- 标题
- 摘要
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- 实验方案
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High power 4.2-cycle mid-infrared pulses from a self-compression optical parametric oscillator
摘要： We demonstrate the generation of few-cycle mid-infrared (MIR) pulses from a self-compressed optical parametric oscillator (OPO), synchronously pumped by a 105 fs Yb3+ doped fiber laser system. By using a ring cavity design, 4.2-cycle (45.3 fs) MIR pulses at a central wavelength of 3250 nm (with a 10-dB bandwidth of 648 nm) are obtained in a simple, practical and compact configuration. Detailed theoretical analysis and numerical simulation are performed to better understand the self-compression mechanism in such an OPO cavity. In addition, when pumped at 3.8 W, the OPO delivers idler output power up to 330 mW and the corresponding pump depletion is 74.7%.
关键词： Nonlinear optics,Pulse compression,Ultrafast lasers
更新于2025-09-11 14:15:04
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High-Quality-Factor AlGaAs-On-Sapphire Microring Resonators
摘要： We realize an AlGaAs-on-sapphire platform through Al2O3-assisted direct wafer bonding and substrate removal processes. The direct wafer bonding process is optimized concerning the intermediate layer deposition and annealing temperature to obtain a high bonding strength between the AlGaAs and sapphire wafers. High quality-factor (Q) microring resonators are fabricated using electron-beam lithography in which the charging effect is mitigated by applying a thin aluminum layer, and a smooth pattern sidewall definition is obtained using a multi-pass (exposure) process. We achieve an intrinsic Q of up to ～460,000, which is the highest Q for AlGaAs microring resonators. Taking advantage of such high Q resonators, we demonstrate an ultra-efficient nonlinear four-wave mixing process in this platform and obtain a conversion efficiency of -19.8 dB with continuous-wave pumping at a power level of 380 μW. We also investigate the thermal resonance shift of microring resonators with different substrate layouts and observe superior temperature stability for devices in the AlGaAs-on-sapphire platform. The realization of the AlGaAs-on-sapphire platform also opens new prospects for AlGaAs devices in nonlinear applications in the mid-infrared wavelength range.
关键词： nonlinear optics,four-wave mixing,optics resonators,Integrated optics
更新于2025-09-10 09:29:36
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Improvement of the third order nonlinear optical properties of nematic liquid crystal under the influence of different compositional percentage of doped SWCNT and the external electric field
摘要： In this research, the nematic liquid crystal (NLC) was doped with varying concentration (0-1 % wt.) of single walled carbon nanotubes (SWCNTs) at room temperature to study the nonlinear optical (NLO) properties of E5CN7@CNT cell.The third order NLO properties such as the nonlinear susceptibility, the nonlinear refraction (NLR) and the nonlinear absorption (NLA) were determined by using Z-scan techniques. The nonlinear studies have been done using a continuous wave (CW) He: Ne laser at 632.8 nm.Doping SWCNTs to eutectic uniaxial NLC (E5CN7) enhanced the third order nonlinear susceptibility, ??(3) and consequently the nonlinearity properties of composite systems improved.It is found that at lower concentration of CNTs (c< 0.75 % wt.), the third order nonlinear susceptibility are increased, but for concentration 0. 5<c<1 % wt., the third order nonlinear susceptibility are decreased. The negative sign of the observed NLR index, indicates that the E5CN7@CNT exhibits self-defocusing type optical nonlinearity. The two photon absorption (TPA) behavior, corresponding to negative sign NLA of samples. The reorientation of samples molecules amplifies upon the application of electric field, then nonlinearity increases.
关键词： Composite materials,Nematic liquid crystal,Carbon nanotubes,Third order nonlinear susceptibility,Nonlinear optics,Electric field,Z-scan method
更新于2025-09-10 09:29:36
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Nonlinear manipulation of surface plasmons on graphene-TMDC Bragg reflectors
摘要： In this study, we benefit from the nonlinear optical tunability of the graphene-transition metal dichalcogenide (G-TMDC) heterostructure and the strong confinement of the electromagnetic fields of surface plasmon polaritons (SPPs) on graphene in order to propose a highly tunable nonlinear optical Bragg reflector. Recently, two-dimensional (2D) TMDCs are the subject of intense researches because of their nonlinear optical properties at near infrared wavelengths which are very intriguing for various optical applications. We choose two kinds of 2D-TMDCs, MoSe2 and WSe2, with the strongest second order optical nonlinearity at near infrared range to properly design the periodic variation of the propagating SPP waves on the graphene layer. We utilize theoretical method of quantum electrostatic heterostructure to compute the dielectric function of graphene-TMDCs. Different nonlinearities of two TMDCs lead to noticeable tuning of the full width at half maximum (FWHM) and the central Bragg wavelength of the reflector which let design various optical devices. We design an add/drop filter, a nonlinear switch, and an AND/OR optical logic gate based on our proposed Bragg reflector. Our finite difference time domain numerical and transfer matrix analytical results reveal that by increment of the optical intensity up to 6 MW/cm2 which is below the pulse damage threshold of graphene, due to the second order nonlinearity, a 10-nm red-shift in central Bragg wavelength is observed and the 20-nm FWHM at linear regime decreases to 1.5 nm. The SPP intensities of 0.8 MW/cm2 and 1.53 MW/cm2 fulfill the requirements for AND and OR logical operations with 57 and 66.51 dB extinction ratios, respectively.
