Contents
2007
Volume: 27 Issue 1
37 Article(s)
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Diffraction and Gratings
Wavefront Measurement by Using Quadratic Grating
[in Chinese], and [in Chinese]
A laser wavefront measurement technique by using a special quadratic grating is reported. The quadratic grating has a different focusing power in nonzero orders, for the grating lines are not line but arcs of circles, and multiple planes can be imaged onto a single image plane. The spacing relation between two planes iA laser wavefront measurement technique by using a special quadratic grating is reported. The quadratic grating has a different focusing power in nonzero orders, for the grating lines are not line but arcs of circles, and multiple planes can be imaged onto a single image plane. The spacing relation between two planes imaged on a single plane was deduced for a convergent beam. The experiments of measuring convergent beam wavefront with a quadratic grating are carried out. It is found that the defocusing aberration is as large as -2.93λ and the spherical aberration is equal to 1.34λ, which are in good agreement with theoretical ones(the defocusing aberration is -2.695λ, λ supposed to be wavelength). This technology can realize real-time wavefront measurement with high spatial resolution, high phase accuracy, low cost and simple structure. Because wavefront of high-energy laser beam usually changes rapidly, this real-time technology is a useful measurement method on this application..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 1 (2007)
Fiber Optics and Optical Communications
Synthetic Subdomain Method for Large-Scale Integrated Optical Waveguides FDTD SImulation
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The synthetic subdomain method (SSDM) of finite-difference time-domain (FDTD) method is used to simulate the large-scale optical waveguides. The waveguide is divided into two or more parts, and the parts whose influence on the simulation result is ignorable are deleted on the condition that the simulating precision doeThe synthetic subdomain method (SSDM) of finite-difference time-domain (FDTD) method is used to simulate the large-scale optical waveguides. The waveguide is divided into two or more parts, and the parts whose influence on the simulation result is ignorable are deleted on the condition that the simulating precision does not deteriorate. In the simulation, the absorption boundary condition is changed accordingly, and the light transmission and loss are also considered. The simulation results agrees with that of conventional method, and no precision decline is found. The two-part method occupies 55% memory and 60% time of the conventional FDTD method. Three-part SSDM uses 31% memory and 28%. It is demonstrated that the SSDM is superior to the conventional FDTD method for large-scale integrated optical waveguide simulation, saves hardware resource and time, and improves the working efficiency..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 5 (2007)
Non-Gaussian Approximation Method for Phase Encoding Optical Code Division Multi-Access System
[in Chinese], [in Chinese], and [in Chinese]
With the key technologies breakthrough of phase encoding, it is necessary to analyze the bit error rate performance of phase encoding optical code division multi-access accurately. A non-Gaussian approximation method, based on the moment generation function of the decision statistic and saddle-point approximation, is iWith the key technologies breakthrough of phase encoding, it is necessary to analyze the bit error rate performance of phase encoding optical code division multi-access accurately. A non-Gaussian approximation method, based on the moment generation function of the decision statistic and saddle-point approximation, is introduced to evaluate the statistic characteristics of multi-access interference, shot noise and thermal noise and cross-correlation. Mumerical comparison between Gaussian approximation method, accurate calculation and non-Gaussian approximation method, proves the high accuracy and efficiency of the proposed method to analyze the bit error rate of the phase encoding system..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 10 (2007)
Research on Bandwidth-Modulated and Temperature-Independent Single Fiber Bragg Grating Displacement Sensing
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The temperature-independent fiber Bragg grating (FBG) displacement measurement based on optical reflection spectrum bandwidth modulation and differential optical power detection is proposed and experimentally demonstrated. A specially designed bending cantilever beam is used to induce Gauss strain distribution along thThe temperature-independent fiber Bragg grating (FBG) displacement measurement based on optical reflection spectrum bandwidth modulation and differential optical power detection is proposed and experimentally demonstrated. A specially designed bending cantilever beam is used to induce Gauss strain distribution along the sensing FBG, resulting in Bragg wavelength shift and bandwidth modulation. Based on the theory of optical waveguide and material mechanics, the causation of reflection spectrum lateral gradient broadening of fiber Bragg grating under the Gauss strain distribution is analyzed, and the force-to-bandwidth broadening relation and force-to-optical power relation are formulized based on cantilever beam special structure with a lateral gradient broadening of FBG spectrum bandwidth and a linear increase of reflection optical power. For a temperature range of -10 ℃～80 ℃, the measured displacement fluctuates less than 1.2% without any temperature compensation..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 15 (2007)
Effect of Turbulent Atmosphere on Quantum Key Distribution Systems
[in Chinese], and [in Chinese]
Free-space quantum key distribution (QKD) system is one of the key parts of global quantum secure communications. So it is important to analyze the effect of turbulent atmosphere channel on quantum key distribution systems. The effect of turbulent atmosphere channel on quantum bit error rate (QBER) of a free-space QKD Free-space quantum key distribution (QKD) system is one of the key parts of global quantum secure communications. So it is important to analyze the effect of turbulent atmosphere channel on quantum key distribution systems. The effect of turbulent atmosphere channel on quantum bit error rate (QBER) of a free-space QKD system based on BB84 protocol is described quantatively by near-field beam propagation theory and statistical method. The results indicate that, when the atmospheric attenuation coefficient is below -3 dB/km, it has a severe influence on the QBER of a free-space QKD system; and that in the area where atmospheric propagation factor coefficient is less than 0.5, QBER of system is ten times of that of the system operating without turbulence..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 21 (2007)
