The Experts below are selected from a list of 9060 Experts worldwide ranked by ideXlab platform

Zongfu Jiang - One of the best experts on this subject based on the ideXlab platform.

  • Adaptive phase correction of dynamic multimode beam based on Modal Decomposition.
    Optics express, 2019
    Co-Authors: Kun Xie, Wenguang Liu, Qiong Zhou, Liangjin Huang, Zongfu Jiang
    Abstract:

    We propose and demonstrate a method for the adaptive phase correction of dynamic multimode fiber beams. The phase of incident beam is reconstructed in real-time based on the complete Modal information, which obtained by using the Modal Decomposition of correlation filter method. For the proof of principle, both of the Modal Decomposition and the phase correction are implemented using the same computer-generated hologram, which was encoded into a phase-only spatial light modulator. We demonstrate the phase correction of dynamic multimode beam at a rate of 5 Hz and achieve a 1.73-fold improvement on the average power-in-the-bucket. The experimental results indicate the feasibility of the real-time phase correction for the large mode area fiber laser by adaptive optics.

  • fast and accurate Modal Decomposition of multimode fiber based on stochastic parallel gradient descent algorithm
    Applied Optics, 2013
    Co-Authors: Pu Zhou, Xiaolin Wang, Zongfu Jiang
    Abstract:

    A new approach for the complete Modal Decomposition of the optical fields emerging from the multimode fiber is presented in this paper. Based on the stochastic parallel gradient descent algorithm, mode coefficients for all the bound modes in the multimode fiber can be exactly calculated by utilizing one intensity profile of the beam. Numerical simulation validates the feasibility, and the reconstructed error is below 0.1%. In the case of six modes within the fiber, the running time is about 2 s.

Michael Duparré - One of the best experts on this subject based on the ideXlab platform.

  • Measurement of the orbital angular momentum density of light by Modal Decomposition
    New Journal of Physics, 2013
    Co-Authors: Christian Schulze, Daniel Flamm, Michael Duparré, Angela Dudley, Andrew Forbes
    Abstract:

    We demonstrate a versatile method for the measurement of the orbital angular momentum (OAM) density of an optical field. By performing a Modal Decomposition with digital holograms, we reconstruct the full optical field from a small set of single-point intensity measurements, from which optical vortices, global OAM and OAM density can be derived. We validate the method on defined OAM-carrying beams yielding fidelities in the OAM density measurement of up to 99%, and subsequently apply the technique to unknown fields from optical fibers.

  • Modal Decomposition for measuring the orbital angular momentum density of light
    Complex Light and Optical Forces VII, 2013
    Co-Authors: Christian Schulze, Daniel Flamm, Andrew Forbes, Angela Dudley, Michael Duparré
    Abstract:

    We present a novel technique to measure the orbital angular momentum (OAM) density of light. The technique is based on Modal Decomposition, enabling the complete reconstruction of optical fields, including the reconstruction of the beams Poynting vector and the OAM density distribution. The Modal Decomposition is performed using a computer-generated hologram (CGH), which allows fast and accurate measurement of the mode spectrum. The CGH encodes the modes of interest, whose powers and relative phase differences are measured from the far-field diffraction pattern of the illuminating optical field with the hologram transmission function. In combination with a classical measurement of Stokes parameters, including a polarizer and a quarter-wave plate in front of the hologram, the polarization state of each mode is measured. As a consequence, any arbitrary vector field can be reconstructed, including amplitude, phase, and polarization. Having all information on the optical field, the Poynting vector and the OAM density can be calculated directly. We applied our method to beams emerging from optical fibers, which allows us to investigate arbitrary coherent superposition of fiber modes with complexly shaped intensity and polarization distributions. The excitation of certain mode mixtures is done by appropriate input coupling and using diffractive phase masks to shape the input beam and hence enhance the excitation efficiency of distinct modes. The accuracy of the achieved results is verified by comparing the reconstructed with the directly measured beam intensity, revealing excellent agreement.

