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On-chip Optical Vector Quadrature De-multiplexer Proposal for QAM De-aggregation by Single Bi-directional SOA-based Phase-sensitive Amplifier
摘要： In this paper, a simple optical vector quadrature de-multiplexer (QD) scheme is proposed for de-aggregating input 10 Gbaud 16/32/64 quadrature amplitude modulation (QAM) signals into two pulse amplitude modulation (PAM) streams. The proposed QD is based on a single bi-directional degenerate phase-sensitive amplifier (PSA), where the wavelength and the polarization status of the extracted in-phase and quadrature components stay the same as the input signal. Since the proposed QD is realized using PSA based on semiconductor optical amplifier (SOA), it is also possible to realize an on-chip QD system, providing an integrated platform for optical signal processing. Through numerical simulation, the transfer characteristics of the proposed QD system show that the SOA-based PSA has a high phase-sensitive gain extinction ratio of 44.1 dB. The constellations, error vector magnitudes (EVMs), and bit-error rates (BERs) of the data streams after the de-aggregation are numerically investigated to verify the proposed QD scheme. For the 10 Gbaud 16/32/64 QAM signals with an input optical signal-to-noise ratio (OSNR) of 25 dB, the de-aggregated PAM4/PAM6/PAM8 signals show 6.1, 5.6, and 8.2 dB receiver OSNR improvements at the BER of 10?3, respectively. Also, to optimize the performance of the subsystem, the BER performance dependence on the phase difference between two arms in the subsystem is also examined. The simulation results reveal that the proposed QD can accomplish the function of optical vector de-aggregation well for the high-level QAM signals. The proposed QD can be applied to information de-aggregation, format conversion, and direct detection for optical vector signals, which may have great potential values for the flexible optical networks.
关键词： Optical fiber communication,semiconductor optical amplifiers,nonlinear optical devices,optical signal processing
更新于2025-09-23 15:22:29
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[IEEE 2018 20th International Conference on Transparent Optical Networks (ICTON) - Bucharest (2018.7.1-2018.7.5)] 2018 20th International Conference on Transparent Optical Networks (ICTON) - Mitigation of Amplitude and Phase Distortions by Using Conjugate-NOLM Regenerator
摘要： In this paper we propose a conjugate nonlinear optical loop mirror scheme (Conj-NOLM) by cascading two NOLMs with an intermediate optical phase conjugator stage (OPC). This new configuration utilizes mid-span spectral inversion to cancel out the nonlinear phase distortion that is introduced by the two NOLM units. Moreover, numerical investigation has been carried out for 16-QAM signals demonstrating increased robustness against accumulated amplitude and phase distortions in the transmission links.
关键词： conjugate nonlinear optical loop mirror,all-optical regenerator,multilevel amplitude and phase noise suppression
更新于2025-09-23 15:22:29
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BaV2O6·H2O: A nonlinear optical crystal with a large bandgap
摘要： The first Ba-containing hydrated vanadate as nonlinear optical (NLO) material, BaV2O6·H2O, was synthesized by facile hydrothermal method. The single-crystal X-ray diffraction result shows that this compound crystallizes in the acentric orthorhombic space group of P212121 with cell parameters a = 7.3993(6) ?, b = 8.9934(7) ?, and c = 9.7206(8) ?. UV–vis-IR diffuse reflectance spectrum shows that the compound has a large bandgap of 4.60 eV and moderate transparency range. The title compound shows second-harmonic generation (SHG) efficiency about 0.5 times of KH2PO4 (KDP). The structure-property relationship of BaV2O6·H2O was clarified by the first-principles studies.
