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    Wyświetlanie 1-11 z 11
    Tytuł:
    Changes in the states of polarization of random electromagnetic beams in atmospheric turbulence
    Autorzy:
    Li, J.
    Zhao, K.
    Lai, Y.
    Powiązania:
    https://bibliotekanauki.pl/articles/174110.pdf
    Data publikacji:
    2017
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    non-Kolmogorov atmospheric turbulence
    random electromagnetic beams
    degree of polarization
    orientation angle
    degree of ellipticity
    Opis:
    Taking the random electromagnetic cosh-Gaussian beam as a typical example of random electromagnetic beams, the analytical expressions for the cross-spectral density matrix element of random electromagnetic cosh-Gaussian beams propagating through non-Kolmogorov atmospheric turbulence are derived, and used to study the changes in the states of polarization (degree of polarization, orientation angle and degree of ellipticity) of random electromagnetic cosh-Gaussian beams in non-Kolmogorov atmospheric turbulence. It is shown that the states of polarization of random electromagnetic cosh-Gaussian beams in non-Kolmogorov atmospheric turbulence are different from those in free space. The degree of polarization decreases, and the orientation angle and degree of ellipticity increase with increasing structure constant. The on-axis degree of polarization and the degree of ellipticity appear to have an oscillatory behavior and the orientation angle has a rapid transition for the larger cosh-part parameter of random electromagnetic cosh-Gaussian beams in atmospheric turbulence.
    Źródło:
    Optica Applicata; 2017, 47, 1; 51-62
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The kurtosis parameter of partially coherent controllable dark hollow beams in free space
    Autorzy:
    Li, J.
    Wang, W W
    Lai, Y
    Powiązania:
    https://bibliotekanauki.pl/articles/173815.pdf
    Data publikacji:
    2014
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    kurtosis parameter
    partially coherent controllable dark hollow beams
    free space
    Opis:
    Based on the extended Huygens–Fresnel principle and the definition of second-order moments of the Wigner distribution function, the analytical expression for the kurtosis parameter of partially coherent controllable dark hollow beams in free space is derived, and used to study the influence of beam parameters on the kurtosis parameter. It is shown that the kurtosis parameter increases with increasing the wavelength and the waist width, or decreasing the scaling factor, however, the effect of the beam order and the spatial correlation length on the kurtosis parameter depends on the propagation distance. The results can be interpreted physically.
    Źródło:
    Optica Applicata; 2014, 44, 4; 533-543
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Sensitive detection of acetylene by second derivative spectra with tunable diode laser absorption spectroscopy
    Autorzy:
    Deng, H.
    Sun, J.
    Li, P.
    Liu, Y.
    Yu, B.
    Li, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/174963.pdf
    Data publikacji:
    2016
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    tunable diode laser absorption spectroscopy
    TDLAS
    signal processing
    Savitzky–Golay filter
    trace gas detection
    Opis:
    A tunable diode laser absorption spectrometer was developed for trace acetylene gas analysis, the system performance was evaluated by combing an appropriate digital signal processing methods, i.e., Savitzky–Golay smoothing and differentiation algorithm. The calculation of the derivative spectra by this method is accompanied by simultaneous data smoothing. Based on the 2nd deriv- ative spectra detection method, the Allan variance technique indicates a C2H2 detection limit of 1.7ppm for 1-s averaging time, and a minimum noise level of 62ppb (parts per billion), at the optimum integration time of ~60s. The calculated 2nd derivative spectra with better resolution, lower detection limits, save signal processing time, and improve the ability to distinguish unresolved spectral signals.
    Źródło:
    Optica Applicata; 2016, 46, 3; 353-363
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Improvement of accuracy of simple methods for design and analysis of a blazed phase grating microstructure
    Autorzy:
    Wang, W.
    Jing, X.
    Zhao, J.
    Li, Y.
    Tian, Y.
