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Masanori Koshiba - One of the best experts on this subject based on the ideXlab platform.

  • design principle for realizing low bending losses in all solid Photonic Bandgap Fibers
    Journal of Lightwave Technology, 2011
    Co-Authors: Tadashi Murao, Kunimasa Saitoh, Koyuru Nagao, Masanori Koshiba
    Abstract:

    In this paper, the structural dependence of factor which mainly affects a bending loss property is theoretically investigated in all-solid Photonic Bandgap Fibers (PBGFs). A design principle for realizing low bending losses is successfully figured out for the first-order Photonic Bandgap (PBG). In particular, one of the origins which causes the variation of bending loss property for each structural parameter is identified. In addition, we show that exploitation of a large pitch relative to a rod diameter, aiming to realize a large-mode area (LMA) structure, leads to a significant degradation of the bending loss property. Moreover, it is demonstrated that a V-value which is proposed for all-solid PBGFs is also reduced significantly for the LMA condition. The origin of the degradation is attributed to the newly-excited Bloch state which determines the second-order PBG edge.

  • multiple resonant coupling mechanism for suppression of higher order modes in all solid Photonic Bandgap Fibers with heterostructured cladding
    Optics Express, 2011
    Co-Authors: Tadashi Murao, Kunimasa Saitoh, Masanori Koshiba
    Abstract:

    In this paper, we propose a novel mechanism for suppression of higher-order modes (HOMs), namely multiple resonant coupling, in all-solid Photonic Bandgap Fibers (PBGFs) with effectively large core diameters. In an analogy to the well-known tight-binding theory in solid-state physics, multiple anti-resonant reflecting optical waveguide (ARROW) modes bound in designedly arranged defects in the cladding make up Bloch states and resultant Photonic bands with a finite effective-index width, which contribute to the suppression of HOMs. In particular, contrary to the conventional method for the HOM suppression using the index-matching of the HOMs in the core of the PBGF and the defect mode arranged in the cladding, the proposed mechanism guarantees a broadband HOM suppression without a precise structural design. This effect is explained by the multiple resonant coupling, as well as an enhanced confinement loss mechanism which occurs near the condition satisfying the multiple resonant coupling. Moreover, we show that the proposed structure exhibits a lower bending loss characteristic when compared to the conventional all-solid PBGFs. The simultaneous realization of the single-mode operation and the low bending loss property is due to the novel cladding concept named as heterostructured cladding. The proposed structure also resolves the issue for the increased confinement loss property in the first-order Photonic Bandgap (PBG) at the same time.

  • effective area limit of large mode area solid core Photonic Bandgap Fibers for fiber laser applications
    Optical Fiber Technology, 2010
    Co-Authors: Kunimasa Saitoh, Tadashi Murao, Lorenzo Rosa, Masanori Koshiba
    Abstract:

    Abstract We investigate the bending characteristics of solid-core Photonic Bandgap Fibers (SC-PBGFs) aiming to achieve large mode area (LMA) and effectively single-mode operation with a practically allowable bending radius for high-power Yb-doped fiber lasers and amplifiers. Through detailed numerical simulations based on the finite element method (FEM), we evaluate the impacts of the order of Photonic Bandgap on the bending performance and point out the limits of core size enlargement in the SC-PBGFs with a 1-cell core structure due to the increment of bending loss. In addition, under practical constraints, we find that the SC-PBGFs having a 7-cell core can achieve sufficient differential bending loss between the fundamental mode and the higher-order modes and a much larger effective area limit as compared with previously-reported index-guiding LMA Fibers.

  • bend insensitive and effectively single moded all solid Photonic Bandgap Fibers with heterostructured cladding
    European Conference on Optical Communication, 2009
    Co-Authors: Tadashi Murao, Kunimasa Saitoh, Toshiki Taru, Takuji Nagashima, Kuniaki Maeda, Takashi Sasaki, Masanori Koshiba
    Abstract:

    We propose a novel concept of cladding structure in all-solid Photonic Bandgap Fibers. It promises low bending and confinement losses with single-mode operation. The mechanism is based on the new concept of heterostructured cladding.

