Multi-cycle reconfigurable THz extraordinary optical transmission using chalcogenide metamaterials

Metamaterials composed of metallic antennae arrays are used as they possess extraordinary optical transmission(EOT)in the terahertz(THz)region,whereby a giant forward light propagation can be created using constructive interference of tunneling surface plasmonic waves.However,numerous applications of THz meta-devices demand an active manipula-tion of the THz beam in free space.Although some studies have been carried out to control the EOT for the THz region,few of these are based upon electrical modulation of the EOT phenomenon,and novel strategies are required for act-ively and dynamically reconfigurable EOT meta-devices.In this work,we experimentally present that the EOT resonance can be coupled to optically reconfigurable chalcogenide metamaterials which offers a reversible all-optical control of the THz light.A modulation efficiency of 88%in transmission at 0.85 THz is experimentally observed using the EOT metama-terials,which is composed of a gold(Au)circular aperture array sitting on a non-volatile chalcogenide phase change ma-terial(Ge2Sb2Te5)film.This comes up with a robust and ultrafast reconfigurable EOT over 20 times of switching,excited by a nanosecond pulsed laser.The measured data have a good agreement with finite-element-method numerical simula-tion.This work promises THz modulators with significant on/off ratios and fast speeds.

The Development of Intelligent Operation Method of Urban Public Infrastructure Driven by Accurate Spatio-temporal Information

Urban public infrastructure is an important basis for urban development.It is of great significance to deepen the research on intelligent management and control of urban public infrastructure.Spatio-temporal information contains the law of state evolution of urban public infrastructure,which is the information base of intelligent control of infrastructure.Due to the needs of operation management and emergency response,efficient sharing and visualization of spatio-temporal information are important research contents of comprehensive management and control of urban public infrastructure.On the basis of summarizing the theoretical research and application in recent years,the basic methods and current situation of the acquisition and analysis of spatio-temporal information,the forecast and early warning,and the intelligent control of urban public infrastructure are reviewed in this paper.

Acoustic transmissive cloaking with adjustable capacity to the incident direction

Zero-refractive-index(ZRI)phononic crystals(PhCs),in which acoustic waves can be transmitted without phase variations,have considerable potential for engineering wavefronts and thus are applicable to invisibility cloaking.However,the creation of the transmissive cloaking achieved by ZRI-PhCs is challenging under an oblique incidence,which substantially hinders their practical applications.Here,we experimentally demonstrate acoustic transmissive cloaking with the adjustable capacity to the incident direction.Acoustic transmissive cloaking of arbitrarily shaped obstacles can be obtained through a hybrid acoustic structure consisting of one outer layer of a programmable phaseengineered metasurface(PPEM)and one inner layer of a double zero-refractive-index(DZRI)-PhC.The DZRI-PhC is functionally the same as an equiphase area and can guide acoustic waves around the obstacle,a process known as acoustic tunneling.The PPEM perpendicularly transfers the incident acoustic waves to the DZRI-PhC and allows the emergent waves from the DZRI-PhC to transmit along the original incident direction.The DZRI-PhC is made of an array of iron squares in the air.The reciprocal of the effective bulk modulus and the effective mass density is approximately zero at a frequency of 3015 Hz(0.5187 v0/a)originating from the zeroth-order Fabry–Pérot(FP)resonance that possesses infinite phase velocities.Each meta-atom of the outer metasurface consists of a line channel and four shunted Helmholtz resonators,which have effective masses that are engineered by a mechanics system.The amplitude and phase of the sound waves propagating through each meta-atom can be controlled continuously and dynamically,enabling the metasurface to obtain versatile wavefront manipulation functions.Acoustic cloaking is visually demonstrated by experimentally scanning the acoustic field over the hybrid structure at a frequency of 3000 Hz(0.5160 v0/a).Our work may provide applications with great potential,including underwater ultrasound,airborne sound,acoustic communication,imaging,etc.