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Nonlinear process-induced spectral changes in hydrogenated amorphous silicon core optical fibre
摘要： In this paper, the spectral properties of temporal double pulses centred at the same central wavelength and two different central wavelengths are numerically presented based on hydrogenated amorphous silicon core optical fibre. In order to characterise the output spectra of double pulses, the group velocity dispersion and various nonlinear processes including self-phase modulation, cross-phase modulation, two-photon absorption, free carrier absorption and free carrier dispersion are considered in the theoretical model. Numerical results show that, under fixed fibre length condition, the widths of the outcome spectra are strongly dependent on the delay times, peak powers and initial chirps of input double pulses, i.e. widths of the output spectra are proportional to the launched peak powers, and the delay times control the separation between two pulses, resulting in the spectral change within a proper delay time, and the spectral widths are compressed or extended by judiciously adjusting the initial chirps imposed on the input pulses.
关键词： nonlinear processes,optical spectrum,optical fibre,Nonlinear optics,hydrogenated amorphous silicon
更新于2025-09-10 09:29:36
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Nonlinear optical conductivity of Weyl semimetals in the terahertz regime
摘要： We analyze the nonlinear optical properties in Weyl semimetals which result from the intraband and the interband contributions around the Weyl points respectively. Based on the Boltzmann equation and the Floquet method to the Schr¨odinger equation under the tight-binding model we can calculate any order of nonlinear optical conductivity in the Terahertz regime with the effective chiral Hamiltonian used. We find that the influences of the interband transition and intraband term on the optical properties of the system are opposite each other when increasing frequency and interband transitions dominates the optical responses. The part of the linear conductivity of the system which is contributed from the intraband electric motion increases when the relaxation time reduces and the part of the linear conductivity from the interband transitions increases with the decrease of the temperature. The part of the third harmonic generation which is contributed to the interband transitions is proportional to ω?3 and will be considerable when the frequency become small enough. The nonlinear terms enhance the optical reponses of Weyl semimetals and provide more information about the critical properties.
关键词： Tera Hertz,Nonlinear Optics,Weyl Semimetal
更新于2025-09-10 09:29:36
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A Review on the Development of Infrared Nonlinear Optical Materials with Triangular Anionic Groups
摘要： Exploration of new nonlinear optical (NLO) materials in the infrared (IR) region is of importance in many civil and military fields. Fundamental building units (FBUs) play the critical roles in the origin of NLO effect for chalcogenide system, such as tetrahedral and triangular anionic groups. Note that some triangular groups can generate the relatively strong NLO effect owing to their distinctive π-conjugated electron orbitals or other unique structures. This review focuses on the metal sulfides with triangular anionic groups and has systematically studied the relationship between structure and performances. Compared to the known materials, the common choice for different MS3 (M = B, Sb, As, Ag, Cu, Te, Sn) units are introduced in detail. This review also summarizes the mechanism of MS3 to provide useful insights into the development of NLO materials with better performances.
关键词： Metal sulfides,Triangular anionic groups,Nonlinear optics
更新于2025-09-10 09:29:36
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Soliton solutions of perturbed nonlinear Schrodinger equation with Kerr law nonlinearity via the modified simple equation method and the subordinary differential equation method
摘要： The objective of this paper was to obtain soliton solutions for a perturbed nonlinear Schrodinger equation with Kerr law nonlinearity using the modified simple equation method and subordinary differential equation method. These methods appear to be efficient and they can be applied in seeking exact solutions of many other nonlinear evolution equations encountered in science and engineering studies.
关键词： third order dispersion,Fiber optics,group velocity dispersion
更新于2025-09-10 09:29:36
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Frequency pair model for selection of signal spectral components to determine position of zero optical-path difference in a pulse-train interferometer
摘要： High-accuracy measurement using phase information of fringe patterns – that is not much affected by amplitude noises – than amplitude information, in a pulse-train interferometer is demonstrated in this study. However, the selection criteria for spectral components of the measured interferogram for regeneration of phase information are not obvious. In this work, a frequency pair model is proposed. The experimental work demonstrates the model’s ability to optimally select signal components. The application field of pulse-train or white-light interferometers may be extended by associating them with the proposed method.
关键词： Metrology,Fringe analysis,Interferometry,Fourier optics and signal processing,Instrumentation, measurement, and metrology
更新于2025-09-10 09:29:36
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Propagation properties of chirped Airy hollow Gaussian wave packets
摘要： Based on the analytic expression of the chirped Airy hollow Gaussian (CAiHG) wave packets derived from the (3+1)-dimensional ((3+1) D) Schr?dinger equation, their propagation properties are investigated in detail for the first time. The results show that a focusing of the chirped Airy Gaussian pulses is found, which leads to the same focusing of the propagation trajectory and the maximum scattering force. The distribution factor can modulate the convergence of the side wave rings at . During the propagation process, with the increase of the , when the is negative, the side wave rings rise along the main wave axis but their moving is opposite when the is positive. When the beam order , the intensity, the angular momentum and the gradient force gradually tend to the center but they move radially when . The direction of the peripheral gradient force points to the center but the direction is opposite in the center. The beam orders only affect the magnitude of the normalized maximum scattering force but have little effects on their distribution.
