations in the loop parameters such as the the loop length, loop gain and coupler 's power coupling coefficient ratio. For a fixed amplifying fiber loop mirror, the input pulse parameters such as pulse shape and initial input power fluctuation and the higher-order effects have small influence on the device performance. The initial frequency chirp of the input pulse has a larger influence on the output pulse-width but a small influence on the output soliton-quality..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 24, Issue 9, 1253 (2004)
Physical Optics
A Small Adaptive Optical Imaging System for Cells of Living Human Retina
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
By using adaptive optics technology, two sets of high-resolution imaging systems for living human retina have been developed. High-resolution imaging of living human retina in scale of cell is realized. In these systems, two novel types of 19- and 37-element small PZT deformable mirrors are used as wavefront correctorsBy using adaptive optics technology, two sets of high-resolution imaging systems for living human retina have been developed. High-resolution imaging of living human retina in scale of cell is realized. In these systems, two novel types of 19- and 37-element small PZT deformable mirrors are used as wavefront correctors respectively, wavefront errors are measured by Hartman-Shack wavefront sensors, light of diode laser reflected from the eye retina is used as the beacon for wavefront sensing, After the wavefront error of human eye has been corrected by the adaptive optics system under the control of a computer, a flash lamp is triggered to illuminate the retina, the high resolution images are captured by a CCD camera. The residual errors are less than λ/6 and λ/10 respectively. The corresponding resolutions at retina are 3.4 μm and 2.6 μm respectively, approaching the diffraction limit. Experiments show that the resolution of the 37-element system is better than the 19-element system..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 24, Issue 9, 1153 (2004)
A New Slicing Method Based on The Principle of Refraction and Reflection
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
To overcome the disadvantage of low contrast in the images taken with the traditional slicing method of reverse engineering, a novel slicing method of reverse engineering based on the principle of refraction and reflection of a prism is proposed to improve the contrast of the cross-sectional images. According to the reTo overcome the disadvantage of low contrast in the images taken with the traditional slicing method of reverse engineering, a novel slicing method of reverse engineering based on the principle of refraction and reflection of a prism is proposed to improve the contrast of the cross-sectional images. According to the reflectivity of the object, one of the illuminating methodsstraight illuminating or inclined illuminatingis adopted to get the sharp contrast images of bright object in dark background, or dark object in bright background. To adjust geometrical distortions caused by the refraction and reflection of the prism, a mathematical transformation model is set up to correct the image by means of software. This method has been applied to some cases of reverse measuring. The research confirms that this new slicing method has not only the advantage of high contrast, but also the clear and reliable contours of the cross-sectional images, what's more, there is no need of contrasting filling materials. It is hopeful that this method will play a great role in the reverse measuring of mechanical parts and models..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 24, Issue 9, 1159 (2004)
Method for Controlling Groove Depth and Duty Cycle of Rectangular Photoresist Gratings
[in Chinese], [in Chinese], and [in Chinese]
Rectangular photoresist gratings can be fabricated by taking advantage of the nonlinearity of photoresist. For rectangular gratings the task of controlling groove profile is simplified to controlling the duty cycle and groove depth. By monitoring diffraction intensity of latent image in photoresist in real time, the opRectangular photoresist gratings can be fabricated by taking advantage of the nonlinearity of photoresist. For rectangular gratings the task of controlling groove profile is simplified to controlling the duty cycle and groove depth. By monitoring diffraction intensity of latent image in photoresist in real time, the optimal exposure dose can be determined. Then, by observing characteristic behavior of the development-monitoring curve, the development process can be stopped at the moment when photoresist at the groove troughs is completely etched away. Therefore, rectangular grooves with clean troughs can be obtained; meanwhile the groove depth is kept equal to the initial photoresist thickness. Further development will reduce the duty cycle. It has been proven reliable by experiments and theoretical analysis. For gratings with 1200 lp/mm groove spacing, the groove depth up to 1 μm has been controlled accurately in authors' present fabrication, and the duty cycle value obtained is in the range 0.2 to 0.6. The experimental results have also demonstrated that good controllability of groove profiles depends on good fringe stability of the laser interference patterns..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 24, Issue 9, 1285 (2004)
Large-Shear Digital Speckle Interferometry Based on Liquid Crystal Phase Modulator
