Radiation Mode

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Lin Zhang - One of the best experts on this subject based on the ideXlab platform.

  • Numerical and Experimental Characterization of Radiation Mode of 45° Tilted Fiber Grating
    Journal of Lightwave Technology, 2019
    Co-Authors: Qinyun He, Zhikun Xing, Kaiming Zhou, Hushan Wang, Lin Zhang
    Abstract:

    In this paper, we have numerically and experimentally investigated the Radiation Mode of 45° tilted fiber grating (45° TFG). By introducing the axial distributions into the volume current method, we have established a three-dimensional theoretical Model to analyze spatial distributions of the Radiation Mode of 45° TFG, and measured the Radiation Mode spatial distributions in experiment. Both numerical and experimental results show that the Radiation Mode of 45° TFG exhibits an exponential reduction along the fiber axial direction, and a quasi-Gaussian profile along the radial direction of fiber. Additionally, we have also measured the detailed polarization-dependent azimuthal intensity distributions of Radiation Modes of both s- and p-polarized core Modes. The degree of polarization of Radiation Mode is around 99.886%, which is independent of the length and the polarization extinction ratio of the grating. Moreover, for the first time, we have experimentally observed a very weak p-polarized component existing in the Radiation Mode, which has matched well with the simulation results.

  • Theoretical analysis of diffraction grating based on 45 degrees-tilted fiber gratings
    2017 Opto-Electronics and Communications Conference (OECC) and Photonics Global Conference (PGC), 2017
    Co-Authors: Guoqing Wang, Chao Wang, Lin Zhang
    Abstract:

    We have theoretically analyzed the diffractive characteristics of Radiation Mode of 45° tilted fiber gratings. The simulated angular dispersion for the 45 ° TFG with 748nm period at 1550nm is around 0.053°/nm, which is quite close to the experimental result.

T.m. Benson - One of the best experts on this subject based on the ideXlab platform.

P.c. Kendall - One of the best experts on this subject based on the ideXlab platform.

  • Applicability of scalar theory for analysis of Mode reflection from an optical dielectric waveguide end
    Optical and Quantum Electronics, 2001
    Co-Authors: A.b. Manenkov, T.m. Benson, P.c. Kendall, P.d. Sewell
    Abstract:

    Scalar and vector theories are compared for weakly guided Modes reflected from a planar optical dielectric waveguide end or laser facet. By utilizing the free space Radiation Mode method the range of validity of the scalar theory over a wide range of reflectivities is given explicitly for the first time.

  • Fast and accurate reflectivity calculations for shaped core optical fibres
    Optical and Quantum Electronics, 2000
    Co-Authors: A.b. Manenkov, T.m. Benson, P.d. Sewell, P.c. Kendall
    Abstract:

    A novel scalar (i.e. paraxial) free space Radiation Mode method is presented for calculating the normal incidence facet reflectivity of the main guided Mode of a step-index optical fibre with generally shaped smooth core. Numerical results are presented and discussed for several cases of the N th order super-elliptical core shape, including the circular, elliptical, rectangular-type and slab limiting cases.

  • Advances in spectral methods for optoelectronic design
    4th International Conference on Telecommunications in Modern Satellite Cable and Broadcasting Services. TELSIKS'99 (Cat. No.99EX365), 1999
    Co-Authors: A. Vukovic, P. Sewell, T.m. Benson, S. Greedy, P.c. Kendall
    Abstract:

    Two advances in spectral methods for the fast and accurate analysis of optical waveguides are reported. The spectral index method has been extended to include arbitrarily shaped rib waveguides in air. Then a half space Radiation Mode method is developed to calculate the facet reflectivity of 2D waveguides buried at a realistic depth.

  • Efficient propagation algorithm for 3D optical waveguides
    IEE Proceedings - Optoelectronics, 1998
    Co-Authors: M. Reed, P. Sewell, T.m. Benson, P.c. Kendall
    Abstract:

    The well established free space Radiation Mode (FSRM) method is extended to the analysis of dielectric waveguide discontinuities and propagation in fully three dimensional structures. Unlike beam propagation methods (BPM) the method intrinsically incorporates continuous reflections and is inherently wide angled in nature. Results are given for a representative selection of practical structures, such as single and double step discontinuities and tapers, for both TE and TM polarisations. The method is computationally efficient with minimal memory requirements.

  • Transcendental equation for the vectorial Modes of buried optical waveguides
    IEEE Photonics Technology Letters, 1997
    Co-Authors: P. Sewell, T.m. Benson, M. Reed, P.c. Kendall
    Abstract:

    The free-space Radiation Mode (FSRM) method is extended to allow full vector modal analysis of buried optical waveguides to be computed semi-analytically in a very fast, efficient, yet accurate, manner. Both TE and TM dominated Modes are investigated, identifying propagation constants via an explicit transcendental equation, and full field profiles.

Shuisheng Jian - One of the best experts on this subject based on the ideXlab platform.