Holography
Composition Optimization of Fluoro-Containing Red-Sensitive Photopolymer Holographic Materials
[in Chinese], [in Chinese], and [in Chinese]
Fluoro-containing polymer with low refractive index was used as the film-forming substance photopolymer holographic material to increase the spatial modulation range of its refractive index. Water soluble, fluoro-containing polymer with low reflective index derived from the copolymers of 2,2,3,3-tetrafluoropropyl methaFluoro-containing polymer with low refractive index was used as the film-forming substance photopolymer holographic material to increase the spatial modulation range of its refractive index. Water soluble, fluoro-containing polymer with low reflective index derived from the copolymers of 2,2,3,3-tetrafluoropropyl methacrylate and methacrylic acid was prepared. The above polymer with low reflective index was used as the film-forming component, together with acrylamide as monomer, methylene blue as light-sensitive dye and triethanol amine as photo-initiator, for the preparation of photopolymer films for holographic recording. The photopolymer with optimized composition exhibited high sensitivity of 19 mJ/cm2 and high diffraction efficiency of 93% at spatial resolution of 1580 lp/mm, better than that with water soluble polyvinyl alcohol (PVA) as the film-forming substance..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 26 (2007)
Anti-Fake Technique by Double Random Phase Encrypted Holographic Mark
[in Chinese], and [in Chinese]
It is a high quality data encryption technique by double random phase encoding with uniformly distributed random phase in both input and Fourier phases. Based on double random phase encoding technology and combination of digital holography and print technology, a new in-line phase holography mark printing anti-fake metIt is a high quality data encryption technique by double random phase encoding with uniformly distributed random phase in both input and Fourier phases. Based on double random phase encoding technology and combination of digital holography and print technology, a new in-line phase holography mark printing anti-fake method with double random phase encryption is proposed. Theoretical analysis proves that the presented technology can recover data of the original image effectively, and the robust anti-interference and anti-bit compression characteristic is verified by computer simulation. Printing and scanning experiments demonstrates that the in-line phase holography mark can be printed on the printed matter (e.g. documents) as the anti-fake mark by common digital printing technique. The in-line phase holography mark can be input into a computer by scanning, and then converted to digital images. The original image data can be recovered by decryption mask..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 31 (2007)
Image Processing
Comparison and Analysis of Algorithms for Digital Image Processing in Autofocusing Criterion
[in Chinese], [in Chinese], and [in Chinese]
The choice of the imaging focusing criterion function is the key of high-quality image acquiring in auto image measurement. The performances of several digital image processing methods used for autofocusing criterion are given. The focusing evaluation functions are compared and analyzed quantitatively through experimenThe choice of the imaging focusing criterion function is the key of high-quality image acquiring in auto image measurement. The performances of several digital image processing methods used for autofocusing criterion are given. The focusing evaluation functions are compared and analyzed quantitatively through experiments in the aspects of calculation speed, unique value, precision and sensitivity. The results show that gradient square algorithm, Laplacian algorithm and second order gradient square algorithm have good behavior at the unique value and the sensitivity; and that both Robert algorithm and gradient mode algorithm have good behavior at the stability and calculation speed. These analysis results of image focusing criterion functions are useful for autofocusing in the automatic image measurement application..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 35 (2007)
Image Fusion Based on Morphological 4-Subband Decomposition Pyramid
[in Chinese], and [in Chinese]
A novel multi-resolution image fusion based on mathematical morphological filtering is proposed. This fusion scheme constructs the low-pass and high-pass filters with morphological opening and closing operators. The original image is then decomposed into 4-subband image pyramid and 4-subband direction contrast image pyA novel multi-resolution image fusion based on mathematical morphological filtering is proposed. This fusion scheme constructs the low-pass and high-pass filters with morphological opening and closing operators. The original image is then decomposed into 4-subband image pyramid and 4-subband direction contrast image pyramid. The image fusion is performed by the direction contrast and region standard deviation to get the fused 4-subband image pyramid. The final fused image is formed with the subband image reconstruction. The fusion experiments indicate this image fusion is superior to the traditional fusion based on the morphological pyramid, contrast pyramid and wavelet decomposition..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 40 (2007)
Interference Hyper-Spectral Images Compression Based on Classification and Curve-Fitting
[in Chinese], and [in Chinese]
A data decomposition algorithm for interference hyper-spectral images based on classification and curve-fitting is proposed, by studying features of hyper-spectral images. Compression of interference hyper-spectral images is realized by combining the embedded bit-plane coding technology, which implements loss and losslA data decomposition algorithm for interference hyper-spectral images based on classification and curve-fitting is proposed, by studying features of hyper-spectral images. Compression of interference hyper-spectral images is realized by combining the embedded bit-plane coding technology, which implements loss and lossless compression in the same algorithm just as in JPEG2000. The data of a spectral line are decomposed into two classes, main-interference class and non-main-interference class. And a similarity-based match method is presented for the data of main-interference class, while the data of non-main-interference class is processed by empirical mode decomposition and second-order curve-fitting algorithm. The data of a spectral line can be approached appropriately by combining the two analytical algorithms, which benefits lossless image compression. The simulation results show that the output rate is decreased by 0.2～0.4 bit per pixel for lossless compression, and the reconstructed image quality is also improved..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 45 (2007)