    Powiązania:
    https://bibliotekanauki.pl/articles/173533.pdf
    Data publikacji:
    2017
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    grating
    effective medium theory
    scalar diffraction theory
    Opis:
    In order to precisely analyze and design the transmittance characteristics of a blazed grating, the validity of both the scalar diffraction theory and the effective medium theory is quantitatively demonstrated. By making a comparison of diffraction efficiencies calculated by the two simplified methods and Fourier modal method, the accuracy can be obtained. It is found that when the normalized period is more than three wavelengths of the incident light, the scalar diffraction theory is useful to calculate the transmittance of the blazed grating within the error of less than 3%. The validity of the scalar diffraction theory increases when the normalized period increases. Importantly, by considering the Fresnel reflection effect, the validity of scalar diffraction theory can be significantly enhanced. Furthermore, when no higher-order diffraction waves appear and only zeroth order diffraction wave propagates, the effective medium theory is accurate to compute the diffraction efficiency within the difference of less than 1% between the zeroth order effective medium theory and Fourier modal method. The polarization characteristics of the validity of effective medium theory are also quantitatively demonstrated. The validity of the two simplified theories is dependent on not only the normalized period of surface microstructure but also the normalized groove depth.
    Źródło:
    Optica Applicata; 2017, 47, 2; 183-198
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Spectral degrees of cross-polarization of stochastic anisotropic electromagnetic beams in modified non-Kolmogorov atmospheric turbulence
    Autorzy:
    Chen, F.
    Chen, J.
    Zhao, Q.
    Chen, Y
    Xin, Y.
    Li, J.
    Pan, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/174614.pdf
    Data publikacji:
    2013
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    quasi-homogenous source
    modified non-Kolmogorov turbulence
    generalized Stokes parameters
    Opis:
    Based on the extended Huygens–Fresnel principle, variations in generalized Stokes parameters of stochastic anisotropic electromagnetic beams propagating through modified non-Kolmogorov atmospheric turbulence have been analyzed. The changes in generalized Stokes parameters with different turbulence parameters and source parameters were analyzed first. After that, the distributions of the spectral degrees of cross-polarization (SDCP) of isotropic beams and anisotropic beams were simulated. The results show that the profiles of distribution of SDCP of these two kinds of beams are very different in the near field, and will fluctuate through the propagation in atmospheric turbulence, but at last, when the propagation distance is long enough, the difference in the source makes a slight difference in the final profiles of SDCP in the output plane. They mainly depended on the turbulence perturbation, and in the weak turbulence, the profiles of final distribution show more flatter features.
    Źródło:
    Optica Applicata; 2013, 43, 4; 773-783
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Image encryption algorithm by using the logistic map and discrete fractional angular transform
    Autorzy:
    Yu, J.
    Li, Y.
    Xie, X.
    Zhou, N.
    Zhou, Z.
    Powiązania:
    https://bibliotekanauki.pl/articles/173813.pdf
    Data publikacji:
    2017
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    image encryption
    logistic map
    discrete fractional angular transform
    Opis:
    A new image encryption scheme based on logistic map and discrete fractional angular transform has been proposed. In the proposed scheme, the original image is encrypted with the random sequence generated by the logistic map, and the encrypted image is subsequently processed by the discrete fractional angular transform, which produces the ciphertext after double encryptions. The parameters of the logistic map and the order of the discrete fractional angular transform serve as the main keys of the image encryption algorithm. Simulation results show that the proposed image encryption algorithm can effectively resist the attacks of statistical analysis, and has acceptable encryption effect and security.
    Źródło:
    Optica Applicata; 2017, 47, 1; 141-155
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Ultrashort pulse propagation recording by using the transmission-type light in flight holography
    Autorzy:
    Fan, Y.
    Li, J.
    Zheng, S.
    Lu, X.
    Zhong, X.
    Powiązania:
    https://bibliotekanauki.pl/articles/174016.pdf
    Data publikacji:
    2017
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    light in flight
    visualization of pulse propagation
    holography
    Opis:
    In this paper, the distortion of the reconstructed images of the propagating light pulse in transmission light-in-flight holography recording was analyzed. Based on the analysis model, for recording the wavefront more accurately, the optimized selection of relevant parameters was made. Furthermore, a cylindrical lens was introduced to correct the image distortion. Additionally, the light-in-flight recording of the wavefront changing during propagation was simulated.
