Contents
2007
Volume: 27 Issue 9
34 Article(s)
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Atmospheric Optics and Oceanic Optics
Monitoring of Total Emission Volume from Pollution Sources Based on Passive Differential Optical Absorption Spectroscopy
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
An optical remote sensing method for determination of total volume of air pollutants (such as SO2, NO2) emitted from sources is studied, by use of a passive differential optical absorption spectroscopic (DOAS) instrument to scan the plume from pollution source on a mobile platform (such as a car). The column density ofAn optical remote sensing method for determination of total volume of air pollutants (such as SO2, NO2) emitted from sources is studied, by use of a passive differential optical absorption spectroscopic (DOAS) instrument to scan the plume from pollution source on a mobile platform (such as a car). The column density of air pollutant is retrieved from processing of the scattered sun light spectra in the zenith sky collected by the instrument by means of the spectral analysis method of passive DOAS. Combination with the meteorological (wind field) information during the measurement, the average flux value of air pollutant during the measurement can be estimated then the total emission value can be derived. DOAS method used to obtain the vertical column density the plume and the method used to derive emission flux are described in detail. The passive DOAS instrument was carried by a car to scan the plume from a thermo-power plant in a field measurement. The measurement results and the comparison with the total volume from an on-line monitoring instrument indicate this method based on passive DOAS can be used for rapid remote sensing of the total emission volume from pollution sources..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1537 (2007)
Annular-Aperture Averaging Factor of Optical Scintillations in Turbulent Atmosphere
[in Chinese], [in Chinese], and [in Chinese]
Based on the theory for the irradiance fluctuations (scintillation) of the spherical wave propagating in the turbulent atmosphere and the annular-aperture filtering function, the expression of annular-aperture averaging factor was obtained. The annular-aperture averaging factor was fitted into a second-order polynomialBased on the theory for the irradiance fluctuations (scintillation) of the spherical wave propagating in the turbulent atmosphere and the annular-aperture filtering function, the expression of annular-aperture averaging factor was obtained. The annular-aperture averaging factor was fitted into a second-order polynomial about a dimensionless parameter, i.e. the ratio of the aperture radius to the Fresnel size. After establishing the relationship between the polynomial coefficients and the ratio of the inner to outer diameter of the aperture, the annular aperture averaging factor is expressed approximately as a function of this dimensionless parameter and the ratio of the inner to outer diameter of the aperture. The valid range and accuracy of the fitted approximation were evaluated by error analysis. The effect of the turbulent inner scale on the annular-aperture averaging factor was also analyzed by using Tatarskii spectrum and modified Hill spectrum. The results reveal that, when other conditions keep invariable, the larger the inner scale is, the weaker the averaging effect of the annular aperture is..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1543 (2007)
Effect of Atmospheric Turbulence on Temporal Coherence of Gaussian Schell-Model Beams Propagating in Slant Path
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
By use of the series representation of the Bessel function of the first kind and zero order, the approximate expression of the wave structure function under all conditions of atmospheric turbulence is derived. Based on the extended Huygens-Fresnel principle, the Hufnagel-Valley profile model of the turbulence which is By use of the series representation of the Bessel function of the first kind and zero order, the approximate expression of the wave structure function under all conditions of atmospheric turbulence is derived. Based on the extended Huygens-Fresnel principle, the Hufnagel-Valley profile model of the turbulence which is dependent on altitude, and the wave structure function under all conditions of atmospheric turbulence, the mutual coherence function of quasi-monochromatic Gaussian Schell-model (GSM) beams propagating in the slant path through turbulent atmosphere is derived analytically. The longitudinal coherence length (that can be derived from the mutual coherence function) of quasi-monochromatic GSM beams is used to characterize the temporal coherence of them, and the effect of atmospheric turbulence on the temporal coherence of those beams is studied. The result shows that the temporal coherence keeps unchanging in the propagation. Lastly, a qualitative explanation is given to this result..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1548 (2007)
Measurement of Telescope Aberrations Using Phase-Diversity Method
[in Chinese], and [in Chinese]
Atmospheric turbulence and telescope aberrations all contribute to image degradation with ground-based telescopes. For measuring the telescope aberration with the disturbance of turbulence, a method based on phase diversity has been developed. Many instantaneous wavefront are independently reconstructed from pairs of sAtmospheric turbulence and telescope aberrations all contribute to image degradation with ground-based telescopes. For measuring the telescope aberration with the disturbance of turbulence, a method based on phase diversity has been developed. Many instantaneous wavefront are independently reconstructed from pairs of simultaneously recorded focused and defocused short-exposure images using phase-diversity method. After that, by averaging these reconstructed wavefronts, the telescope aberrations are separated from dynamic wavefront induced by turbulence. The computer simulation of estimation of telescope aberration using phase-diversity method is conducted. The simulation shows phase-diversity method can estimate the telescope aberrations effectively and root-mean-square error is about 0.08 wavelengths..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1553 (2007)
Diffraction and Gratings
