Contents
2005
Volume: 25 Issue 11
29 Article(s)
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Atmospheric Optics and Oceanic Optics
CS2 Measurement with Differential Optical Absorption Spectroscopy
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
CS2, a kind of poisonous gas, with bad smell, is very harmful to people. In China, precise and real-time CS2 monitoring is required in many big cities. With traditional measurement method, it is expensive and time-consuming, moreover it is very difficult to achieve real-time monitoring. A new CS2 measurement method wasCS2, a kind of poisonous gas, with bad smell, is very harmful to people. In China, precise and real-time CS2 monitoring is required in many big cities. With traditional measurement method, it is expensive and time-consuming, moreover it is very difficult to achieve real-time monitoring. A new CS2 measurement method was developed, based on differential optical absorption spectroscopy (DOAS), and the data processing method was discussed in detail. The selection of measurement waveband, steps of data processing and the spectrum dealing with nonlinear method were involved. Also the nonlinear dealing method of standard cross section was realized based on the analysis of lamp spectrum structure in the measuring waveband. With this method, not only the influence of lamp spectrum structure in the CS2 measurement band was effectively avoided, but also high measurement precision was gotten. Three different concentration cells were measured with this method, and high linear relativity was achieved. In the process of real-time and continuous monitoring in some place of Nanjing, a good result was gotten..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 11, 1441 (2005)
Effects of Large Telescope Aberrations on Speckle Imaging
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The effect of the optical system aberrations on the restoration imagery is investigated when the speckle imaging technique is used to process the images of the astronomic telescope. Under the basis of analyzing the method and the theory on the restoration of the modulus and the phase, a speckle imaging model which inclThe effect of the optical system aberrations on the restoration imagery is investigated when the speckle imaging technique is used to process the images of the astronomic telescope. Under the basis of analyzing the method and the theory on the restoration of the modulus and the phase, a speckle imaging model which includes the Labeyrie's speckle interferometry and the Knox-Thompson imaging technique is presented. The effects of telescope aberrations on the involving the modulus and the phase of object Fourier transform due to the random wave front phase distribution of system trarfer function and the restoration of the object phase are discussed. The deterministic optical aberrations are submerged in the random phase of the transfer function introduced by the atmospheric turbulence. The restoration image shows that the speckle imaging technique can remove the effects of the deterministic aberrations and atmospheric turbulence on the estimated images, and the high resolution image is obtained. A method of compensating optical system aberrations is proposed..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 11, 1447 (2005)
Diffraction and Gratings
Optical Characteristics Analysis and Simulation of Grating Light Valve
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The grating light valve (GLV), and optical modulator based on microelectromechanical systems (MEMS), with the changable components mobile ribbons on its surface, can serve as a diffractive grating, and be used in projection and display fields. The optical performance of GLV is analyzed in details and simulated with intThe grating light valve (GLV), and optical modulator based on microelectromechanical systems (MEMS), with the changable components mobile ribbons on its surface, can serve as a diffractive grating, and be used in projection and display fields. The optical performance of GLV is analyzed in details and simulated with interference and diffraction theory. All these indicate that when the GLV is in on state, the mobile ribbons should drop a quarter of the incident wavelength. When the reflectivity of the air gap is different, the effect of the duty ratio on the optical properties is different. The best matching value of duty ratio and reflectivity is presented..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 11, 1452 (2005)
Experimental Study of the Holographic Grating to Produce the Laguerre-Gaussian Modes
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Laguerre-Gaussian (LG) mode is the eigen-state of the orbital angular momentum of photon. It has potential applications in the fields of optical tweezer, quantum information process and computation. Two kinds of recording mediumsholographic plate and ink-jet transparent film are used to manufacture the holographic gratLaguerre-Gaussian (LG) mode is the eigen-state of the orbital angular momentum of photon. It has potential applications in the fields of optical tweezer, quantum information process and computation. Two kinds of recording mediumsholographic plate and ink-jet transparent film are used to manufacture the holographic grating. Laguerre-Gaussian (LG) modes with topological indices from the first order to high order have been observed in the experiment. It is also noticed the high order modes are spatial unstable. Furthermore, the related controlling parameters, such as the exposure time and intensity which influence the diffraction efficiency, are discussed in detail..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 11, 1457 (2005)
