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Super Gaussian pulse generation in a passively mode-locked fiber laser
摘要： The generation of self-similar super Gaussian-like pulses from a passively mode-locked fiber laser is numerically demonstrated. The laser cavity utilizes a long period fiber grating as a pulse-shaping element. The model is based on the normalized complex Ginzburg-Landau equation and the nonlinear coupled mode equations of the grating. The numerical results show stable super Gaussian pulses with a linear frequency chirp, a 1.5 ps pulse duration and 2 nJ energy. The generated pulses are scalable and exhibits no bifurcation or instability as the gain is increased.
关键词： Mode-locked fiber lasers,Ginzburg-Landau equation,Kerr nonlinearity,Self-similar pulses,Numerical methods
更新于2025-09-11 14:15:04
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Classifying Complex Faraday Spectra with Convolutional Neural Networks
摘要： Advances in radio spectro-polarimetry o?er the possibility to disentangle complex regions where relativistic and thermal plasmas mix in the interstellar and intergalactic media. Recent work has shown that apparently simple Faraday Rotation Measure spectra can be generated by complex sources. This is true even when the distribution of Rotation Measures in the complex source greatly exceeds the errors associated with a single component ?t to the peak of the Faraday spectrum. We present a convolutional neural network that can di?erentiate between simple Faraday thin spectra and those that contain multiple (2) Faraday thin sources. We demonstrate that this network, trained for the upcoming Polarisation Sky Survey of the Universe’s Magnetism early science observations, can identify two component sources 99% of the time, provided that the sources are separated in Faraday depth by >10% of the FWHM of the Faraday Point Spread Function, the polarized ?ux ratio of the sources is >0.1, and that the signal-to-noise ratio of the primary component is >5. With this S/N cut-o?, the false positive rate (simple sources mis-classi?ed as complex) is <0.3%. Work is ongoing to include Faraday thick sources in the training and testing of the convolutional neural-network.
关键词： methods: statistical,polarization,methods: data analysis,methods: numerical,methods: analytical
更新于2025-09-10 09:29:36
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Hard limits on the postselectability of optical graph states
摘要： Coherent control of large entangled graph states enables a wide variety of quantum information processing tasks, including error-corrected quantum computation. The linear optical approach offers excellent control and coherence, but today most photon sources and entangling gates—required for the construction of large graph states—are probabilistic and rely on postselection. In this work, we provide proofs and heuristics to aid experimental design using postselection. We introduce a versatile design rule for postselectable experiments: drawn as a graph, with qubit as vertices and gates and photon-pair sources as edges, an experiment may only contain cycles with an odd number of sources. We analyse experiments that use photons from postselected photon-pair sources, and lower bound the number of accessible classes of graph state entanglement in the non-degenerate case—graph state entanglement classes that contain a tree are are always accessible. The proportion of graph states accessible by postselection shrinks rapidly, however. We list accessible classes for various resource states up to 9 qubits. Finally, we apply these methods to near-term multi-photon experiments.
关键词： photon sources,entanglement,graph states,linear optical quantum computing,postselection,numerical methods,photonic experiment design
更新于2025-09-09 09:28:46
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Propagation of Electromagnetic Waves through an Invisible Gradient-Index Lens with Negative Refractive Index
摘要： A radially inhomogeneous (gradient-index) lens made of material with a negative refractive index, invisible from the viewpoint of geometrical optics, is proposed and designed. The design includes derivation and solution of an equation for determining the refractive index profile, as well as derivation of an expression allowing calculation of the ray trajectories in the lens. Propagation of a plane wave through a cylindrical modification of the proposed lens both for the case of E-polarization and for the case of H-polarization is analyzed numerically using the hybrid projection method. The results obtained for the RCS of the lens are compared to the similar performance of a positive-index lens described in the previous publications.
关键词： numerical methods,RCS,geometrical optics,invisible lens,Electromagnetic wave propagation,negative refractive index,gradient-index lens
更新于2025-09-09 09:28:46
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THE GABOR FRAME AS A DISCRETIZATION FOR THE 2D TRANSVERSE-ELECTRIC SCATTERING-PROBLEM DOMAIN INTEGRAL EQUATION
摘要： We apply the Gabor frame as a projection method to numerically solve a 2D transverse-electric-polarized domain-integral equation for a homogeneous medium. Since the Gabor frame is spatially as well as spectrally very well convergent, it is convenient to use for solving a domain integral equation. The mixed spatial and spectral nature of the Gabor frame creates a natural and fast way to Fourier transform a function. In the spectral domain we employ a coordinate scaling to smoothen the branchcut found in the Green function. We have developed algorithms to perform multiplication and convolution efficiently, scaling as O(N log N ) on the number of Gabor coefficients, yielding an overall algorithm that also scales as O(N log N ).
关键词： electromagnetic scattering,domain integral equation,numerical methods,transverse-electric polarization,Gabor frame
更新于2025-09-04 15:30:14