  • detailed theoretical investigation of bending properties in solid core Photonic Bandgap Fibers
    Optics Express, 2009
    Co-Authors: Tadashi Murao, Kunimasa Saitoh, Masanori Koshiba
    Abstract:

    In this paper, detailed properties of bent solid-core Photonic Bandgap Fibers (SC-PBGFs) are investigated. We propose an approximate equivalent straight waveguide (ESW) formulation for Photonic Bandgap (PBG) edges, which is convenient to see qualitatively which radiation (centripetal or centrifugal radiation) mainly occurs and the impact of bend losses for an operating wavelength. In particular, we show that cladding modes induced by bending cause several complete or incomplete leaky mode couplings with the core mode and the resultant loss peaks. Moreover, we show that the field distributions of the cladding modes are characterized by three distinct types for blue-edge, mid-gap, and red-edge wavelengths in the PBG, which is explained by considering the cladding Bloch states or resonant conditions without bending. Next, we investigate the structural dependence of the bend losses. In particular, we demonstrate the bend-loss dependence on the number of the cladding rings. Finally, by investigating the impacts of the order of PBG and the core structure on the bend losses, we discuss a tight-bending structure.

Kunimasa Saitoh - One of the best experts on this subject based on the ideXlab platform.

  • large mode area all solid Photonic Bandgap Fibers for the mitigation of optical nonlinearities
    IEEE Journal of Selected Topics in Quantum Electronics, 2016
    Co-Authors: Liang Dong, Kunimasa Saitoh, Fanting Kong, Guancheng Gu, Thomas W Hawkins, Maxwell Jones, Joshua Parsons, Monica T Kalichevskydong, Benjamin Pulford, Iyad Dajani
    Abstract:

    There is still significant need for power scaling of fiber lasers. Large-mode-area Fibers are a key for the mitigation of optical nonlinearities. In recent years, mode instability has shown itself to be an additional significant limiting factor for single-mode power scaling in the regime of a few hundred watts to kilowatts. It is better appreciated now that further power scaling requires significant high-order-mode suppression in addition to a large effective mode area in a fiber. In recent years, we have shown that all-solid Photonic Bandgap Fibers are a superior approach due to their unsurpassed higher-order-mode suppression in large-mode-area designs, making them well suited for applications at high average powers. We will review of some of the recent progress, challenges, and prospects of all-solid Photonic Bandgap Fibers in this invited paper.

  • Yb-Doped Photonic Bandgap Fiber Lasers with Record Core Diameter
    CLEO: 2014, 2014
    Co-Authors: Guancheng Gu, Kunimasa Saitoh, Fanting Kong, Thomas Hawkins, Maxwell Jones, Joshua Parsons, Christopher Dunn, Monica T. Kalichevsky-dong, Liang Dong
    Abstract:

    We have demonstrated ytterbium-doped fiber lasers in 50µm-core Photonic Bandgap Fibers with robust single mode output, a record core diameter for active Photonic Bandgap Fibers, with slope efficiency exceeding 70%.

  • design optimization of large mode area all solid Photonic Bandgap Fibers for high power laser applications
    Journal of Lightwave Technology, 2014
    Co-Authors: Shota Saitoh, Kunimasa Saitoh, Masahiro Kashiwagi, Shoichiro Matsuo, Liang Dong
    Abstract:

    We optimized the structural parameters of large-mode-area all-solid Photonic Bandgap Fibers for high-power laser applications with numerical simulations. We obtained an effective mode area of greater than 1000 μm 2 in bending condition while maintaining single-mode operation and realizing compact packaging for both 7- and 19-cell core Fibers. We also found out that a core diameter of larger than 115 μm could be achieved for the 19-cell core Fibers.

  • All-solid Photonic Bandgap Fibers for fiber laser applications
    2013 Conference on Lasers and Electro-Optics Pacific Rim (CLEOPR), 2013
    Co-Authors: Kunimasa Saitoh, Shota Saitoh, Masahiro Kashiwagi, Shoichiro Matsuo, Liang Dong
    Abstract:

    Core size scaling in all-solid Photonic Bandgap Fibers (AS-PBGFs) is discussed. It is shown that the effectively single-mode AS-PBGF with 100-μm core diameter can be achievable with 40-cm bending radius operating in the 3rd PBG.

