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Strong self-focusing of a chirped pulse laser in thermal quantum plasma under density transition
摘要： In the present manuscript, an analysis has been done on strong self-focusing of a chirped pulse laser in thermal quantum plasma under exponential plasma density transition. It is observed that the beam width parameter reduces up to great extent which in turns enhances the process of self-focusing. It is observed that in the embellishment of self-focusing of laser beam, thermal quantum plasma contributes significantly. Further, it is seen that with change in different parameters like intensity of the laser beam, chirped parameter value and plasma frequency, self-focusing is sensitive and becomes stronger at higher values of these parameters. The present work may have important applications in field of laser interaction with the quantum plasma, laser driven particle accelerators etc.
关键词： thermal quantum plasma,Chirped pulse Laser,self-focusing,exponential plasma density transition
更新于2025-09-12 10:27:22
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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) - Superfilament Spatial Dynamics and Energy Deposition under Various Focusing Conditions
摘要： One of the distinctive features of femtosecond laser ?lamentation is intensity and plasma concentration clamping. Arising due to the dynamical competition between Kerr focusing and plasma defocusing this phenomenon limits the peak intensity to the values 1014 W/cm2 and plasma concentration level to 1016 – 1017 cm?3. Further increase of the beam power leads to the beam splitting and multi?lament formation rather than to an intense single ?lament with high plasma density. However it have been recently shown that fusing several ?laments by introducing additional weak focusing one can obtain signi?cant enhancement of energy deposition in the extended region around the focus resulting in higher plasma concentration and intensity [1,2,3]. This report aims to present the comprehensive picture of super?lament evolution including its formation from merging ?laments and dissipation stages. We discuss energy deposition during the multi?lament evolution and its dependency of the pulse energy as well as the in?uence of additional focusing conditions on super?lament formation.
关键词： femtosecond laser ?lamentation,super?lament,energy deposition,plasma concentration,focusing conditions
更新于2025-09-12 10:27:22
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Polarization controllable plasmonic focusing based on nanometer holes
摘要： Two kinds of plasmonic lenses are proposed based on phase compensation. controllable foci focusing of the second kind of plasmonic lens can be utilized as dependence focusing. Two or four foci of the first kind of plasmonic lens and two Each kind of plasmonic lens is comprised of four sets of nanohole arrays, and two sets principles make the proposed plasmonic lenses show the different polarization the surface plasmon polaritons reaching to the focal spot. The different design optical switch and logic judgment. Theoretic analysis, numerical calculations and experiment measurement verify the focusing performance of our proposed plasmonic and the rotation angle of holes compensates respectively for the phase difference of of face-to-face nanohole arrays are planar symmetric. The adjustment of separation Polarization controllable plasmonic focusing based on
关键词： Nanoholes,Plasmonic focusing,Surface plasmon polaritons,Polarization
更新于2025-09-12 10:27:22
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Electromagnetic Energy Redistribution in Coupled Chiral Particle Chain-Film System
摘要： Metal nanoparticle-film system has been proved that it has the ability of focusing light in the gap between particle and film, which is useful for surface-enhanced Raman scattering and plasmon catalysis. The rapid developed plasmonic chirality can also be realized in such system. Here, we investigated an electromagnetic energy focusing effect and chiral near-field enhancement in a coupled chiral particle chain on gold film. It shows large electric field enhancement in the gap between particle and film, as well as chiral near field. The enhancement properties at resonant peaks for the system excited by left circularly polarized light and right circularly polarized light are obviously different. This difference resulted from the interaction of circularly polarized light and the chiral particle-film system is analyzed with plasmon hybridization. The enhanced optical activity can provide promising applications for the enhancement of chiral molecule sensor for this chiral particle chain-film system.
关键词： Chiral near-field enhancement,Chiral plasmonic nanostructures,Chiral focusing,Electromagnetic energy focusing
更新于2025-09-11 14:15:04
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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) - High Energy Pulsed Operation of a Yb Fibre MOPA with Amplified Spontaneous Emission Output
摘要： High energy pulsed fibre lasers are attractive to numerous applications in areas including industry, science, metrology and defense due to their excellent characteristics such as high average powers, a diffraction-limited beam quality, compactness and high flexibility in operation. However, their pulse energy is often limited by nonlinear optical phenomena, such as SBS (Stimulated Brillouin Scattering), SRS (Stimulated Raman scattering), self-focusing, etc., due to the small core size, resulting in unstable operation and catastrophic damage of the fibre. Enlarging the core size along with shortening the fibre length is a simple and straightforward way to overcome this problem, but at the expense of beam quality degradation and increased thermal effects. Fibre-based superfluorescent sources (FSS), sometimes referred to as amplified-spontaneous-emission (ASE) fibre light sources, can be an alternative way to achieve higher pulse energy from a typical step-index fibre while preserving the good beam characteristics of the fibre laser. Since the FSS has a broad spectrum without longitudinal modes, its spectral power is smaller than that of the fibre laser, increasing SBS threshold and, hence, generation of a high energy pulse. In this study, we report pulsed operation of the fibre-based superfluorescent light source. From a Yb fibre MOPA using an ASE source as a seed, we successfully generated high energy superfluorescent light pulses and investigated its performance for different repetition rates, pulse widths, and spectral linewidths. Furthermore, the results were compared with those of a Yb fibre laser.
