Non-classical Beams Research Articles

Design, numerical analysis and experiments of different types auxetic beams for vibration based energy harvester

In this study, different types of auxetic beams were designed and their vibration characteristics were investigated experimentally and numerically for to improve output electrical power in energy harvesting applications. In order to analyze the energy harvesting performance of all designed beams, different frequency conditions were investigated. To see the vibration-based energy harvesting potential of all auxetic beams, the displacement responses under vibration were analyzed using different methods. Firstly experimental modal analysis of non-traditional beams were made and compare with the FEM methods numerically. The displacement of beam were obtained under forced vibration by numerical harmonic analysis to evaluate beams in terms of energy harvesting performance. Then, sinusoidal vibration experiments in the electro-mechanical shaker were carried out in order to verify numerical modal analyses results for non-classical beams. Finally, galloping geometry was attached to the ends of all auxetic samples produced and exposed to wind load. The effect of air flow on beam vibrations and energy harvesting performance was investigated experimentally.

Experimental and numerical analysis of vibration-based hybrid energy harvesting from non-classical beam structures

It is known that the displacement and stress on beams will directly affect the energy harvesting performance. For this purpose, structural changes are made on the beam elements. Behaviours of these beam structures are investigated by designing different non-classical beam geometries. This study examines vibration-based electromagnetic and piezoelectric energy harvesting from the non-classical beam structures under various conditions. Before analysing the non-classical beam structure, studies are performed for a classical beam for electromagnetic and piezoelectric energy harvesting studies. In the electromagnetic energy harvesting analysis, the effects of magnitude of magnetic field and the distance between the coil and the permanent magnet on the harvesting performance are studied by free vibration experiments. In this regard, a neodymium permanent magnet is attached to the vibrating aluminium beam endpoint. During the free vibration period, the coil and the magnet interact closely. As a result, a voltage output is obtained by inducing an electric field on the coil side. Secondly, voltage outputs of piezoelectric energy harvesting structures are experimentally evaluated for a classical beam and used for the verification of numerical simulations. Using the verified numerical simulations, new types of beam structures so-called non-classical beams are designed to obtain higher voltage outputs. Finally, by introducing the phenomenon of continuous vibration with the effect of air, the hybrid energy performance is analyzed for the proposed structure. The continuous vibration is created by the air-flow on the square galloping geometry.

Dynamic buckling of classical/non-classical curved beams by nonlocal nonlinear finite element accounting for size dependent effect and using higher-order shear flexible model

This paper investigates the dynamic snap-through buckling of classical and non-classical curved beams subjected to a suddenly applied step load. The small scale effect prevalent in non-classical beams, viz, micro and nanobeam, is modeled using the nonlocal elasticity approach. The formulation accounts for moderately large deflection and rotation. The governing equilibrium equations are derived using the dynamic version of the principle of virtual work and are subsequently simplified in terms of the generalized displacements for the development of a nonlocal nonlinear finite element model. The spatial domain comprises of 3-noded higher-order curved beam elements based on shear flexible theory associated with sine function. The nonlinear governing equations are solved using the incremental stiffness matrices and by adopting direct time integration method. The critical dynamic buckling load is identified by the smallest load at which there is a sudden rise in the amplitude of vibration. The efficacy of model here is compared against the available analytical studies for the local and nonlocal beams. A detailed study is made to highlight the effects of the geometric parameter, initial condition, nonlocal parameter, load duration, and boundary conditions on the dynamic stability of both classical and non-classical curved beams. The nature and degree of participation of various eigen modes accountable for the dynamic snap-through behavior are examined a posteriori using the modal expansion approach. Some interesting observations made here are valuable for the optimal design of such structural members against fatigue and instability.

Higher order mode entanglement in a type II optical parametric oscillator.

Nonclassical beams in high order spatial modes have attracted much interest but they exhibit much less squeezing and entanglement than the fundamental spatial modes, limiting their applications. We experimentally demonstrate the relation between pump modes and entanglement of first-order Hermite Gauss modes (HG10 entangled states) in a type II OPO and show that the maximum entanglement of high order spatial modes can be obtained by optimizing the pump spatial mode. To our knowledge, this is the first time to report this. Utilizing the optimal pump mode, the HG10 mode threshold can be reached easily without HG00 oscillation and HG10 entanglement is enhanced by 53.5% over HG00 pumping. The technique is broadly applicable to entanglement generation in high order modes.

