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- 实验方案
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Derivation and Experimental Verification of the near-field 2D and 3D optical intensities from a finite-size light emitting diode (LED)
摘要： We derive the near-field light intensity distributions of an inorganic LED on its surface and in volumetric space. Our closed-form solution for 3D intensity distribution for a finite-size LED is consistent with Lambert’s Cosine Law, which provides the 3D intensity distribution for an infinitesimal, flat light source. We also derive the formula for the 2D intensity distribution on a diode surface showing its similarity to a Gaussian function, which is typically used to approximate the surface light intensity profile for an LED and a laser diode. Our 2D intensity distribution function produces light propagation similar to the Gaussian beam propagation in space. However, unlike the Gaussian approximation, our formula invariably produces this behavior without assuming the refractive index inside the diode follows a quadratic function of the transverse spatial domains. Our 2D and 3D spatial intensity formulas in near-field for LEDs offer a unique way to calculate the peak intensity that occurs at the center of the flat LED source. We demonstrate, as expected, that the peak intensity increases with the size of the LED source as well as the brightness of each radiative electron-hole pair, which is a function of the drive current and quantum efficiency of the LED.
关键词： Near-field Photometry,Optical Waveguides,Display,Optical Wave Propagation,Closed-Form Solutions,and Lighting.,Lasers,Light Emitting Diodes,Mathematical Physics
更新于2025-09-16 10:30:52
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Soliton propagation of electromagnetic field vectors of polarized light ray traveling in a coiled optical fiber in Minkowski space with Bishop equations
摘要： In this paper, we ?rstly obtain the evolution equations of the magnetic ?eld and electric ?eld vectors of polarized light ray propagating along a coiled optical ?ber in Minkowski space. Then we de?ne new kinds of binormal motions and new kinds of Hasimoto transformations to relate these evolution equations into the nonlinear Schrodinger’s equation. During this procedure, we use a parallel adapted frame or more commonly known as Bishop frame to characterize the coiled optical ?ber geometrically. We also propose perturbed solutions of the nonlinear Schr¨odinger’s evolution equation that governs the propagation of solitons through the electric ?eld (E) and magnetic ?eld (M) vectors. Finally, we provide some numerical simulations to supplement the analytical outcomes.
关键词： polarized light,Minkowski space,nonlinear Schr?dinger’s equation,coiled optical fiber,soliton propagation,Bishop equations
更新于2025-09-16 10:30:52
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Problem of Coupled Electromagnetic TE-TE Wave Propagation in a Layer Filled with Nonlinear Medium with Saturation
摘要： Propagation of coupled electromagnetic TE-TE wave in a nonlinear plane layer is considered. The layer is located between two half-spaces with constant permittivities. The permittivity in the layer is described by nonlinearity with saturation. The physical problem is reduced to a nonlinear two-parameter eigenvalue problem for a system of (nonlinear) ordinary differential equations. Existence and uniqueness of solution to the two-parameter eigenvalue problem is proved. Iteration method for solving given problem is presented. Convergence theorem of the iteration method is proved.
