Contents
2003
Volume: 23 Issue 11
25 Article(s)
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Research Article
Research on Optimal Geodesic Waveguide Lenses
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The purpose is to optimize geodesic waveguide lenses. A general expression is chosen for the round edge of geodesic lens based on the design of perfect geodesic waveguide lenses free of singularity of curvature. The curvature in the round area is discussed for different round area functions to depress loss due to bend.The purpose is to optimize geodesic waveguide lenses. A general expression is chosen for the round edge of geodesic lens based on the design of perfect geodesic waveguide lenses free of singularity of curvature. The curvature in the round area is discussed for different round area functions to depress loss due to bend. An optimal round area function and a particular solution for the lens are given. Through numerical computation, the generating curve is achived. The machining of the aspheric surface is finished, and an optimized perfect geodesic waveguide lens is developed. Measurements show that the lens has no spherical aberration across the total effective aperture of 8 mm, and for a 4 mm-width beam and a lens with 20 mm focal length, the width of the focus is about 4 μm..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 23, Issue 11, 1320 (2003)
Optimization of Optical System Capable of Off-Surface Displacement Measurement
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
To achieve the measurement for complicated three-dimensional object surface outline and the longitudinal displacement or vibration of object within a small space, it′s necessary to develop optical detection system with high resolution and non-contact. Laser Doppler technology is preferentially applied in longitudinal dTo achieve the measurement for complicated three-dimensional object surface outline and the longitudinal displacement or vibration of object within a small space, it′s necessary to develop optical detection system with high resolution and non-contact. Laser Doppler technology is preferentially applied in longitudinal displacement measurement of complex three-dimensional object because it has high accuracy, quick dynamic response, good linearity, great measuring range and is noncontact. However, the signal got from the scattered light of object measured is faint, so improving the intensity and signal-to-noise ratio of the signal are pivotal. Laser Doppler technique and statistic law of random changing of scattered light phase are studied and a reference optics with high spatial resolution is designed. The measurement result is satisfying when the system is applied to the off-surface displacement measurement, with a relative error of 0.3%..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 23, Issue 11, 1375 (2003)
Sal inity Measurement Based on Position Sensitive Detector and Optical Technology
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The developed salinity measurement setup exploits beam deviation caused by refraction due to the salinity of measured water at the receiving end face of a measurement cell. Based on a differential refractometry, a reference water cell filled with distilled water to reduce influence of temperature drift effectively is pThe developed salinity measurement setup exploits beam deviation caused by refraction due to the salinity of measured water at the receiving end face of a measurement cell. Based on a differential refractometry, a reference water cell filled with distilled water to reduce influence of temperature drift effectively is partitioned by an oblique optical-transmission plate from a horizontal rectangular water tank, which, as a measurement element, is filled with measured salt water. Beam deviation caused by salinity change is detected by a position sensitive detector. Experimental results indicate the feasibility of the developed system with a measurement resolution of 0.012‰ and repeatability error less than ±0.3‰. Errors which will affect the measurement performance are discussed and analyzed in detail. The results indicate that temperature and light power drifts have little influence on the measurement accuracy..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 23, Issue 11, 1379 (2003)
Three-Dimensional Measurement of Object by Using Gray Gradient of CCD Image
[in Chinese], and [in Chinese]
A kind of method of measuring three-dimensional surface, gray gradient method, to use gray gradient of CCD image, is proposed. To use mid-variable skillfully, the mapping relation between gray gradient of CCD image and gradient of focused image surface(FIS) has been found, and the gray restricting equation has been chaA kind of method of measuring three-dimensional surface, gray gradient method, to use gray gradient of CCD image, is proposed. To use mid-variable skillfully, the mapping relation between gray gradient of CCD image and gradient of focused image surface(FIS) has been found, and the gray restricting equation has been changed into solvable monadic equation to find depth information on the FIS. By the restriction of geometry optics and space conjugate symmetric relation between focused image surface and object, the FIS is changed into trim size, so the aim to measure three-dimensional is turned into reality. Finally, the error factors affecting the system have been analyzed. The method overcomes the defect that traditional light-sectioning method is low efficient because of the tedious number of images, and its restricting conditions are not rigorous. The experiment with sphere and cylinder, error ratio of which is 6.0% and 4.85% respectively, shows the method is effective in the definite range..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 23, Issue 11, 1384 (2003)
