SIDEBANDS OF X-RAY DIFFRACTION IN AGE-HARDENED Cu-Ti ALLOY

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Parametric generation and phase locking of multiple sidebands in the regime of full-back-conversion

Parametric interaction allows both forward and backward energy transfers among the three interacting waves.The back-conversion effect is usually detrimental when unidirectional energy transfer is desired.In this theoretical work,we manifest that the back-conversion effect underpins the direct generation of the picosecond pulse train without the need for a laser resonator.The research scenario is an optical parametric amplification(OPA)that consists of a second-order nonlinear medium,a quasi-continuous pump laser and a sinusoidal amplitude-modulated seed signal.The back-conversion of OPA can transfer the modulation peaks(valleys)of the incident signal into output valleys(peaks),which inherently induces spectral sidebands.The generation of each sideband is naturally accompanied with a phase shift of±π.In the regime of full-back-conversion,the amount and amplitude of the sidebands reach the maximum simultaneously,and their phase constitutes an arithmetic sequence,leading to the production of a picosecond pulse train.The generated picosecond pulse train can have an ultrahigh repetition rate of 40 GHz or higher,which may facilitate ultrafast applications with ultrahigh speed.

Numerical simulation and mechanism analysis of freak waves

A numerical wave model based on the modified fourth-order nonlinear Schroe dinger equation （mNLSE） in deep water was developed to simulate the formation of freak waves and a standard split - step, pseudo-spectral method was used to solve the equation. The validation of the model is firstly verified, then the simulation of freak waves was performed by changing sideband conditions, and the variation of wave energy was also analyzed in the evolution. The results indicate that Benjamin - Feir instability （ sideband instability） is an important mechanism for freak wave formation.

Quasi-Static and Dynamic Behaviors of Helical Gear System with Manufacturing Errors

Time?varying mesh stiffness(TVMS) and gear errors include short?term and long?term components are the two main internal dynamic excitations for gear transmission. The coupling relationship between the two factors is usually neglected in the traditional quasi-static and dynamic behaviors analysis of gear system. This paper investigates the influence of short?term and long?term components of manufacturing errors on quasi?static and dynamic behaviors of helical gear system considering the coupling relationship between TVMS and gear errors. The TVMS, loaded static transmission error(LSTE) and loaded composite mesh error(LCMS) are determined using an improved loaded tooth contact analysis(LTCA) model. Considering the structure of shaft, as well as the direction of power flow and bearing location, a precise generalized finite element dynamic model of helical gear system is developed, and the dynamic responses of the system are obtained by numerical integration method. The results suggest that lighter loading conditions result in smaller mesh stiffness and stronger vibration, and the corresponding resonance speeds of the system become lower. Long?term components of manufacturing errors lead to the appearance of sideband frequency components in frequency spectrum of dynamic responses. The sideband frequency components are predominant under light loading conditions. With the increase of output torque, the mesh frequency and its harmonics components tend to be enhanced relative to sideband frequency components. This study can provide effective reference for low noise design of gear transmission.

Efficient Simulation of Freak Waves in Random Oceanic Sea States

Numerical simulations of freak wave generation are studied in random oceanic sea states described by JONSWAP spectrum. The evolution of initial random wave trains is namerically carried out within the framework of the modified fourorder nonlinear Schroedinger equation （mNLSE）, and some involved influence factors are also discussed. Results show that if the sideband instability is satisfied, a random wave train may evolve into a freak wave train, and simultaneously the setting of the Phillips paranleter and enhancement coefficient of JONSWAP spectrum and initial random phases is very important for the formation of freak waves. The way to increase the generation efficiency of freak waves thsough changing the involved parameters is also presented.

Analysis and Simulation for Planetary Gear Fault of Helicopter Based on Vibration Signal

Fault diagnosis for helicopter's main gearbox based on vibration signals by experiments always requires high costs. To solve this problem,a helicopter's planetary gear system is taken as an example. Firstly,a simulation model is established by McFadden,and analyzed under ideal condition. Then this model is developed and improved as the delay-time model of the vibration signal which determines the phase-change of sidebands when the system is running. The cause and change-rules of planetary gear system's vibration signal are analyzed to establish the fault diagnosis model.At the same time,the vibration signal of fault condition is simulated and analyzed. This simulation method can provide a reference for fault monitoring and diagnosis for planetary gear system.

Ground-state cooling based on a three-cavity optomechanical system in the unresolved-sideband regime

In the unresolved sideband regime,we propose a scheme for cooling mechanical resonator close to its ground state in a three-cavity optomechanical system,where the auxiliary cavities are indirectly connected with the mechanical resonator through standard optomechanical subsystem.The standard optomechanical subsystem is driven by a strong pump laser field.With the help of the auxiliary cavities,the heating process is suppressed and the cooling process of the mechanical resonator is enhanced.More importantly,the average phonon number is much less than 1 in a larger range.This means that the mechanical resonator can be cooled down to its ground state.All these interesting features will significantly promote the physical realization of quantum effects in multi-cavity optomechanical systems.