Diffraction Properties of Local Volume Holographic Grating Read by an Ultra-Short Pulsed Laser Beam
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Based on the two-dimensional (2D) coupled-wave theory, the temperal and spatial diffraction properties of an overlapping finite size volume holographic grating read by an ultra-short pulsed laser beam are studied. The temporal and spatial distribution of the diffracted and transmitted light intensity along the output bBased on the two-dimensional (2D) coupled-wave theory, the temperal and spatial diffraction properties of an overlapping finite size volume holographic grating read by an ultra-short pulsed laser beam are studied. The temporal and spatial distribution of the diffracted and transmitted light intensity along the output boundary of the grating is obtained. Taking LiNbO3 as an example, the effects of the two-dimensional grating size, incident angle, the grating's refractive-index modulation and the pulse width of the input ultra-short laser pulse upon the intensity distributions of the diffracted and transmitted pulsed laser beams along the output boundary of the grating, pulse shaping and the total diffraction efficiency are given. By comparison with the diffraction properties of one-dimensional volume holographic grating read by ultra-short pulsed laser beams and the diffracgtion properties of the grating read by continuous waves, the method of choosing grating parameters and input conditions to obtain the diffracted pulsed laser beams with uniform-distributed pulse and larger total diffraction efficiency is presented..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1558 (2007)
Experiments and Structural Optimization of Micro-Electro-Mechanical System-Based Grating Moving Light Modulator
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The experimental research for micro-electro-mechanical system (MEMS)-based grating moving light modulator (GMLM) is important for its further applications. Interference optical signal processing system with GMLM module was carried on, with He-Ne laser as light source, filter placed on the frequency spectrum plane, and The experimental research for micro-electro-mechanical system (MEMS)-based grating moving light modulator (GMLM) is important for its further applications. Interference optical signal processing system with GMLM module was carried on, with He-Ne laser as light source, filter placed on the frequency spectrum plane, and microscope and CCD placed on the imaging plane and used for magnifying and recording imaging. The laser beam from He-Ne laser was incident on the GMLM as parallel light after passing a beam expander and a collimating lens, the GMLM is placed on the input plane of the interference optical signal processing system and the result is consistent to theoretical result. The optimization of GMLM model was achieved, the grating frame and cantilevers are processed as non-reflective, and as a result the total reflective surface composed of the movable grating and the nether mirror is integer multiple of grating period. The optimized model was theoretically analyzed in details by scalar diffraction theory, with optical efficiency of 81.06%, filling factor of 74.67% and contrast ratio higher than 5000∶1 in the condition of grating period of 8 μm, duty ratio of 0.5,grating frame of 2 μm, and period number of 6..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1565 (2007)
Fiber Optics and Optical Communications
Suppression of Interchannel Interference Noise in 40 Gb/s Optical Code Division Multiplexing System
[in Chinese], [in Chinese], and [in Chinese]
The 280 G-chip/s encoding and decoding rate is experimentally demonstrated. The encoder and decoder consisting of superstructured fiber Bragg gratings (SSFBGs) are fabricated using “equivalent phase shift” method. Interchannel interference noise is also considered and evaluated, and the 40 Gb/s×2 channel signal muThe 280 G-chip/s encoding and decoding rate is experimentally demonstrated. The encoder and decoder consisting of superstructured fiber Bragg gratings (SSFBGs) are fabricated using “equivalent phase shift” method. Interchannel interference noise is also considered and evaluated, and the 40 Gb/s×2 channel signal multiplexing is illustrated. In addition, a nonlinear optical loop mirror (NOLM) within the receiver is introduced to improve the system performance under two-channel operation, which reflects low-intensity signals, and transmits the high-intensity signal. The NOLM can act as a nonlinear processing element capable of reducing both the pedestal and the width of the associated code recognition pulse, and the original 7.7 ps decoded pulse is compressed to 3.8 ps. The agreement between experimental and calculated results is excellent, and the feasibility of all optical high-rate encoding and decoding using SSFBG and NOLM is verified. High speed all optical encoding and decoding can be used in point to point optical code division multiplexing (OCDM) system and optical packet-switched networks..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1570 (2007)
Development of Novel Fiber Bragg Grating Underwater Acoustic Sensor
[in Chinese], [in Chinese], and [in Chinese]
A new type of optical fiber underwater acoustic sensor (hydrophone) constructed with two fiber Bragg gratings (FBG) with signal self-demodulation function is presented. This fiber Bragg grating hydrophone uses a pair of matched fiber Bragg gratings with push-pull structure for both sensing and demodulating, which greatA new type of optical fiber underwater acoustic sensor (hydrophone) constructed with two fiber Bragg gratings (FBG) with signal self-demodulation function is presented. This fiber Bragg grating hydrophone uses a pair of matched fiber Bragg gratings with push-pull structure for both sensing and demodulating, which greatly reduces system complexity. The cylindrical structure of the hydrophone improves the sensitivity of the bare fiber Bragg grating acoustic sensors and also can compensate temperature. Simulation and preliminary experimental results indicate that the dynamic range of the hydrophone unit is beyond 100 dB and the measurement sensitivity can reach 0.36 nm/MPa for underwater acoustic pressure range 100～200 dB re 1 μPa..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1575 (2007)
A Novel Scheme for Generation of Optical Dark Return-to-Zero Label Signals
