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- 2019
- Distributed optical fiber sensing
- Optical frequency domain reflection
- Polynomial regression algorithm
- Nonlinear tuning compensation
- Optoelectronic Information Science and Engineering
- Hebei University of Technology
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Characterization of Polarization Pulling in Fiber Optical Parametric Amplifiers
摘要： In fiber optical parametric amplifiers (FOPAs), the output states of polarization (SOPs) of both the signal and the idler are affected by the pump SOP through the polarization pulling effect. We proposed a normalized model to characterize the general dynamics of polarization pulling in degenerated pump FOPAs. By using this model, we determined the relationship between the output degree of polarization (DOP) and the gain of the FOPAs over three orders of magnitude changes in polarization-mode dispersion (PMD) coefficient. We demonstrated numerically that when fibers with typical PMD coefficients are used, the output signals of the FOPAs can achieve higher DOP than those of co-propagating fiber Raman amplifiers, which depends on whether the parametric gain is sufficiently large to compensate the PMD-induced phase mismatch. We also found that for FOPAs using different types of fibers with moderate PMD coefficients, this DOP-gain relationship exhibits highly similar behaviors. We thus adopted a set of modified empirical formulas to analyze this relationship. This formula can also describe the relationship between the output DOP and the conversion efficiency of the idler. The results indicate that in all cases studied, FOPAs achieve much stronger polarization pulling to the idlers than the signals.
关键词： Nonlinear optics,parametric oscillators and amplifiers,polarization-selective devices
更新于2025-09-23 15:22:29
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[IEEE 2018 2nd International Conference on Telematics and Future Generation Networks (TAFGEN) - Malaysia (2018.7.24-2018.7.26)] 2018 2nd International Conference on Telematics and Future Generation Networks (TAFGEN) - Modelling of Different Types of SOA Characteristics
摘要： An investigation of gain, optical power, and amplified spontaneous emission (ASE) noise characteristics of different types of semiconductor optical amplifier (SOA) operating in the conventional (C-) band is carried out. The types of SOAs include linear, nonlinear and in-line SOA that are customized configuration through OptiSystem software. These SOAs are further simulated in MATLAB using a numerical steady-state model to determine and evaluate their performance. The results showed that the linear SOA has the most ideal and distinct characteristics, as compared to the nonlinear and in-line SOAs rendering it more suitable as gain medium in the multiwavelength fiber laser (MWFL) application.
关键词： modelling,linear and nonlinear types,semiconductor optical amplifier,multiwavelength fiber laser
更新于2025-09-23 15:22:29
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Dual frequency-comb spectroscopy of chromophores in condensed phases
摘要： Femtosecond time-resolved spectroscopy and frequency-comb spectroscopy have been individually developed to achieve better time and frequency resolutions, respectively. The two spectroscopic techniques have been developed for different systems, even though they use mode-locked laser in common. Recently, there was an interesting merge of the two techniques into a dual frequency-comb (DFC) spectroscopy, resulting in a new femtosecond spectroscopy with simple instrumentation and high data acquisition speed compared to conventional femtosecond spectroscopic techniques. By slightly detuning the repetition rates of two phase-locked frequency-comb lasers, both automatic time-delay scanning and parallel data recording with single point detectors are possible. Thus, we anticipate that the DFC spectroscopy would allow one to expand the application limits of the conventional femtosecond spectroscopic methods. In this Perspective article, we provide reviews of linear and nonlinear DFC spectroscopy theory and applications with a perspective on the development of coherent multidimensional frequency-comb spectroscopy.