关键词： wave propagation,perturbation method,saturated nonlinearity,plane nonlinear waveguide,Maxwell’s equations
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Genetically Optimized Photonic Crystal for Spatial Filtering of Reinjection into Broad-Area Diode Lasers
摘要： Modern high-power broad-area semiconductor laser diodes (BASLDs) deliver optical output powers of several ten Watts at high electro-optical conversion efficiencies, which makes them highly relevant for numerous industrial, medical and scientific applications. However, lateral multimode behavior in BASLDs due to thermal lensing turns out highly detrimental, as it results in poor focusability and decreased laser beam brightness. Approaches to overcome this issue include improved epitaxial layer design, the optimization of evanescent spatial filtering by tailoring the emitter geometry and facet reflectivity, or Fourier spatially filtered reinjection from an external resonator. Here, we consider the usage of longitudinally chirped photonic crystals (PhC) within the external cavity (EC) for tailoring the spatial filter properties. The corresponding EC setup, consisting of a slow-axis collimating lense, a 2D photonic crystal, and the external mirror (R=4%), is shown in Fig. 1a). While free space propagation in the EC is modeled by Fresnel diffraction integrals, optical propagation through the PhC requires accurate treatment of lateral angular dispersion. For the sake of efficiency of the time-domain BASLD simulator, we use a beam propagation method (BPM) based on Rayleigh-Sommerfeld diffraction theory. The chirp of the longitudinal PhC periods is optimized with a genetic algorithm. The transmission amplitude of the optimized structure suppresses lateral propagation angles between 2° and 4°, cf. Fig. 1b), and shows excellent agreement with an exact rigorous coupled wave analysis (RCWA) for calculating PhC transmission and almost vanishing reflection amplitudes. In a next step, we performed numerical simulations of a 1mm long and 100μm broad BASLD subject to PhC spatially filtered reinjection. We found a significant improvement of the lateral far-field profile and increase of beam brightness by a factor 1.5, cf. Fig. 1c). However, for BASLDs with a longer emitter length, lateral waveguide dispersion considerably limits the effectiveness of our scheme. In summary, we demonstrated theoretically that spatial filtering with photonic crystals is a viable alternative to Fourier slit spatial filtering schemes, and offers increased flexibility for designing tailored angular transmission profiles by suitably optimized longitudinal PhC chirp.
关键词： genetic algorithm,beam propagation method,photonic crystals,spatial filtering,broad-area semiconductor laser diodes
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Direct Observation of Topological Edge States in Silicon Photonic Crystals
摘要： The concept of topology has proven immensely powerful in physics, describing new phases of matter with unique properties. There has been a recent surge in attempts to implement topological protection in the photonic domain, owing to the application potential of robust transport immune to scattering at disorder. A famous class of electronic topological insulators relies on the quantum spin-Hall effect (QSHE). Photonic analogues of QSHE were recently predicted to occur in photonic crystals with special symmetries [1, 2]. Interestingly, topological photonic crystals employing QSHE offer the possibility to access their properties via far-field radiation [3]. Here we directly observe topological photonic states at telecom wavelengths in photonic crystals in silicon-on-insulator (SOI) technology, and characterize their inherent spin, dispersion, and propagation. We reveal that the radiation of the topological states carries a signature of their origin in photonic spin-orbit coupling, linking unidirectional propagation to circular polarization (see Fig. 1a). The employed photonic crystals (inset of Fig. 1a) employ higher-order symmetry breaking to open bandgaps of different topological order at the Γ point [1, 2]. The edge between two domains supports topological states of differing pseudospin. We analyze these states by dispersing normal-incidence reflected intensity in both frequency and angle, mapping the edge state dispersion (in Fig. 1b). It displays the characteristic linear dispersion of edge states, with measured group velocity ～ c/6 and quality factor ～ 450. The positive and negative group velocity modes can be selectively excited with opposite circular polarization. Conversely, the states’ pseudospin can be probed directly in the far field through the S3 Stokes parameter obtained from polarimetry (Fig. 1c). Our Fourier spectroscopic measurements moreover reveal a small gap at the edge state crossing that is related to spin-spin scattering. This coupling is inherent to the symmetry breaking at the edge, and a defining difference between photonic and electronic topological insulators. Through the far-field spin-orbit link, we selectively excite edge states in opposite directions, and image their propagation in real-space microscopy. Figure 1d shows the routing of the edge state at a sharp waveguide junction. Interestingly, we observe an absence of backscattering or forward scattering, demonstrating the topological protection of unidirectional propagation. In fact, the states closely follow the photonic crystal edge — defined by the junction’s chiral structure of sub-unit cell size — even though their transverse extent is significantly larger. In conclusion, we observe the unique nature of topologically protected light transport in photonic crystals, through a technique that holds great promise for developing novel topological systems for various applications, including integrated photonic components, quantum optical interfaces, enantiomeric sensing, and nanoscale lasing.
