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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) - Quasi-Phase-Matched Third Harmonic Generation in Periodic Stacks of Polymer Bilayers
摘要： Quasi-phase-matching (QPM) is widely used for nonlinear frequency conversion with quadratic media, in which QPM is achieved by periodically reversing the signs of the nonlinear optical coefficients. Although efficient third harmonic generation (THG) can be realized by cascading two quadratic processes, direct QPM THG with isotropic media is of fundamental interest. For an isotropic cubic medium, however, reversal of the sign of the nonlinearity is not possible. Recently, we reported the first experimental realization QPM THG in isotropic polymer films with alternatingly deposited multilayers of a highly nonlinear organic material and a passive resin up to four periods [1]. Here, we investigated the QPM characteristics by measuring the THG output while tuning the fundamental wavelength around the QPM condition.
关键词： Quasi-phase-matching,third harmonic generation,isotropic polymer films,nonlinear optical coefficients
更新于2025-09-16 10:30:52
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Growth of 4-N,N-Dimethylamino-4'-N'-methyl-stilbazolium Tosylate (DAST) Organic Single Crystals Controlled by Oleic Acid
摘要： 4-N,N-dimethylamino-4'-N'-methyl-stilbazolium tosylate (DAST) organic single crystals controlled by (Z)-Octadec-9-enoic acid (oleic acid, OA) was grown by a slow-cooling method. The as-grown DAST single crystals were systematically characterized by FTIR, X-ray diffraction, second harmonic generation, and UV-vis spectroscopy. Results indicate that addition of OA into the DAST solutions leads to the controlled growth of DAST single crystals and consequently, the crystal quality and optical properties can be modified. Particularly, the DAST crystals grown under the control of OA exhibit larger sizes, higher crystallinities, and better optical qualities with higher optical band gaps and lower defect density, compared with those grown in the absence of OA. These results are helpful for better understanding the controlled growth of DAST organic single crystals and modifying their properties for practical applications.
关键词： nonlinear optical materials,crystal growth,additives,DAST single crystals
更新于2025-09-16 10:30:52
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Density Functional Theory Investigation of Nonlinear Optical Properties of T-Graphene Quantum Dots
摘要： Using density functional theory calculations, we have analyzed nonlinear optical properties of a series of T-graphene quantum dots differing in their shape and size. Electronic polarizability, first-order and second-order hyperpolarizability of these systems are investigated and shed light on their stability and electronic properties. Negative cohesive energy shows that they are energetically stable. The effect of size and incident frequency on their nonlinear responses are comprehensively discussed. Most of the systems exhibit strong NLO response and it enhanced in the presence of external field. All these systems show absorption maximum ranging from UV to visible window. Overall, this theoretical framework highlighted the nonlinear optical properties of T-graphene quantum dots that may provide valuable information in designing potential NLO materials.
关键词： T-graphene quantum dot,electron delocalization,nonlinear optical property,UV-visible absorption spectra,Density functional theory
更新于2025-09-16 10:30:52
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Yttrium oxide as a Q-switcher for the near-infrared erbium-doped fiber laser
摘要： Yttrium oxide (Y2O3) has been widely used in metal-reinforced composites, microelectronics, waveguide lasers, and high-temperature protective coatings because of its good physical and photoelectric properties. However, few studies have been done on the nonlinear optical applications of Y2O3 as saturable absorbers (SAs) in fiber lasers so far. Here, a passively Q-switched near-infrared fiber laser using Y2O3 as a Q-switching device is demonstrated. The optical nonlinear properties of the Y2O3 SA prepared by the magnetron sputtering method were measured by the twin-detector measurement technique, and the modulation depth of the proposed Y2O3 SA was found to be 46.43%. The achieved Q-switched laser delivers an average output power of 26 mW at 1530 nm with a pulse duration of 592.7 ns. To the best of our knowledge, this is the first report on the optical nonlinearity of Y2O3 as a Q-switcher for the near-infrared fiber laser, which may deepen the understanding of the optical nonlinear properties of Y2O3 and make inroads into the potential market of optical modulation and optoelectronic devices.