[in Chinese], and [in Chinese]
The large-shear digital speckle interferometry are employed to measure the out-of-displacement of concrete structure. Based on the phase-modulation theory of liquid crystal variable retarder, a retarder is an optical device that resolves a light wave into two orthogonal linear polarization components and produces a phaThe large-shear digital speckle interferometry are employed to measure the out-of-displacement of concrete structure. Based on the phase-modulation theory of liquid crystal variable retarder, a retarder is an optical device that resolves a light wave into two orthogonal linear polarization components and produces a phase shift between them. The liquid-crystal phase shifter is successfully incorporated into the large-shear digital speckle interferometry system to enhance the measuring sensitivity and accuracy. From the experiment used to measure the out-of-displacement of an object, the optimum performance of the method is confirmed. In the meantime, the new technique is provided to evaluate the mechanical behavior of concrete structure with different curing time with non-contact, high accuracy, full-field, real-time and in-situ. The experimental results show that the strength of concrete structure will be enhanced as its curing time goes on, and after 21 days the strength value will be approaching to the design value..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 24, Issue 9, 1292 (2004)
Thin Films
Green-Light Optical Storage Properties of Spin-Coated Thin Film of AgTCNQ Derivative
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A novel electron transfer composite Ag-TCNQ (C2H4COOCH3)2 film is described with spin-coating, absorption spectra, green-light (514.5 nm) static rewritable optical recording properties, and rewritable mechanism of this film is studied. The results show that there are two strong absorption peaks respectively at 388 nm aA novel electron transfer composite Ag-TCNQ (C2H4COOCH3)2 film is described with spin-coating, absorption spectra, green-light (514.5 nm) static rewritable optical recording properties, and rewritable mechanism of this film is studied. The results show that there are two strong absorption peaks respectively at 388 nm and 675 nm, which can be assigned to electronic transitions in anion radical TCNQ(C2H4COOCH)-2. Typical experimental results are as follows.
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 24, Issue 9, 1164 (2004)
Design of 90° Reflection-Induced Phase Retarder
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
When copper vapour laser mirror is used at an abnormal incidence the different phase shift of the polarization states may occurred. An optimum technique has been used to determine the layer thickness for a coating design that produce a 90° phase shift between the p- and s-polarization components over 490～530 nm whWhen copper vapour laser mirror is used at an abnormal incidence the different phase shift of the polarization states may occurred. An optimum technique has been used to determine the layer thickness for a coating design that produce a 90° phase shift between the p- and s-polarization components over 490～530 nm while the average reflectivity is above 99.998%. The thickness of Ag layer is insensitive to the phase shift. There is no effect on the transmittance when the thickness is larger than a constant. A tolerance analysis indicates that the deposition rate should be controlled within ±1% to achieve ±15.28° phase shift error, with a convergence of the phase shift about 504 nm. The phase shift error could reach ±12.77° within ±1% of the refractive index variation over the designed wavelength range. The variation of the outmost layer's thickness also is controlled within ±1% to achieve ±5.5°, and the phase shift error caused by the layers from 2 to 5 and 9 to 16 is above ±0.5°, but the other film layers have little influence on the phase shift. The incidence angle also is controlled within ±1% to achieve ±2.86° phase shift error over the designed wavelength range, the waveband around 530 nm is insensitive to the incident angle..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 24, Issue 9, 1169 (2004)
The Study of Antireflection Coatings of 600～700 nm at Wide Angle Incidence
[in Chinese], [in Chinese], and [in Chinese]
A method of designing antireflection multilayer using the theory of inhomogeneous coatings was presented. The cause of difference of transmittance is analysed by polarized light and in the case of incidence at wide angle. Antireflection multilayer of 500～600 nm at incidence angle from 0° to 80° have been desiA method of designing antireflection multilayer using the theory of inhomogeneous coatings was presented. The cause of difference of transmittance is analysed by polarized light and in the case of incidence at wide angle. Antireflection multilayer of 500～600 nm at incidence angle from 0° to 80° have been designed using Ta2O5 and SiO2 as materials of refractive index of smultilayer, using BK7 as material of substrate. A new way of film design has been explored. It shows the result of optimization is perfect. This method can increase the ratio of utilization of optical energy, and it can find the applications in the fields of solar energy, optical fiber communication, aerospace industry, laser and so on..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 24, Issue 9, 1173 (2004)
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