关键词： Vanadate,Nonlinear optical material,Large bandgap,Hydrothermal method
更新于2025-09-23 15:22:29
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Nonlinear optical response of a two-dimensional semi-Dirac system in terahertz regime
摘要： We demonstrate a strong nonlinear optical response in a two-dimensional semi-Dirac system in the terahertz regime. By applying the Boltzmann transport theory for the intra-band process and a quantum mechanics method for the inter-band process, we obtained the three-photon current response. It is found that both the intra- and inter-band excitations make significant contributions to the nonlinear response. The third order conductivities (TOCs) σyy(3) are about two magnitudes higher than that of σxx(3). Interestingly, for the inter-band TOCs, there is a sign change when the chemical potential varies across the saddle point in the conduction band in kx direction (that is parabolic), due to the competition between the two opposite nonlinear current contributed by the electrons at states k > kD and k < kD, respectively. Finally, we show that the nonlinear response in terahertz regime is significant at experimentally accessible field strengths. Our results suggest that this system could be of potential applications in photonic device for frequency up-conversion.
关键词： black phosphorous,semi-Dirac system,nonlinear optical response,Boltzmann transport theory
更新于2025-09-23 15:22:29
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Linear and non linear optical properties of Sb2Se3 thin films elaborated from nano-crystalline mechanically alloyed powder
摘要： Sb2Se3 powder is achieved by mechanical milling of Sb and Se elements. X-ray diffraction analysis indicated the formation of Sb2Se3 orthorhombic phase. The latter finding is confirmed by both X-ray photoelectron spectroscopy characterization and Raman spectroscopy. Magnetic measurement revealed the ferromagnetic character of Sb2Se3 powder. Thin films were obtained by thermal deposition using Sb2Se3 powder as a precursor. Optical measurements carried out on thin films showed a high absorption coefficient and a direct band gap of 1.61 eV. The material has then potential application in photovoltaic conversion. Thin film refractive index dispersion (n) obeys Cauchy dispersion equation. n is investigated and found to comply with Wemple–DiDomenico single oscillator dispersion model. The energy E0 of the oscillator and Ed dispersion energy are derived from the refractive index investigation. Spitzer–Fan model exploitation was allowed to derive the high-frequency dielectric constant ε∞ and the carrier density N/m* ratio. Additionally, Verdet constant V is determined based on the refractive index dispersion study. Furthermore, the nonlinear susceptibility χ(3) as well as nonlinear refractive index are determined for Sb2Se3 thin films. The nanostructure of the material is likely responsible not only for the high nonlinear characteristics but also for the low magnetic character in Sb2Se3.
关键词： Nonlinear optical properties,Optical properties,Thermal deposition,Sb2Se3,Mechanical milling
更新于2025-09-23 15:21:21
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Preparation of composite Ag@Au core–shell nanoparticles and their linear and nonlinear optical properties
摘要： We herein report the preparation of composite Ag@Au core–shell nanoparticles (NPs) through galvanic replacement reaction and the investigations of linear and nonlinear optical properties. TEM micrographs envisage the formation of core–shell NPs. EDS elemental mapping images demonstrate the homogeneous distribution of the elements and their chemical composition. The powder XRD pattern confirms the formation of highly crystalline composite Ag@Au core–shell NPs. The UV–Vis absorption spectrum shows contribution of Ag and Au characteristic absorption bands and the slight red shift provides the strong evidence for coating of Au shell over the Ag core. Moreover, the linear optical parameters such as the extinction coefficient, reflectance, refractive index, conductivity, susceptibility and polarizability are studied. z-scan analysis reveals the enhanced nonlinear optical properties of the composite Ag@Au core–shell NPs with nonlinear refraction coefficient (n2) being ten times higher than that of Ag NPs and eight times increase in comparison with that of Au NPs.