Fiber Optics and Optical Communications
Study on a Small Probe Optical Liquid Level Sensor Based on the Connected Vessels
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Both of the theoretical analysis and experiments show that when the diameter of the waveguide and the light wavelength are fixed, the optical power loss increases linearly with the increase of the Hg cladding optical waveguide (HCOW) length. The theory and signal processing of the optical liquid level sensor with HCOW Both of the theoretical analysis and experiments show that when the diameter of the waveguide and the light wavelength are fixed, the optical power loss increases linearly with the increase of the Hg cladding optical waveguide (HCOW) length. The theory and signal processing of the optical liquid level sensor with HCOW as its probe are analyzed, it works based on the theory of connected vessel, which converts the change of liquid level to the change of the length of the HCOW. By optimized design, the real time detection of the liquid level with high precision can be got. The experimental results show that the measurement accuracy is 5.2 mm within 10 m liquid level, its theory precision can up to 0.02%. The research of this liquid level senor may offer significant metrological improvement by reason of its safety in corrosive or explosive environments, especially in the liquid level detection of oil depot..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 11, 1461 (2005)
40 Gb/s All-Optical 3R Regeneration
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A novel 40 Gb/s 3R regenerator was proposed and demonstrated based on two-ring injection mode-locked fiber laser as the clock recovery and electroabsorption modulator as the reshaping optical gate. The effect of the shape of the transmission spectrum of the optical filter on the output pulses of actively mode locked fiA novel 40 Gb/s 3R regenerator was proposed and demonstrated based on two-ring injection mode-locked fiber laser as the clock recovery and electroabsorption modulator as the reshaping optical gate. The effect of the shape of the transmission spectrum of the optical filter on the output pulses of actively mode locked fiber ring laser has been studied experimentally and numerically. It was found that, with the same 3 dB bandwidth, the filter which had a super-Gaussian profile tended to generate narrow pulses. With this scheme, an optical clock pulse train with a spectrum bandwidth of 0.44 nm, a pulse-width of about 6 ps and a timing jitter of <1 ps was recovered. The transmission function of optical gate was improved by optimizing the design of parameters to approach the step function. The width of the switching window was also optimized. With this regenerator, error-free 3R regeneration was performed from 40 Gb/s RZ signal that was degraded by residual dispersion..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 11, 1467 (2005)
SFDM/CWDM of Fiber-Optic Fizeau Strain Sensors
[in Chinese], [in Chinese], and [in Chinese]
A novel method for a large number of multiplexing fiber-optic Fizeau sensors using coarse wavelength division multiplexing (CWDM) and spatial-frequency division multiplexing (SFDM) is proposed and demonstrated. A CWDM device is used to multiplex signals from different sensor channels occupying different wavelength regiA novel method for a large number of multiplexing fiber-optic Fizeau sensors using coarse wavelength division multiplexing (CWDM) and spatial-frequency division multiplexing (SFDM) is proposed and demonstrated. A CWDM device is used to multiplex signals from different sensor channels occupying different wavelength regions divided by the CWDM. The structure and principle of multiplexing fiber-optic Fizeau sensor are described, and the effect and reduction of cross-talk resulted from the multiplexing are analyzed. More than 10 Fizeau sensors arranged in a single channel can be multiplexed by using SFDM due to the long cavity length of the Fizeau sensor. The experimental results show that a strain accuracy of 5 με is achieved. There is little cross-talk between adjacent CWDM channels and also between two adjacent Fizeau strain sensors with certain cavity length difference. This system improves the multiplexing capability of Fizeau strain sensors significantly. It is anticipated that such a sensor system could find important applications in smart materials and health monitoring for large structures..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 11, 1472 (2005)
Image Processing
Adaptive Rate Control Algorithm for Interference Multi-Spectral Image Compression
