Nonlinear coherent perfect photon absorber in asymmetrical atom–nanowires coupling system

Coherent perfect absorption provides a method of light-controlling-light and has practical applications in optical communications. Recently, a cavity-based nonlinear perfect photon absorption extends the coherent perfect absorber（CPA）beyond the linear regime. As nanowire-based system is a more competitive candidate for full-optical device, we introduce a nonlinear CPA in the single two-level atom–nanowires coupling system in this work. Nonlinear input–output relations are derived analytically, and three contributions of atomic saturation nonlinearity are explicit. The consociation of optical nonlinearity and destructive interference makes it feasible to fabricate a nonlinear monoatomic CPA. Our results also indicate that a nonlinear system may work linearly even when the incoming lights are not weak any more. Our findings show promising applications in full-optical devices.

Nonlinear terahertz devices utilizing semiconducting plasmonic metamaterials

The development of responsive metamaterials has enabled the realization of compact tunable photonic devices capable of manipulating the amplitude,polarization,wave vector and frequency of light.Integration of semiconductors into the active regions of metallic resonators is a proven approach for creating nonlinear metamaterials through optoelectronic control of the semiconductor carrier density.Metal-free subwavelength resonant semiconductor structures offer an alternative approach to create dynamic metamaterials.We present InAs plasmonic disk arrays as a viable resonant metamaterial at terahertz frequencies.Importantly,InAs plasmonic disks exhibit a strong nonlinear response arising from electric field-induced intervalley scattering,resulting in a reduced carrier mobility thereby damping the plasmonic response.We demonstrate nonlinear perfect absorbers configured as either optical limiters or saturable absorbers,including flexible nonlinear absorbers achieved by transferring the disks to polyimide films.Nonlinear plasmonic metamaterials show potential for use in ultrafast terahertz(THz)optics and for passive protection of sensitive electromagnetic devices.

Bending vibration control of pipes conveying fluids by nonlinear torsional absorbers at the boundary

A nonlinear torsional absorber,which can overcome the influence of the fluid velocity on the natural frequency,is employed at the boundary to restrain the bending vibration of a pipe for the first time.By using the rotating angle at the end of the pipe,the bending vibration energy is pumped to the boundary absorber.The nonlinearly coupled pipe-absorber governing equations are obtained by the generalized Hamilton’s principle.Steady-state responses subjected to a basement excitation are discussed by the modal-correction-harmonic-balance-method.According to this method,the boundaries of the pipe are treated as the generalized governing equations.In this way,those nonlinearities and time-dependent terms in the boundary are involved in the response completely.A direct simulation method,called the differential quadrature element method(DQEM),is used to verify these analytical results.The investigation indicates that the nonlinear boundary absorber owns two outstanding advantages.The first one is that the natural characters remain the same and the absorber can capture the resonance of the pipe automatically.The second one is that the absorber works at all natural modes.Especially,by using the nonlinear damping,the absorber will not worsen the weak vibration in the non-resonance region.The parameters of the absorber are investigated to optimize the efficiency in detail.The result finds that good efficiency can be achieved with a tiny mass.Meanwhile,the efficiency becomes better as the damping increases.With the help of these investigations,the work provides a new strategy to protect pipes conveying fluids from being destroyed by the vibration.

Nonlinear terahertz metamaterial perfect absorbers using GaAs[Invited]

We investigate the nonlinear response of terahertz(THz) metamaterial perfect absorbers consisting of electric split ring resonators on GaAs integrated with a polyimide spacer and gold ground plane. These perfect absorbers on bulk semi-insulating GaAs are characterized using high-field THz time-domain spectroscopy. The resonance frequency redshifts 20 GHz and the absorbance is reduced by 30% as the incident peak field is increased from 30 to 300 kV/cm. The nonlinear response arises from THz field driven interband transitions and intervalley scattering in the GaAs. To eliminate the Fresnel losses from the GaAs substrate, we design and fabricate a flexible metamaterial saturable perfect absorber. The ability to create nonlinear absorbers enables appealing applications such as optical limiting and self-focusing.

利用强非线性减振器的模态能量再分配缓解大型结构的冲击响应

采用一种轻型几何非线性附件,强非线性减振器(SNA),以抑制线性大型九层结构的冲击响应.SNA的作用不仅是耗散能量,而且重新分配结构模态之间的冲击能量.本文研究单自由度(SDOF)和双自由度(Two-DOF)的SNAs.冲击能量再分配的定量结果表明,在强几何非线性的情况下,这种结构可以实现从低频到高频的非线性单向能量传递.具体而言,在锁定SNA、单自由度SNA和双自由度SNA的情况下,较高结构模态耗散的冲击能量百分比分别为0.08%,0.43%和30.04%.结果表明,与单自由度SNA相比,双自由度SNA能够将更多的能量快速散射到更高的频域,从而更快地降低主结构的冲击响应.还研究了在不同冲击强度下SNA性能的鲁棒性,其中双自由度SNA在从低频到高频散射冲击能量时表现出更强的鲁棒性.最后,采用等效阻尼技术来验证和量化主结构中模态能量的重新分布,并讨论这种新型被动减震方法的潜在应用.