关键词： ASE fibre light sources,self-focusing,fibre-based superfluorescent sources,nonlinear optical phenomena,amplified spontaneous emission,SBS,SRS,Yb fibre MOPA,High energy pulsed fibre lasers
更新于2025-09-11 14:15:04
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Symmetry and asymmetry nonlinear modes in dual cylinder waveguide shells coupled by a rotating double-well connection
摘要： We study the fundamental nonlinear modes in a dual-cylinder waveguide shell, which features a self-focusing Kerr e?ect, coupled by a double-well connection. This double-well connection is twisted by a pitch rate and creates a spatial dependent linear mixing, which plays the role of an e?ective rotating double-well potential. Symmetry transition between the waveform and the power distribution of the fundamental nonlinear modes in this system can be induced both by the total power and by the rotation speed of the connection. Four types of modes (cid:1)(cid:1)(cid:1) wave symmetry and power symmetry (WSPS), wave symmetry and power asymmetry (WSPA), wave asymmetry and power symmetry (WAPS) and wave asymmetry and power asymmetry (WAPA) (cid:1)(cid:1)(cid:1) are found from the system. The dependence of these modes on the total power of the light ˉeld, the rotation speed and the coupling strength of the connection are systematically studied through the paper. The ˉnding of this paper may o?er potential applications in fabrication of new types of nonlinear all-optical devices.
关键词： self-focusing,Symmetry breaking,rotating systems,double-well coupling
更新于2025-09-11 14:15:04
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Optical-trapping of a red Bessel beam controlled by co-propagating green Gaussian beam in azobenzene liquid crystal
摘要： Simultaneous co-propagation of red nondiffracting Bessel beam and green Gaussian beam at milliwatt powers in a photosensitive azobenzene liquid crystal has been studied. The fine displacement of the narrow-width Gaussian beam relative to the Bessel beam central maximum showed the Bessel beam distortion and controlled bending of its core in the direction opposite to the location of green Gaussian beam. After switching off the green beam, the dynamics of restoration of Bessel beam demonstrated the pronounced optical-trapping feature of its central core and transient soliton-like propagation with reduced diameter and increased intensity and propagation depth thus forming a waveguiding channel.
关键词： spatial soliton,Bessel beam,self-focusing,azobenzene liquid crystal,photo-isomerization
更新于2025-09-11 14:15:04
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Generation of terahertz radiation from beating of two intense cosh-Gaussian laser beams in magnetized plasma
摘要： An analytical and numerical study has been carried out for the generation of terahertz (THz) radiation by beating of two intense cosh-Gaussian laser beams (decentered Gaussian beams) in the rippled density magnetized plasma under the relativistic–ponderomotive regime. In this process, both laser beams exert a relativistic–ponderomotive force on plasma electrons at the beat frequency and impart them an oscillatory velocity in the presence of a static magnetic field. Due to coupling between this nonlinear oscillatory velocity with density ripple, nonlinear current is generated that excites the THz radiation at the different frequency. Higher-order paraxial-ray approximation (non-paraxial theory) has been used in this study. The effects of the decentered parameter, magnetic field, and density ripple on the THz radiation generation in ripple density magnetized plasma have been investigated. Further, the effect of beating of laser beams on the THz field amplitude and the efficiency of THz radiation have been studied. The amplitude and efficiency of the emitted radiation are found to be highly sensitive to the decentered parameter, magnetic field, and density ripple. It has been found that the amplitude and efficiency of the generated THz radiation increase significantly with increasing the values of decentered parameter, magnetic field, and density ripple.
关键词： relativistic–ponderomotive nonlinearity,magnetized plasma,cross-focusing,terahertz radiation,Cosh-Gaussian laser beams
更新于2025-09-11 14:15:04
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[Laser Institute of America ILSC? 2019: Proceedings of the International Laser Safety Conference - South Kissimmee, Florida, USA (March 18–21, 2019)] International Laser Safety Conference - Simulated supercontinuum generation in the human eye
摘要： Femtosecond laser pulses of sufficiently high intensity are prone to undergo a number of nonlinear effects while propagating in media. The increasing use of high intensity, femtosecond laser systems underscores the need to understand the retinal hazards generated by nonlinear optical effects, the generation of supercontinuum. Current laser safety standards such as ANSI Z136.1 for pulse wavelengths of 1200 nm - 1400 nm have been determined from experimental studies using pulse durations longer than 100 fs and linear pulse simulations. The combination of strong absorption, broad bandwidth, and dispersive effects makes standard nonlinear pulse simulation methods, based on the slowly varying envelope approximation, unsuitable for the study of near-infrared pulses in biological tissues. To model retinal hazards, we leverage an existing model for linear ultrafast pulse propagation that does not rely on an envelope approximation and simulate spectral broadening in water. Using one-dimensional simulations incorporating the effect of self-focusing, we validate the model using previous experiments for white-light supercontinuum generation in water. We then simulate propagation of 10 fs - 1 ps, 1200 nm - 1400 nm pulses at the current ANSI MPE limit for pulses under 10 ps.
关键词： nonlinear effects,supercontinuum generation,femtosecond laser pulses,self-focusing,ANSI Z136.1,retinal hazards
更新于2025-09-11 14:15:04
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Electrically Controlled Self-Focusing and Self-Localization in the Guided Channels
摘要： In this paper, we demonstrate the potential of liquid crystals (LCs) on the applications of small, simple, and tunable optical guided channels. Experimental results show that three operation modes of beam coupling can be achieved, depending on the feature of the electrically controllable refractive index, the incident position, and the specific design of electrodes. The dependence of the beam polarization on self-focusing and coupling effect are also discussed. The electrically controllable self-focusing and beam coupling are highly potential on integrated photonic circuits.
关键词： electrically controllable,self-focusing,liquid crystals (LCs),beam coupling,guided channels
更新于2025-09-11 14:15:04