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A method for interference multi-spectral image coding is proposed based on region of interest (ROI) coding of embedded block coding with optimized truncation (EBCOT). After wavelet transform, the vertical wavelet decomposition is taken for the ROI which include the multi-spectral information in the high frequency subbaA method for interference multi-spectral image coding is proposed based on region of interest (ROI) coding of embedded block coding with optimized truncation (EBCOT). After wavelet transform, the vertical wavelet decomposition is taken for the ROI which include the multi-spectral information in the high frequency subband,and the coefficients of ROI are lifted by bit-plane. The different significant weights are given to different coding passes in different bit-planes, which are encoded in the significant weights order in T1 encoder. T2 encoder gives feedback to control the coding depth according to the accumulated bit rate, and the rate-distortion optimization truncation is completed at last. The experimental results show that the proposed scheme can improve the reconstructed image quality and efficiently reduce the computational complexity and memory usage of EBCOT (for test image at bpp=1, the average peak signal-noise ratio of the whole, the ROI and the background increases more than 0.1 dB, and the average computational complexity and memory usage reduces more than 40% and 60%), which is suitable for hardware implementation of interference multi-spectral image compression system..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 11, 1477 (2005)
An Improved Reconstruction Algorithm for Optical Tomography
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Adjoint differentiation method is used in reconstruction algorithm for optical tomography by Alexander D. Klose, but the algorithm of getting derivatives with respect to optical parameters is mistakenly proposed by him, and it can only implement the computation of derivative with respect to optical parameters on the boAdjoint differentiation method is used in reconstruction algorithm for optical tomography by Alexander D. Klose, but the algorithm of getting derivatives with respect to optical parameters is mistakenly proposed by him, and it can only implement the computation of derivative with respect to optical parameters on the boundary, those derivatives with respect to the internal parameters cannot be obtained there. This will lead to the failure of the reconstruction. Based on the adjoint differentiation method, an improved algorithm with a tree structure is proposed for the computation of derivatives, and a specific method about the derivative with respect to internal optical parameters is put forward. In order to decrease the computation complexity, an approximate strategy about gradient computation is adopted in the experiment. Experimental results show that this kind of algorithm can implement the computation of derivatives with respect to internal optical parameters effectively. The approximate algorithm can make the computation less complex, improve the speed of computation and get good quality of reconstruction at the same time..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 11, 1483 (2005)
Instrumentation, Measurement and Metrology
Research on the Method of High Accuracy Measurement by Use of Low Accuracy CCD
[in Chinese], [in Chinese], and [in Chinese]
For higher measurement accuracy of linear charge coupled device (CCD), a new method of using CCD was proposed. Several linear CCDs were fit together, and staggered by the distance of H/N, H was space between pixels, N was CCD amount. The photo electric signals were collected in-phase by multicenter A/D, and saved in meFor higher measurement accuracy of linear charge coupled device (CCD), a new method of using CCD was proposed. Several linear CCDs were fit together, and staggered by the distance of H/N, H was space between pixels, N was CCD amount. The photo electric signals were collected in-phase by multicenter A/D, and saved in memorizer. Then accurate value was obtained through analyzing all these data. Diameters of 5.000 mm, 8.000 mm and 12.000 mm of three standard poles were measured by single CCD and two staggered CCD with 30 mm stagger long. The result showed that accuracy using two staggered CCD was twice as high as that using single CCD. The method could avoid space between pixels astriction theoretically, so higher measurement accuracy was gained..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 11, 1488 (2005)
Two-Beam-Contracted Radial Shearing Interferometer for Measuring the Gas Temperature Field
[in Chinese], and [in Chinese]
A new two-beam-contracted radial shearing interference optical system is developed to study on the large field of gas temperature. Methods of fast Fourier transform (FFT) and phase unwrap were used to demodulate the phase of the interferogram obtained from experiment, distortion of wavefront disturbed by temperature flA new two-beam-contracted radial shearing interference optical system is developed to study on the large field of gas temperature. Methods of fast Fourier transform (FFT) and phase unwrap were used to demodulate the phase of the interferogram obtained from experiment, distortion of wavefront disturbed by temperature fluctuation which equals to phase shift induced by refractive index change was calculated, and a way of axisymmetric temperature field reconstruction was put into reshowing a layer of the gas temperature distribution. By comparing, the difference is equivalent to that of the mini-thermocouple. Experimental result shows that the optical system is reasonably sensitive and precise. It is suitable for measuring the phase object of which the lateral size is the larger and the longitudinal size is the shorter, when the difference of the temperature is little compared with the environment..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 11, 1493 (2005)