Optimal Unbiased Method with Adaptive Weights in Crossing Measurement
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In the process of measuring the aerial object with measuring stations, the crossing measurement results of every two stations are not absolutely consistent. And sometimes there may exist distinct differences. An optimal unbiased method with adaptive weights is proposed. Based on the least square principle, the expressiIn the process of measuring the aerial object with measuring stations, the crossing measurement results of every two stations are not absolutely consistent. And sometimes there may exist distinct differences. An optimal unbiased method with adaptive weights is proposed. Based on the least square principle, the expression of the least square result is deduced. The optimal weights are given with the constrained optimization method. Considering that the weights are related to the position of the target image on the CCD plane, the idea of adaptive weights is introduced, i.e. the weights can be adjusted as the position of the target image changes. Compared with the traditional methods, this method utilizes the measurement information from different stations sufficiently, and improves the accuracy evidently. The test results show that the optimal method with adaptive weights can decrease the average error to 40% compared with the traditional methods..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 23, Issue 11, 1389 (2003)
Optimization of a Practical Real-Time Temperature Measurement System
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Based on the Kirchhoff law, a practical real-time temperature measurement system using laser diode and LiTaO 3 pyroelectric detector is developed. According to the relations between main specifications(temperature measurement resolving power, standard deviation and range) and main technical parameters of the instrumentBased on the Kirchhoff law, a practical real-time temperature measurement system using laser diode and LiTaO 3 pyroelectric detector is developed. According to the relations between main specifications(temperature measurement resolving power, standard deviation and range) and main technical parameters of the instrument, such as laser energy and wavelength of emitting source, bandwidth of amplifier and relative aperture of optical system, the above technical parameters are optimized. Experimental results show that temperature measurement accuracy is better than 0.3% and temperature resolution is better than 0.4 K at 673～1473 K. They are both in accordance with the requirement..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 23, Issue 11, 1394 (2003)
Angular Distribution of Backscattered Light from Locally Pathological Tissues Irradiated by Pencil Light
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Semi-infinite normal tissues embedded a heterogeneous layered tissue is chosen as the simplified tissue model of local-pathological-changed tissues. Based on the model, double-adding method is introduced to calculate the angular distribution of backscattered light from local-pathological-changed tissues. According to tSemi-infinite normal tissues embedded a heterogeneous layered tissue is chosen as the simplified tissue model of local-pathological-changed tissues. Based on the model, double-adding method is introduced to calculate the angular distribution of backscattered light from local-pathological-changed tissues. According to the numerical calculations, the effects of geometrical and optical parameters of tissue models on the angular distribution of backscattered light are analyzed comprehensively. It is concluded that the variation of light intensity originated from local-pathological-changes tissues highly depends on the exit angle of backscattered light——the variation of backscattered light with small exit angle is much more obviously than that of backscattered light with large exit angle. The results also show that the angular distribution of backscattered light is much more sensitive to the geometrical parameters than the optical parameters of pathological-changes tissues. Finally,the angular distributions of backscattered light applied in diagnosing the abnormal object hided in normal tissues..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 23, Issue 11, 1402 (2003)
Fiber Optics and Optical Communications
Design of an Etched Diffraction Grating with Flat-Field Input/Output
[in Chinese], [in Chinese], and [in Chinese]