Myopic Image Deconvolution of Point Source Based on Joint Estimation of Object and Point Spread Function
[in Chinese], [in Chinese], and [in Chinese]
In the classical deconvolution based on wave-front sensing (DWFS), point spread function (PSF) is considered to be accurately achieved and therefore Wiener filter can be used in retrieval. However, for the inevitable noise with PSF, the object image cannot be restored perfectly. A myopic deconvolution method based on jIn the classical deconvolution based on wave-front sensing (DWFS), point spread function (PSF) is considered to be accurately achieved and therefore Wiener filter can be used in retrieval. However, for the inevitable noise with PSF, the object image cannot be restored perfectly. A myopic deconvolution method based on joint estimation of the object and PSF to overcome this limitation is proposed. It takes into account the available a priori information on the object to be restored as well as on PSF. The a priori information is used as constraint of the object and PSF, and therefore a better estimation of the restored object can be obtained. The principles and experimental procedure are presented. The experimental results for the indoor point source show that the myopic DWFS can give a better object restoration than Wiener filter method..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 52 (2007)
Instrumentation, Measurement and Metrology
Optical Measurement of Object's Surface Three-Dimensional Shape in Water
[in Chinese], and [in Chinese]
A three-dimensional measurement method of objects' shape in water by using light stripe projection is proposed. Usually, three-dimensional measurement is executed under the assumptions that cameras and objects are in aerial environments. However, stripe image distortion occurs when vision sensors measure objects inA three-dimensional measurement method of objects' shape in water by using light stripe projection is proposed. Usually, three-dimensional measurement is executed under the assumptions that cameras and objects are in aerial environments. However, stripe image distortion occurs when vision sensors measure objects in liquid, for the refraction of the light on the air and water interface, and brings errors in a triangulation. The proposed method can measure accurately three-dimensional coordinates of objects' surface in water, and calculate the geometrical size of the object. The validity of the proposed method is proved experimenally. By considering the refraction of light, the three-dimensional measurement of objects in water becomes same as in air and the measurement has a higher accuracy and speed because of the epipolar constraint and sub-pixel technology..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 58 (2007)
MEMS Dynamic Testing Technique Based on Differential Laser Doppler Effect
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A system used for testing transient velocities and displacements of the micro-electronic-mechanical system (MEMS) devices is presented. A differential laser Doppler technique is adopted to measure the in-plane vibration of MEMS resonator and vibration velocity which is perpendicular to the optical axis of the measuringA system used for testing transient velocities and displacements of the micro-electronic-mechanical system (MEMS) devices is presented. A differential laser Doppler technique is adopted to measure the in-plane vibration of MEMS resonator and vibration velocity which is perpendicular to the optical axis of the measuring system. A CCD camera with imaging system to observe the position adjustment and resonator vibration status is introduced to the optical arrangement. The Doppler frequency is extracted by processing circuit from the high-frequency output of the optical system, and powerful Labview & Matlab are used in time-frequency analysis to measure the movement parameters. In the system, a tiny location device is used to scan the whole plane of the MEMS devices. As a result the transient velocity field, which provides certain basis and necessary support for the higher-order spectral analysis and torsion analysis, is achieved..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 63 (2007)
Application of Three-Dimensional Phase Unwrapping Algorithm in Precision Motion Measurement
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Three-dimensional phase unwrapping algorithm is an expansion of the spatial phase unwrapping algorithm in time, which contains one-dimensional temporal and two-dimensional spatial information and is very useful for motion measurement. Firstly, mathematic formula of one-dimensional temporal phase unwrapping algorithm isThree-dimensional phase unwrapping algorithm is an expansion of the spatial phase unwrapping algorithm in time, which contains one-dimensional temporal and two-dimensional spatial information and is very useful for motion measurement. Firstly, mathematic formula of one-dimensional temporal phase unwrapping algorithm is introduced in this paper. Then, the working principle, limitation conditions and the process of the new algorithm are discussed for precise measurement of micro-motion. In final, the micro-structure motion of micro-oscillators is measured. The results show that the new algorithm, due to time information taken into consideration, not only gets rid of the request for static reference point or reference plane for distortion measurement, but also achieves off-plane motion in the level of nanometer while surface distortion is measured at the same time..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 68 (2007)
Tolerance Limit of Collimated Lens During Transparence Testing
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