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A novel scheme to generate binary optical dark return-to-zero (RZ) signals with tunable duty cycle and extinction ratio is proposed, through modifying the process of precoding, modulating and coding. The optical dark return-to-zero signals are easily generated only by using a dual-arm Mach-Zehnder LiNbO3 modulator alonA novel scheme to generate binary optical dark return-to-zero (RZ) signals with tunable duty cycle and extinction ratio is proposed, through modifying the process of precoding, modulating and coding. The optical dark return-to-zero signals are easily generated only by using a dual-arm Mach-Zehnder LiNbO3 modulator along with an electrical signal time-delay device. It is demonstrated experimentally that the optical dark return-to-zero signals can be directly measured by a conventional binary intensity modulation-direct detection (IM-DD) receiver. When the electrical signal time-delay device at 2.5 Gbit/s is adjusted, the changes of optical spectra, the bit-error rate curves, and the eye diagrams of the optical dark return-to-zero signal for duty of cycles 0.25, 0.35, 0.60 and 0.80 are obtained experimentally. Moreover, optical dark return-to-zero signals generated by this novel scheme can be used as labels, in optical label switched networks..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1580 (2007)
Transfer Matrix Method for Analyzing Transmission Characteristics of Microring Resonator Arrays
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The microring resonator is one of the promising building blocks for future high-density and large-scale integrated optics. One of its important development trends is multiplying and arraying it. Recently, microring resonator arrays have become research topics. Based on transfer matrices of cells of directional couplersThe microring resonator is one of the promising building blocks for future high-density and large-scale integrated optics. One of its important development trends is multiplying and arraying it. Recently, microring resonator arrays have become research topics. Based on transfer matrices of cells of directional couplers, ring resonators and straight waveguide resonators, a transfer matrix model for analyzing the transmission characteristics of microring resonator arrays is established. The effects of the distance between two adjacent columns on the transmission characteristics are discussed, and the transmission characteristics are numerically simulated under conditions of odd and even rows for different dimensions. With the proposed model, the schemes of improving filtering characteristics by changing the dimensions and coupling coefficients of microring resonator array are discussed. Finally, the relation between the transmission characteristics and intercavity coupling coefficients of the microring resonator array with the smallest dimension is numerically studied..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1585 (2007)
Polarization-Independent Bidirectional 2×2 and 4×4 Free-Space Optical Switch
[in Chinese], and [in Chinese]
A novel 2×2 optical switch is proposed with conventional polarization controlling technology by using phase spatial-light modulator (PSLM), polarized beam splitter (PBS) and mirror. This new kind optical switch grants the features of less optical components, compact structure, efficient performance, convenient conA novel 2×2 optical switch is proposed with conventional polarization controlling technology by using phase spatial-light modulator (PSLM), polarized beam splitter (PBS) and mirror. This new kind optical switch grants the features of less optical components, compact structure, efficient performance, convenient control and function insensitive to polarization of signal beam. In addition, the straight and the exchange functions of 2×2 optical switch are implemented bidirectionally in free-space. Furthermore, a new optical experimental module of 4×4 optical switch is presented by cascading polarization-independent bidirectional 2×2 optical switch. Moreover, the routing state table of 4×4 optical switch to perform all-permutation output and nonblocking switch for the input signal beams, is achieved by choosing and controlling routing. Finally, the function properties and operational process of 4×4 optical switch are discussed in detail..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1593 (2007)
Image Processing
Image Reconstruction for the Computed-Tomography Imaging Interferometer
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
An algorithm of image spectral data cube reconstruction for the computed-tomography imaging interferometer (CTII) is presented. Computed-tomography imaging interferometer combines advantages of both conventional spatially modulated Fourier transformation imaging spectrometer (FTIS) and computed-tomography imaging spectAn algorithm of image spectral data cube reconstruction for the computed-tomography imaging interferometer (CTII) is presented. Computed-tomography imaging interferometer combines advantages of both conventional spatially modulated Fourier transformation imaging spectrometer (FTIS) and computed-tomography imaging spectrometer (CTIS) such as high through put, high spectral resolution and high spatial resolution. The working principle of computed-tomography imaging interferometer and the characteristics of the images acquired form computed-tomography imaging interferometer are analyzed, and the method of data cube reconstruction is given. The convolution back-projection (CBP) is used in computed-tomography (CT) reconstruction, which is suitable for multiangular projection. The steps of image reconstruction and corresponding mathematical expression are introduced in detail. The simulations are carried out under the illumination of D65, a target of 396×396 pixels is projected at the range of 0～180°, and the projection interval is 0.5°. Part of the reconstructed images is displayed. The experimental results prove that the method is feasible..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1600 (2007)
Multi-Sensor Image Fusion Based on Improved Laplacian Pyramid Transform
[in Chinese], and [in Chinese]