Terahertz field-induced modulations of intersubband absorptions in quantum wells

Nonlinear optical properties of intersubband electrons in a 3-level quantum well under intense terahertz field are investigated by using a density matrix approach. The results show that the terahertz fields with different frequencies cause the distinct modulations of the intersubband absorptions. The terahertz-indueed sideband and Autler-Towns splitting in the absorption spectrum are obtained, respectively for the terahertz-photon energy below and close to the transition energy between the ground and first excited state.

Effective sideband cooling in an ytterbium optical lattice clock

Sideband cooling is a key technique for improving the performance of optical atomic clocks by preparing cold atoms and single ions into the ground vibrational state.In this work,we demonstrate detailed experimental research on pulsed Raman sideband cooling in a 171 Yb optical lattice clock.A sequence comprised of interleaved 578 nm cooling pulses resonant on the 1st-order red sideband and 1388 nm repumping pulses is carried out to transfer atoms into the motional ground state.We successfully decrease the axial temperature of atoms in the lattice from 6.5μK to less than 0.8μK in the trap depth of 24μK,corresponding to an average axial motional quantum number<nz><0.03.Rabi oscillation spectroscopy is measured to evaluate the effect of sideband cooling on inhomogeneous excitation.The maximum excitation fraction is increased from 0.8 to 0.86,indicating an enhancement in the quantum coherence of the ensemble.Our work will contribute to improving the instability and uncertainty of Yb lattice clocks.

Investigation on Mesh and Sideband Vibrations of Helical Planetary Ring Gear Using Structure, Excitation and Deformation Symmetries

Time?variant excitations in planetary gear trains can cause excessive noise and vibration and even damage the system on a permanent basis. This paper focuses on the elastic vibrations of a helical planetary ring gear subjected to mesh and planet?pass excitations. Motivated by the structure, excitation and deformation symmetries, this paper proposes dual?frequency superposition and modulation methods to capture the mesh and sideband vibrations. The transi?tion between ring gear tooth and planet is introduced to address the excitations and vibrations. The phasing e ect of ring gear tooth and planet on various deformations is formulated. The inherent connections between the two types of vibrations are identified. The vibrations share identical exciting rules and the wavenumber and modulating signal order both equal the linear combination of tooth and planet counts. The results cover in?plane bending and extensional, out?of?plane bending and torsional deformations. Main findings are verified by numerical calculation and comparisons with the open literature. The analytical expressions can be used to determine whether the sideband is caused by component fault or only by elastic vibration. The methods can be extended to other power?transmission systems because little restriction is imposed during the analysis.

Sideband manipulation of population inversion in a three-level Λ atomic system

Sideband manipulation of population inversion in a three-level A atomic configuration is investigated theoretically. Compared with the case of a nearly monochromatic field, a population inversion between an excited state and a ground state has been found in a wide sideband intensity range by increasing the difference in frequency between three components. Furthermore, the population inversion can be controlled by the sum of the relative phases of the sideband components of the trichromatic pump field with respective to the phase of the central component. Changing the sum phase from 0 to π, the population inversion between the excited state and the ground state can increase within nearly half of the sideband intensity range. At the same time, the sideband intensity range that corresponds to the system exhibiting inversion ρ00 〉 ρ11 also becomes wider evidently.

Raman sideband cooling of rubidium atoms in optical lattice

We develop a simple and practical scheme to apply sideband cooling to a cloud of rubidium atoms. A sample containing 4 × 10^（70） ^（87）Rb is trapped in a far red detuned optical lattice. Through optimizing the relevant parameters, i.e., laser detuning, magnetic field, polarization, and duration time, a temperature around 1.5 μK and phase space density close to 1/500 are achieved. Compared with polarization gradient cooling, the temperature decreases by around one order of magnitude. This technique could be used in high precision measurement such as atomic clocks and atom interferometer. It could also serve as a precooling means before evaporation cooling in a dipole trap, and may be a promising method of achieving quantum degeneracy with purely optical means.

Vibrational Spectrum and Luminescence Properties of CaAl2B2O7∶Eu3+

The vibrational spectrum of the CaAl2B2O7 was investigated. It was shown that the vibrations of the BO3 groups are present in the region of 1400600 cm-1, and the bands at 519 nm-1 may originate from the AlO6 vibration. The luminescence properties of Eu3+ in CaAl2B2O7 were investigated. It was found that the Eu3+ ion in CaAl2B2O7 occupies two different sites. Investigation on the phonon sideband of Eu3+ indicates that BO3 groups are present in the surroundings of Eu3+ ions.

Synthesis and Characterization of Lanthanide Complexes Involving Cyclopentadienyl and Benzohydroximic Acid Ligand

The glasses of 59 5H 3BO 3 40XF n 0 5Eu 2O 3 (X=Ca, Mg, Y, Pb, n =2 or 3) were prepared. The measurement of phonon sideband was performed. The higher energy range of phonon sideband spectra was fitted by Gaussian function, and the electron phonon coupling constant was calculated. The decreasing order of electron phonon coupling constant is from CaF 2, YF 3, MgF 2 to PbF 2, and the phonon sideband spectra are coincide with Raman scattering spectra.