During the optical interference testing, the measurement accuracy of the tested surface is influenced by the system structure of interferometer, which will decrease the reliability of the measurement. To obtain high measurement precision, it is necessary to analyze the testing system and build the relationship between During the optical interference testing, the measurement accuracy of the tested surface is influenced by the system structure of interferometer, which will decrease the reliability of the measurement. To obtain high measurement precision, it is necessary to analyze the testing system and build the relationship between the measurement error and system structures. With the Fresnel diffraction approximation method, the influences of the collimated lens and standard lens surface errors on the transparence testing are analyzed in Fizeau interferometer. Through analyzing the propagation of the wavefront phase, we obtain the correlation between the wavefront error and system structure parameters, remove the empty system error, optimize the structure parameter, and build up the expression about the tolerance limit of the collimated lens. We draw the conclusion that when the aberration of the tested surface is 0.2λ, the measurement error can reach 0.02λ, and the aberration of the collimated lens 0.8λ will be enough..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 73 (2007)
Temperature-Insensitive Fiber Bragg Grating Pressure Sensing with Plane Round Metal Diaphragm
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A novel temperature-insensitive pressure sensor based on fiber Bragg grating (FBG) broadened bandwidth technique using a plane round metal diaphragm is studied theoretically and experimentally. Considering the strain modulating trait of the diaphragm, the smart box structure is adopted and FBG is affixed radially, withA novel temperature-insensitive pressure sensor based on fiber Bragg grating (FBG) broadened bandwidth technique using a plane round metal diaphragm is studied theoretically and experimentally. Considering the strain modulating trait of the diaphragm, the smart box structure is adopted and FBG is affixed radially, with the axis center of FBG aiming at the zero strain zone of the diaphragm. Temperature-independent pressure sensing is measured by bandwidth of FBG due to the bandwidth is sensitive to strain but temperature. This approach shows a pressure resolution of ±0.15 MPa and a pressure sensitivity of 0.34 nm/MPa in the range 0～0.75 MPa, with the spectral resolution of the spectral analyzer of 0.05 nm. The experimental results match the theoretical analysis well..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 80 (2007)
Photoconduction-Type CdS Detector Irradiated by Two Laser Beams
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
PC-type CdS detector is irradiated by 532 nm in-band and 1319 nm out-of-band continuous wave (CW) lasers simultaneously. The voltage responses are recorded when the power of the two laser beams changes separately. It is shown that the detector responses to the irradiation of both in-band and out-of-band lasers, but thePC-type CdS detector is irradiated by 532 nm in-band and 1319 nm out-of-band continuous wave (CW) lasers simultaneously. The voltage responses are recorded when the power of the two laser beams changes separately. It is shown that the detector responses to the irradiation of both in-band and out-of-band lasers, but the response to the irradiation of out-of-band laser is opposite to that of in-band laser. The voltage response to the out-of-band laser increases with the rise of line-working in-band laser power and decreases rapidly while the in-band laser power approaches to the saturation threshold. Analysis shows that the response to the out-of-band laser is related to laser excited hot carriers, which is due to the carrier absorption of the incident photons resulting in an intra-band transition. In-band laser irradiation has an effect on the absorption coefficient of the out-of-band laser..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 85 (2007)
Lasers and Laser Optics
Laser Diode-Pumped Passively Q-Switched Monolithic Microchip Laser Based on Liquid Phase Epitaxy
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A novel monolithic passively Q-switched microchip laser is presented with a microcavity by directly growing a thin Cr4+:YAG film with saturable absorption on the surface of the laser medium Nd3+:YAG by liquid phase epitaxy. Because of the homogeneous epitaxial process, a good interface property is achieved between actiA novel monolithic passively Q-switched microchip laser is presented with a microcavity by directly growing a thin Cr4+:YAG film with saturable absorption on the surface of the laser medium Nd3+:YAG by liquid phase epitaxy. Because of the homogeneous epitaxial process, a good interface property is achieved between active medium Nd3+:YAG and saturable absorber Cr4+:YAG. Pumped by 1 W output of a fiber-coupled laser diode, the novel laser produces Q-switched pulses sequence with wavelength 1.064 μm, pulse duration 1.8 ns, pulse repetition over 4 kHz, TEM00 mode and peak power nearly 1 kW. Except for the detailed descriptions of the performance of the laser, the potential advantages of the structure and relevant processes are also discussed..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 90 (2007)
Structural Resonances in Absorption Spectrum of Quartz Microsphere
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The quartz microspheres with different diameters are fabricated by melting the taper fibers with corresponding diameters using CO2 laser. The spherical microcavity coupling system is constructed with taper fiber and the quartz microsphere. In the experiment, a coupling system is made of fiber taper with the diameter ofThe quartz microspheres with different diameters are fabricated by melting the taper fibers with corresponding diameters using CO2 laser. The spherical microcavity coupling system is constructed with taper fiber and the quartz microsphere. In the experiment, a coupling system is made of fiber taper with the diameter of 3.1 μm and a quartz microsphere with 143.1 μm diameter. The spectrum of this system is scanned using the tunable diode laser with the resolution of 1 pm, and the discrete structural resonance in the absorption spectra of the quartz microsphere is observed. According to the spherical microcavity theory, the above structural resonance is analyzed, and the Mie scattering theory is used to calculate the position of the first order TE modes and their spacing distance. The calculated result is in accordance with the observed resonance, with an error of only 0.03%..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 94 (2007)
Reconstruction Theory of Laser Beam Intensity Temporal and Spatial Distribution Measurement by Thermal Image Method
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
