Contents
2006
Volume: 26 Issue 12
26 Article(s)
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Atmospheric Optics and Oceanic Optics
Error Analysis of Wind Lidar Based on Fizeau Interferometer
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The method error of gravity method and the measurement error due to system shot noise in wind lidar based on Fizeau interferometer are analyzed in detail. The correction technique of the method error is given, the formula of measurement error is derived. The low troposphere signal simulated by Monte-Carlo technique is The method error of gravity method and the measurement error due to system shot noise in wind lidar based on Fizeau interferometer are analyzed in detail. The correction technique of the method error is given, the formula of measurement error is derived. The low troposphere signal simulated by Monte-Carlo technique is used to retrieve the wind velocity. The results show that the method error is related to aerosol-molecule backscattering ratio and the measurement error is related to signal intensity and aerosol-molecule backscattering ratio. At altitude of 0 to 5 km, wind velocity error measured by using fringe technique is below 1m/s..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 26, Issue 12, 1761 (2006)
Effects of Atmospheric Scattering on Thermal Infrared Remote Sensing of the Earth
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The effects of scattering caused by atmospheric aerosol are become more and more important. So the effects are studied by using radiation transfer equation in detail. The influences on radiant flux transfer, especially the energy balance and total signal-to-noise ratio of remote sensor induced by atmospheric aerosol, wThe effects of scattering caused by atmospheric aerosol are become more and more important. So the effects are studied by using radiation transfer equation in detail. The influences on radiant flux transfer, especially the energy balance and total signal-to-noise ratio of remote sensor induced by atmospheric aerosol, which are ignored in the past studies, are rigorously analyzed. The simulation results for parameters of altitude of remote sensor and visibility show that the scattering of the thermal infrared radiation by atmospheric aerosol differ in 1～2 magnitude order of that with aerosol ignored. This is due to the fact that the scattering is not only component of the infrared radiation extinction, but also an important factor determining the emergence of new types radiant fluxes in the thermal infrared remote sensing of the earth..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 26, Issue 12, 1766 (2006)
Fiber Optics and Optical Communications
Propagation Characteristic Analysis and Applications of Spatial Four-Waveguide SystemZh
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
By employing Marcatili's principle, the two-dimensional spatial four-waveguide system is decomposed as two perpendicular five-layer slab waveguides independently in the cross-section of the waveguides. The analytical model that can be interpreted appropriately by variable seperation method is proposed. The first orBy employing Marcatili's principle, the two-dimensional spatial four-waveguide system is decomposed as two perpendicular five-layer slab waveguides independently in the cross-section of the waveguides. The analytical model that can be interpreted appropriately by variable seperation method is proposed. The first order correction for deviations of the model and practical structure is done by perturbation theory. The expressions of the first and second order propagation constants, static field distributions, coupling coefficient and propagation characteristic are presented. The feasibility and accuracy of the model are demonstrated by comparing the calculation results with finite difference solving semi-vector wave equation and beam propagation method. A coarse wavelength demultiplexer based on spatial four-waveguide system, including three common wavelengths 1.31 μm, 1.49 μm, and 1.55 μm of the triplex transistor in today's fiber-to-home, is designed with the insertion loss 0.68 dB. Further optimization of the separate outputs and waveguide structure can obtain higher qualities..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 26, Issue 12, 1772 (2006)
Simultaneous Modulation of Different-Channel Light Based on Single-Channel Electrooptic Modulator