  • Modal Decomposition without a priori scale information
    Optics express, 2012
    Co-Authors: Christian Schulze, Michael Duparré, Sandile Ngcobo, Andrew Forbes
    Abstract:

    The Modal Decomposition of an arbitrary optical field may be done without regard to the spatial scale of the chosen basis functions, but this generally leads to a large number of modes in the expansion. While this may be considered as mathematically correct, it is not efficient and not physically representative of the underlying field. Here we demonstrate a Modal Decomposition approach that requires no a priori knowledge of the spatial scale of the modes, but nevertheless leads to an optimised Modal expansion. We illustrate the power of the method by successfully decomposing beams from a diode-pumped solid state laser resonator into an optimised Laguerre-Gaussian mode set. Our experimental results, which are in agreement with theory, illustrate the versatility of the approach.

  • Wavefront reconstruction by Modal Decomposition
    Optics express, 2012
    Co-Authors: Christian Schulze, Daniel Flamm, Andrew Forbes, Darryl Naidoo, Oliver Schmidt, Michael Duparré
    Abstract:

    We propose a new method to determine the wavefront of a laser beam based on Modal Decomposition by computer-generated holograms. The hologram is encoded with a transmission function suitable for measuring the amplitudes and phases of the modes in real-time. This yields the complete information about the optical field, from which the Poynting vector and the wavefront are deduced. Two different wavefront reconstruction options are outlined: reconstruction from the phase for scalar beams, and reconstruction from the Poynting vector for inhomogeneously polarized beams. Results are compared to Shack-Hartmann measurements that serve as a reference and are shown to reproduce the wavefront and phase with very high fidelity.

  • Comparison of two Modal Decomposition techniques
    Laser Resonators Microresonators and Beam Control XIV, 2012
    Co-Authors: Robert Brüning, Daniel Flamm, Christian Schulze, Oliver A. Schmidt, Michael Duparré
    Abstract:

    Higher oder modes in multi mode fibers determine fundamental beam properties. Hence, the knowledge about the Modal content becomes essential to understand the underlying physical effects. Therefore, different Modal Decomposition techniques have been developed. In this paper we present a comparison of two methods. At first the Modal Decomposition by a correlation filter method (CFM) and secondly using a numerical phase retrieval algorithm. Limitations of both techniques are demonstrated and theirs overcoming by combining both is presented.

Pu Zhou - One of the best experts on this subject based on the ideXlab platform.

  • Preliminary study on the Modal Decomposition of Hermite Gaussian beams via deep learning
    arXiv: Optics, 2019
    Co-Authors: Tianyue Hou, Liangjin Huang, Jinyong Leng, Lijia Yang, Pu Zhou
    Abstract:

    The Hermite-Gaussian (HG) modes make up a complete and orthonormal basis, which have been extensively used to describe optical fields. Here, we demonstrate, for the first time to our knowledge, deep learning-based Modal Decomposition (MD) of HG beams. This method offers a fast, economical and robust way to acquire both the power content and phase information through a single-shot beam intensity image, which will be beneficial for the beam shaping, beam quality assessment, studies of resonator perturbations, and other further research on the HG beams.

  • multimode fiber Modal Decomposition based on hybrid genetic global optimization algorithm
    Optics Express, 2017
    Co-Authors: Jinyong Leng, Pu Zhou, Jinbao Chen
    Abstract:

    Numerical Modal Decomposition (MD) is an effective approach to reveal Modal characteristics in high power fiber lasers. The main challenge is to find a suitable multi-dimensional optimization algorithm to reveal exact superposition of eigenmodes, especially for multimode fiber. A novel hybrid genetic global optimization algorithm, named GA-SPGD, which combines the advantages of genetic algorithm (GA) and stochastic parallel gradient descent (SPGD) algorithm, is firstly proposed to reduce local minima possibilities caused by sensitivity to initial values. Firstly, GA is applied to search the rough global optimization position based on near- and far-field intensity distribution with high accuracy. Upon those initial values, SPGD algorithm is afterwards used to find the exact optimization values based on near-field intensity distribution with fast convergence speed. Numerical simulations validate the feasibility and reliability.

  • fast and accurate Modal Decomposition of multimode fiber based on stochastic parallel gradient descent algorithm
    Applied Optics, 2013
    Co-Authors: Pu Zhou, Xiaolin Wang, Zongfu Jiang
    Abstract:

    A new approach for the complete Modal Decomposition of the optical fields emerging from the multimode fiber is presented in this paper. Based on the stochastic parallel gradient descent algorithm, mode coefficients for all the bound modes in the multimode fiber can be exactly calculated by utilizing one intensity profile of the beam. Numerical simulation validates the feasibility, and the reconstructed error is below 0.1%. In the case of six modes within the fiber, the running time is about 2 s.