The shortcoming of the traditional Laplacian pyramid (LP) transform is pointed out, and the principle and reconstruction of the improved Laplacian pyramid transform are introduced. The new reconstruction method can restrain the noise produced in the reconstruction process. The noise in the processing of the image fusioThe shortcoming of the traditional Laplacian pyramid (LP) transform is pointed out, and the principle and reconstruction of the improved Laplacian pyramid transform are introduced. The new reconstruction method can restrain the noise produced in the reconstruction process. The noise in the processing of the image fusion is analyzed theoretically and experimentally. The new reconstruction method can restrain the noise in the reconstruction process rather than in the index processing produre. The image fusion framework using the improved Laplacian pyramid transform is proposed and the way to determine the coefficients and the fusion procedure are introduced in detail. The subjective and objective indexes of simulation show that the proposed algorithm works better in preserving the edge and texture information than other Laplacian pyramid methods..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1605 (2007)
Imaging Systems
Optical Synthesis Aperture Circle-Array Optimization Based on Genetic Algorithm
[in Chinese], [in Chinese], and [in Chinese]
An optimized model of circle array was set up from the basic optical synthesis aperture circle-array imaging principle. The sub-apertures array was optimized by adopting genetic algorithm with an improved real coding method coding the location of sub-apertures array. The objective function was designed by maximizing thAn optimized model of circle array was set up from the basic optical synthesis aperture circle-array imaging principle. The sub-apertures array was optimized by adopting genetic algorithm with an improved real coding method coding the location of sub-apertures array. The objective function was designed by maximizing the distances between u-v coverage dots and minimizing redundant array. The point spread function, optical transfer function and diffractive imaging of two-dimensional (2D) circle array synthetic aperture imaging system were analyzed. The optimized result of 8～16 sub-apertures on a two-dimensional circle array was obtained and compared with the result by simulated annealing algorithm. Using the emulator program, the point spread function was analyzed and contrasted to that of a uniform circle array. Results show that the improved real coding genetic algorithm can resolve the synthesis aperture array optimization well, cost less time and get an even better optimization compared with simulated annealing algorithm..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1611 (2007)
Nonuniformity-Correction Algorithm for Infrared Focal Plane Arrays Based on Wavelet Transform
[in Chinese], [in Chinese], and [in Chinese]
Nonuniformity of infrared focal plane arrays (IRFPA) is a key problem that must be solved in its applications. Based on the theory of wavelet transform, a scene-based nonuniformity-correction (NUC) technique for IRFPA is presented. In this algorithm, the infrared image sequence is decomposed by the discrete sequence waNonuniformity of infrared focal plane arrays (IRFPA) is a key problem that must be solved in its applications. Based on the theory of wavelet transform, a scene-based nonuniformity-correction (NUC) technique for IRFPA is presented. In this algorithm, the infrared image sequence is decomposed by the discrete sequence wavelet transform with an appropriate wavelet function. Its corresponding statistics are calculated, and then coefficients of the offset and the gain for IRFPA NUC are achieved ultimately. The algorithm achieves good nonuniformity-correction capability, which is validated by experiments of real infrared imaging procedure. And the algorithm can auto-adapt to the slow-change parameters that affect the NUC and can restrain the “artificial ghost” in some degree that appears in other scene-base NUC methods..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1617 (2007)
Spot Diagram Analysis for Wavefront Coding Imaging Systems with an Odd-Symmetrical Phase Plate
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The ray tracing method in geometric optics is applied to acquire the asymptotic expressions of ray aberrations for phase plates of free form illuminated by collimated beams with large field of view, with which the spot diagram characteristics of the wavefront coding imaging system with anti-symmetric phase plates, inclThe ray tracing method in geometric optics is applied to acquire the asymptotic expressions of ray aberrations for phase plates of free form illuminated by collimated beams with large field of view, with which the spot diagram characteristics of the wavefront coding imaging system with anti-symmetric phase plates, including spot size, boundaries, and ray intersection structures, and ray aberrations enhancements and spot shape variations due to the large view-field angle are analyzed. The corresponding asymptotic expressions to describe the above characteristics are presented. With this spot diagram characteristics analysis, a deeper insight into the wavefront coding imaging systems is acquired and instructions for designing real systems are found..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1621 (2007)
Instrumentation, Measurement and Metrology
Study of a Genetic Algorithm Used in an Adaptive Optical System
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
For correcting the phase aberration in wavefront, a wavefront sensor-less adaptive optical (AO) system was set up, and a real number encoding Gauss mutation genetic algorithm which was applied to control a 61-channel deformable mirror (DM) was developed. Phase aberration generated by randomly adding voltages to the 61 For correcting the phase aberration in wavefront, a wavefront sensor-less adaptive optical (AO) system was set up, and a real number encoding Gauss mutation genetic algorithm which was applied to control a 61-channel deformable mirror (DM) was developed. Phase aberration generated by randomly adding voltages to the 61 channels of DM was brought to an ideal incident wavefront. Several simulation experiments have been done. The simulation results demonstrated that this algorithm could find the optimum DM shape which was applied to correct phase aberration. After the phase aberration in incident wavefront was corrected with this technique, the peak light intensity on the focal plane could at most be improved by a factor of 30, and the encircled energy Strehl ratio was increased to 0.96 from 0.032. It is also found that the convergence and stability of the 61 voltages on the DM is quite well..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1628 (2007)