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A new method by which several light beams can be synchronously modulated based on attenuated total reflection (ATR) polymer electrooptic modulator with single pair of electrodes is proposed. Absorption peaks of ATR are corresponding to waveguide resonance modes, respectively. In the experimental system, the absorption A new method by which several light beams can be synchronously modulated based on attenuated total reflection (ATR) polymer electrooptic modulator with single pair of electrodes is proposed. Absorption peaks of ATR are corresponding to waveguide resonance modes, respectively. In the experimental system, the absorption peaks of ATR are used as the modulation channels. Several light beams can be modulated simultaneously through that every incident angle is related to a work angle of different waveguide resonant modes, respectively. Double-channel modulation results using three modulation types have been demonstrated. Results show that the lower guide mode acting as the modulation channel is, the larger modulation index can be obtained. 42.9% modulation efficiency can be obtained when the lowest guide mode acts as the modulation channel at the 832 nm wavelength..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 26, Issue 12, 1777 (2006)
Characteristic Analysis of Spatial Multiwaveguide System Based on Weakly Coupled-Mode Theory
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The coupling among waveguides on different planes occurs in both transverse and vertical directions. Using the spatial multiwaveguide system, we can interconnect devices in different layers effectively. Based on the weakly coupled-mode theory, the planar waveguide coupling theory is generalized to spatial multiwaveguidThe coupling among waveguides on different planes occurs in both transverse and vertical directions. Using the spatial multiwaveguide system, we can interconnect devices in different layers effectively. Based on the weakly coupled-mode theory, the planar waveguide coupling theory is generalized to spatial multiwaveguide system, and the coupled-mode equations of the spatial multiwaveguide system are presented. As an application example, the coupled-mode equation is applied to analyze the coupling properties in spatial three- and four-waveguide systems. The analytical expressions of light intensity distributions and coupling length in the two specific cases are given, and the three-dimensional full-vector beam propagation method is used to verify the analytical results. The analysis result shows that the spatial multiwaveguide system permits uniform and nonuniform power splitting in two orthogonal directions. These analytical formulas are useful in designing three-dimensional directional couplers, which is based on spatial multiwaveguide coupling..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 26, Issue 12, 1781 (2006)
Design and Attenuation Analysis for Fiber-Typed Variable Optical Attenuator Based on Thermo-Optic Effect
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A fiber-type variable optical attenuator (VOA) based on thermo-optic effect is proposed. The VOA is fabricated by etching down a certain depth and length of the cladding of optical fiber and covering with polymer with large thermo-optic coefficient. The relationship of the attenuation and the refractive index of the suA fiber-type variable optical attenuator (VOA) based on thermo-optic effect is proposed. The VOA is fabricated by etching down a certain depth and length of the cladding of optical fiber and covering with polymer with large thermo-optic coefficient. The relationship of the attenuation and the refractive index of the substitute is theoretically analyzed in terms of the mode field distribution (MFD) of the fiber. The attenuation of the VOA is measured in different substitutes of cladding. It is shown theoretically and experimentally that the attenuation varies significantly when the refractive index of the substitute has a little change, as long as the refractive index is slightly larger than that of the cladding. Moreover, the longer the etched fiber or the thinner the cladding is, the larger the attenuation of the VOA is. Therefore, this fiber-type VOA, which is substituted by a polymer with large thermo-optic coefficient and refractive index slightly higher than that of the cladding, is of large dynamic range, low insertion loss, low polarization-dependent loss, low power consumption and easily coupled or integrated with other fiber-optic components..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 26, Issue 12, 1787 (2006)
Theoretical and Experimental Study on Power Spectrum of Atmospheric Scintillation with Large-Aperture Receiver for Satellite-to-Ground Downlink