To measure the far-field temporal and spatial distribution of laser intensity by using the calorimetric method, the reconstruction theory of incident laser intensity temporal and spatial distribution by calorimeter based target surface temperature inversion is studied. The reconstructing formula to inverse laser beam tTo measure the far-field temporal and spatial distribution of laser intensity by using the calorimetric method, the reconstruction theory of incident laser intensity temporal and spatial distribution by calorimeter based target surface temperature inversion is studied. The reconstructing formula to inverse laser beam temporal and spatial distribution with target surface temperature distribution is derived, for different back surface boundary conditions, convection-irradiation heat current boundary and constant temperature boundary. The achieved expression is of extensive application for general materials. A generalized parameter F0=α/L2 is introduced, and the reconstructing formula is cataloged for F01 and F01 respectively. The above inversion algorithm is numerically simulated for F1. The numerical results show that the retrieved laser beam intensity distribution agrees well with the initial laser beam, and there exists a retrieving-time origin τ0 related to Fourier number of targets. The theoretical result can be applied to the development of high-intensity laser far-field parameters measurement system..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 98 (2007)
Materials
Fabrication of Nanostructures on 6H SiC Crystal Induced by Femtosecond Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Laser-induced periodic nanostructures have been observed in several kinds of material including dielectric, semiconductor, metal and polymer. Fabrication of nanostructures on 6H SiC crystal illuminated by 800 nm and 400 nm femtosecond laser is studied. Interference ripples with period of 150 nm and 80 nm are produced bLaser-induced periodic nanostructures have been observed in several kinds of material including dielectric, semiconductor, metal and polymer. Fabrication of nanostructures on 6H SiC crystal illuminated by 800 nm and 400 nm femtosecond laser is studied. Interference ripples with period of 150 nm and 80 nm are produced by linearly polarized 800 nm and 400 nm femtosecond pulses, respectively. Spherical nanoparticles with diameter about 100 nm are formed after irradiation with circularly polarized 800 nm femtosecond pulses. Alignment of nanoparticles about 100 nm is obtained after simultaneous irradiation with 400 nm and 800 nm linearly polarized femtosecond laser pulses. The direction of the alignment changes to the polarization direction of 400 nm incident laser pulses, along with the increase of its pulses energy. With the help of the second harmonic generation, the formation mechanisms of these nanostructures are discussed..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 105 (2007)
Influence of Ba/Mg Ratio on Crystal Structure and Luminescent Characteristics of Eu2+-Doped (BaxMg)2/(x+1)Al10O17Blue-Emitting Phosphors
[in Chinese], [in Chinese], and [in Chinese]
The (BaxMg)2/(x+1)Al10O17: Eu2+ (0.6≤x≤1.2) (BAM) phosphors with different Ba/Mg ratio were successfully prepared by solution combustion method at 600 ℃. The influence of Ba／Mg ratio on the crystal structure and luminescent properties of the obtained samples were mainly investigated. The results show that the samples aThe (BaxMg)2/(x+1)Al10O17: Eu2+ (0.6≤x≤1.2) (BAM) phosphors with different Ba/Mg ratio were successfully prepared by solution combustion method at 600 ℃. The influence of Ba／Mg ratio on the crystal structure and luminescent properties of the obtained samples were mainly investigated. The results show that the samples are of single phase, and the lattice parameters increase with the Ba/Mg ratio. Moreover, the intensity of the fluorescence of the resulting phosphors increases obviously with the Ba/Mg ratio, and the maximum emission intensity is reached at Ba/Mg=0.9 . However , as Ba／Mg ratio was higher than 0.9, the intensity of the fluorescence is reduced reversely. Furthermore, with the decrease of the Ba/Mg ratio, the emission peak of the phosphors shifts to the longer wavelength due to the crystal field enhancement and electron cloud expansion. Moreover, the luminescent property of BAM phosphor is considerably influenced by Eu2+ concentration. In an appropriate Eu2+ doping concentration range, the intensity of the fluorescence of BAM increase obviously with Eu2+ doping concentration and reaches a maximum, owing to more luminescent centers and faster energy transfer between Eu2+ ions. However, as the Eu2+ doping concentration is higher than a critical value, the intensity of the fluorescence is reduced reversely, due to the concentration quenching as the energy transfer rate between Eu2+ ions exceeds the emission rate..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 111 (2007)
Spectral Characteristics of Mn2+:BeAl2O4 Crystals
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The pink Mn2+-doped BeAl2O4crystals in the size of 45 mm×80 mm without bubble, cloud and cores have been grown by Czochralski (CZ) technique under the technical conditions of choosing BeO:Al2O3:MnO raw chemical compositions in molar ratio of 100:99.85:0.3, taking twice melting process of the raw materials and usiThe pink Mn2+-doped BeAl2O4crystals in the size of 45 mm×80 mm without bubble, cloud and cores have been grown by Czochralski (CZ) technique under the technical conditions of choosing BeO:Al2O3:MnO raw chemical compositions in molar ratio of 100:99.85:0.3, taking twice melting process of the raw materials and using ～60 ℃ temperature gradient of solid-liquid interface and 1 mm/h growth rate. The excitation and absorption spectra of the Mn2+:BeAl2O4 from different parts were recorded. It is found that the pink color of the crystal becomes deeper along the Mn2+ growing direction. An emission band at 543 nm is observed in the emission spectra of Mn2+:BeAl2O4 crystal, which attributes to the electron transition of 4T1(4G)→6A1(6S) level. An excitation band at 218 nm is also observed in the excitation spectra, which corresponds to the electron transition from the ground state to the conduction band (CB). It can be deduced from the green emission that the Mn2+ substitutes Be2+ in BeAl2O4 crystal to form the tetrahedron. From the excitation intensity and color of different parts, it can be convinced that the effective distribution coefficient of Mn2+ ion in BeAl2O4 crystal is less than 1..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 116 (2007)
Influence of Silver-Doped Nanoparticles on Photo-Induced Isomerization of Azo Polymer