关键词： Q-switched laser,saturable,fiber lasers,absorbers,nonlinear optical materials
更新于2025-09-16 10:30:52
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Wideband saturable absorption in Metal-organic frameworks (MOFs) for mode-locking Er- and Tm-doped fiber laser
摘要： We fabricate a Metal-organic frameworks (MOFs) Saturable absorber (SA) based on a microfiber. Nonlinear optical absorption of the MOF SA is characterized systmatically. The modulation depth is measured to be 6.57 % and 14.25 % at 1.5 and 2 μm spectral ranges, respectively. We report ultrashort pulse generation in both Er- and Tm-doped fiber lasers by using a same microfiber-based MOF SA, operating 384 fs and 1.3 ps pulse duration at 1563 nm and 1882 nm, respectively. To the best of our knowledge, this is the first report on a MOF based fiber laser at near infrared spectral ranges. Our findings validate the applicability of MOF as a broadband SA for ultrafast photonic applications.
关键词： Ultrafast photonics,Saturable absorber,Metal-organic frameworks,Fiber laser,Nonlinear optical absorption
更新于2025-09-16 10:30:52
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Electrically controlled growths of 4-N,N-dimethylamino-4a?2-Na?2-methyl-stilbazolium tosylate (DAST) organic microcrystals
摘要： 4-N,N-dimethylamino-4′-N′-methyl-stilbazolium tosylate (DAST) is one of the most important organic nonlinear optical (NLO) materials, but its controlled growth remains a challenge. Herein, we describe a novel method to control the growth of DAST on the surfaces of indium tin oxides coated with the patterned photoresists by electric field. Results indicate that zero-dimensional (0D) spherical DAST microcrystals tend to grow along the photoresist lines if an electric field with a low frequency of 500 Hz is applied. Rather differently, one-dimensional (1D) DAST microwires preferentially grow along the gaps of the photoresist lines under the control of an electric field with a high frequency of 1000 Hz. Growth of DAST microcrystals controlled by electric field leads to the increase in the crystallinity, but the chemical structures remain unchanged. Moreover, second harmonic generation signal was measured from the as-grown DAST microcrystals. The results presented in this work are helpful for rationally controlling the growth of 0D or 1D DAST microcrystals, and particularly, the strategy can be further expanded to control the growth of DAST derivatives or other organic NLO materials with similar chemical structures.
关键词： Spectral analyses,Growth mechanism,Electric field induction,DAST microcrystals,Nonlinear optical material
更新于2025-09-16 10:30:52
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Enhanced Nonlinear Optics Properties of a Bromine Chalcone from a novel Polymorph
摘要： This work presents crystallization, structural elucidation and a thorough study on nonlinear optical (NLO) properties calculated at DFT/CAM-B3LYP/6-311+G(d) level of a new bromine chalcone monoclinic polymorph (BRC-m). Both linear polarizability and second hyperpolarizability associated to NLO process of the intensity dependent refractive index (IDRI) were calculated. The dynamic third-order NLO susceptibility (χ(3)(―ω;ω,ω,―ω)) for BRC-m are higher than obtained experimentally for other chalcone derivatives. Furthermore, the theoretical results for BRC-m were compared with triclinic bromine chalcone (BRC-t); and the change of crystalline state (BRC-t to BRC-m) enhanced the third-order NLO susceptibility from 0.257 × 10―20m2/V2 to 2.48 × 10―20??2/??2 at 1064nm, respectively. This observation shows that future research on crystallization process of known NLO materials is a promising way to improve even more their potential optical application and improve the crystal quality.