Tunable second-order sideband effects in hybrid optomechanical cavity assisted with a Bose-Einstein condensate

We theoretically investigated a second-order optomechanical-induced transparency(OMIT) process of a hybrid optomechanical system(COMS), which a Bose-Einstein condensate(BEC) in the presence of atom-atom interaction trapped inside a cavity with a moving end mirror. The advantage of this hybrid COMS over a bare COMS is that the frequency of the second mode is controlled by the s-wave scattering interaction. Based on the traditional linearization approximation, we derive analytical solutions for the output transmission intensity of the probe field and the dimensionless amplitude of the second-order sideband(SS). The numerical results show that the transmission intensity of the probe field and the dimensionless amplitude of the SS can be controlled by the s-wave scattering frequency. Furthermore, the control field intensities,the effective detuning, the effective coupling strength of the cavity field with the Bogoliubov mode are used to control the transmission intensity of the probe field and the dimensionless amplitude of the SS.

A High-Linear Radio Frequency Quadrature Modulator with Improved Sideband Suppression and Carrier Leakage Performance

The quadrature modulator is a crucial block in transmitters that upconverts baseband signals to theRadio Frequency(RF)band of interest using local oscillator frequencies.In this paper,non-ideal factors thatinfluence the performance of the quadrature modulator are considered,and solutions are accordingly taken inthe quadrature modulator design.A high-linear RF quadrature modulator with improved sideband suppressionand carrier leakage performance is presented in this work.The quadrature modulator implemented in the0.18-μm SiGe process uses the current bleeding technique to improve the general performance of the doublebalanced active Gilbert mixers.An on-chip prescaler followed by two cascaded limiting amplifiers is designed toprovide accurate quadrature local oscillator signals.Predrivers at quadrature baseband signal input ports areproposed to eliminate DC offsets.The measured sideband suppression achieves a performance of better than−43 dBc and carrier leakage is less than−38 dBm over the output RF frequency range of 30 MHz to 2.15 GHz.The output 1 dB compression point equals 11.4 dBm at 800 MHz.

Microwave photonic sideband selector based on thin-film lithium niobate platform

We propose and demonstrate an integrated microwave photonic sideband selector based on the thin-film lithium niobate(TFLN)platform by integrating an electro-optic Mach-Zehnder modulator(MZM)and a thermo-optic tunable flat-top microring filter.The sideband selector has two functions:electro-optic modulation of wideband RF signal and sideband selection.The microwave photonic sideband selector supports processing RF signals up to 40 GHz,with undesired sidebands effectively suppressed by more than 25 d B.The demonstrated device shows great potential for TFLN integrated technology in microwave photonic applications,such as mixing and frequency measurement.

Demonstration of fully-connected quantum communication network exploiting entangled sideband modes

Quantum communication network scales point-to-point quantum communication protocols to more than two detached parties,which would permit a wide variety of quantum communication applications.Here,we demonstrate a fully-connected quantum communication network,exploiting three pairs of Einstein–Podolsky–Rosen(EPR)entangled sideband modes,with high degree entanglement of 8.0 dB,7.6 dB,and 7.2 dB.Each sideband modes from a squeezed field are spatially separated by demultiplexing operation,then recombining into new group according to network requirement.Each group of sideband modes are distributed to one of the parties via a single physical path,making sure each pair of parties build their own private communication links with high channel capacity better than any classical scheme.

Sideband-free dispersion-managed Yb-doped mode-locked fiber laser with Gires–Tournois interferometer mirrors

High-order dispersion introduced by Gires–Tournois interferometer mirrors usually causes spectral sidebands in the nearzero dispersion region of mode-locked fiber lasers.Here,we demonstrate a sideband-free Yb-doped mode-locked fiber laser with dispersion-compensating Gires–Tournois interferometer mirrors.Both the simulation and the experiment demonstrate that the wavelength and energy of the sidebands can be tuned by changing the transmission coefficient of the output mirror,the pump power,and the ratio of the net cavity dispersion to the net third-order dispersion in the cavity.By optimizing these three parameters,the laser can generate a sideband-free,Gaussian-shaped spectrum with a 13.56-nm bandwidth at-0.0232 ps^(2)net cavity dispersion,which corresponds to a 153-fs pulse duration.

Photonic generation of ASK microwave signals with SSB format

Optical beating is the usual approach to generation of microwave signals.However,the highest frequency achievable for microwave signals is limited by the bandwidths of optoelectronic devices.To maximize the microwave frequency with a limited bandwidth of a photodetector(PD)and relieve the bandwidth bottleneck,we propose to generate microwave signals with the single sideband(SSB)format by beating a continuous wave(CW)light with an optical SSB signal.By simply adjusting the frequency diference between the CW light and the carrier of the optical SSB signal,the frequency of the generated microwave SSB signal is changed correspondingly.In the experiment,amplitude shift keying(ASK)microwave signals with the SSB format are successfully generated with diferent carrier frequencies and coding bit rates,and the recovered coding information agrees well with the original pseudo random binary sequence(PRBS)of 2^(7)−1 bits.The proposed approach can signifcantly relieve the bandwidth restriction set by optoelectronic devices in high-speed microwave communication systems.