Wavelength division multiplexing(WDM) is in a great development recent years to meet the fast-grown demand for the communication capacity, and dense wavelength division multiplexing(DWDM) has been put into a successful commercial use. As a key device in a DWDM system, etching diffraction grating(EDG) is a planar waveguWavelength division multiplexing(WDM) is in a great development recent years to meet the fast-grown demand for the communication capacity, and dense wavelength division multiplexing(DWDM) has been put into a successful commercial use. As a key device in a DWDM system, etching diffraction grating(EDG) is a planar waveguide DWDM device with a great potential. Although an EDG is harder to fabricate than an AWG(arrayed waveguide grating), it has a better spectral fineness and can easily implement more output channels. A design method for an EDG of flat input/output is presented. The scalar diffraction theory is used to verify the design, the numerical results show that the designed EDG has a good performance. A conventional EDG design is based on the Rowland circle on which the end points of the input and output waveguides are located. This configuration has a good focal property but needs the fabricating of the output channels to couple the light with output fibers. An EDG of flat-field input/outputs can also maintain a good linear dispersion and a perfect focused field as a conventional EDG..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 23, Issue 11, 1306 (2003)
The Influence of Pumping Configuration in Hybrid Raman Fiber Amplifier on Its Performance
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The performance of forward-and backward-pumped Raman fiber amplifier/erbium doped fiber amplifier(EDFA) hybrid amplifiers was experimentally compared. 75 km standard single mode fiber(SSMF) was employed as the transmission line. 20 channels in C-band with a total power of -2.86 dBm, ranging from 1537.377 to 1560.605 nmThe performance of forward-and backward-pumped Raman fiber amplifier/erbium doped fiber amplifier(EDFA) hybrid amplifiers was experimentally compared. 75 km standard single mode fiber(SSMF) was employed as the transmission line. 20 channels in C-band with a total power of -2.86 dBm, ranging from 1537.377 to 1560.605 nm on the ITU-T grid were used as the incident signals of hybrid amplifiers. Each channel was modulated by an electro-absorption(EA) modulator using a 2.5 Gb/s nonreturn-to-zero(NRZ) format, with a 27-1 long pseudo-random bit sequence(PRBS) signal. Experimental results have suggested some of relative merits of forward-pumped RFA/EDFA hybrid amplifiers. The improvement of noise figure(NF) arranged from 2.24 dB to 6.55 dB. The gain increase was higher than 5 dB for any channel in forward-pumped hybrid amplifiers in comparison with backward-pumped hybrid amplifiers. However, the optical signal-to-noise ratio(OSNR) is higher than 26.9 dB in either pumped configuration for hybrid amplifiers..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 23, Issue 11, 1311 (2003)
Research on Lasing Wavelength of Fiber Grating Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
In the research work of fiber Bragg grating(FBG) based lasers, it was found out that the lasing light shifted away from the Bragg wavelength of the FBG. The lasing wavelength can either be longer or shorter than the Bragg wavelength of the FBG. Further study on erbium- and ytterbium-doped fiber grating lasers with bothIn the research work of fiber Bragg grating(FBG) based lasers, it was found out that the lasing light shifted away from the Bragg wavelength of the FBG. The lasing wavelength can either be longer or shorter than the Bragg wavelength of the FBG. Further study on erbium- and ytterbium-doped fiber grating lasers with both ring and linear cavity has shown that, the phenomenon of wavelength shift was caused by the anisotropy of the laser cavity. The maximum wavelength shifting value was limited mostly by the bandwidth of the fiber grating. Through the online polarization controller, the lasing wavelength can be controlled within the bandwidth of the FBG..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 23, Issue 11, 1315 (2003)
Two2Dimensional Wide-Angle Finite Difference Beam Propagation Method Based on the Square Root Operator
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The finite difference beam propagation method(FD-BPM)is very powerful and has been widely used for optical waveguide design. The precision of the method is decided by the order of Padé approximation and the step of calculation, which means higher order and smaller step will introduce smaller error, but the calculaThe finite difference beam propagation method(FD-BPM)is very powerful and has been widely used for optical waveguide design. The precision of the method is decided by the order of Padé approximation and the step of calculation, which means higher order and smaller step will introduce smaller error, but the calculation time will be longer. For the purpose to obtain higher precision and shorter calculation time, some trial methods are used, and some new second order formulas expanded from the square root operator for BPM are got, and the numerical simulations show that the coefficients of those new second order formulas are more precise than that of the conventional one. Furthermore, the analysis also indicates that those trial methods can be applied to the higher order formulas for the FD-BPM..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 23, Issue 11, 1325 (2003)