  • mode area scaling with all solid Photonic Bandgap Fibers
    Optics Express, 2012
    Co-Authors: Fanting Kong, Kunimasa Saitoh, Thomas Hawkins, Devon Mcclane, Guancheng Gu, Liang Dong
    Abstract:

    There are still very strong interests for power scaling in high power fiber lasers for a wide range of applications in medical, industry, defense and science. In many of these lasers, fiber nonlinearities are the main limits to further scaling. Although numerous specific techniques have studied for the suppression of a wide range of nonlinearities, the fundamental solution is to scale mode areas in Fibers while maintaining sufficient single mode operation. Here the key problem is that more modes are supported once physical dimensions of waveguides are increased. The key to solve this problem is to look for fiber designs with significant higher order mode suppression. In conventional waveguides, all modes are increasingly guided in the center of the waveguides when waveguide dimensions are increased. It is hard to couple a mode out in order to suppress its propagation, which severely limits their scalability. In an all-solid Photonic Bandgap fiber, modes are only guided due to anti-resonance of cladding Photonic crystal lattice. This provides strongly mode-dependent guidance, leading to very high differential mode losses. In addition, the all-solid nature of the fiber makes it easily spliced to other Fibers. In this paper, we will show for the first time that all-solid Photonic Bandgap Fibers with effective mode area of ~920μm2 can be made with excellent higher order mode suppression.

Liang Dong - One of the best experts on this subject based on the ideXlab platform.

  • large mode area all solid Photonic Bandgap Fibers for the mitigation of optical nonlinearities
    IEEE Journal of Selected Topics in Quantum Electronics, 2016
    Co-Authors: Liang Dong, Kunimasa Saitoh, Fanting Kong, Guancheng Gu, Thomas W Hawkins, Maxwell Jones, Joshua Parsons, Monica T Kalichevskydong, Benjamin Pulford, Iyad Dajani
    Abstract:

    There is still significant need for power scaling of fiber lasers. Large-mode-area Fibers are a key for the mitigation of optical nonlinearities. In recent years, mode instability has shown itself to be an additional significant limiting factor for single-mode power scaling in the regime of a few hundred watts to kilowatts. It is better appreciated now that further power scaling requires significant high-order-mode suppression in addition to a large effective mode area in a fiber. In recent years, we have shown that all-solid Photonic Bandgap Fibers are a superior approach due to their unsurpassed higher-order-mode suppression in large-mode-area designs, making them well suited for applications at high average powers. We will review of some of the recent progress, challenges, and prospects of all-solid Photonic Bandgap Fibers in this invited paper.

  • Yb-Doped Photonic Bandgap Fiber Lasers with Record Core Diameter
    CLEO: 2014, 2014
    Co-Authors: Guancheng Gu, Kunimasa Saitoh, Fanting Kong, Thomas Hawkins, Maxwell Jones, Joshua Parsons, Christopher Dunn, Monica T. Kalichevsky-dong, Liang Dong
    Abstract:

    We have demonstrated ytterbium-doped fiber lasers in 50µm-core Photonic Bandgap Fibers with robust single mode output, a record core diameter for active Photonic Bandgap Fibers, with slope efficiency exceeding 70%.

  • design optimization of large mode area all solid Photonic Bandgap Fibers for high power laser applications
    Journal of Lightwave Technology, 2014
    Co-Authors: Shota Saitoh, Kunimasa Saitoh, Masahiro Kashiwagi, Shoichiro Matsuo, Liang Dong
    Abstract:

    We optimized the structural parameters of large-mode-area all-solid Photonic Bandgap Fibers for high-power laser applications with numerical simulations. We obtained an effective mode area of greater than 1000 μm 2 in bending condition while maintaining single-mode operation and realizing compact packaging for both 7- and 19-cell core Fibers. We also found out that a core diameter of larger than 115 μm could be achieved for the 19-cell core Fibers.

  • All-solid Photonic Bandgap Fibers for fiber laser applications
    2013 Conference on Lasers and Electro-Optics Pacific Rim (CLEOPR), 2013
    Co-Authors: Kunimasa Saitoh, Shota Saitoh, Masahiro Kashiwagi, Shoichiro Matsuo, Liang Dong
    Abstract:

    Core size scaling in all-solid Photonic Bandgap Fibers (AS-PBGFs) is discussed. It is shown that the effectively single-mode AS-PBGF with 100-μm core diameter can be achievable with 40-cm bending radius operating in the 3rd PBG.