A Data Processing Method for Abel Inversion in Arc Plasma Diagnostics
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A method is proposed for calculating the radially distributed emission coefficients of arc plasmas from the projections. The reconstruction is implemented by using a simple and accurate discrete Abel inversion method which is based on Bockasten’s polynomial spline technique. The collected data are filtered in the frequA method is proposed for calculating the radially distributed emission coefficients of arc plasmas from the projections. The reconstruction is implemented by using a simple and accurate discrete Abel inversion method which is based on Bockasten’s polynomial spline technique. The collected data are filtered in the frequency domain with a lowpass filter to reduce the noise, followed by interpolation for avoiding problems caused by undersampling and increasing data space resolution, and symmetrization for obtaining more accurate results. The arc temperature distribution deduced by the algorithm shows that for a 200 A, 5 mm argon arc, the highest temperature near the cathode is more than 22000 K, which agrees well with results of other researches. This algorithm effectively reduces the influence of noises, and it is very steady and fast, which makes advantages in the processing of large amounts of data..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1633 (2007)
Gas Temperature Measurement with Tunable Diode Laser Absorption Spectroscopy
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A new kind of non-contact temperature measurement technique based on tunable diode laser absorption spectroscopy (TDLAS) was investigated. Temperature measurement principle and modulation absorption spectroscopy were introduced, and the influence of modulation amplitude on gas temperature measurement was analyzed. A paA new kind of non-contact temperature measurement technique based on tunable diode laser absorption spectroscopy (TDLAS) was investigated. Temperature measurement principle and modulation absorption spectroscopy were introduced, and the influence of modulation amplitude on gas temperature measurement was analyzed. A pair of oxygen absorption lines, 13163.78 cm-1 and 13164.18 cm-1, were optimally selected. Oxygen temperature and concentration were measured simultaneously with a high-temperature experimental setup. By analysis of second-harmonic signals, the collisional width and the temperature index of the spectral line 13164.18 cm-1 in the temperature range of 823～1323 K were acquired. Experimental results show that the linear error and maximum fluctuation of temperature measurement are 0.65% and ±15 K, respectively within the temperature range of 823～1323 K..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1639 (2007)
Integrated Optics
Analysis of Overlap Factor between Pump- and Signal-Light Intensity profiles in Er-Doped Waveguide Amplifier
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The normalized overlap factor between pump- and signal-light intensity profiles in the waveguide (Γ) is introduced, and be taken into account in the theoretic model of the Er-doped glass waveguide amplifier (EDWA). For an EDWA with buried graded refractive-index profile which is fabricated by Ag+-Na+ two-step ion-exchaThe normalized overlap factor between pump- and signal-light intensity profiles in the waveguide (Γ) is introduced, and be taken into account in the theoretic model of the Er-doped glass waveguide amplifier (EDWA). For an EDWA with buried graded refractive-index profile which is fabricated by Ag+-Na+ two-step ion-exchange on process Er-doped phosphate glass, the two dimensional refractive-index profiles, and the guide modes of both pump and signal light in the channel waveguide is obtained using the numerical methods. The normalized value of Γ with different fabrication parameters is calculated, and its effect on the gain of EDWA has been investigated. The results show that by tailoring the fabrication parameters, the overlap factor between pump and signal light in the waveguide can be optimized and the gain of EDWA can be enhanced. With Γ enhanced from 0.5 to 0.8, the gain of EDWA can be improved nearly 6 dB..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1643 (2007)
A Novel Y-Branch Waveguide Based on Surface Plasmon Polaritons
[in Chinese], [in Chinese], and [in Chinese]
A key technique of nano-integrated optics is the development of novel and highly efficient nano-scale waveguide devices. As a basic optical splitting and light-connecting device, nano-scale Y-branch waveguide is the basis of designing and developing nano-scale optical devices. A novel Y-branch waveguide based on surfacA key technique of nano-integrated optics is the development of novel and highly efficient nano-scale waveguide devices. As a basic optical splitting and light-connecting device, nano-scale Y-branch waveguide is the basis of designing and developing nano-scale optical devices. A novel Y-branch waveguide based on surface plasmon polaritons (SPPs) is proposed for high integration, and the finite-difference time-domain (FDTD) method is used to study its propagation properties. The simulation results show that the proposed Y-branch waveguide realizes optical splitting with large splitting angle in the optical communication band, and the transmission efficiency is still over 92.8% for 180° splitting angle. Besides, it is characterized by its nano-scale size, guiding wave with good performance being insensitive to the defect at the joint of the splitter, and large tolerance. The study of the novel waveguide devices can offer some valuable guidances to the research and application of nano-integration devices..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1649 (2007)
Lasers and Laser Optics