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Based on the temporal covariance of logarithmic amplitude and the practical conditions, the analytical expression is obtained for aperture receiving power spectrum of atmospheric scintillation of satellite-to-ground downlink. The effect of the receiving aperture and zenith angle on the power spectrum of atmospheric sciBased on the temporal covariance of logarithmic amplitude and the practical conditions, the analytical expression is obtained for aperture receiving power spectrum of atmospheric scintillation of satellite-to-ground downlink. The effect of the receiving aperture and zenith angle on the power spectrum of atmospheric scintillation is analyzed. The experiment of detecting stellar intensity is accomplished with a large antenna. The real power spectrum of atmospheric scintillation is obtained. The results of experiment accord well with these of theoretical analysis. The results show that the power spectrum of atmospheric scintillation includes low-frequency and high-frequency spectrum. The amplitude of low-frequency spectrum is constant. The high-frequency spectrum obeys the power law and the value of power-law is -11/3. The amplitude of power spectrum gradually reduces with the aperture scale adding or the zenith decreasing, and the shape of power spectrum is unvariable..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 26, Issue 12, 1792 (2006)
Coupling Characteristics of Star Waveguide Coupler
[in Chinese], and [in Chinese]
As the eigen field distribution of the TE0 mode optical waveguide, Rayleigh-Sommerfeld diffraction integral formula and coupling efficiency formula between driving source and receiving optical waveguide are engaged, the expressions of the normalized emission and receiving coefficients of optical waveguide end faces areAs the eigen field distribution of the TE0 mode optical waveguide, Rayleigh-Sommerfeld diffraction integral formula and coupling efficiency formula between driving source and receiving optical waveguide are engaged, the expressions of the normalized emission and receiving coefficients of optical waveguide end faces are presented, the expression of coupling efficiency between two non-contact optical waveguides is derived. Then, as the expression of Gaussian approximation for the mode field distribution of optical waveguide is adopted, a compact expression of coupling efficiency between two non-contact optical waveguides is presented. Finally, as the characteristic of the structural parameters of star waveguide coupler is considered, the accumulative operation is replaced by integral operation approximately, the relationship between the total receiving efficiency of receiving waveguides of star waveguide coupler and the basic parameters of this coupler is derived, and the coupling characteristic of this coupler is explained..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 26, Issue 12, 1797 (2006)
Imaging Systems
Instantaneous Three-Dimemsional Profile Measurement Based on Temporal Wavelet Transform
[in Chinese], and [in Chinese]
The method for the phase extraction of a continual deformation object based on the temporal wavelet transform is proposed. By introducing the temporal wavelet transform method to analyze the time-sequence fringe patterns, the modulated phase distribution relative to the fundamental frequency is obtained. The gray valueThe method for the phase extraction of a continual deformation object based on the temporal wavelet transform is proposed. By introducing the temporal wavelet transform method to analyze the time-sequence fringe patterns, the modulated phase distribution relative to the fundamental frequency is obtained. The gray value along time is evaluated point by point by using the continuous wavelet transform. Due to the frequency localization property of the continuous wavelet, the instantaneous velocity and high-quality three-dimensional surface-profile at different instants of a continuoual deformation object is obtained. A cantilever beam with a continual deformation is detected. The experimental result well demonstrates the validity of this method and retrieves the process of the continual vibrating of the beam. The temporal wavelet transform method provides a new method to analyze the kinetic characteristic of a continual deformation object..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 26, Issue 12, 1803 (2006)
Property of Wave-Front Coding Imaging Systems for Extending the Depth of Field
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
New mathematical tools are used to explore and analyze the well-known properties of imaging system for extending the depth of field from spatial and frequency domain, respectively. In the spatial domain, canonical projection of the Wigner distribution function of the associated pupil function to show the insensitivity New mathematical tools are used to explore and analyze the well-known properties of imaging system for extending the depth of field from spatial and frequency domain, respectively. In the spatial domain, canonical projection of the Wigner distribution function of the associated pupil function to show the insensitivity of the system's point spread function to the defocus-related aberrations is mainly used, and in the frequency domain, it is shown that the optical transfer function of such a system is also insensitive to misfocus through a geometrical description of the so-called Cornu spiral. The involved digital image processing is also briefly discussed and a digital simulated experiment is done to affirm these excellent properties of the wave-front coding imaging system..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 26, Issue 12, 1807 (2006)