Measurement System of Ultra-Wideband Frequency Response Based on Optical Heterodyne Technique
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
An ultra-wideband frequency response measurement system for optoelectronic devices has been established using the optical heterodyne detection method utilizing a tunable laser and wavelength-fixed distributed feedback-laser diode. By controlling the laser diode cavity length, the beat frequency is swept from DC to beyoAn ultra-wideband frequency response measurement system for optoelectronic devices has been established using the optical heterodyne detection method utilizing a tunable laser and wavelength-fixed distributed feedback-laser diode. By controlling the laser diode cavity length, the beat frequency is swept from DC to beyond 100 GHz, and ultra-wideband frequency response character can be measured without using any high-speed light modulation source and additional calibration. This is the major advantage of this method. In the measurement, two InGaAs p-i-n detectors have been tested, and their 3 dB bandwidths are 14.4 GHz and 40 GHz, respectively. Experiments show that this method is accurate and easy to carry out. Finally, several suggestions for improving measurement accuracy are given..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 11, 1497 (2005)
Improvement of the Position Accuracy and Linearity in One-Dimensional Position Sensitive Detector
[in Chinese], and [in Chinese]
In a conventional, strip-type one-dimensional (1-D) position sensitive detector (PSD) the sensitive area and the position resistance area are combined together, the ohmic contact structure of the device is handicapped, so its accuracy and linearity is affected adversely. The sensitive area and position resistance area In a conventional, strip-type one-dimensional (1-D) position sensitive detector (PSD) the sensitive area and the position resistance area are combined together, the ohmic contact structure of the device is handicapped, so its accuracy and linearity is affected adversely. The sensitive area and position resistance area in a comb-type 1-D PSD are separated to become the comb teeth and comb ridge area respectively, moreover the position resistance area is made very narrow, even if the doping concentration is rather high, the position resistance can also be made quite large, so that the restriction that is imposed on the contact structure previously can be lifted. The position characteristic curve measured on two different kinds of 1-D PSDs verified authors' theoretical analysis, and showed that the accuracy and linearity of the comb-type 1-D PSD has been increased markedly; the average position error of the comb-type 1-D PSD is reduced to 26 μm from 55 μm of the strip-type 1-D PSD, and the RMS nonlinearity of the comb-type 1-D PSD is reduced to 0.09 % from 0.94 % of the strip-type 1-D PSD..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 11, 1501 (2005)
Lasers and Laser Optics
Pulse Duration Effect on the Ponderomotive Accelerating Electron
[in Chinese], [in Chinese], and [in Chinese]
Electron acceleration from the interaction of a Gaussian laser pulse with initial axial electron is investigated,using a single test electron model in vacuum. Under the different laser parameters, the electron energy gain depends on the laser intensity, focal spot size and pulse width.The electron energy gain have a opElectron acceleration from the interaction of a Gaussian laser pulse with initial axial electron is investigated,using a single test electron model in vacuum. Under the different laser parameters, the electron energy gain depends on the laser intensity, focal spot size and pulse width.The electron energy gain have a optimum focal spot size. There are no evident energy gain when the focal spot size is too big or small. Given the laser intensity,the optimum focal size increases with the pulse width, and the ratio of the optimum focal size to the pulse width is fixed..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 11, 1506 (2005)
Materials
Effects on the Morphology and Field Emission Properties of Carbon Nanotubes Treated by High-Energy Ball Milling
[in Chinese], [in Chinese], and [in Chinese]
Multi-walled carbon nanotubes (CNTs) deposited by chemical vapor deposition (CVD) were treated by ball-milling with different time, the morphology and structure of which were explored with scanning electron microscope and Raman spectra. The field emission properties of the cathode made of CNTs under different ball-millMulti-walled carbon nanotubes (CNTs) deposited by chemical vapor deposition (CVD) were treated by ball-milling with different time, the morphology and structure of which were explored with scanning electron microscope and Raman spectra. The field emission properties of the cathode made of CNTs under different ball-milling conditions were tesed. The results showed that, high-energy ball milling brought obvious effects on the morphology, structure and field emission property of the CNTs. A ball-milling time of 0.5～1.0 h resulted in a more even and uniform surface of the CNTs, enhanced the field emission properties, and also greatly increased uniform luminescent spots on the anode. The field emission properties can be degraded if the milling time is too long (>1 h), due to the resulting amorphism and graphitization of CNTs..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 11, 1510 (2005)