Performance Simulation of Laser Diode Two-Sides-Pumped Transverse Flow Continuous Liquid Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The laser diode (LD) two-sides-pumped transverse flow Nd3+∶POCl3∶ZrCl4 solution is adopted to eliminate the thermal effects in an inorganic liquid laser system. The theoretical model for a liquid laser is established, the influence of working parameters on the energy conversion efficiency and medium thermal effect is aThe laser diode (LD) two-sides-pumped transverse flow Nd3+∶POCl3∶ZrCl4 solution is adopted to eliminate the thermal effects in an inorganic liquid laser system. The theoretical model for a liquid laser is established, the influence of working parameters on the energy conversion efficiency and medium thermal effect is analyzed, and the energy conversion efficiency, the far field intensity and the laser beam luminance distributions at different absorbing coefficient and different velocity of flow are simulated. The simulation shows that the energy-conversion efficiency is very high and the light beam quality is excellent with a laser diode pump source. The output power and laser beam quality match best and the laser beam luminance reaches a peak value when the absorbing coefficient is about 2.5～3.0 cm-1, the velocity of flow is about 25 m/s and the unilateral pump intensity is 800 W/cm2 at a determined pumping volume..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1653 (2007)
Switchable Dual-Wavelength Erbium-Doped Fiber Laser with a Tilted Fiber Bragg Grating
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A four-wave mixing (FWM) assisted dual-wavelength erbium-doped fiber laser with a tilted fiber Bragg grating (TFBG) for wavelength switch is reported. The transverse-offset-spliced tilted fiber grating on single-mode fiber ensures that the two effective reflectivities of the reverse LP01 mode and LP11 mode are close enA four-wave mixing (FWM) assisted dual-wavelength erbium-doped fiber laser with a tilted fiber Bragg grating (TFBG) for wavelength switch is reported. The transverse-offset-spliced tilted fiber grating on single-mode fiber ensures that the two effective reflectivities of the reverse LP01 mode and LP11 mode are close enough to realize the dual-wavelength switch for laser. FWM process induced by high-nonlinearity photonic crystal fiber (HNL-PCF) avoids mode competition and ensures stable dual-wavelength oscillation at room temperature. The conjunction of a polarization controller (PC) and a polarizer introduces wavelength-dependent cavity loss and balances the reflectivity difference of the two wavelengths. By adjusting the intracavity polarization state, the proposed laser can operate in stable dual-wavelength or switch between two wavelengths at room temperature. The two lasing lines have a high signal-noise-ratio (OSNR) more than 45 dB and a maximum power fluctuation of 0.8 dB..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1658 (2007)
High-Power Widely Tunable Yb-Doped Photonic Crystal Fiber Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A forward output and a backward output tunable Yb-doped photonic crystal fiber laser (PCFL) with a blazing grating as a tuning element are demonstrated. For the forward output tunable PCFL, when the absorbed pump power is 5.75 W, a tuning range of 59.6 nm from 1050.6～1110.2 nm is obtained. The 3 dB bandwidth is around A forward output and a backward output tunable Yb-doped photonic crystal fiber laser (PCFL) with a blazing grating as a tuning element are demonstrated. For the forward output tunable PCFL, when the absorbed pump power is 5.75 W, a tuning range of 59.6 nm from 1050.6～1110.2 nm is obtained. The 3 dB bandwidth is around 0.1 nm. Side-mode extinction is more than 44 dB. A maximum output power of 677 mW is obtained with a slope efficiency of 14% for a tuning wavelength of 1085 nm. Over the whole tuning range, the variety of output power is less than ±0.34 dB. For the backward output configuration, it is tunable over 50.9 nm when the absorbed pump power is 4.43 W. For all tuning wavelengths, the 3 dB bandwidth is less than 0.08 nm, side-mode extinction is better than 50 dB. When the tuning wavelength is 1075 nm, a maximum output power of 2.21 W is obtained with a slope efficiency of 73%. For the two configurations tunable PCFL, output of both two lasers are linearly polarized and the polarization extinction ratio is more than 89.5％. The effect of re-absorption in ytterbium doped active fiber on the tuning range is also discussed..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1663 (2007)
Nonlinear Optics
The Interaction of Multi-Spatial Solitons in Strongly Nonlocal Media
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The characteristic and law of interaction of multi-spatial solitons (more than two) in strongly nonlocal nonlinear media is discussed. Based on Snyder-Mitchell's linear model, the solution is achieved by the method of linear superposition. In addition solitons have been treated as particles. The interaction of threThe characteristic and law of interaction of multi-spatial solitons (more than two) in strongly nonlocal nonlinear media is discussed. Based on Snyder-Mitchell's linear model, the solution is achieved by the method of linear superposition. In addition solitons have been treated as particles. The interaction of three and four beams with spatial slanting symmetrical incidence is studied , and the rule of the interaction of multi-spatial solitons is obtained. The exact analytical solution of (2+1) solitons interaction has been achieved. From the solution the light intensity contour lines in solitons propagation are drawn. Multi-spatial solitons can form stable bound states when they propagate. Their spiraling is decided by the initial directions of incidence. There is no energy transfer in the process of propagation. The interaction has nothing to do with the beam's initial phases. When the solitons are treated as particles, the same rule of their interaction is obtained..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1668 (2007)
OPTICAL DATA STORAGE
Photochemistry Dynamics of Photopolymer Holographic Recording Material Bused on Methylene Blue and Erythrosin B