关键词： Nonlinear optical materials and devices,Surface plasmons,Nonlinear optics,Optical switches,Bragg grating
更新于2025-09-10 09:29:36
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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 properties of donor-acceptor dyads formed between phthalocyanine and fullerene
摘要： A new type of metallophthalocyanine/metallofullerene complex, ZnPc/Li@C60, is proposed and characterized by using density functional theory. This donor-acceptor complex shows better thermal stability owing to the π–π stacking interaction between ZnPc and Li@C60 subunits, and the large vertical ionization energy (VIE) is able to force this complex stacked into the desired form. The long range interaction and intramolecular charge transfer indicate that this kind of complex may exhibit excellent ?rst hyperpolarizability. The calculated static hyperpolarizability (β0) of ZnPc/Li@C60 shows large value in the range of 11.64 ～ 32.05 × 10?30 esu. This means that metallophthalocyanine/metallofullerene hybrids have great potential for the design and preparation of materials science and will stimulate more extensive studies on the donor-acceptor complexes.
关键词： charge tranfer,nonlinear optics,Density function theory
更新于2025-09-10 09:29:36
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Enhancement of the Second Harmonic Generation from WS <sub/>2</sub> Monolayers by Cooperating with Dielectric Microspheres
摘要： Herein, a 20-fold enhancement of the optical second harmonic generation (SHG) from WS2 monolayers by cooperating with SiO2 dielectric microspheres (MSs) is reported. Detailed experiment and simulation studies indicate that the SHG enhancement is dominantly originated by the enhanced excitation intensity and enlarged collection efficiency produced by the SiO2 MSs. The size effect of the SiO2 MS on the SHG enhancement is also systematically investigated. Moreover, the SHG enhancement is found to be very sensitive to the surrounding refractive index of the SiO2 MS, which advocates great promise for the photonic sensing applications. This work provides a low-cost and efficient approach to enhancing the SHG emission, and demonstrates great potential for functional nanodevices based on hybrid dielectric structures.
关键词： second harmonic generation,nanodevices,WS2 monolayers,nonlinear optics,photonic nanojets
更新于2025-09-10 09:29:36
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All-optical mode conversion and temperature sensing via transient-grating in step-index fiber
摘要： We demonstrate the formation of Kerr-induced transient long period grating in a standard single-mode ?ber (SMF28) using sub-nanosecond laser pulses and it’s application as an ef?cient all-optical mode conversion and temperature sensing. The ?ber supports LP01 and LP11 spatial modes at 1064 nm wavelength. The beating between two guided modes induces refractive index grating exploiting the Kerr effect. The probe beam co-propagating with the pump at the same wavelength but with different polarization, exhibits ef?cient mode conversion ef?ciency from LP01 to LP11 mode. Temperature sensitivity is measured owing to the change in mode conversion ef?ciency due to the shift in resonant peak wavelength with the increase in temperature. The change in temperature is manifested by the change in spectral power of probe beam at the output. Experimental result demonstrates an average temperature sensitivity of 0.15 Watt/oC. The transient nature of the grating with high sensitivity makes our approach unique from the existing results and can open a route for potential applications.
关键词： Fiber nonlinear optics,optical sensing,Fiber mode coupling
更新于2025-09-10 09:29:36
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Generation of Nearly Flattop Ultra-Broadband Response in a QPM Device Using a Phase Shifter
摘要： We have theoretically demonstrated the efficient generation of nearly flattop ultra-broadband response in a periodic quasi-phase matching (QPM) device using a single phase shifter (PS) domain. The flat broadband response is generated using optical parametric generation (OPG) with a QPM device of grating period Λ = 27 μm. The choice of grating period and pump source depends on the group velocities of signal and idler wavelengths to match close to the degeneracy point. We have identified the location of phase shifter domain, which generates a nearly flattop OPG gain bandwidth of ?λ = 1.41 μm. The variations in broadband response are studied when the location and width of phase shifter domains are altered. When compared to a periodic device, the phase shifter domain included QPM structure exhibits higher tolerance to temperature in retaining the smoothness of the broadband response. Furthermore, we have generated the same ultra-broadband response by introducing multiple phase shifter domains at suitable locations in a periodic QPM device.
关键词： optical superlattices,optical mixing,Nonlinear optics,optical harmonic generation
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