关键词： nonlinear spectroscopy,optical frequency-comb,time-resolved spectroscopy,coherent two-dimensional spectroscopy,solvation dynamics,dual comb spectroscopy
更新于2025-09-23 15:22:29
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3-D Fast Nonlinear Simulation for Beam-Wave Interaction of Sheet Beam Traveling-Wave Tube
摘要： In this paper, a 3-D fast time-domain nonlinear algorithm (FTDNA-3-D) based on particle-in-cell method for the beam–wave interaction of the sheet beam slow wave structure (SWS) is presented. Calculation equations of the circuit electric field and the space charge electric field are given. Calculation approaches of the energy exchange and the particle mover are displayed. A simplified coupling impedance simulation approach for sheet beam SWS is indicated. The FTDNA-3-D takes the transverse electric field and the focusing magnetic field into consideration. The FTDNA-3-D could reach a high simulation speed. This novel algorithm gives a faster accurate choice for the design of sheet beam traveling-wave tube (TWT). It could be used to enhance the design efficiency of sheet beam TWT. A Ka-band staggered double vane TWT is used to verify the FTDNA-3-D. Simulation results of output power and gain versus frequency from FTDNA-3-D are compared with results from CST particle studio. The results of FTDNA-3-D are in accord with CST particle studio well.
关键词： beam–wave interaction,sheet beam traveling-wave tube (TWT),3-D nonlinear algorithm
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE International Ultrasonics Symposium (IUS) - Kobe, Japan (2018.10.22-2018.10.25)] 2018 IEEE International Ultrasonics Symposium (IUS) - A Hybrid 3D Thermal / 1D Piezoelectric Finite Element Model for Rapid Simulation of FBAR Filter Response Under High Power
摘要： The increasingly stringent power requirements imposed on BAW filter technologies has made coupling between thermal and piezoelectric physics relevant to the design process. Existing lumped filter models do not account for the effect of a 3D temperature distribution over each resonator. Here we report a new finite element based method for rapid simulation of filter response under high power that captures the effect of heat flow within the filter die as well as its path through the PCB to thermal ground.
关键词： thermo-piezoelectric,BAW,self-heating,nonlinear,FBAR,FEM,fully coupled
更新于2025-09-23 15:22:29
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Generation of optical signal and terahertz idler photons by spontaneous parametric down-conversion
摘要： Frequency-angular characteristics of signal and idler photons generated under spontaneous parametric down-conversion are studied in a strongly frequency nondegenerate regime, without paraxial approximation, accounting for possible inherent absorption of idler waves in a nonlinear crystal, classical thermal field fluctuations, and the multimode character of parametric interaction induced by transverse spatial limitation of the pump beam. Spatial limitation is shown to lead to a huge increase in angular divergence of the idler photons generated at terahertz frequencies. General expressions are obtained for the frequency-angular sensitivity function of the nonlinear-optical terahertz wave detector and for power densities of the signal and idler photon fluxes. The absorption-induced difference in the parametric conversion coefficients for the noise and externally incident radiation of the idler frequency is shown to be described by approximately the same loss factor for all active spatial idler modes. Two different parametric contributions of the internal thermal noise to the number of output idler photons were revealed with different dependence on the idler-wave absorption. Expressions for the loss factors, which describe absorption-induced effects in signal and idler channels, are obtained and shown to be turning into one another by changing the sign of the absorption coefficient. Relative contribution of thermal and quantum field fluctuations into the intrinsic radiation of a nonlinear crystal at signal and idler frequencies is analyzed accounting for the crystal absorption properties.
关键词： nonlinear optics,thermal fluctuations,terahertz,quantum fluctuations,absorption,spontaneous parametric down-conversion
更新于2025-09-23 15:22:29
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Ultra-broadband second harmonic generation in ZnO nano-tetrapod with over-one-octave bandwidth
摘要： Broadband nonlinear optical frequency conversion has attracted considerable interest in many applications such as optical communication, frequency comb generation and so on. Here, we report on the ultra-broadband second harmonic generation (SHG) from the Zinc oxide nano-tetrapod with less stringent phase-matching requirement. Using a super-continuum source together with an optical parametric oscillator as the excitation light, a broadband SHG with over-one-octave bandwidth spanning from the ultraviolet to near-infrared (375-1100 nm) is readily obtained. The SHG dependence of pump polarization and pump power is also characterized systematically. This nanoscale ultra-broadband optical converter may open a new way for various applications ranging from imaging to on-chip all-optical signal processing operations.