  • mode area scaling with all solid Photonic Bandgap Fibers
    Optics Express, 2012
    Co-Authors: Fanting Kong, Kunimasa Saitoh, Thomas Hawkins, Devon Mcclane, Guancheng Gu, Liang Dong
    Abstract:

    There are still very strong interests for power scaling in high power fiber lasers for a wide range of applications in medical, industry, defense and science. In many of these lasers, fiber nonlinearities are the main limits to further scaling. Although numerous specific techniques have studied for the suppression of a wide range of nonlinearities, the fundamental solution is to scale mode areas in Fibers while maintaining sufficient single mode operation. Here the key problem is that more modes are supported once physical dimensions of waveguides are increased. The key to solve this problem is to look for fiber designs with significant higher order mode suppression. In conventional waveguides, all modes are increasingly guided in the center of the waveguides when waveguide dimensions are increased. It is hard to couple a mode out in order to suppress its propagation, which severely limits their scalability. In an all-solid Photonic Bandgap fiber, modes are only guided due to anti-resonance of cladding Photonic crystal lattice. This provides strongly mode-dependent guidance, leading to very high differential mode losses. In addition, the all-solid nature of the fiber makes it easily spliced to other Fibers. In this paper, we will show for the first time that all-solid Photonic Bandgap Fibers with effective mode area of ~920μm2 can be made with excellent higher order mode suppression.

Zhi Wang - One of the best experts on this subject based on the ideXlab platform.

  • high order resonances between core mode and cladding supermodes in long period fiber gratings inscribed in Photonic Bandgap Fibers
    Optics Express, 2010
    Co-Authors: Zhi Wang, Jianbo Xu, Weijun Tong
    Abstract:

    High order resonances between fundamental core mode and cladding LP01 supermodes are demonstrated in long period fiber gratings (LPFGs) inscribed in all-solid Photonic Bandgap Fibers for the first time to our knowledge. The resonance wavelengths of the LPFGs calculated by way of Photonic Bandgap theory agree with the experimental results. The temperature responses of these resonance peaks have been theoretically and experimentally investigated. In addition, the mechanism of LPFG formation has been researched deeply through coupled-mode theory (CMT) and the cutback experiments.

  • ultraviolet inscribed long period gratings in all solid Photonic Bandgap Fibers
    Optics Express, 2008
    Co-Authors: Zhi Wang, Xiaoyi Dong
    Abstract:

    Long period fiber gratings are fabricated in the cladding rods of all-solid Photonic Bandgap Fibers (PBGFs) by point-by-point side UV illumination. Resonant couplings from fundamental mode to guided and radiative supermodes (rod modes), and Bandgap-like modes are identified. We obtained a detailed insight over the modal and dispersive properties of the PBGF through a series of theoretical and experimental investigations on the spectral characteristics and the responses to temperature and high-index liquid of the LPGs.

  • Bandgap and mode area analysis of all-solid square-lattice Photonic Bandgap Fibers
    Proceedings of SPIE, 2007
    Co-Authors: Zhi Wang, Fuyun Lv, Xiaoyi Dong
    Abstract:

    Using the plane-wave expansion method and finite element method, we investigate the properties of all-solid square-lattice Photonic Bandgap Fibers. The comparison of different r / Λ values in the proposed fiber is convenient to optimize the fiber design. The simulation results demonstrate that the effective mode area of all-solid square-lattice Photonic Bandgap Fibers is 1.25 times larger than triangular-lattice ones and the confinement loss of the Fibers is no more than 0.1dB/m within the selected Bandgap.

  • coupling in dual core Photonic Bandgap Fibers theory and experiment
    Optics Express, 2007
    Co-Authors: Zhi Wang, T A Birks, J C Knight, Toshiki Taru, Jiangbing Du
    Abstract:

    We have theoretically and experimentally investigated dual-core Photonic Bandgap Fibers (PBGFs), which consist of a cladding with an array of high-index rods and two cores formed by omitting two nearby rods. We find novel features in their coupling characteristics such as maxima and minima in coupling length, complete decoupling of the cores, and an inversion of the usual ordering of supermodes so that the odd supermode has the higher propagation constant. This behavior is understood by considering the field distribution in the rods between the cores.