    Źródło:
    Optica Applicata; 2017, 47, 2; 283-294
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Feature extraction of molten pool for laser welding quality real-time inspection
    Autorzy:
    Zhang, J
    Yin, H
    Huang, H
    Yang, R
    Yang, J
    Li, Y
    Powiązania:
    https://bibliotekanauki.pl/articles/173597.pdf
    Data publikacji:
    2015
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    laser materials processing
    process monitoring and control
    image analysis
    Opis:
    This paper proposed an image feature extraction method for laser welding molten pool inspection based on cellular neural network. TC4 titanium alloy thin plates were welded by Nd:YAG pulsed laser. A coaxial machine vision system was designed to acquire molten pool images. An auxiliary lighting source was employed to improve the molten pool image quality. By analyzing molten pool images, the welding defects such as fenestration or insufficient depth were identified. These results can be used as a feedback signal for laser power control. Experimental results showed that the proposed method can be used to improve laser welding quality.
    Źródło:
    Optica Applicata; 2015, 45, 4; 523-533
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Dispersion-compensating en/decoder for a time-spreading/wavelength-hopping optical code-division multiplexing (OCDM) system
    Autorzy:
    Zheng, J.
    Wang, R.
    Pu, T.
    Lu, L.
    Fang, T.
    Su, Y.
    Li, L.
    Yang, Q.
    Chen, X.
    Powiązania:
    https://bibliotekanauki.pl/articles/174365.pdf
    Data publikacji:
    2013
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    optical code-division multiplexing (OCDM)
    fiber Bragg grating (FBG)
    dispersion
    Opis:
    A novel dispersion-compensating fiber Bragg grating (FBG)-based en/decoder is proposed to compensate both the out-band and in-band dispersion in a time-spreading/wavelength-hopping (TS/WH) optical code-division multiplexing (OCDM) system. The experimental realization of such en/decoders only needs a uniform-pitch phase mask and a sub-micrometer precision moving stage. Such an en/decoder pair with the ability of compensating the dispersion of transmission in 20-km single mode fiber (SMF) is simulated and experimentally fabricated. Both the simulation and experimental results show that the decoded pulse can be recovered without any distortion owing to the elimination of dispersion.
    Źródło:
    Optica Applicata; 2013, 43, 3; 485-495
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Colloidal crystal cladded microfiber for refractive index sensing
    Autorzy:
    Yan, H. T.
    Zhao, X Y
    Zhang, Ch.
    Zhen, Z Q
    Li, Q Z
    Cao, J X
    Xia, L X
    Powiązania:
    https://bibliotekanauki.pl/articles/174902.pdf
    Data publikacji:
    2014
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    microfibers
    colloidal crystals
    refractive index sensing
    Opis:
    We investigate the evanescent field of a microfiber wrapped by colloidal crystals. The microfiber has the diameter of about 1 μm that is drawn from a single-mode fiber with an alcohol lamp. The colloidal spheres are further attached to the microfiber through thermal evaporation, then they self-assemble to crystal-like structures. The 400 nm, 590 nm, and 710 nm-diameter SiO2 colloidal spheres are used, respectively. The spectral responses are studied theoretically and experimentally, and the results agree with each other. It is revealed that the evanescent field of a microfiber could be modulated by the photonic band-gap of colloidal crystals. This characteristic is very useful in refractive index sensing for liquids.
    Źródło:
    Optica Applicata; 2014, 44, 2; 309-315
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Real-time optical demultiplexing with the chirped pulses
    Autorzy:
    Li, Y.
    Zhang, X.
    Yuan, J.
    Kang, Z.
    Sang, X.
    Kang, S.
    Kang, X.
    Yan, B.
    Wang, K.
    Yu, C.
    Powiązania:
    https://bibliotekanauki.pl/articles/175106.pdf
    Data publikacji:
    2018
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    linearly chirped pulse
    parametric process
    real-time optical demultiplexing
    Opis:
    A scheme for real-time optical demultiplexing is proposed by utilizing the time-broadened and linearly chirped pulses instead of the conventional mode-locked pulses. The copies of the optical-time-division-multiplexed signal are acquired through a dual-pump parametric gate and used as the parametric multicast block. Simulation results show that the demultiplexing from 160 Gb/s down to sixteen 10 Gb/s tributaries can be achieved only by using a sampling source of 10 GHz. The proposed scheme can effectively reduce the complexity of parallel processing, and find important applications in the high-speed all-optical signal processing.
    Źródło:
    Optica Applicata; 2018, 48, 4; 621-632
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-11 z 11

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