Lasers and Laser Optics
Threshold of One-Dimensional Photonic Crystal Band Edge Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
On the basis of Maxwell’s equations coupled with the rate equations, the lasing threshold of one-dimensional photonic band edge laser is investigated by finite-difference time-domain method with the introduced effective gain distribution factor (EGDF). The size and position in the photonic crystal of gain mdeium directOn the basis of Maxwell’s equations coupled with the rate equations, the lasing threshold of one-dimensional photonic band edge laser is investigated by finite-difference time-domain method with the introduced effective gain distribution factor (EGDF). The size and position in the photonic crystal of gain mdeium directly influence the output properties of the photonic band edge laser, and the EGDF describes the spatial distribution of gain medium in photonic crystal. The numerical results show that the lasing threshold of an eigenmode depends on the EGDF, different eigenmode has different value of EGDF. Those eigenmodes corresponding to higher value of EGDF have lower threshold. With suitable design of size and position of the gain medium, higher EGDF can be obtained, which directly leads to a lower value of lasing threshold. This gives a new approach to decrease the lasing threshold of the photonic band edge laser..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 26, Issue 12, 1813 (2006)
Tunnel Regeneration High-Power Semiconductor Laser with Four Active Regions
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The principle of tunnel regeneration is used to raise the optical output power of semiconductor lasers at lower injected current. The optical modes are analyzed through the transfer matrix method for the tunnel regeneration semiconductor laser with four optical coupled active regions. It is shown that TE3 should be theThe principle of tunnel regeneration is used to raise the optical output power of semiconductor lasers at lower injected current. The optical modes are analyzed through the transfer matrix method for the tunnel regeneration semiconductor laser with four optical coupled active regions. It is shown that TE3 should be the lasing mode, and there exists an optimum thickness for the inner cladding layers. Devices with inner cladding layer thickness of 0.3 μm, 0.5 μm and 0.7 μm are epitaxiallly grown by metal organic chemical vapor deposition method (MOCVD), respectively. The device with 0.5 μm inner cladding thickness exhibits the best P-I characteristics, the optical power exceeds 5 W under 2 A driving current without facet coating, and the slope efficiency reaches 2.74 W/A. The results show that the thickness of the inner cladding layers should be designed properly so that a higher optical output power can be obtained..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 26, Issue 12, 1819 (2006)
Microscopy
Construction of Random-Access Scanning Multiphoton Fluorescence Microscope System
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Multiphoton fluorescence microscopy is a powerful tool for studying biology. However, the current scanning method is not fast enough to fulfill the requirement for fast functional event detection in the neuroimaging field. A random-access scanning multiphoton fluorescence microscope system is reported. Two-dimensional Multiphoton fluorescence microscopy is a powerful tool for studying biology. However, the current scanning method is not fast enough to fulfill the requirement for fast functional event detection in the neuroimaging field. A random-access scanning multiphoton fluorescence microscope system is reported. Two-dimensional acousto-optic deflectors (AODs) are used to scan rapidly the femtosecond excitation laser.The system is capable of achiering the scanning speed of 10 μs per scanning spot in the regin of thterest, and increases the effective scanning speed greatly. A single prism is used to compensate the severe dispersion of the excitation light introduced by the AODs. Using a 170 nm fluorescent bead, the lateral resolution of the system is measured to be 0.3 μm and the axial resolution is about 1.3 μm. Multiphoton fluorescence image of a fluorophore-labelled cell is acquired by using the random-access scanning system and a commercial multiphoton fluorescence microscope, respectively. The result proves the multiphoton fluorescence collection efficiency of the system..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 26, Issue 12, 1823 (2006)
Optical Devices
Double Mode High-Precision Adjustable Superresolving Pupil Filter