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The photochemical theoretical model and dynamic parameters of the photopolymer are studied. A new holographic photopolymer sensitized by methylene blue (MB) and erythrosine B (ErB) is prepared .This material is tested to obtain transmissivity versus exposure condition and the photochemical parameters with the fixed expThe photochemical theoretical model and dynamic parameters of the photopolymer are studied. A new holographic photopolymer sensitized by methylene blue (MB) and erythrosine B (ErB) is prepared .This material is tested to obtain transmissivity versus exposure condition and the photochemical parameters with the fixed exposure wavelength of 633nm and intensity of 65 mW/cm2. Experimental results show that photobleaching coefficient k and quantum yield Φ of photopolymer increase with the exposure wavelength and increase of light intensity. At the intensity of 65 mW/cm2 transmissivity drops under short wave, photobleaching coefficient k is negative, but the molar-absorption coefficient ε shows different changes in different conditions..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1675 (2007)
Optical Design and Fabrication
Algorithm for the Design of Diffractive Optical Elements for Laser Beam Shaping
[in Chinese], [in Chinese], and [in Chinese]
Iterative algorithm based on fuzzy control theory (IAFC) is put forward for designing diffractive optical elements for laser beam shaping, aiming at decreasing both mean square error and top beam uniformity of the output beam. Derived from Gercherg-Saxton (G-S) algorithm, the profile-smoothing algorithm is put forward,Iterative algorithm based on fuzzy control theory (IAFC) is put forward for designing diffractive optical elements for laser beam shaping, aiming at decreasing both mean square error and top beam uniformity of the output beam. Derived from Gercherg-Saxton (G-S) algorithm, the profile-smoothing algorithm is put forward, which can effectively improve the uniformity of top beam, but has a poor performance at the mean square error. Combining the profile-smoothing algorithm and the Gercherg-Saxton algorithm by fuzzy control theory, the iterative algorithm based on fuzzy control theory, can decrease both mean square error and uniformity of beam top. Computer-designed result by using the iterative algorithm based on fuzzy control theory leads to an excellent output beam, and the mean square error and top beam uniformity of beam are 0.75% and 0.46% respectively, while the energy conversion efficiency is up to 94.91%..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1682 (2007)
Optical Devices
Lifetime Prolongation by Graded Junction for Blue Organic Light Emitting Diodes
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Blue organic light emitting diode (OLED) with a graded junction at hole transporting layer (HTL) and emitted layer (EML) interface was constructed (Cell-GJ). Compared with conventional heterojunction OLED (Cell-HJ), it exhibited significantly improved lifetime, and the half lifetime achieved 8460 h at initial luminanceBlue organic light emitting diode (OLED) with a graded junction at hole transporting layer (HTL) and emitted layer (EML) interface was constructed (Cell-GJ). Compared with conventional heterojunction OLED (Cell-HJ), it exhibited significantly improved lifetime, and the half lifetime achieved 8460 h at initial luminance 100 cd/m2, more than 6 times longer than that of Cell-HJ. This improvement is attributed to the elimination of local electric field across the non-abrupt heterojunction, which thereby decreases the production of Joule heat and enhances the lifetime of device. However, the efficiency of Cell-GJ is lower than that of Cell-HJ. In order to redeem the decrease in efficiency of Cell-GJ, another device with a GaQ thin layer inserted in the TBADN/AlQ interface was made (Cell-GJGaQ). For the LUMO energy level of GaQ is between the energy level of AlQ and TBADN, the multi-step energy barrier between AlQ-GaQ-TBADN improves the electron (minority) injection greatly, so the luminescence efficiency is greatly improved. This Cell-GaQ shows efficiency 20% higher than that of Cell-GJ and also 5 times longer half lifetime than that of Cell-HJ. The whole performance is greatly improved..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1687 (2007)
Analysis on Multimode Interference Coupler-Based 1×3 Optical Switch with Mono-Compound Modulation Region
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
By employing the self-imaging properties of multimode interference, a 1×3 optical switch with mono-compound modulation region is presented. When at different switching states, a multiple relation exists in the acquired modulation magnitudes in the connecting arms, and therefore, the phase shifters in the arms can By employing the self-imaging properties of multimode interference, a 1×3 optical switch with mono-compound modulation region is presented. When at different switching states, a multiple relation exists in the acquired modulation magnitudes in the connecting arms, and therefore, the phase shifters in the arms can compose a mono-compound modulation region (MCMR). By contimuously changing the refractive indices in the MCMR, light incident from any input port can be switched alternatively to arbitrary output port. Based on Al0.07Ga0.93As/GaAs ridge structure, the proposed device was optimized and theoretically demonstrated by employing BEAMPROP software. The extinction ratio is as high as 30.3 dB. The crosstalk between adjacent channels is less than -29.8 dB. In a wide spectral range (～50 nm) around 1.31 μm wavelength, the crosstalk keeps lower than -20 dB. This device may greatly simplify the modulating scheme of traditionaly multichannel switch and relax the complextity of external controlling..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1691 (2007)
OPTOELECTRONICS
Narrow Band Interleaver Based on One-Dimensional Photonic Crystal with Positive-Negative Index Alternant Multilayer
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The transmission spectrum of one-dimensional (1D) photonic crystal (PC) with positive-negative index alternant multilayer is studied with transfer-matrix method. The result reveals that this type of 1D PC has broad-flat forbidden band and narrow-sharp transmitted band. The transmission-spectrum character is affected byThe transmission spectrum of one-dimensional (1D) photonic crystal (PC) with positive-negative index alternant multilayer is studied with transfer-matrix method. The result reveals that this type of 1D PC has broad-flat forbidden band and narrow-sharp transmitted band. The transmission-spectrum character is affected by Bragg scattering, Fabry-Pérot resonating and the =0 forbidden band. The position of transmitted band is determined by Fabry-Pérot resonating. A new narrow-band interleaver applied to dense wavelength division multiplexing (DWDM) system is designed by this type of one-dimensional photonic crystal. The simulation result of 0.8 nm channel spacing interleaver is presented. It is shown that this new interleaver has narrow channel spacing, flat forbidden band and narrow transmitted band. The channel spacing can be adjusted by change of the unit period optical thickness of one-dimensional photonic crystal..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1695 (2007)