Filtering Out the First-Order Mode and Its Application in Y-Branch and Multimode Interferometric Structure
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The Y-branch and multimode interferometric(MMI) structure are used in many kinds of planar lightwave circuits, and the symmetrical output of Y-branch or MMI structure takes important role in these apparates. The main factor that introduces asymmetry into the output of Y-branch or MMI structure is the first-order mode gThe Y-branch and multimode interferometric(MMI) structure are used in many kinds of planar lightwave circuits, and the symmetrical output of Y-branch or MMI structure takes important role in these apparates. The main factor that introduces asymmetry into the output of Y-branch or MMI structure is the first-order mode guided by them. A coupler in which the waveguides which can only guide the fundamental modes are located on both sides of the multimode waveguide is designed, and this coupler can filter out the first order mode guided by it. This coupler is used in Y-branch and MMI structure, and the simulation results show that the output of Y-branch and MMI structure with this coupler has better symmetry in comparison with traditional structure..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 23, Issue 11, 1330 (2003)
Fourier Optics and Signal Processing
Study on Signal-to-Noise Ratio Estimation and Compression Method of Operational Modular Imaging Spectrometer Multi-Spectral Images
[in Chinese], and [in Chinese]
The text adopts two methods named local standard deviation and de-correlation to estimate the signal-to-noise ratio of operational modular imaging spectrometer(OMIS) multi-spectral images. The methods have reduced the influence of object texture change to a very low extent. In this way, after atmosphere correction the The text adopts two methods named local standard deviation and de-correlation to estimate the signal-to-noise ratio of operational modular imaging spectrometer(OMIS) multi-spectral images. The methods have reduced the influence of object texture change to a very low extent. In this way, after atmosphere correction the signal-to-noise ratio characteristic of OMIS images can reflect that of the OMIS instrument sufficiently. With regard to the image compression, the text proposes to control the peak signal-to-noise ratio of resumed image of each band exactly bigger than the signal-to-noise ratio of original image of the same band, which limits the noise brought by the compression algorithm of self within the noise of original images. Combining the thought dimensioned above, with discrete cosine transform-based and DWT-based compression algorithms, the OMIS multi-spectral images are compressed. The results indicate that the resumed image information is almost lossless in the bands of high signal-to-noise ratio is 45.86 dB..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 23, Issue 11, 1335 (2003)
Geometric Optics
Numerical Analysis of Micro-Aperture Laser for Near Field Optical Data Storage
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The very small aperture laser(VSAL) is an important light source used in the near-field optical storage system. The near-field property of VSAL′s output light is studied. The optical characteristics and the intensity distribution in the near-field of the output region,that is, micro-aperture metallic film, of the VSAL The very small aperture laser(VSAL) is an important light source used in the near-field optical storage system. The near-field property of VSAL′s output light is studied. The optical characteristics and the intensity distribution in the near-field of the output region,that is, micro-aperture metallic film, of the VSAL have been numerically simulated by using two-dimensional nonlinear finite difference time domain(2D-NL-FDTD) method and the Fox-Li method with angle spectrum. Through analyzing the results from the viewpoint of the optics, the possible application in the near-field optical recording have been discussed, and some curves indicating the near-field optical charactersistics of the output light have been presented. It is found that because of the localized surface plasmon ehnancement for the TM mode, the output of TM mode is about ten times stronger than the one of TE mode and more suitable for being used in the near-field optical storage system..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 23, Issue 11, 1281 (2003)
Lasers and Laser Optics
Figure-Eight Shape Actively and Passively Mode-Locked Erbium-Doped Fiber Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The advantages of using NOLM as saturable absorber to compress pulse in mode-locked fiber lasers are analyzed theoretically. Experimentally the NOLM is placed in an actively mode-loked erbium-doped fibre ring laser to form a figure-eight actively and passively mode-locked fibre laser. 12 ps mode-locked pulses centered The advantages of using NOLM as saturable absorber to compress pulse in mode-locked fiber lasers are analyzed theoretically. Experimentally the NOLM is placed in an actively mode-loked erbium-doped fibre ring laser to form a figure-eight actively and passively mode-locked fibre laser. 12 ps mode-locked pulses centered at 1.543 μm were obtained at the modulation frequency of 2.498749 GHz, with time-bandwidth product of 0.33. 3.715 mW output power is achieved with 50 mW pump power. Meanwhile, 2～4 rational harmonic(RH) mode-locked pulses with uniform amplitude were obtained at the modulation frequency of 2.499344 GHz, 2.499114 GHz, and 2.498999 GHz respectively..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 23, Issue 11, 1341 (2003)