关键词： Chirping,Mathematical model in optics,Wave propagation
更新于2025-09-10 09:29:36
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Approximating vibronic spectroscopy with imperfect quantum optics
摘要： We study the impact of experimental imperfections on a recently proposed protocol for performing quantum simulations of vibronic spectroscopy. Specifically, we propose a method for quantifying the impact of these imperfections, optimizing an experiment to account for them, and benchmarking the results against a classical simulation method. We illustrate our findings using a proof of principle experimental simulation of part of the vibronic spectrum of tropolone. Our findings will inform the design of future experiments aiming to simulate the spectra of large molecules beyond the reach of current classical computers.
关键词： quantum optics,boson sampling,squeezed light,quantum simulation,vibronic spectroscopy,quantum chemistry
更新于2025-09-10 09:29:36
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Daytime optical turbulence and wind speed distributions at the Baikal Astrophysical Observatory
摘要： Atmospheric turbulence limits the angular resolution of ground-based optical telescopes. The daytime turbulence conditions for solar observations are stronger and more complicated than the turbulence observed at night. The Baikal Astrophysical Observatory is the site of the 1-m Large Solar Vacuum Telescope (LSVT) located near Lake Baikal (East Siberia, Russia), which is the largest freshwater lake in the world. The region hosts unique weather regimes and natural phenomena, including local winds and giant ice rings. Because the LSVT has ongoing and planned programmes in adaptive optics (AO), statistical knowledge of atmospheric turbulence and wind speed distributions is essential for designing and optimizing AO systems. We present the first seasonal study of the vertical distribution of wind speed and daytime optical turbulence conditions at the Baikal Astrophysical Observatory. Site measurements of the daytime Fried parameter were collected using the Shack–Hartmann wavefront sensor in the LSVT AO system. Reanalysis data from the National Centers for Environmental Prediction (NCEP) and the National Centers for Atmospheric Research (NCAR) were used to characterize the wind speed distribution. The results demonstrate seasonal variation in both solar seeing and wind speed profile. The strongest wind speed was detected in winter and in November, while the weakest wind speed occurred during summer. The strongest daytime turbulence conditions were observed in the winter. The best solar seeing β0 ≈ 1 arcsec was detected in the summer.
关键词： site testing,atmospheric effects,instrumentation: adaptive optics
更新于2025-09-10 09:29:36
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Room Temperature Valley Polarization and Coherence in Transition Metal Dichalcogenide-Graphene van der Waals Heterostructures
摘要： Van der Waals heterostructures made of graphene and transition metal dichalcogenides (TMD) are an emerging platform for opto-electronic, -spintronic and -valleytronic devices that could benefit from (i) strong light-matter interactions and spin-valley locking in TMDs and (ii) exceptional electron and spin transport in graphene. The operation of such devices requires significant valley polarization and valley coherence, ideally up to room temperature. Here, using a comprehensive Mueller polarimetry analysis, we report artifact-free room temperature degrees of valley polarization up to 40 % and, remarkably, of valley coherence up to 20 % in monolayer tungsten disulfide (WS2)/graphene heterostructures. At a temperature of 20 K, we measure a record degree of valley coherence of 60 %, a value that exceeds the degree of valley polarization (50 %) and indicates that our samples are minimally affected by pure dephasing processes. Valley contrasts have been particularly elusive in molybdenum diselenide (MoSe2), even at cryogenic temperatures. Upon interfacing monolayer MoSe2 with graphene, the room temperature degrees of valley polarization and coherence are as high as 14 % and 20 %, respectively. Our results are discussed in light of recent reports of highly efficient interlayer exciton and carrier transfer in TMD/graphene heterostructures and hold promise for room temperature chiral light-matter interactions and opto-valleytronic devices.
关键词： Mueller polarimetry,spin-valley locking,Transition metal dichalcogenides,graphene,chiral optics,opto-valleytronics,excitons
更新于2025-09-10 09:29:36
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Adjoint method and inverse design for nonlinear nanophotonic devices
摘要： The development of inverse design, where computational optimization techniques are used to design devices based on certain specifications, has led to the discovery of many compact, non-intuitive structures with superior performance. Among various methods, large-scale, gradient-based optimization techniques have been one of the most important ways to design a structure containing a vast number of degrees of freedom. These techniques are made possible by the adjoint method, in which the gradient of an objective function with respect to all design degrees of freedom can be computed using only two full-field simulations. However, this approach has so far mostly been applied to linear photonic devices. Here, we present an extension of this method to modeling nonlinear devices in the frequency domain, with the nonlinear response directly included in the gradient computation. As illustrations, we use the method to devise compact photonic switches in a Kerr nonlinear material, in which low-power and high-power pulses are routed in different directions. Our technique may lead to the development of novel compact nonlinear photonic devices.
关键词： nanophotonics,Inverse design,integrated photonics,optical switching,nonlinear optics
更新于2025-09-10 09:29:36