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A double-mode adjustable superresolving pupil filter based on birefringent filter is proposed. This filter can obtain superresolution in two modes of adjustment and is continuously adjustable. In the transversal rotation mode, the pupil filter acts as complex amplitude filter and as pure phase filter in the longitudinaA double-mode adjustable superresolving pupil filter based on birefringent filter is proposed. This filter can obtain superresolution in two modes of adjustment and is continuously adjustable. In the transversal rotation mode, the pupil filter acts as complex amplitude filter and as pure phase filter in the longitudinal tilting mode. By analyzing two superresolving parameters, the optimal designing parameters are got, which ensure a large field of view, a large superresolving range and a high setting accuracy. This filter can provide more flexibility in practical applications..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 26, Issue 12, 1829 (2006)
Theoretical Study of Multiple Tunable Liquid Crystals Filters
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The theory on voltage-tunable multiple liquid crystal filters is discussed, and designing examples are given. The multiple filters composed of three single liquid crystal filters are mainly discussed. The three filters in the system may have the same thickness or proportional thickness. Both forms are effective. The fiThe theory on voltage-tunable multiple liquid crystal filters is discussed, and designing examples are given. The multiple filters composed of three single liquid crystal filters are mainly discussed. The three filters in the system may have the same thickness or proportional thickness. Both forms are effective. The filters having proportional thicknesses can change the transmitted wavelength by tuning the voltage, and the scope of the transmitted peak is 400～800 nm, covering the whole visible spectrum. The filters with the same thickness can be used to select certain desired wavelengths from multiline spectrum..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 26, Issue 12, 1835 (2006)
OPTOELECTRONICS
A Numerical Method to Calculate and Analyze of Defect Modes in Two-Dimensional Photonic Crystal
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A numerical method based on the modified finite-difference time-domain (FDTD) method for calculating and analyzing defect modes in a two-dimensional photonic crystal is presented. An ideal plane wave incident at different angles is realized by using the auxiliary one-dimensional FDTD method and linear interpolation at A numerical method based on the modified finite-difference time-domain (FDTD) method for calculating and analyzing defect modes in a two-dimensional photonic crystal is presented. An ideal plane wave incident at different angles is realized by using the auxiliary one-dimensional FDTD method and linear interpolation at the total field-scattered field interface. Perfect matched layer technique is employed to absorb the out going wave efficiently. Numerical simulations show that all defect modes can be excited by an incident plane wave along a non-symmetric direction of the photonic crystal. The values of electric field are recorded by choosing a suitable detector position, and all resonant frequencies can be obtained by fast Fourier transform. The relationship between the resonant frequency in a two-dimensional square photonic crystal consisting of dielectric rods and the radius and dielectric constant of the rods is also investigated. The numerical results show that the value of the resonant modes of the photonic crystal can be modulated by changing the radius and dielectric constant..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 26, Issue 12, 1841 (2006)
Density of Sates and Local Density of States of Two-Dimensional Photonic Crystals with Cylinder Scatter in Square Lattice
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Two-dimensional photonic crystal possess only pseudo photonic band gaps, so it is interesting and meaningful that whether the spontaneous emission of the atoms in two-dimensional photonic crystals can be controlled effectively. The density of photonic states and local density of photonic states are most important to deTwo-dimensional photonic crystal possess only pseudo photonic band gaps, so it is interesting and meaningful that whether the spontaneous emission of the atoms in two-dimensional photonic crystals can be controlled effectively. The density of photonic states and local density of photonic states are most important to determine the properties of atomic spontaneous emission. the density of states and local density of states of the two-dimensional photonic crystal composed of air cylinders on square lattice are investigated by plane wave expansion method and group theory. The air cylinder as scatter is positioned on uniform dielectric background, the calculated results show that the density of states and local density of states exhibit nonzero values but evidently lower than those outside the peseudo-gap range in the frequency range of pseudo-gap, and it may be regarded as a quasi-photonic band gap. The local density of states takes much larger values in the air cylinders areas and drops down at the boundary between the air cylinders and dielectric medium background, and this phenomenon is due to the continuity of electric displacement vector. Considering that the above two characteristics are also found in other two-dimensional photonic crystal sample, it is believed they are universal in two-dimensional photonic crystal..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 26, Issue 12, 1847 (2006)