关键词： structural elucidation,nonlinear optical properties,bromine chalcone,Crystallization,third-order susceptibility,monoclinic polymorph
更新于2025-09-16 10:30:52
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Complexity in Biological and Physical Systems - Bifurcations, Solitons and Fractals || Self-Organization, Coherence and Turbulence in Laser Optics
摘要： In the last decades, rapid progress in modern nonlinear science was marked by the development of the concept of dissipative soliton (DS). This concept is highly useful in many different fields of science ranging from field theory, optics, and condensed matter physics to biology, medicine, and even sociology. This chapter aims to present a DS appearance from random fluctuations, development and growth, the formation of the nontrivial internal structure of mature DS and its breakup, in other words, a full life cycle of DS as a self-organized object. Our extensive numerical simulations of the generalized cubic-quintic nonlinear Ginzburg-Landau equation, which models, in particular, dynamics of mode-locked fiber lasers, demonstrate a close analogy between the properties of DS and the general properties of turbulent and chaotic systems. In particular, we show a disintegration of DS into a noncoherent (or partially coherent) multisoliton complex. Thus, a DS can be interpreted as a complex of nonlinearly coupled coherent “internal modes” that allows developing the kinetic and thermodynamic theory of the nonequilibrious dissipative phenomena. Also, we demonstrate an improvement of DS integrity and, as a result, its disintegration suppression due to noninstantaneous nonlinearity caused by the stimulated Raman scattering. This effect leads to an appearance of a new coherent structure, namely, a dissipative Raman soliton.
关键词： dissipative solitons,chaos in nonlinear optical systems,generalized cubic-quintic nonlinear Ginzburg-Landau equation,dissipative Raman soliton,optical turbulence
更新于2025-09-12 10:27:22
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Quasi-Phase-Matching Efficiency Optimization for Coupled Second-Order Nonlinear Processes
摘要： It is well known how to tailor the conversion ef?ciency grid of a single quasi-phase-matching (QPM) grating when the involved processes are uncoupled. However, it becomes much more sophisticated in the presence of coupling between multiple processes. In this case, different processes compete for the same QPM “resources” throughout the grating, and one process can outweigh the others over a certain range of interaction. Here we propose the generalized iterative domino (GID) algorithm to meet these challenges for the ?rst time (to our best knowledge). Instead of tailoring the strength of each “global” Fourier coef?cient, GID algorithm can properly adjust the spatially varying “local” Fourier coef?cients in favor of the ?nal yield. Three methods, including cascaded single-period (C1P) structure, quasi-periodic optical superlattice (QPOS), and hyper?ne aperiodic optical superlattice (HAOS) optimized by GID, are numerically and experimentally investigated under the platform of third-harmonic generation (THG). It shows that the THG ef?ciency of HAOS + GID can exceed the record achieved by C1P structure by 33%. This method is applicable to general wavelength converters involving with multiple coupled nonlinear processes.
关键词： Optical wavelength conversion,optimization methods,nonlinear optical device,optical harmonic generation
更新于2025-09-12 10:27:22
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Temperature extraction for Brillouin optical fiber sensing system based on extreme learning machine
摘要： The use of extreme learning machine (ELM) network to extract temperature distribution from the measured Brillouin gain spectra (BGSs) along the sensing fiber obtained by Brillouin optical fiber sensors is proposed and demonstrated experimentally. Compared with conventional curve fitting method (CFM), ELM network trained by a set of ideal BGSs can extract temperature information directly from the measured BGSs obtained by Brillouin optical time domain reflectometer (BOTDR) system without the need of determining Brillouin frequency shift (BFS) and converting BFS to temperature. The BGSs linewidth is taken into account to construct the ideal BGSs by using Pseudo-Voigt curve for ELM training. The performance of ELM is analyzed in detail and compared with that of widely-used Lorentzian CFM, and the experiment results show that ELM can provide higher accuracy even at large frequency scanning step and faster processing speed. Therefore, the proposed ELM approach is feasible and effective for temperature extraction in Brillouin optical fiber sensing system.
关键词： Nonlinear optical signal processing,Brillouin scattering,Temperature extraction,Optical fiber sensors,Extreme learning machine
更新于2025-09-12 10:27:22