  • tunable highly birefringent Photonic Bandgap Fibers
    Optics Letters, 2005
    Co-Authors: Chunshu Zhang, Zhi Wang, Shuzhong Yuan, Xiaoyi Dong
    Abstract:

    A novel tunable highly birefringent Photonic Bandgap fiber (PBGF) is designed theoretically by filling its air holes with high-index material. The transmission band can be continuously tuned by changing the refractive index of the filling material. Accordingly, the tunable modal birefringence and polarization mode dispersion of the PBGFs are investigated by adjusting the refractive index of the filling material. Furthermore, we have also analyzed the effect of surface modes in the Photonic Bandgap on the characteristics of the tunable PBGFs. The simulation results show the feasibility of constructing birefringence-tunable Photonic crystal Fibers and related fiber devices in practical applications.

D. J. Richardson - One of the best experts on this subject based on the ideXlab platform.

  • microbending effects in hollow core Photonic Bandgap Fibers
    2016
    Co-Authors: Eric Numkam Fokoua, D. J. Richardson, Yong Chen, F Poletti
    Abstract:

    We developed a model for the study of how microbends affect the operation of hollow-core Photonic Bandgap Fibers. Increased loss due to intermodal coupling is predicted. Preliminary experimental observations are in good agreement with the model’s predictions.

  • accurate modelling of fabricated hollow core Photonic Bandgap Fibers
    Optics Express, 2015
    Co-Authors: Eric Numkam Fokoua, M N Petrovich, N V Wheeler, N K Baddela, D. J. Richardson, Yong Chen, J R Hayes, S R Sandoghchi, Gregory T Jasion, F Poletti
    Abstract:

    We report a novel approach to reconstruct the cross-sectional profile of fabricated hollow-core Photonic Bandgap Fibers from scanning electron microscope images. Finite element simulations on the reconstructed geometries achieve a remarkable match with the measured transmission window, surface mode position and attenuation. The agreement between estimated scattering loss from surface roughness and measured loss values indicates that structural distortions, in particular the uneven distribution of glass across the thin silica struts on the core boundary, have a strong impact on the loss. This provides insight into the differences between idealized models and fabricated Fibers, which could be key to further fiber loss reduction.

  • high sensitivity methane and ethane detection using low loss mid ir hollow core Photonic Bandgap Fibers
    OFS2014 23rd International Conference on Optical Fiber Sensors, 2014
    Co-Authors: M N Petrovich, Alexander M. Heidt, N V Wheeler, N K Baddela, D. J. Richardson
    Abstract:

    We present sub-ppm sensitivity, broadband gas absorption measurements using improved hollow-core Photonic-Bandgap Fibers with low loss in the range 3-3.6 µm. The sensitivity levels, unprecedented for a fiber-based sensor system, were achieved by addressing the strong mid-IR vibrational bands through use of a high-intensity supercontinuum source and by exploiting long interaction lengths in the HC-PBGFs. We measured mixtures of methane (1034 ppm) and ethane (50.4 ppm) and attained 7 and 0.9 ppm sensitivities for 0.925 and 5.69 m long HC-PBGF samples, respectively, from high-resolution (0.2 nm) spectra. Significant scope for further sensitivity improvement exists through use of longer Fibers in combination with more sophisticated sensing schemes.

  • accurate loss and surface mode modeling in fabricated hollow core Photonic Bandgap Fibers
    Optical Fiber Communication Conference, 2014
    Co-Authors: Eric Numkam Fokoua, M N Petrovich, N V Wheeler, N K Baddela, D. J. Richardson, Yong Chen, J R Hayes, S R Sandoghchi, F Poletti
    Abstract:

    We present a method to reconstruct the cross-sectional profile of fabricated hollow-core Photonic Bandgap Fibers from SEM images. For the first time, numerical simulations show a good agreement with measured loss and surface mode position.

  • impact of structural distortions on the performance of hollow core Photonic Bandgap Fibers
    Optics Express, 2014
    Co-Authors: Eric Numkam Fokoua, D. J. Richardson, F Poletti
    Abstract:

    We present a generic model for studying numerically the performance of hollow-core Photonic Bandgap Fibers (HC-PBGFs) with arbitrary cross-sectional distortions. Fully vectorial finite element simulations reveal that distortions beyond the second ring of air holes have an impact on the leakage loss and bandwidth of the fiber, but do not significantly alter its surface scattering loss which remains the dominant contribution to the overall fiber loss (providing that a sufficient number of rings of air holes (> or = 5) are used). We have found that while most types of distortions in the first two rings are generally detrimental, enlarging the core defect while keeping equidistant and on a circular boundary the glass nodes surrounding the core may produce losses half those compared to "idealized" fiber designs and with no penalty in terms of the transmission bandwidth.