The Effect of GeO2 on the Optical Spectra of Bi2O3-B2O3-ZnO Glass Doped with Eu3+ Ions
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The (60-χ)Bi2O3-χTeO2-30B2O3-10ZnO(χ]5,10,20,30, mole fraction) with Eu3+ doped in 1% were fabricated by melting method. The differential thermal analysis (DTA) curves, emission and excitation spectra of the glasses were measured. The Ω2 and Ω4 parameters of Eu3+ for optical transition were calculated from their emissiThe (60-χ)Bi2O3-χTeO2-30B2O3-10ZnO(χ]5,10,20,30, mole fraction) with Eu3+ doped in 1% were fabricated by melting method. The differential thermal analysis (DTA) curves, emission and excitation spectra of the glasses were measured. The Ω2 and Ω4 parameters of Eu3+ for optical transition were calculated from their emission spectra in terms of reduced matrix U(t) (λ=2,4,6) character for optical transitions. The results indicate that the intensity parameters Ω2 and Ω4 increase with the increase of GeO2 contents. It suggests that the symmetry becomes lower, the band of Eu and O atoms becomes stronger and the covalency increases. The glass transition temperature (Tg) increases with increase of GeO2 content. When the content of GeO2 is about 10%, the different temperature between the glass transition and the crystallization onset temperature, about 146 ℃, reaches the biggest among the samples, indicating that the glass has the best thermal stability..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 11, 1515 (2005)
Medical Optics and Biotechnology
Impact of Higher-Order Wavefront Aberrations of Human Eyes on Vision Performance
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Accurate measurement of higher-order wavefront aberrations helps to improve retinal image quality and has an important clinical value. Wavefront aberrations of human eyes have been measured and the impact of higher-order aberrations on vision has been evaluated in this article. Hartmann-Shack wavefront sensor is used tAccurate measurement of higher-order wavefront aberrations helps to improve retinal image quality and has an important clinical value. Wavefront aberrations of human eyes have been measured and the impact of higher-order aberrations on vision has been evaluated in this article. Hartmann-Shack wavefront sensor is used to measure the aberrations and the eye's vision is evaluated with modulation transfer function (MTF), contrast sensitivity function (CSF) and Strehl ratio. Visual acuity and CSF values were directly given from wavefront aberrations and the retinal aerial image modulation (AIM) of human eyes. After correcting defocus and astigmatism, the average visual acuity of subjects is 1.0, the CSF value is about 52 for lower frequency (20 c/mm) and about 1 for higher frequency (80 c/mm). After removing the 2nd,3rd and 4th Zernike aberrations, the average acuity reached 1.2, the CSF value is about 96 for lower frequency (20 c/mm) and about 7 for higher frequency (80 c/mm). Different people has its specific aberrations, so different order of aberrations must be corrected to reach the satisfactory imaging. After correcting the 2nd up to 9th Zernike aberrations, the Strehl ratios of three subjects are all in the ideal state and the average value is greater than 0.8..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 11, 1519 (2005)
Nonlinear Optics
The Ablation Mechanism and Ultra-Fast Dynamics Property of Lithium Fluoride with the Ultra-Short Pulse Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The ablation mechanism and ultra-fast dynamics property of LiF crystal are studied. By means of SEM and AFM the damage features induced by femtosecond laser are observed. Based on the logarithmic dependence of the ablated area on laser pulse energy, the ablation threshold fluence of LiF crystal is calculated. MeanwhileThe ablation mechanism and ultra-fast dynamics property of LiF crystal are studied. By means of SEM and AFM the damage features induced by femtosecond laser are observed. Based on the logarithmic dependence of the ablated area on laser pulse energy, the ablation threshold fluence of LiF crystal is calculated. Meanwhile, stretching the pulse duration up to 800 fs with dispersive material, the threshold fluence of LiF is got as a function of pulse duration. By use of pump-probe technique, the dependence of reflectivity of LiF crystal on delay time is got while irradiated by 800 nm femtosecond laser with 70 fs and 500 fs pulse duration respectively. Then based on the avalanche mode and the relationship between the reflectivity and the dielectric constant, a calculation in theory is made. The theoretical calculation results agree well with the experimental results. Finally the variety of the density of conduction band electrons in the ablation process is discussed and the experimental result with avalanche mode is interpreted..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 11, 1526 (2005)
Studies on the Threshold Effect of the Ultraviolet-Light-Induced Absorption Change in Congruent LiNbO3∶Mg