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The optical anisotropy caused by photo-induced isomerization of azo polymer has been investigated by experimental measurement. And a method to influence the photo-induced isomerization of azo polymer has also been reported. Silver nanoparticles with different spacing distances have been doped into the azo polymer, and The optical anisotropy caused by photo-induced isomerization of azo polymer has been investigated by experimental measurement. And a method to influence the photo-induced isomerization of azo polymer has also been reported. Silver nanoparticles with different spacing distances have been doped into the azo polymer, and the He-Cd laser with wavelength 442 nm has been used to excite the plasmon resonance effect of the silver nanoparticles. The intensity of electromagnetic field around the nano-particles has been enhanced while the mass concentration of Ag is 0.12 μg/ml and the plasmon resonance of silver nanoparticles in the thin sample is triggered. The conversion efficiency of photo-induced isomerization is also advanced greatly. In addition, we changed the mesogenic side groups of azo polymer and investigated the influence of interaction between mesogenic side groups and silver nanoparticles on the photo-induced isomerization. And a method to efficiently control the photo-induced isomerization effect has been presented..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 119 (2007)
Medical Optics and Biotechnology
Fluorescent Spectrum of Skin with Trichrome Vitiligo
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Fluorescent spectrum was used to study the property of trichrome vitiligo skin. Melanin content and distribution were analyzed and optical model was developed based on the measurement of skin fluorescence and study of skin pathology. Monte Carlo simulation based on this optical model shows good agreement with the experFluorescent spectrum was used to study the property of trichrome vitiligo skin. Melanin content and distribution were analyzed and optical model was developed based on the measurement of skin fluorescence and study of skin pathology. Monte Carlo simulation based on this optical model shows good agreement with the experimental result. The study suggests that, trichrome vitiligo skin is an ideal model to study skin melanin content and distribution; fluorescence spectrum can be used to study melanin distribution or other tissue properties in deeper skin (e.g. dermis); the optical model developed and the method to develop it, as well as the spectrum ratio method, can be used in other study of skin optics..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 124 (2007)
Identification of Auricularia Auricula from Different Regions by Fourier Transform Infrared Spectroscopy
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Fourier transform infrared spectroscopy (FTIR) was used to identify five kinds of Auricularia auricula from different regions. The results show the infrared spectrum of Auricularia auricula is mainly composed of the absorption of protein, aliphatic compound and polysaccharide. The spectra of five samples are very similFourier transform infrared spectroscopy (FTIR) was used to identify five kinds of Auricularia auricula from different regions. The results show the infrared spectrum of Auricularia auricula is mainly composed of the absorption of protein, aliphatic compound and polysaccharide. The spectra of five samples are very similar. Two regions of 1750～1500 cm-1 and 1200～1000 cm-1 in infrared absorption spectra were selected for evaluating the correlation coefficients. The correlation coefficients of five samples between 1750 cm-1 and 1500 cm-1 are located from 0.895 to 0.994, which indicates the spectra have good correlation. The correlation coefficients are located from 0.441 to 0.981 between 1200 cm-1 and 1000 cm-1. There are obvious differences about the spectra among the mushrooms in the northeast and southwest. The differences in the range 1200～1000 cm-1 and other characteristics of absorption peaks might be used to identify Auricularia auricula from different regions. It is proved that mushrooms can be identified rapidly and conveniently by Fourier transform infrared spectroscopy..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 129 (2007)
Nonlinear Optics
Second-Harmonic Generation at Retracing Point of Phase Matching with Pre-Chirp Compensation
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A novel second-harmonic generation scheme is proposed to compensate group velocity dispersion effects. In the scheme, a proper pre-chirp is introduced to the fundamental harmonic pulse to interact with dispersion, actively control its pulse width and raise the conversion efficiency. The result shows that the method impA novel second-harmonic generation scheme is proposed to compensate group velocity dispersion effects. In the scheme, a proper pre-chirp is introduced to the fundamental harmonic pulse to interact with dispersion, actively control its pulse width and raise the conversion efficiency. The result shows that the method improves the conversion efficiency of high harmonic greatly. For KD*P crystal with 12.6% deuterium, at the retracing point of phase matching, the conversion efficiency of the fundamental harmonic reaches the top at the crystal center, nearly 22%, and the optimal chirp compensation is obtained, for pulse width of 30 fs and central wavelength of 1053 nm. The relationship of conversion efficiency, conversion bandwidth and the crystal length is also studied..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 133 (2007)
Ultra-Short Gaussian Pulse Expansion and Deformation by High-Order Group Velocity Dispersion
[in Chinese], and [in Chinese]
The pulse expansion and deformation caused by group velocity dispersion in optical parametric effect of the negative uniaxial crystal CsLiB6O10 are studied, by momentum conservation and coupling wave equations. The numerical results show that, under the conditions of hyperbola secant wave form, no chirp modulation, pulThe pulse expansion and deformation caused by group velocity dispersion in optical parametric effect of the negative uniaxial crystal CsLiB6O10 are studied, by momentum conservation and coupling wave equations. The numerical results show that, under the conditions of hyperbola secant wave form, no chirp modulation, pulse width of 50 fs and crystal length of 10 nm, the pulse expansion caused by group velocity dispersion for incident wavelength of 532 nm is 1.6 times of that for wavelength of 213 nm. The pulse expansion is related to the incident light wavelength and crystal length, and the pulse expansion and deformation are more severe for shorter wavelength and crystal length. The wave form symmetry is destroyed and the side band phenomena is also introduced by the pulse expansion..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 138 (2007)
Experimental Observation of Strong Nonlocal Optical Spatial Solitons in Nematic Liquid Crystals