Christian Schulze - One of the best experts on this subject based on the ideXlab platform.

  • Measurement of the orbital angular momentum density of light by Modal Decomposition
    New Journal of Physics, 2013
    Co-Authors: Christian Schulze, Daniel Flamm, Michael Duparré, Angela Dudley, Andrew Forbes
    Abstract:

    We demonstrate a versatile method for the measurement of the orbital angular momentum (OAM) density of an optical field. By performing a Modal Decomposition with digital holograms, we reconstruct the full optical field from a small set of single-point intensity measurements, from which optical vortices, global OAM and OAM density can be derived. We validate the method on defined OAM-carrying beams yielding fidelities in the OAM density measurement of up to 99%, and subsequently apply the technique to unknown fields from optical fibers.

  • Modal Decomposition for measuring the orbital angular momentum density of light
    Complex Light and Optical Forces VII, 2013
    Co-Authors: Christian Schulze, Daniel Flamm, Andrew Forbes, Angela Dudley, Michael Duparré
    Abstract:

    We present a novel technique to measure the orbital angular momentum (OAM) density of light. The technique is based on Modal Decomposition, enabling the complete reconstruction of optical fields, including the reconstruction of the beams Poynting vector and the OAM density distribution. The Modal Decomposition is performed using a computer-generated hologram (CGH), which allows fast and accurate measurement of the mode spectrum. The CGH encodes the modes of interest, whose powers and relative phase differences are measured from the far-field diffraction pattern of the illuminating optical field with the hologram transmission function. In combination with a classical measurement of Stokes parameters, including a polarizer and a quarter-wave plate in front of the hologram, the polarization state of each mode is measured. As a consequence, any arbitrary vector field can be reconstructed, including amplitude, phase, and polarization. Having all information on the optical field, the Poynting vector and the OAM density can be calculated directly. We applied our method to beams emerging from optical fibers, which allows us to investigate arbitrary coherent superposition of fiber modes with complexly shaped intensity and polarization distributions. The excitation of certain mode mixtures is done by appropriate input coupling and using diffractive phase masks to shape the input beam and hence enhance the excitation efficiency of distinct modes. The accuracy of the achieved results is verified by comparing the reconstructed with the directly measured beam intensity, revealing excellent agreement.

  • Modal Decomposition without a priori scale information
    Optics express, 2012
    Co-Authors: Christian Schulze, Michael Duparré, Sandile Ngcobo, Andrew Forbes
    Abstract:

    The Modal Decomposition of an arbitrary optical field may be done without regard to the spatial scale of the chosen basis functions, but this generally leads to a large number of modes in the expansion. While this may be considered as mathematically correct, it is not efficient and not physically representative of the underlying field. Here we demonstrate a Modal Decomposition approach that requires no a priori knowledge of the spatial scale of the modes, but nevertheless leads to an optimised Modal expansion. We illustrate the power of the method by successfully decomposing beams from a diode-pumped solid state laser resonator into an optimised Laguerre-Gaussian mode set. Our experimental results, which are in agreement with theory, illustrate the versatility of the approach.

  • Wavefront reconstruction by Modal Decomposition
    Optics express, 2012
    Co-Authors: Christian Schulze, Daniel Flamm, Andrew Forbes, Darryl Naidoo, Oliver Schmidt, Michael Duparré
    Abstract:

    We propose a new method to determine the wavefront of a laser beam based on Modal Decomposition by computer-generated holograms. The hologram is encoded with a transmission function suitable for measuring the amplitudes and phases of the modes in real-time. This yields the complete information about the optical field, from which the Poynting vector and the wavefront are deduced. Two different wavefront reconstruction options are outlined: reconstruction from the phase for scalar beams, and reconstruction from the Poynting vector for inhomogeneously polarized beams. Results are compared to Shack-Hartmann measurements that serve as a reference and are shown to reproduce the wavefront and phase with very high fidelity.