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The ultraviolet-light-induced absorption (UV-LIA) coefficient change is investigated in congruent LiNbO3 crystals doped with Mg2+ of different concentrations. By measuring the UV-LIA coefficient change and the two-color recording sensitivity in congruent LiNbO3∶Mg, it is found that the UV-LIA coefficient change in congThe ultraviolet-light-induced absorption (UV-LIA) coefficient change is investigated in congruent LiNbO3 crystals doped with Mg2+ of different concentrations. By measuring the UV-LIA coefficient change and the two-color recording sensitivity in congruent LiNbO3∶Mg, it is found that the UV-LIA coefficient change in congruent LiNbO3∶Mg has a threshold effect with respect to the Mg2+-doping concentration. It is only when the molar fraction of Mg2+ is more than 3.0% that the UV-LIA change from the near-UV to the near-infrared spectral regions appears. The threshold behaviour is further confirmed by the measurement of the two-color recording sensitivity. This threshold molar fraction is lower than the so-called optical damage-resistant threshold concentration of 4.6% in LiNbO3∶Mg. The UV-LIA absorption effect is assumed to be related to the decrease and even elimination of the antisite defect NbLi in LiNbO3∶Mg..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 11, 1531 (2005)
Optical Design and Fabrication
Design on Athermal Infrared Diffractive/Refractive Hybrid Optical System in 8～14 μm
[in Chinese], [in Chinese], and [in Chinese]
Most optical instruments for military and aerospace application are expected to perform over a wide temperature range. The variation of the temperature will change the len's curvature, thickness and interval, as well as their refractive index and the refractive index of the surrounding. Because of the large temperaMost optical instruments for military and aerospace application are expected to perform over a wide temperature range. The variation of the temperature will change the len's curvature, thickness and interval, as well as their refractive index and the refractive index of the surrounding. Because of the large temperature coefficient of the matcerial's refractive index, infrared optical systems often suffer from the performance degradation seriously. For this reason, several active or passive compensation mechanisms have to be appended to thermal imaging systems to compensate the performance degradation with temperature changes. Thermal properties of the refractive lens and diffractive lens are studied, and a method for designing athermal diffractive-refractive hybrid system in infrared region is introduced. An infrared diffractive-refractive hybrid optical system in 8～14 μm with 16°field of view is designed. In this system, two materials of Zinc selenide and Germanium are used, and the image quality of the system achieves diffractive limit at the temperature ranging from -20 ℃ to 60 ℃, with a compact structure and light weight..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 11, 1535 (2005)
Optical Design of Large Working Area F-Theta Lens
[in Chinese], and [in Chinese]
The working area of F-Theta lens is generally not larger than 420 mm in diameter interiorly when used in laser marking system. F-Theta lenses with larger working areas overseas are of complicated structures. F-Theta lens with its working area as large as 680 mm in diameter is obtained by determining the parameters of iThe working area of F-Theta lens is generally not larger than 420 mm in diameter interiorly when used in laser marking system. F-Theta lenses with larger working areas overseas are of complicated structures. F-Theta lens with its working area as large as 680 mm in diameter is obtained by determining the parameters of initial structure through analysis of the primary aberration and optimizing the initial structure with optical design software. The designed system is compact and composed of only four spherical lenses made up of two kinds of common optical glasses. Its tube length is less than 100 mm. But its focusing performance is diffraction-limited and its distortion relative to the F-Theta linear relation is small. The system satisfies the requirements of marking on a large area..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 11, 1539 (2005)
Optical Devices
Design of an Optical Add-Drop Multiplexer Based on Grating-Assisted Asymmetric Coupler
[in Chinese], and [in Chinese]
The design of an optical add-drop multiplexer (OADM), using an asymmetric coupler and a slanted Bragg grating, is presented. By employing 3-D normal modes, theoretical analysis is made over three possible structures to choose the grating-on-wide-waveguide one. Through coupled-mode theory, the simulation of the couplingThe design of an optical add-drop multiplexer (OADM), using an asymmetric coupler and a slanted Bragg grating, is presented. By employing 3-D normal modes, theoretical analysis is made over three possible structures to choose the grating-on-wide-waveguide one. Through coupled-mode theory, the simulation of the coupling properties of the slanted grating is given to optimize its tilt angle. Moreover, by utilizing the back-reflection-peak-wavelength method, the wavelength to be added and dropped is located within the wavelength division multiplexing (WDM) signal channels while the peak wavelengths of the reflective spectrum are located outside of the WDM signal channels, improving the performance of the proposed device greatly. Simulations show that the device has a crosstalk about -30 dB and a return loss about -25 dB. Meanwhile, the increase in key process tolerance enables mass production of the device easier. The device has a crosstalk below -28 dB and a return loss below -22 dB with the tilt angle of the slanted grating fluctuating from 2.5° to 4.5°..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 11, 1543 (2005)