  • analysis of coupling from core Mode to counter propagating Radiation Modes in tilted fiber bragg gratings
    Science in China Series F: Information Sciences, 2010
    Co-Authors: Shaohua Lu, Ou Xu, Suchun Feng, Xiaowei Dong, Shuisheng Jian
    Abstract:

    Radiation-Mode coupling is stronger and more efficient in tilted fiber Bragg gratings than in other fiber gratings; it has good advantage in such fields as optical communication and optical sensors. A simplified coupled-Mode theory (CMT) approach is proposed for what we believe to be the first time, whose validity is demonstrated by comparing its simulation results with that of the complete CMT equations. With the simplified CMT approach, a theoretical spectral analysis of coupling from core Mode to counter-propagating Radiation Modes in reflective tilted fiber Bragg gratings is presented. The influence of grating length, refractive index modulation amplitude and tilt angle is exhaustively investigated on the transmission spectrum characteristics. The different dependences between s-polarized and p-polarized Radiation-Mode coupling on grating tilt angle are discussed, and the coupling strength of 45°-tilted gratings shows the greatest polarization dependence with the limitation of backward-propagating Radiation-Mode coupling.

  • Analysis of Radiation-Mode coupling in reflective and transmissive tilted fiber Bragg gratings
    Journal of The Optical Society of America A-optics Image Science and Vision, 2008
    Co-Authors: Shaohua Lu, Ou Xu, Suchun Feng, Shuisheng Jian
    Abstract:

    Radiation-Mode coupling is stronger and more efficient in tilted fiber Bragg gratings than in other fiber gratings; it can be used to good advantage in such fields as optical communication and optical sensors. A simplified coupled-Mode theory (CMT) approach to the analysis of Radiation-Mode coupling is proposed for what we believe to be the first time, whose validity and accuracy is demonstrated by comparing its simulation results with that of the complete CMT equations and the volume current method (VCM). With the simplified CMT approach, a theoretical spectral analysis of coupling from core Mode to Radiation Modes in both reflective and transmissive tilted fiber Bragg gratings is presented. The influence of tilt angle on the transmission spectrum characteristics is comprehensively investigated. The different dependences between s-polarized and p-polarized Radiation-Mode coupling on grating tilt angle are discussed, and an analysis is performed on how to obtain a high-performance in-fiber polarizer that involves a compromise between polarization extinction and insertion loss.

  • Theoretical analysis of Radiation-Mode resonance in long-period fiber gratings
    Proceedings of SPIE, 2004
    Co-Authors: Kai Zheng, Weijun Liang, Fangcheng Yang, Shuisheng Jian
    Abstract:

    When the long period fiber grating (LPG) is surrounded with dielectric material whose refractive index is higher than that of cladding, core Mode to Radiation Mode coupling occurs. In this paper, a theoretical method to analyze the Radiation-Mode resonance in LPG is presented. The coupled-Mode equations of LPG are derived based on Amnon Yariv’s coupled-Mode theory. Here, the Radiation-Mode theory is used. The electric field of individual Radiation Mode is given based on the weakly guiding approximation of three-layer optical waveguide. The expansion of the total Radiation Modes, which is a Fourier-Bessel integral, is presented. It’s noted that the weight of the integral is not one. The normalization of the individual Radiation Mode is discussed in detail. It’s found that the normalization integral is unbounded but changed to a Dirac function. Thus, it’s calculated only through theoretical derivation. The approximate numerical method to deal with the coupled-Mode equations is presented. The transmission spectra of LPG, which are surrounded with several surrounding refractive indices, are numerically calculated.

Yahei Koyamada - One of the best experts on this subject based on the ideXlab platform.

  • Numerical analysis of core-Mode to Radiation-Mode coupling in long-period fiber gratings
    IEEE Photonics Technology Letters, 2001
    Co-Authors: Yahei Koyamada
    Abstract:

    This letter presents, to the best of our knowledge, the first analysis of core-Mode to Radiation-Mode coupling in long-period fiber gratings (LPGs) that are surrounded with dielectric material whose refractive index is higher than that of the cladding. We calculated core-Mode transmission spectra through LPGs by integrating numerically the coupled-Mode equations between the core Mode and a continuum of Radiation Modes. We show calculated core-Mode transmission spectra that exhibit such loss band continuums as have already been observed experimentally but not yet theoretically estimated.

  • analysis of core Mode to Radiation Mode coupling in fiber bragg gratings with finite cladding radius
    Journal of Lightwave Technology, 2000
    Co-Authors: Yahei Koyamada
    Abstract:

    Fiber Bragg gratings (FBGs) are often surrounded with dielectric material whose refractive index is higher than that of cladding. The purpose is to prevent cladding Modes because coupling to cladding Modes may cause undesirable dips on the short wavelength side of the main Bragg band in the core-Mode transmission spectrum. In such FBGs, core-Mode to Radiation-Mode coupling can cause a loss band continuum. Until now, however, reported analyses of this core-Mode to Radiation-Mode coupling have been limited to hypothetical FBGs with an infinite cladding radius. This paper presents, to the best of our knowledge, the first analysis of core-Mode to Radiation-Mode coupling in real FBGs with a finite cladding radius. We derive a formula to calculate the core-Mode transmission loss caused by the Radiation-Mode coupling. We show calculated core-Mode transmission spectra that exhibit such fringes as have already been observed experimentally but not yet theoretically estimated.