Microfluidic integrated metamaterials for active terahertz photonics

A depletion layer played by aqueous organic liquids flowing in a platform of microfluidic integrated metamaterials is experimentally used to actively modulate terahertz(THz)waves.The polar configuration of water molecules in a depletion layer gives rise to a damping of THz waves.The parallel coupling of the damping effect induced by a depletion layer with the resonant response by metamaterials leads to an excellent modulation depth approaching 90%in intensity and a great difference over 210°in phase shift.Also,a tunability of slow-light effect is displayed.Joint time-frequency analysis performed by the continuous wavelet transforms reveals the consumed energy with varying water content,indicating a smaller moment of inertia related to a shortened relaxation time of the depletion layer.This work,as part of THz aqueous photonics,diametrically highlights the availability of water in THz devices,paving an alternative way of studying THz wave–liquid interactions and developing active THz photonics.

High-sensitivity modulation of electromagnetically induced transparency analog in a THz asymmetric metasurface integrating perovskite and graphene

Active control of the electromagnetically induced transparency(EIT)analog is desirable in photonics development.Here,we theoretically and experimentally proposed a novel terahertz(THz)asymmetric metasurface structure that can possess high-sensitivity modulation under extremely low power density by integrating perovskite or graphene.Using the novel metasurface structure with the perovskite coating,the maximum amplitude modulation depth(AMD)of this perovskite-based device reached 490.53%at a low power density of 12.8037 mW/cm^(2).In addition,after the novel THz metasurface structure was combined with graphene,this graphene-based device also achieved high AMD with the maximum AMD being 180.56%at 16.312 mW/cm^(2),and its transmission amplitude could be electrically driven at a low bias voltage.The physical origin of this modulation was explained using a two-oscillator EIT model.This work provides a promising platform for developing high-sensitivity THz sensors,light modulators,and switches.