Noise correlations controlled by dressed suppression and enhancement

The intensity noise correlations between anti-Stokes and Stokes fields, generated from spontaneous parametric four-wave mixing (SP-FWM) process have been investigated in a ladder-type three-level system of sodium atomic vapor. By introduction of an external dressing field, the strengthened (weakened) correlations are obtained under enhancement (suppression) condition of SP-FWM. Besides, sharp correlations have been obtained as attributed to a pair of non-classical beams generated from amplified spontaneous emission.

Vibration of nonclassical shear beams with Winkler-Pasternak-type restraint

Transverse vibration of the shear beams containing rotary inertia and with a two-parameter elastic foundation is studied. Using asymptotic analysis of Timoshenko beam theory, we derive explicit characteristic equations of the nonclassical shear beams with Winkler-Pasternak elastic restraint and with both ends linked to translational and rotational springs. The condition of the nonclassical shear beams reducing to the classical ones is found. Natural frequencies of the nonclassical modes are evaluated for free- and pinned-elastically restrained shear beams with or without bracing. The influences of elastic restraint stiffness and rotary inertia on the natural frequencies are discussed. Some extreme cases can be recovered from the present. The obtained results are helpful in the design of a tall frame building.

Quantum correlated light beams from non-degenerate four-wave mixing in an atomic vapor: the D1 and D2 lines of ^85Rb and ^87Rb

We present experimental results showing that quantum correlated light can be produced using non-degenerate, off-resonant, four-wave mixing (4WM) on both the D1 (795 nm) and D2 (780 nm) lines of (85)Rb and (87)Rb, extending earlier work on the D1 line of (85)Rb. Using this 4WM process in a hot vapor cell to produce bright twin beams, we characterize the degree of intensity-difference noise reduction below the standard quantum limit for each of the four systems. Although each system approximates a double-lambda configuration, differences in details of the actual level structure lead to varying degrees of noise reduction. The observation of quantum correlations on light produced using all four of these systems, regardless of their substructure, suggests that it should be possible to use other systems with similar level structures in order to produce narrow frequency, non-classical beams at a particular wavelength.

Non-classical neutron beams for fundamental and solid state research

The curious dual nature of the neutron, sometimes a particle, sometimes a wave, is wonderfully manifested in the various non-local interference and quantum contextuality effects observed in neutron interferometry. Non-classical states may become useful for novel fundamental and solid state research. Here we discuss unavoidable quantum losses as they appear in neutron phase-echo and spin rotation experiments and we show how entanglement effects in a single particle system demonstrate quantum contextuality. In all cases of interactions, parasitic beams are produced which cannot be recombined completely with the original beam. This means that a complete reconstruction of the original state would, in principle, be impossible which causes a kind of intrinsic irreversibility. Even small interaction potentials can have huge effects when they are applied in quantum Zeno-like experiments. Recently, it has been shown that an entanglement between external and internal degrees of freedom exists even in single particle systems. This contextuality phenomenon also shows that a quantum system carries much more information than usually extracted. The path towards advanced neutron quantum optics will be discussed.

Beam splitting and Hong-Ou-Mandel interference for stored light

Storing and release of a quantum light pulse in a medium of atoms in the tripod configuration are studied. Each of these operations is realized by switching on and off two sets of properly chosen control fields. The system constitutes a kind of a flexible beam splitter in which the input and output ports concern photons of the same direction but well separated in time. A version of Hong-Ou-Mandel interference is discussed. It is also shown that a stored nonclassical light is split into two nonclassical beams, with their statistical properties being steered by a choice of the control fields.

Quantum entanglement and squeezing of the quadrature difference of bright light fields

In this paper we present a scheme in which the amplitude-quadrature difference and phase-quadrature difference of two bright nonclassical beams serve as a pair of observed complementary variables that can be measured directly and can form a new squeezed state. Mixing such two quadrature-difference squeezed-state beams on a beam splitter produces characteristic of the Einstein-Podolsky-Rosen quantum entanglement. The experimental schemes producing such nonclassical beams and its possible applications in quantum information are discussed.

Quantum statistics of a nonlinear asymmetric coupler with strong pumping

We derive the quantum statistical properties of light beams involved in an asymmetric nonlinear coupler composed of a linear waveguide and a nonlinear waveguide operating using second harmonic generation. Examining quadrature and integrated intensity fluctuations, photon number distribution, reduced factorial moments and the uncertainty product, we demonstrate non-classical behaviour of single and compound modes. We show that squeezing of vacuum fluctuations, sub-Poissonian photon statistics and oscillations in photon number distribution created by nonlinear dynamics can be transferred to the linear signal mode. Also effects of non-classical incident beams and smoothing effects of external noise are demonstrated.