  • Comparison of two Modal Decomposition techniques
    Laser Resonators Microresonators and Beam Control XIV, 2012
    Co-Authors: Robert Brüning, Daniel Flamm, Christian Schulze, Oliver A. Schmidt, Michael Duparré
    Abstract:

    Higher oder modes in multi mode fibers determine fundamental beam properties. Hence, the knowledge about the Modal content becomes essential to understand the underlying physical effects. Therefore, different Modal Decomposition techniques have been developed. In this paper we present a comparison of two methods. At first the Modal Decomposition by a correlation filter method (CFM) and secondly using a numerical phase retrieval algorithm. Limitations of both techniques are demonstrated and theirs overcoming by combining both is presented.

Andrew Forbes - One of the best experts on this subject based on the ideXlab platform.

  • Measurement of the orbital angular momentum density of light by Modal Decomposition
    New Journal of Physics, 2013
    Co-Authors: Christian Schulze, Daniel Flamm, Michael Duparré, Angela Dudley, Andrew Forbes
    Abstract:

    We demonstrate a versatile method for the measurement of the orbital angular momentum (OAM) density of an optical field. By performing a Modal Decomposition with digital holograms, we reconstruct the full optical field from a small set of single-point intensity measurements, from which optical vortices, global OAM and OAM density can be derived. We validate the method on defined OAM-carrying beams yielding fidelities in the OAM density measurement of up to 99%, and subsequently apply the technique to unknown fields from optical fibers.

  • Modal Decomposition for measuring the orbital angular momentum density of light
    Complex Light and Optical Forces VII, 2013
    Co-Authors: Christian Schulze, Daniel Flamm, Andrew Forbes, Angela Dudley, Michael Duparré
    Abstract:

    We present a novel technique to measure the orbital angular momentum (OAM) density of light. The technique is based on Modal Decomposition, enabling the complete reconstruction of optical fields, including the reconstruction of the beams Poynting vector and the OAM density distribution. The Modal Decomposition is performed using a computer-generated hologram (CGH), which allows fast and accurate measurement of the mode spectrum. The CGH encodes the modes of interest, whose powers and relative phase differences are measured from the far-field diffraction pattern of the illuminating optical field with the hologram transmission function. In combination with a classical measurement of Stokes parameters, including a polarizer and a quarter-wave plate in front of the hologram, the polarization state of each mode is measured. As a consequence, any arbitrary vector field can be reconstructed, including amplitude, phase, and polarization. Having all information on the optical field, the Poynting vector and the OAM density can be calculated directly. We applied our method to beams emerging from optical fibers, which allows us to investigate arbitrary coherent superposition of fiber modes with complexly shaped intensity and polarization distributions. The excitation of certain mode mixtures is done by appropriate input coupling and using diffractive phase masks to shape the input beam and hence enhance the excitation efficiency of distinct modes. The accuracy of the achieved results is verified by comparing the reconstructed with the directly measured beam intensity, revealing excellent agreement.

  • Modal Decomposition without a priori scale information
    Optics express, 2012
    Co-Authors: Christian Schulze, Michael Duparré, Sandile Ngcobo, Andrew Forbes
    Abstract:

    The Modal Decomposition of an arbitrary optical field may be done without regard to the spatial scale of the chosen basis functions, but this generally leads to a large number of modes in the expansion. While this may be considered as mathematically correct, it is not efficient and not physically representative of the underlying field. Here we demonstrate a Modal Decomposition approach that requires no a priori knowledge of the spatial scale of the modes, but nevertheless leads to an optimised Modal expansion. We illustrate the power of the method by successfully decomposing beams from a diode-pumped solid state laser resonator into an optimised Laguerre-Gaussian mode set. Our experimental results, which are in agreement with theory, illustrate the versatility of the approach.

  • Wavefront reconstruction by Modal Decomposition
    Optics express, 2012
    Co-Authors: Christian Schulze, Daniel Flamm, Andrew Forbes, Darryl Naidoo, Oliver Schmidt, Michael Duparré
    Abstract:

    We propose a new method to determine the wavefront of a laser beam based on Modal Decomposition by computer-generated holograms. The hologram is encoded with a transmission function suitable for measuring the amplitudes and phases of the modes in real-time. This yields the complete information about the optical field, from which the Poynting vector and the wavefront are deduced. Two different wavefront reconstruction options are outlined: reconstruction from the phase for scalar beams, and reconstruction from the Poynting vector for inhomogeneously polarized beams. Results are compared to Shack-Hartmann measurements that serve as a reference and are shown to reproduce the wavefront and phase with very high fidelity.