关键词： Nonlinear optics,Nanostructured materials
更新于2025-09-23 15:22:29
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Integration of Solar PV with Low-Voltage Weak Grid System: using Maximize-M Kalman Filter and Self-tuned P&O Algorithm
摘要： This paper introduces a novel 'self-tuned perturb and observe (P&O)' (SPO) algorithm for quick maximum power point tracking (MPPT) and a novel maximize-M Kalman filter (MMKF) based control technique for optimal operation of 'grid-integrated solar PV system, where linear/nonlinear loads are attached at PCC (Point of Common Coupling)'. Proposed SPO is the improved form of perturb and observe (P&O) algorithm, where inherent problems of traditional P&O like steady-state oscillation, slow dynamic responses and fixed step size issues, are successfully mitigated. Therefore, SPO tracks maximum power peak (MPP) very rapidly and it very accurately extracts maximum power from the PV array. The extracted power is used to meet the active power requirement of loads, and after meeting the load demand, the excess power is supplied to the grid. During power feeding, the power quality and power management are maintained by the MMKF based control technique. In control strategy, the MMKF is used for fundamental harmonic component extraction from the grid voltage and load current, even when the grid voltage is characterized by adverse situations, like sag, swell, harmonic distortion, DC offset etc. Here, the SPO MPPT algorithm and MMKF based control techniques, are tested on a developed prototype. The efficient and reliable performances of SPO MPPT algorithm and MMKF based control algorithm, in dynamic as well as in steady-state condition, are demonstrated under insolation variation conditions, nonlinear loading, as well as in different grid disturbances such as over-voltage, under-voltage, phase imbalance, harmonics distortion in the grid voltage etc.
关键词： MPPT,Solar PV,MMKF,Power quality,Nonlinear Load,SPO
更新于2025-09-23 15:22:29
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On the Complexity Reduction of the 2nd-order Volterra Nonlinear Equalizer for IM/DD systems
摘要： To cope with the various nonlinear signal distortions in IM/DD transmission systems, a theoretical analysis on the Volterra nonlinear equalizer (VNLE) is provided, focusing on computational complexity aspects. The analysis yields a simple reduced-complexity scheme for the 2nd-order VNLE (R2-VNLE) based on a performance-complexity trade-off. An experimental verification is performed with single-sideband 28-GBaud PAM-4 electro-absorption modulated signals, generated by a distributed-feedback laser, over transmission distances of up to 80-km of standard single-mode fiber in the C-band. A comparison of the results for different equalization schemes, including a signal-signal beat interference mitigation technique, shows superior performance for the R2-VNLE.
关键词： PAM-4,Volterra filter,direct detection,Nonlinear equalization,optical interconnects,intensity modulation
更新于2025-09-23 15:22:29
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Donor Impurity States in Semiconductor Zincblende Nitride Quantum Systems as a Source of Nonlinear Optical Response
摘要： The optical absorption and the optical rectification coefficients associated to hydrogenic impurity interstate transitions in zincblende GaN-based nanostructures of the quantum wire type are investigated. The system is assumed to have cylindrical shape and the influence of external tuning probes such as hydrostatic pressure and static electric fields is particularly taken into account. The electron states are obtained within the effective mass approximation, via the exact diagonalization of the donor-impurity Hamiltonian with parabolic confinement. The nonlinear optical coefficients are calculated using a nonperturbative solution of the density-matrix Bloch equation. Our results show that the resonance-related features of the optical response become shifted in the frequency range of the incident radiation due to the effect of the hydrostatic pressure, the strength of the applied field and the change in the impurity center position.
关键词： Quantum Wire,Nonlinear Optics,Hydrostatic Pressure,Zincblende GaN
更新于2025-09-23 15:22:29