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The propagation of nonlocal spatial solitons in nematic liquid crystals is studied experimentally. On the basis of propagation equation of nonlinear nematic liquid crystals solitons, we obtain the analytical solution of solitons by using Gaussian trial solution and compare our model with Snyder's strong nonlocal soThe propagation of nonlocal spatial solitons in nematic liquid crystals is studied experimentally. On the basis of propagation equation of nonlinear nematic liquid crystals solitons, we obtain the analytical solution of solitons by using Gaussian trial solution and compare our model with Snyder's strong nonlocal solitons model. In experiment, we observe the propagation of solitons in nematic liquid crystals, and determine the critical power of optical spatial solition in different beam width, for example, when the beam width is 2 μm, the critical power is 2.0 mW. The relaxation process of optical solitons in nematic liquid crystals is discovered and it is noticed that the molecule of nematic liquid crystals takes several seconds to respond, and the generation of optical solition is not fast..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 143 (2007)
Photorefractive Grating Dynamics under Large Modulation and Strong Applied Electric Field
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Strong applied electric field and large modulation have been widely applied in photorefractive effect research. Photorefractive band transport equations are rigorously solved based on the algorithm of general collocation software for partial differential equations (PDECOL). Temporal evolutions of space-charge field andStrong applied electric field and large modulation have been widely applied in photorefractive effect research. Photorefractive band transport equations are rigorously solved based on the algorithm of general collocation software for partial differential equations (PDECOL). Temporal evolutions of space-charge field and charge carrier density in photorefractive crystal have been achieved under different light modulations, and effects of an applied electric field have also been considered. Material equations and coupled wave equations are jointly solved to get the coupling coefficient and phase shift of light pattern during the dynamic procedure of photorefractive grating formation. It is found that, under strong modulation, the intensity coupling and phase coupling between two recording beams are both markedly enhanced, while the analytic equations, which neglect the effects of strong applied electric field and large light modulation on the coupling of the phase of the space charge filed, are not valid any more. Numerical results also show that both the light pattern and index grating are bent and do not keep parallel..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 148 (2007)
OPTOELECTRONICS
Influence of Mode Split upon Resonance Curve of Fabry-Pérot Optical Fiber Hydrophone
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Working principles of Fabry-Pérot optical fiber hydrophone is referred, and the reason for working point choosing and system solution are given. Under ideal circumstance, the resonance curve of Fabry-Pérot optical fiber interference is drawn. Stress birefringence of optical fiber and mode split within resonanWorking principles of Fabry-Pérot optical fiber hydrophone is referred, and the reason for working point choosing and system solution are given. Under ideal circumstance, the resonance curve of Fabry-Pérot optical fiber interference is drawn. Stress birefringence of optical fiber and mode split within resonance cavity are analyzed by photoelasticity theory. With the theory of mode split, the distortion of resonance curve of hydrophone is explained and math formulas describing the distortion of resonance curve are given, and then the interference process of hydrophone after mode split is simulated by MathCAD and the theoretical curve is plotted. The result of experiments is consistent with the theoretical simulation. It shows that it is feasible to explain the distortion of resonance curves by the theory of mode split..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 155 (2007)
Modelling of Fiber Radio Link Using Mach-Zehnder Modulator
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Based on the detailed theoretical modelling of Mach-Zehnder Modulator (MZM), considering non-ideal parameters such as extinction ratio and driven-signal unbalanced ratio, a fundamental fibre radio link is presented including optical source, dual-electrode-drive MZM, optical transmission module and photodiode. The all-oBased on the detailed theoretical modelling of Mach-Zehnder Modulator (MZM), considering non-ideal parameters such as extinction ratio and driven-signal unbalanced ratio, a fundamental fibre radio link is presented including optical source, dual-electrode-drive MZM, optical transmission module and photodiode. The all-order analytic responses using dual side band (DSB) and single side band (SSB) modulation schemes are derived. The analysis concentrates on how MZM affects the amplitude and phase (time delay) response performance of a fibre radio link under different modulation modes. According to the theoretical and numerical results, the extinction ratio and driven-signal unbalanced ratio affect only the amplitude response performance of DSB modulation link but affect both the amplitude and the phase response performance of SSB modulation link. The theoretical model and numerical results can provide the basis of qualitative and quantitative analysis of fibre radio application system using MZM such as radio over fibre (RoF) and optical controlled microwave beam forming network..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 159 (2007)
Physical Optics
Evolution of Gaussian Beams in Photorefractive Crystal Biased Spatial Modulation Electric Field
[in Chinese], [in Chinese], and [in Chinese]
The evolution of Gaussian beams in photorefractive crystal biased by spatial modulation electric filed is investigated. The results show that the filed distribution of the Gaussian beams is modulated and varies with the applied external field. The interactions of the beams with same-phase, anti-phase and phase differenThe evolution of Gaussian beams in photorefractive crystal biased by spatial modulation electric filed is investigated. The results show that the filed distribution of the Gaussian beams is modulated and varies with the applied external field. The interactions of the beams with same-phase, anti-phase and phase difference of π/2 in the photorefractive crystal are studied emphatically. Many novel and practical properties are found when the distribution of applied external field is linearly increased. By adjusting the distribution of external electric field, one can make the separation of the same-phase beams closer without mergence, deflection of the anti-phase beams and power transfer of the beams with phase difference of π/2 controllable. In simulation, it is found that the linearly increased field distribution can be substituted by a stopped one, so it is possible to realize it in engineering..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 166 (2007)