Symmetrically Side2Pumped Sol id2State Laser with Single Diode Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A new configuration of laser diode side-pumped solid-state laser is put forward. The pumping configuration divides the pumping beam of one laser diode bar into four equal portions and produces a symmetric pumping the laser medium. A ray trace simulation of the pumping beam absorption in the rod medium is made, and the A new configuration of laser diode side-pumped solid-state laser is put forward. The pumping configuration divides the pumping beam of one laser diode bar into four equal portions and produces a symmetric pumping the laser medium. A ray trace simulation of the pumping beam absorption in the rod medium is made, and the effect of the absorption coefficient and laser rod diameter on the uniformity of the absorbed pumping energy distribution and the energy absorption ratio is got. An optimization of proper parameters also is made. The configuration is simple, it is very easy to obtain high beam quality output laser beam with it. A novel laser head is made with this configuration, and the initial experimental results are fairly good, which show the feasibility of this configuration..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 23, Issue 11, 1370 (2003)
Materials
Ultraslow Group Velocity in Photonic Crystal with a Dispersive Defect
[in Chinese], and [in Chinese]
By means of transfer matrix method, The complex transmission coefficient through one-dimensional photonic crystal with a dispersive defect which is described by the Lorentz oscillator model is calculated. The equivalent index of refraction defined through the complex transmission coefficient is calculated and the groupBy means of transfer matrix method, The complex transmission coefficient through one-dimensional photonic crystal with a dispersive defect which is described by the Lorentz oscillator model is calculated. The equivalent index of refraction defined through the complex transmission coefficient is calculated and the group velocity of an optical pulse with frequency spectrum around the defect mode frequency is investigated. It is found that the equivalent dispersion of the photonic crystals relies strongly on the dispersion of the defect because the transmission spectrum depends sensitively on the optical thickness of the defect which varies with frequency. Since the pulse is composed of a variety of monochromatic field and the transmitted pulse is a re-superposition of all transmitted monochromatic components, the behavior of the pulse propagation is determined by the equivalent dispersion of the medium. Compared with the case that the defect is non-dispersive, the dispersion of the defect layer leads to an ultraslow group velocity. By changing the strength of the oscillator, the group velocity can be changed from subluminal(slower than the vacuum light speed) to superluminal(faster than the vacuum light speed)..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 23, Issue 11, 1287 (2003)
Investigating the Fiber Bragg Grating in the Scope of the Photonic Crystal
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The band structure and the transmission properties of the fiber Bragg grating are investigated in the scope of the photonic crystal. The plane wave expansion method is used to analyze the photonic crystal, and is translated into the scope of the fiber Bragg gratings. The optical properties of the fiber Bragg grating arThe band structure and the transmission properties of the fiber Bragg grating are investigated in the scope of the photonic crystal. The plane wave expansion method is used to analyze the photonic crystal, and is translated into the scope of the fiber Bragg gratings. The optical properties of the fiber Bragg grating are obtained after plenty of numerical computations. It shows that there are many reflection peak-value frequencies, which are integer times to the fundamental frequency. Every peak-value frequency reflects a photonic band gap, its center frequency and band width are related with the grating parameters, such as the grating length, the index modulation depth, and the duty ratio of the material with high dielectric constant. All results are same as those from the conventional coupling mode theory..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 23, Issue 11, 1291 (2003)
Nonlinear Optics
The Z-Scan Study of Azo Disperse Red Polymer Film