关键词： photonic spin-orbit coupling,topological photonic states,unidirectional propagation,silicon-on-insulator,circular polarization
更新于2025-09-16 10:30:52
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A chaotic state in the transition from single- toward multiple pulse for soliton fiber lasers
摘要： High-order soliton in anomalous-dispersion ultrafast fiber lasers is rarely researched due to its intrinsic instability in dissipative systems. For the first time, we numerically demonstrate the ultrafast pulse in fiber lasers will deviate from the fundamental soliton under strong pulse energy before splitting into multiple pulses. High-order soliton effect results in the single-pulse splitting into the dual-pulse. Sustaining switching between the single- and dual-pulse induced by the high-order soliton evolution and cross-gain-modulation was observed and analyzed. The results offer significant and novel insights for the soliton shaping dynamics and instability in anomalous-dispersion fiber lasers.
关键词： Mode-locked lasers,nonlinear fiber optics,temporal soliton and pulse propagation
更新于2025-09-16 10:30:52
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The Effect of the Limited Aperture of an Emitter on the Width and Divergence Angle of a Laser Beam
摘要： The conditions necessary for the correct measurement of the width and divergence angle of a laser beam have been determined with consideration for the finite dimensions of the aperture of an emitter by the method based on the estimation of initial spatial moments. It has been shown that the severe requirements disregarded in the corresponding developed standards are imposed on the shape of the spatial intensity distribution in a laser beam cross section in this case.
关键词： diameter,width,spatial laser beam intensity distribution,propagation factor,divergence
更新于2025-09-16 10:30:52
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Wave Scattering and Power Flow in Straight-Helical-Straight Waveguide Structure
摘要： The knowledge of wave scattering and power flow in waveguide structures is important for many engineering applications. In this paper, power flow and scattering in a straight-helical-straight waveguide structure are investigated using the wave and finite element (WFE) method. For simple (straight or helical) waveguides, wave scattering (and subsequently the power flow and scattering) can be resolved analytically. This is not the case for complex waveguides such as laminated or sandwiched waveguides or waveguides with noncanonical cross-sections. In such cases, the WFE method is used to model the wave behavior in each waveguide in the structure. The power flow is then studied by considering how waves reflect and transmit at the boundaries that join the straight waveguides with the helical waveguide. We present three numerical examples but analytical solutions can be obtained for the first example only; for the second and third examples, the WFE is used in earnest since the wave behavior and subsequently the power flow would at best be extremely difficult to formulate analytically.
关键词： wave propagation,power flow,Wave and finite element,power scattering,helical waveguides
更新于2025-09-16 10:30:52
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Thermo-mechanical analysis of blister formation on a rigid substrate in blister-actuated laser-induced forward transfer
摘要： The paper presents an analytic model of glass-interface-polyimide structure for predicting the blister formation during blister-actuated laser-induced forward transfer. In order to investigate the dynamic process of the heating and vaporizing of polymer in laser/matter interaction and crack propagation of glass/polymer interface in blister expansion, a discrete quasi-static analysis method is proposed. In the frame of fracture mechanics, the energy release rate is calculated and introduced to analyze interfacial crack propagation of glass/polymer interface. In additional, the blister expansion and formation are also computed based on a finite element model, and the analytical predictions are shown to be in good agreement with simulated results. The results show that blister height and crack length are sensitive to laser fluence. A higher laser fluence is much easier to induce higher blister height. The crack will propagate as the laser fluence is larger than the critical laser fluence.
关键词： polymer,blister formation,virtual crack closure technique,blister-actuated laser-induced forward transfer,crack propagation
更新于2025-09-16 10:30:52
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Nonlinear propagation of coupled surface TE and leaky TM electromagnetic waves
摘要： Propagation of the coupled electromagnetic wave, which is a superposition of TE surface and TM leaky waves, in the Goubau line (a perfectly conducting cylinder covered by a concentric dielectric layer) filled with nonlinear inhomogeneous medium is studied (if the permittivity is linear, the coupled wave does not exist). Nonlinear coupled TE–TM wave is characterised by two (independent) frequencies and two (coupled) propagation constants (propagation constants). The physical problem is reduced to a nonlinear two-parameter transmission eigenvalue problem for Maxwell’s equations. Existence of coupled TE–TM waves is proved. Intervals of localisation of propagation constants are found.
关键词： nonlinear waveguide,Nonlinear coupled TE–TM waves,Kerr nonlinearity,Maxwell’s equations,two-parameter eigenvalue problem,coupled propagation constants
更新于2025-09-16 10:30:52