Jones Vectors for Incident and Refracted Electric Fields of a Birefringent Crystal and Modification of Fresnel Equations on Interface
[in Chinese], [in Chinese], and [in Chinese]
In order to express the polarization states of the incident and refracted rays of a birefringent crystal more accurately by Jones vectors, with the aid of ellipsoid of wave normals and material equations, the electric fields of incident and refracted beams are considered as combination of o component and e component whIn order to express the polarization states of the incident and refracted rays of a birefringent crystal more accurately by Jones vectors, with the aid of ellipsoid of wave normals and material equations, the electric fields of incident and refracted beams are considered as combination of o component and e component which can be decomposed into directions parallel and perpendicular to the incident plane. The relationship between electric components of incident and refracted waves is expressed by transmission coefficients from Fresnel equations. Considering the differences between the electric field vector and displacement vector of e ray, Fresnel equations are modified to meet the boundary conditions. Finally, Jones vectors for the electric fields of the incident and refracted rays are obtained. And numerical examples are given to show that there is difference between conventional and modified transmission coefficients, and the difference between the electric field vector and displacement vector of e ray cannot be neglected..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 171 (2007)
Thin Films
Effect of Nitrogen Partial Pressure on Color of ZrN
[in Chinese], and [in Chinese]
CIE 1976 LAB color space coordinate is an important technical index of ZrN film, and nitrogen partial pressure has a critical effect on ZrN film color coordinate. Mid-frequency reactive magnetron sputtering is adopted to deposite ZrN layer, and through measuring the color of ZrN films and nitrogen partial pressure, theCIE 1976 LAB color space coordinate is an important technical index of ZrN film, and nitrogen partial pressure has a critical effect on ZrN film color coordinate. Mid-frequency reactive magnetron sputtering is adopted to deposite ZrN layer, and through measuring the color of ZrN films and nitrogen partial pressure, the curves of CIE L*, a* and b* values of ZrN films versus nitrogen partial pressure are obtained. The results show that the curve of a* and b* values is a loop curve and L* values decrease with the rise of nitrogen partial pressure. The theoretical analysis is given by metal free-electron model. As the nitrogen partial pressure increases, the variation of color coordinate is caused by decrease of free electrons number of the films and decrease of plasma frequency. The results of X-ray diffraction (XRD) and resistivity measurement indicate that the distinct decrease of L* value at high nitrogen partial pressure is caused by that band gap of Zr3N4 is less than limit of visible light..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 177 (2007)
Ultrafast Optics
Aberration-Free Stretcher Based on Concentric Diffraction for Sub-10 fs Pulses
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In the process of updating 5 TW/40 fs table-top Ti:sapphire laser system, a 10 fs pulse source is introduced, and a new type aberration-free pulse stretcher and compressor is proposed and designed. Compared with other stretchers, the specialty of the proposed one is that the diffraction point of input pulses and revertIn the process of updating 5 TW/40 fs table-top Ti:sapphire laser system, a 10 fs pulse source is introduced, and a new type aberration-free pulse stretcher and compressor is proposed and designed. Compared with other stretchers, the specialty of the proposed one is that the diffraction point of input pulses and reverting point of stretched pulses coincide in the centre of the concave mirror, i.e. concentric structure. Imaging problems related to other methods don't appear in the concave mirror, and the focal length and adaxial approximation of the concave mirror are not involved in the stretching function. This stretcher system, aberration-free, compact, easy to adjust precisely, provides broad bandwidth, permits the stretching of sub-10 fs seed pulse to nanosecond level, and is suitable for 100 TW ultrafast laser system..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 181 (2007)
X-Ray Optics
Fabrication of Normal Incident Cr/C High-Reflecting Mirror for 4.48 nm Soft X-Ray Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Near normal incident high-reflecting multilayered mirrors at 4.48 nm wavelength are designed and fabricated for Ni-like Ta soft X-ray laser and its applied experiments. Materials Cr and C are chosen to make up the high-reflecting mirror. The periodic thickness, thickness ratio of two materials and periodic number are cNear normal incident high-reflecting multilayered mirrors at 4.48 nm wavelength are designed and fabricated for Ni-like Ta soft X-ray laser and its applied experiments. Materials Cr and C are chosen to make up the high-reflecting mirror. The periodic thickness, thickness ratio of two materials and periodic number are calculated and optimized. The influence of the imperfect interface on the reflectivity of the multilayer is simulated. The Cr/C multilayer of 200 periods is deposited on the super smooth silicon substrate by the direct current magnetron sputtering technique. The periodic thickness and structure of the multilayer are measured by X-ray diffractometer (XRD). The reflectivity of the multilayer is measured at Bessy Ⅱ synchrotron radiation (SR), and the peak reflectivity is measured to be 7.5%. The grazing incident reflection index curve measured by XRD and reflection index curve by SR are fitted. The fitted thickness ratio and interface roughness of the two curves are close to each other. The measurements show the Cr/C multilayer has a good structure and a reflective peak on the demanded wavelength, which meet the design requirement..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 1, 187 (2007)
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