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A new type of optical storing material, the film sample of azobenzene disperse red polymer is measured by using the single beam Z-scan technique. The experimental results show that the nonlinear refractive index of the sample is a negative value. For eliminating the influence of nonlinear absorption, the Z-scan curve wA new type of optical storing material, the film sample of azobenzene disperse red polymer is measured by using the single beam Z-scan technique. The experimental results show that the nonlinear refractive index of the sample is a negative value. For eliminating the influence of nonlinear absorption, the Z-scan curve with an aperture is treated with the Z-scan curve without the aperture. The nonlinear refractive index of this type of azo polymer film is determinated as -5.5×10 -6 cm2/W according to the experimental data of Z-scan curve. The value of azo polymer film is larger 8～9 scales than the common inorganic materials. This material will have a very good prospect in the application of optical storage. The reason of large nonlinear refractive index in this material is discussed. Through pilot study, under the irradiation of linear polarized beam, azo molecules became anisotropic. These molecules just like liquid crystal are relevant each other well, response of molecular orientation to outside irritation is a collective effect, therefore they have have very large nonlinear response..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 23, Issue 11, 1296 (2003)
Third Harmonic Generation Property of 1064 nm in Nonlinear Optical Crystal BiB3O6 of Low Symmetry
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
By high-temperature solution method, BIBO crystal with high optical quality is grown out successfully. The size reached 24 mm×19 mm×35 mm, and the weight is 48 g. For BIBO crystal the orientation, as well as the refractive index on the main optical axis, is measured. The third harmonic generation(THG) propertBy high-temperature solution method, BIBO crystal with high optical quality is grown out successfully. The size reached 24 mm×19 mm×35 mm, and the weight is 48 g. For BIBO crystal the orientation, as well as the refractive index on the main optical axis, is measured. The third harmonic generation(THG) property of 1064 nm in BIBO crystal, including phase-matching(PM) angle, effective nonlinear optical coefficient(d eff), angler acceptance, and walk-off angle is discussed. The results show that the optimum configuration for the THG of 1064 nm in BIBO crystal is at the Type-I PM direction(137.7°,130°), which has a d eff of 3.60 pm/V. Among PM directions located in principal planes,(146.4°,90°) has the largest d eff value, i.e. 3.16 pm/V. In extra-cavity THG experiments of 1064 nm, the conversion efficiency of(146.4°,90°) BIBO crystal reached 39.5 %, and the half-width of its angular acceptance is measured to be 0.22 mrad·cm, which is in good consistent with the calculated value, 0.175 mrad·cm. For(33.6°,90°) BIBO crystal, because the deff is very small(0.31 pm/V), its THG conversion efficiency is lower than 5%..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 23, Issue 11, 1300 (2003)
Physical Optics
A Simple Method for Computing Optimum Weighting Table for Colorimetric Tristimulus Integration
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The computation of tristimulus values is a basic step for obtaining various colourimetric quantities. Firstly, the definition of CIE tristimulus values and their numerical computation methods are reviewed. Secondly, three types of ASTM weighting tables used in industrial applications and Venable optimum weighting tableThe computation of tristimulus values is a basic step for obtaining various colourimetric quantities. Firstly, the definition of CIE tristimulus values and their numerical computation methods are reviewed. Secondly, three types of ASTM weighting tables used in industrial applications and Venable optimum weighting tables are briefly described and discussed. Finally, based on the work of Venable, a criterion different from that of Venable's in form for determining the optimum weighting factors to minimize the influence of errors in measurement of spectral reflectance is proposed, and a new and simple method for computing the optimum weighting table is given. The new method is simpler and easier to program and thus is possible to be used as a standard method, as compared with other existing weighting tables. Numerical simulation results show that the tristimulus values computed by using the method proposed are closest to the CIE definition compared with those computed by using the three types of ASTM weighting tables. Therefore, it is expected that the new method for computing weighting tables will find wide industrial applications..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 23, Issue 11, 1346 (2003)
Interferometric Measurement of the Line Density of Varied-Line-Space Gratings