Crosstalk Caused by Fabrication Errors about Polyimide Waveguide Interleaver and its Improvement
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A simple model to analyse the influence of the random change of waveguide width caused by fabrication error on the spectral character of fluorinated polyimide Mach-Zehnder (M-Z) waveguide interleaver is presented in this paper. The working parameters of fluorinated polyimide Mach-Zehnder waveguide interleaver are the cA simple model to analyse the influence of the random change of waveguide width caused by fabrication error on the spectral character of fluorinated polyimide Mach-Zehnder (M-Z) waveguide interleaver is presented in this paper. The working parameters of fluorinated polyimide Mach-Zehnder waveguide interleaver are the central wavelength of 1550 nm, wavelength interval of 0.8 nm, and 40 channels. The simulation calculation indicates that the main influence is the increase of the crosstalk among channels, the crosstalk of the central wavelength of 1550 nm is decreased from -40 dB to -12 dB. Based on this result, we propose a new structure to improve the crosstalk performance of the device by cascaded micro-ring resonator filters, and then the crosstalk of 40 channels was decreased to less than -30 dB..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 11, 1549 (2005)
OPTOELECTRONICS
Omnidirectional Photonic Crystal Reflector Used in Ultraviolet Region
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
According to the incident angle domain principle, the design of omnidirectional one-dimensional photonic crystal reflector in ultraviolet region is realized with all-dielectric coating series on quartz glass substrate. Two one-dimensional photonic crystals without omnidirectional reflective band are added in angle domaAccording to the incident angle domain principle, the design of omnidirectional one-dimensional photonic crystal reflector in ultraviolet region is realized with all-dielectric coating series on quartz glass substrate. Two one-dimensional photonic crystals without omnidirectional reflective band are added in angle domain by using transmission matrix method, it is worked out theoretically that there exists omnidirectional forbidden band for synthesized photon, wavelength rangle of the forbidden band is 328.95～352.11 nm, relative bandwidth is 6.80%. Synthesized photonic crystal is fabricated on quartz glass substrate with two coating materials HfO2 and SiO2 by electron beam vaporization. If transmissivity is below 1%, it is photonic crystal forbidden band, the wavelength range of the forbidden band is 331.2～350.4 nm, the relative bandwidth is 5.63%. The result validates the angle domain addition design..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 11, 1554 (2005)
Physical Optics
Theoretical and Experimental Study on the Interference of Convergent Polarized Light for a Biaxial Crystal
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Many important information of a crystal is included in the convergent polarized light interference pattern, and can be completely utilized by numerical analysis of the pattern. Based on the relationship of wave vectors on crystal interface, accurate formulas calculating phase difference between two refracted waves are Many important information of a crystal is included in the convergent polarized light interference pattern, and can be completely utilized by numerical analysis of the pattern. Based on the relationship of wave vectors on crystal interface, accurate formulas calculating phase difference between two refracted waves are deduced. Changes of light polarization in each interface are analyzed and the method to calculate total amplitude in convergent polarized light interference is proposed. The conoscopic interference patterns of crystals are calculated for any orientation biaxial crystal, which include information of isochromatic curve and isogyre. The interference patterns are simulated by digital image and the changes of the patterns are discussed. Experiment of the conoscopic interference is completed for four pieces of KTP crystals with different orientation. Comparison of the experimental patterns and theoretical patterns can judge which Sellmeier's equation is best..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 11, 1558 (2005)
Ultrashort Pulsed Elegant Laguerre-Gaussian Beams
[in Chinese], [in Chinese], and [in Chinese]