Wigner Functions of Two-Mode Excited Squeezed Vauccm States
[in Chinese], [in Chinese], and [in Chinese]
Using the Wigner operator in the entangled-state representation we construct the Wigner functions of the two-mode excited squeezed vacuum states (TESVS). In term of the variations of the Wigner functions with respect to the parameters m, n and r in the ρ-γ phase space, the quantum interference properties and squeezing Using the Wigner operator in the entangled-state representation we construct the Wigner functions of the two-mode excited squeezed vacuum states (TESVS). In term of the variations of the Wigner functions with respect to the parameters m, n and r in the ρ-γ phase space, the quantum interference properties and squeezing effects of the TESVS are discussed. The results show that, for different values of m and n, the TESVS have different quantum interference effects, however for different squeezing parameters r the TESVS exhibit different squeezing effects. Furthermore, the physical meaning of the Wigner functions is identified according to the marginal distributions of the Wigner functions for the TESVS..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1700 (2007)
Scattering
Aerosol Mass Density Algorithm Based on Average Mass
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Based on Mie scattering theory, the formula for calculating mass concentration of spherical particles by optical particle counter was established. Considering non-spherical particles, starting from particles size distribution, the concept of the average mass was put forward, and the theoretical formula for calculating Based on Mie scattering theory, the formula for calculating mass concentration of spherical particles by optical particle counter was established. Considering non-spherical particles, starting from particles size distribution, the concept of the average mass was put forward, and the theoretical formula for calculating mass density of non-spherical particles was derived. Using this theoretical formula, the rationality of the calculation formula of optical particle counter for non-spherical particles was verified. The aerosol mass density algorithm based on average mass was proposed, and only two coefficients need to be calibrated in the algorithm. The experimental results agree well with the mass density values calculated by the algorithm, the slope of fitting line is 0.9713 and the correlation coefficient is 0.9998. This algorithm offers a feasible way for the optical particle counter to measure aerosol mass density in real time..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1706 (2007)
Light Scattering of Plane Wave/Gaussian Beam from Two Adjacent Objects
[in Chinese], [in Chinese], and [in Chinese]
Based on the equivalence principle and the reciprocity theorem, the problem of light scattering of plane wave/Gaussian beam from arbitrary two adjacent objects is considered and a solution that accounts for multiple scattering up to second-order is evaluated. In general, the first-order solution can easily be obtained.Based on the equivalence principle and the reciprocity theorem, the problem of light scattering of plane wave/Gaussian beam from arbitrary two adjacent objects is considered and a solution that accounts for multiple scattering up to second-order is evaluated. In general, the first-order solution can easily be obtained. However, due to the difficulty in formulating the coupled scattering field, it is impossible to find an exact analytical solution for the second-order scattered field. In order to overcome this difficulty, the second-order solution of light scattering of plane wave/Gaussian beam from two adjacent conducting/dielectric objects is derived by employing the reciprocity theorem and this solution is simplified from volume integral to surface integral form by using the equivalence principle. In specific, the composite scattering field from two adjacent spheres is calculated. The bi-static scattering is discussed, and the results are compared with numerical computations based on time-domain integral equation method (TDIEM). Meanwhile, the dependence of the scattering section and the degree of polarization on the beam-waist radius and the locations of the objects are also discussed..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1711 (2007)
Vision, Color, and Visual Optics
Piecewise Partition Model for Accurate Colorimetric Characterization of Liquid Crystal Displays
[in Chinese], and [in Chinese]
In order to improve the accuracy of colorimetric characterization of liquid crystal display (LCD), a piecewise partition model (PP model) was proposed concerning the LCD's poor performance of constant channel chromaticity and channel independence. The model involved two steps, first the relationship between the triIn order to improve the accuracy of colorimetric characterization of liquid crystal display (LCD), a piecewise partition model (PP model) was proposed concerning the LCD's poor performance of constant channel chromaticity and channel independence. The model involved two steps, first the relationship between the tristimulus values and their corresponding discrete integer values of individual color channel was regressed by using of piecewise quadratic polynomial, and then the proper interferential items were inserted according to different RGB subspaces' color characteristics for colorimetric characterization of LCD. The experimental results showed that the average/maximum color differences of this PP model were 1.5881/6.0249 CIELAB unit when the numbers of training and testing samples were 91 and 512 respectively. Compared with the methods of three-dimensional look-up table (3D-LUT), Mask, S-curve and two-primary crosstalk (TPC) models, the PP model performed best for the case of less training samples..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 27, Issue 9, 1719 (2007)
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