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Varied-line-space grating is very useful in synchrotron radiation devices and laser fusion devices, but there are no good ways to measure them. The line density of varied-line-space gratings have been measured by using interferometry. The principle and geometry are introduced, the methods of data processing and the resVaried-line-space grating is very useful in synchrotron radiation devices and laser fusion devices, but there are no good ways to measure them. The line density of varied-line-space gratings have been measured by using interferometry. The principle and geometry are introduced, the methods of data processing and the results are given. On the surface of grating to be tested, quantity and density of diffracted light interferometric fringes are difference of interferometric fringes of incident light and grating groove quantity multiplied. Two sets of waves are in the common path, it is easier to make adjustment and measurement. Interference in interferometric image is removed by mid-value filtering method. Two projects are put forward for different interference fringes. The invariance of relative density is brought forward. The grating diffracts two coherent incident waves, the fringes appear, the density relates to groove density, if the incidence angles and the diffraction orders and the position of fringes are known, the groove density can be calculated. The method can satisfy the requirements of varied-line-space gratings, and its is suitable in the measurement of varied-line-space gratings and can reach some precision. Finally, the method is suggested into fabrication of holographic varied-line-space gratings..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 23, Issue 11, 1354 (2003)
Design and Fabrication of Subwavelength Antireflection Gratings
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
To reduce the polarization sensitivity of antireflection gratings, a particular rectangular structure was analyzed by genexating equivalent medium theory(EMT) to two-dimensional subwavelength structure. An approximate equivalent coefficient for two-dimensional subwavelength was obtained with the related expressions of To reduce the polarization sensitivity of antireflection gratings, a particular rectangular structure was analyzed by genexating equivalent medium theory(EMT) to two-dimensional subwavelength structure. An approximate equivalent coefficient for two-dimensional subwavelength was obtained with the related expressions of grating structure. A two-dimensional subwavelength antireflection grating designed for 10. 6 μm was fabricated on a Si substrate by using binary optical processing. The results show that this grating st ructure was similar to a single antireflection film at 10. 6 μm..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 23, Issue 11, 1359 (2003)
Thin Films
Analysis of the Reflectivity of Mo/Si Multilayer Film for Sof t X-Ray
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Because of interface imperfections such as interfacial roughness and diffuseness, the practical reflectivity of soft X-ray multilayer film is lower than the calculated one. Stearn scattering method describes the scattering of single non-ideal interface and is applicable for soft X-ray short wavelength region. Its matheBecause of interface imperfections such as interfacial roughness and diffuseness, the practical reflectivity of soft X-ray multilayer film is lower than the calculated one. Stearn scattering method describes the scattering of single non-ideal interface and is applicable for soft X-ray short wavelength region. Its mathematical model is used to describe the multilayer interface roughness, and the least square curve fitting, which is based on the test of fit, is used to fit the experimental reflectivity of Mo/Si multiplayer film by using synchrotron radiation, and good fitting results are obtained. Meanwhile the multilayer period thickness, the ratio of thickness, the interface width and the instrumental spectral resolution are analyzed. The parameters of multilayer such as roughness, diffuseness, period thickness and so on, impact of instrument′s spectral resolution on the reflectivity of multilayer were determined, and at the same time the fitting for the analysis of the structural parameters of multilayers is essential in the future fabrication of multilayers..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 23, Issue 11, 1362 (2003)
The Relationship Between Porous Ratio and Refractive Index in Nanoporous Film
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The finite difference time domain(FDTD) method is used to construct the model of nanoporous film and to simulate the propagation of plane lightwave in the film and calculate some refractive indices according to different ratios of pore. From these simulation results, it is found that equivalent refractive index of nanoThe finite difference time domain(FDTD) method is used to construct the model of nanoporous film and to simulate the propagation of plane lightwave in the film and calculate some refractive indices according to different ratios of pore. From these simulation results, it is found that equivalent refractive index of nanoporous film will decrease with increase of porous ratio. By using equivalent dielectric constant theory of composite media in solid-state matercal science a theoretical model called composite media in parallel is proposed to explain the connection between the porous ratio and equivalent refractive index of the nanoporous film, and function expression between them is obtained. With the comparison between the function curve and the simulation results, it is found that the function curve based on the theoretical model of composite media in parallel is in accord with the results simulated by FDTD method..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 23, Issue 11, 1366 (2003)
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