From the ultrashort pulsed Gaussian beams, based on the properties of Laguerre polynomial, a family of solutions are found in theory, which represents a new family of ultrashort pulsed beams called ultrashort pulsed elegant Laguerre-Gaussian beams. These pulsed beams with arbitrary available frequency all have a nearlyFrom the ultrashort pulsed Gaussian beams, based on the properties of Laguerre polynomial, a family of solutions are found in theory, which represents a new family of ultrashort pulsed beams called ultrashort pulsed elegant Laguerre-Gaussian beams. These pulsed beams with arbitrary available frequency all have a nearly elegant Laguerre-Gaussian profile, an arbitrary temporal shape, and an equal diffractive distance. These solutions can be even used to describe the ultrashort pulsed beam whose pulse duration is shorter than one optical oscillation period. The ultrashort pulsed elegant Laguerre-Gaussian beams and their propagation properties in free space have been studied detailedly, such as intensity on the axis, transversal distribution of intensity, diffractive property, pulse polarity reversal, pulse time delay etc. The time and spatial singularity of the pulsed beams is also discussed when the slowly varying envelope approximation is introduced..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 11, 1563 (2005)
Quantum Optics
Quantum Key Distribution Based on Six-Photon Quantum Error-Avoiding Code
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Noise that unavoidably exists in the quantum channel will distort transmitted information and destroy the communication. The superior scheme to overcome the noise at present is quantum error-avoiding code (QEAC). The quantum key distribution (QKD) using the QEAC will be robust in the quantum noisy channel without complNoise that unavoidably exists in the quantum channel will distort transmitted information and destroy the communication. The superior scheme to overcome the noise at present is quantum error-avoiding code (QEAC). The quantum key distribution (QKD) using the QEAC will be robust in the quantum noisy channel without complex system. Six-photon error-avoiding code (SPEAC) is constituted and a robust QKD scheme based on it is proposed. In order to improve the qubit efficiency and the security of QKD, all the possible quantum states in the SPEAC are assembled, and as a result,an optimal scheme is developed,by which two key bits can be encoded in each state and Bob can decode the information successfully with an average probability of 7/16. Compared with the recent QKD scheme based on four-photon QEAC, the qubit efficiency of the authors' scheme increases by 16.67%, and the security is 3.5 times of it..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 11, 1568 (2005)
Anti-Bunching Effects of the Photon-Depleted Squeezed Vacuum States
[in Chinese], [in Chinese], and [in Chinese]
Applying the inverse operator of the Boson creation operator and the Boson annihilation operator to the usual squeezed vacuum state, deplete squeezed vaccum states are fabricated and their anti-bunching properties of photons are studied by calculating their corresponding second-order correlation functions, respectivelyApplying the inverse operator of the Boson creation operator and the Boson annihilation operator to the usual squeezed vacuum state, deplete squeezed vaccum states are fabricated and their anti-bunching properties of photons are studied by calculating their corresponding second-order correlation functions, respectively. For both cases, the theoretical results show that for these quantum states anti-bunching effects appear when k, the number of depleted photons, are even, and bunching effects appear when k are odd. The parameter η of the squeezed vacuum states corresponding to the anti-bunching effects is related to k. With the inverse operator of the Boson creation operator acting on the squeezed vacuum states the range of parameter η expands with the increase of k, which are contrary to the situation with the Boson annihilation operator acting on. The relation curves between the second-order correlation function of the deplete squeezed vacuum states and the parameter η are also plotted to describe the anti-bunching effects..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 11, 1573 (2005)
Thin Films
Design and Fabrication the Polarizing Elements of Reflection Multilayer Film in Water Window Wave Band
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Water window is a special wave band for microscopy in soft X-ray range, which makes the research in water window polarization great significance. With Fresnel formula, the maximum reflectivity is calculated for different materials at corresponding wavelength in water window, the influence of the multilayers' periodWater window is a special wave band for microscopy in soft X-ray range, which makes the research in water window polarization great significance. With Fresnel formula, the maximum reflectivity is calculated for different materials at corresponding wavelength in water window, the influence of the multilayers' periods and surface roughness on the element performance is analysed. Three W/B4C multilayers are produced for polarizing elements in special wavelengths 2.40 nm, 3.00 nm and 4.30 nm based on ultrahigh vacuum magnetron sputtering equipment, the periodic thickness of elements by X-ray diffraction instrument is measured. The results with little windage prove practical. The work is essential in the study of polarizing elements of reflection multilayeres in water window which provides the theory and the suitable parameters for mutilayeres fabrication..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 25, Issue 11, 1581 (2005)
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