Physical Optics
Lateral and Transverse Shift of Arbitrarily Polarized Beam in Total Internal Reflection
[in Chinese], [in Chinese], and [in Chinese]
The totally reflected beam by a dielectric interface actually exhibits a lateral shift from the position of geometric reflection in the plane of incidence, and a transverse shift normal to the plane of incidence. The lateral and transverse shift of an arbitrarily polarized beam is investigated by the improved energy flThe totally reflected beam by a dielectric interface actually exhibits a lateral shift from the position of geometric reflection in the plane of incidence, and a transverse shift normal to the plane of incidence. The lateral and transverse shift of an arbitrarily polarized beam is investigated by the improved energy flux method. It is shown that the lateral shift is independent of the phase difference of the TE and TM components of the incident beam, but closely associated with the light intensity of the two components, and its form can be expressed as weighed average of the shifts of the TE and TM polarized beam in accordance with their light intensity. The transverse shift is not only dependent on the light intensity of the two components, but also closely asscociated with the phase difference of the components. Besides, whether the incident beam is elliptically polarized or linearly polarized( with polarization state other than TE or TM), the reflected beam will exhibit a transverse shift..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 26, Issue 12, 1852 (2006)
Influence of Reflection-Induced-Retardance of Non-Polarizing Beam Splitter upon the Polarization State of the Output Light of Faraday Mirror Optical Current Transformer
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Elliptical degeneration of output light of optical current transformer is caused by linear birefringence and refection-induced retardance, which results in reduction of sensitivity. Faraday mirror-typed optical current transformer (FMOCT) can effectively solve this problem. Non-polarizing beam splitter (NPBS) is the coElliptical degeneration of output light of optical current transformer is caused by linear birefringence and refection-induced retardance, which results in reduction of sensitivity. Faraday mirror-typed optical current transformer (FMOCT) can effectively solve this problem. Non-polarizing beam splitter (NPBS) is the core apparatus in this project. In order to exactly master the capability and function of NPBS, matrix model of NPBS and Faraday mirror-typed optical current transformer is built by Jones matrix. The influence of reflection-induced-retardance of NPBS upon the polarization state of the output light of FMOCT is analyzed. Then the project of measuring the value of reflection-induced-retardance of NPBS whose actual value is 5.02°under normal temperature is proposed and experimental temperature curve is drawn. The curve of polarization state of output light of system is simulated by the software MathCAD and the relation between elliptical ratio and reflection-induced-retardance is analyzed. Drift range of reflection-induced-retardance which is 0.2 grade allowed in metering level of optical current transformer is less than 0.1%. The result might have reference on the practical application investigation of FMOCT..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 26, Issue 12, 1857 (2006)
Singularity Feature of Gaussian Beam Propagating in Absorptive Kerr Medium
[in Chinese], and [in Chinese]
From the nonlinear Schrdinger equation of beam propagating in Kerr absorbing medium, a set of evolution equations describing Gaussian beam waist radius have bean deduced. As taking no account of high order expanded term, the evolution of beam waist radius in medium without or with absorption has bean analyzed theoretiFrom the nonlinear Schrdinger equation of beam propagating in Kerr absorbing medium, a set of evolution equations describing Gaussian beam waist radius have bean deduced. As taking no account of high order expanded term, the evolution of beam waist radius in medium without or with absorption has bean analyzed theoretically. And the result is that the beams would form solitary wave only as inputting at waist, no absorption are acquired. As taking account of high order expanded terms, there exists no solitary wave in beam propagation by numerical analysis without or with absorption, and the beams are controlled by input intensity. When input intensity is smaller, the beam would behave self-focusing only. Along with the increasing of input intensity, there is a threshold. As the input intensity is below this threshold, the input beam behaves self-focusing still; but as the input intensity surpasses this threshold, the input beam behaves diffraction strongly, no self-focusing occurs at all..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 26, Issue 12, 1861 (2006)