关键词： Nonlinear optical properties,Ag@Au core–shell nanoparticles,z-scan technique,Galvanic replacement reaction,Linear optical properties
更新于2025-09-23 15:21:21
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Pb <sub/>2</sub> GaF <sub/>2</sub> (SeO <sub/>3</sub> ) <sub/>2</sub> Cl: Band Engineering Strategy by Aliovalent Substitution for Enlarging Bandgap while Keeping Strong Second Harmonic Generation Response
摘要： Wide bandgap and strong second-order generation (SHG) effect are two crucial but contradictory conditions for practical nonlinear optical (NLO) materials. Herein, a new NLO crystal Pb2GaF2(SeO3)2Cl (I) containing novel functional (GaO3F3)6? octahedra is designed and synthesized by a rational band engineering strategy with aliovalent substitution. Benefiting from the removal of transition metal cations and the introduction of bridged F anions, I exhibits the widest bandgap among all reported phase-matchable NLO selenites. Meanwhile, a strong SHG response more than 4.5 times of KH2PO4 (KDP) is maintained. The dominate role of the (GaO3F3)6? groups to the enlarged bandgap in I are elucidated by first-principles studies.
关键词： aliovalent substitution,second harmonic generation,nonlinear optical materials,selenites,band engineering
更新于2025-09-23 15:21:21
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Anisotropic third-order nonlinearity in pristine and lithium hydride intercalated black phosphorus
摘要： Two-dimensional (2D) black phosphorus (BP) displays unique anisotropic properties in its linear optical responses, but its third-order nonlinearity (Kerr effect) has remained relatively unexplored. Here we measured the third-order nonlinear optical responses in exfoliated BP and in lithium hydride intercalated BP (LiH-BP) flakes using polarization-resolved microscopic femtosecond Z-scan technique. Strong optical Kerr nonlinearities were measured for single flakes of BP and LiH-BP, with third-order nonlinear susceptibilities that are larger than many 2D materials. The nonlinear coefficients of LiH-BP are higher than those of BP, indicating that lithium hydride intercalation enhances not only the ambient stability of BP but also its nonlinear optical response. Highly anisotropic polarization-dependent Kerr nonlinearities of both BP and LiH-BP flakes were observed. The strong nonlinear and anisotropic optical responses of BP and LiH-BP indicate great potential of these materials in nonlinear photonics device applications.
关键词： in-plane anisotropy,nonlinear optical responses,lithium hydride intercalated black phosphorus,Kerr nonlinearity,Black phosphorus
更新于2025-09-23 15:21:21
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Light control through a nonlinear lensing effect in a colloid of biosynthesized gold nanoparticles
摘要： Biosynthesis of four samples of colloidal suspensions of gold nanoparticles is achieved using hydroalcoholic extract and three different separated compounds of the plant Bacopa procumbens. The nonlinear optical properties of each sample are characterized with the Z-scan technique. In all cases, the Z-scan curves indicate a negative or self-defocusing response, which is mainly attributed to thermal effects. Among the four samples, the hydroalcoholic extract was noted to have the highest nonlinear optical response and was selected to demonstrate the formation of self-collimated beams (SCBs). This kind of beams are obtained when a convergent CW laser, with only few tens of milliwatts of optical power, is introduced into the sample and induces a negative-lens effect that shifts the focal spot forward. As a result, the otherwise highly focused beam propagate with little divergence over lengths of up to 10 mm. Moreover, an SCB is capable of controlling and steering a weak probe beam of a different wavelength, since the probe experiences the lensing induced by the pump. Noteworthy, the response time of the material was found to be less than 0.07 s, which makes it a plausible candidate for photonic applications.
关键词： gold nanoparticles,Nonlinear optics,nonlinear optical materials,self-effects
更新于2025-09-23 15:21:01
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Nonlinear Optics || Optically Induced Damage and Multiphoton Absorption
摘要： A topic of great practical importance is optically induced damage of optical components. Optical damage is important because it ultimately limits the maximum amount of power that can be transmitted through a particular optical material. Optical damage thus imposes a constraint on the efficiency of many nonlinear optical processes in that it limits the maximum field strength E that can be used to excite the nonlinear response. In this context, it is worth pointing out that present laser technology can produce laser beams of sufficient intensity to exceed the damage thresholds of all known materials.
关键词： multiphoton absorption,nonlinear optical processes,laser technology,optical damage,damage thresholds
更新于2025-09-23 15:21:01