Spectroscopy
Dependence of CH Molecular Beam Intensity on Ratio of CH4Buffering in Helium and Vibration and Rotation Temperatures Calculation of CH(A2Δ)
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The CH molecular beam was generated by DC pulsed discharging methane seeded in helium in the supersonic expansion to study the generation and features of CH molecular beams. The variation of the CH spectral intensity with the different time delay of discharging relative to valve opening was recorded experimentally. It The CH molecular beam was generated by DC pulsed discharging methane seeded in helium in the supersonic expansion to study the generation and features of CH molecular beams. The variation of the CH spectral intensity with the different time delay of discharging relative to valve opening was recorded experimentally. It is found that the most intense signal is achieved when the time delay is about 460 μs. The dependence of the spectral intensity of CH on the ratio of methane was studied at total pressure fixed at 3 atm and discharge voltage fixed at -4 kV. A theoretical model was proposed, by which the calculation agrees well with experimental results. The stable discharging process and relatively strong charging intensity result in intense CH radical beam, with a pressure ratio of CH4 to helium about 1∶99. Under the above ratio, the emission spectra of the (0,0) band in the A2Δ-X2Π system was detected and analyzed, and the vibration and rotational temperatures were determined to be about 4575 K and 2455 K, respectively. The CH number was estimated to be about 1013～1014 per pulse in this experimental condition..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 26, Issue 12, 1866 (2006)
Thin Films
Study on Applicability of Effective Medium Approximation to Optical Properties of Cu-MgF2Composite Nanoparticle Films
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Cu-MgF2 composite nanoparticle films with the copper volume fraction of 15% and 30% were prepared by radio-frequency magnetron co-sputtering technique. The transmission electron microscopy (TEM) images of Cu-MgF2 composite films show that the films are mainly made of amorphous ceramic MgF2 matrix with embedded Cu nanopCu-MgF2 composite nanoparticle films with the copper volume fraction of 15% and 30% were prepared by radio-frequency magnetron co-sputtering technique. The transmission electron microscopy (TEM) images of Cu-MgF2 composite films show that the films are mainly made of amorphous ceramic MgF2 matrix with embedded Cu nanoparticles with various grain shapes. The optical constants spectra of the composite films are determined as a function of wavelength in the range of 270～830 nm by spectroscopic ellipsometry. The theoretical optical constants spectra of the composite films are calculated in the same wavelength range by effective medium approximation in which grain shape effect is incorporated. The optical properties of the two composite films are analyzed and discussed by combining TEM images with experimental and theoretical optical constants spectra. The conclusion is drawn that Maxwell-Garnett model in which the depolarization factor of Cu grains is 0.33 is suitable to explain the optical properties of 15% Cu-MgF2 film, and the optical properties of 30% Cu-MgF2 film may be better interpreted with the depolarization factor of Cu grains 0.6..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 26, Issue 12, 1871 (2006)
Ultrafast Optics
Theoretical Studies on Propagation of Ultraintense Laser Pulses in Preformed Narrow Plasma Channel
[in Chinese]
The steady propagation of an ultraintense laser pulse in a preformed narrow plasmas channel with the width in the order of laser wavelength is investigated, considering relativistic and ponderomotive nonlinearities and global charge conservation. A simplified two-dimensional model is derived to describe the structures The steady propagation of an ultraintense laser pulse in a preformed narrow plasmas channel with the width in the order of laser wavelength is investigated, considering relativistic and ponderomotive nonlinearities and global charge conservation. A simplified two-dimensional model is derived to describe the structures of laser pulses and the channels and exact analytical solutions describing the cross-sectional structures of the laser amplitude and plasma density are presented. The influences of the channel width, plasma density, laser intensity and mode of electromagnetic field on laser pulse propogation in the plasma channel are also discussed. It is proved that if there is a preformed channel, the laser pulse can still propagate in the channel of pulse-duration order, even if the plasma density is much higher than the critical density (e.g. 20 times critical density). If the channel is wider, the plasma density is lower and when the laser intensity is higher, the laser pulses will propagate more easily. In the same channel condition, a higher laser intensity is needed for TE1 mode propogating at the same group velocity as for TE0 mode..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 26, Issue 12, 1877 (2006)
Spatiotemporal Self-Compression of Circularly Polarized and Linearly Polarized Pulses in Normally Dispersive Media
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Spatiotemporal self-compression of high-intensity femtosecond pulses with linear and circular polarization in normally dispersive media is experimentally studied. In the experiment, a piece of BK7 glass plate is used as the normally dispersive media. The temporal and spectral behavior of the pulse transmitting in the gSpatiotemporal self-compression of high-intensity femtosecond pulses with linear and circular polarization in normally dispersive media is experimentally studied. In the experiment, a piece of BK7 glass plate is used as the normally dispersive media. The temporal and spectral behavior of the pulse transmitting in the glass material under different input pulse conditions is studied. The compressed pulses are much shorter in duration and narrower in spectral bandwidth by using circularly polarized pulses than linearly polarized pulses. The 50 fs pulses with circular polarization are successfully compressed to 19fs, with a compression ratio more than 2.5..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 26, Issue 12, 1882 (2006)
Application of Acoustic-Optic Programmable Dispersive Filter in 10 Hz Femtosecond Regenerative Amplifier System
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The spectrum width is expanded from 38 nm to 66 nm, and the output laser pulse is consequently squeezed from 35 fs to 20 fs in the 10 Hz femtosecond regenerative amplifier, with an acoustic-optic programmable dispersive filter(AOPDF) for dispersion pre-compensation and spectrum shaping of the input seed pulses. The expThe spectrum width is expanded from 38 nm to 66 nm, and the output laser pulse is consequently squeezed from 35 fs to 20 fs in the 10 Hz femtosecond regenerative amplifier, with an acoustic-optic programmable dispersive filter(AOPDF) for dispersion pre-compensation and spectrum shaping of the input seed pulses. The experimental results show that the AOPDF can make spectrum shaping and dispersion compensation in a large range simultaneously and independently, depress effectively the spectrum gain narrowing in the chirped pulse amplification and compensate the residual dispersion in the Ti∶sapphire laser system. The result paves the way for the development for 20 fs, 10 TW Ti∶sapphire laser..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 26, Issue 12, 1887 (2006)
X-Ray Optics
Effect of Energy Monochromaticity and Interfacial Roughness on Multilayer Reflectivity
[in Chinese]
Both the interfacial roughness of multilayer and energy Monochromaticity of the incident light influence the practical reflectivity of multilayer. With convolution integral, a new formulation for describing the relation of soft X-ray reflectivity of multilayer with the different energy Monochromaticity of incident lighBoth the interfacial roughness of multilayer and energy Monochromaticity of the incident light influence the practical reflectivity of multilayer. With convolution integral, a new formulation for describing the relation of soft X-ray reflectivity of multilayer with the different energy Monochromaticity of incident light is deduced. Using this formulation, the effect of different energy Monochromaticity and interfacial roughness on the reflectivity spectrum of Mo/Si multilayer is analyzed respectively. The results of theoretical analysis show that the low energy resolution reduces sharply the peak reflectivity of Mo/Si multilayer but increases the background intensity, which leads to the increase of the full width of half maximum of reflectivity spectrum and the distortion of reflectivity spectrum. However, the interfacial roughness of multilayer only decreases the value of the reflectivity and does not change the shape of reflectivity spectrum and full width of half maximum of reflectivity spectrum. These results illustrate that the influence of energy Monochromaticity of incident light on the reflectance of multilayers is different from that of the interfacial roughness..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 26, Issue 12, 1892 (2006)
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