Effective control of terahertz radiation requires fast and efficient modulators with a large modulation depth-a challenge that is often tackled by using metamaterials.Metamaterial-based active modulators can be create...Effective control of terahertz radiation requires fast and efficient modulators with a large modulation depth-a challenge that is often tackled by using metamaterials.Metamaterial-based active modulators can be created by placing graphene as a tuneable element shunting regions of high electric field confinement in metamaterials.However,in this common approach,the graphene is used as a variable resistor,and the modulation is achieved by resistive damping of the resonance.In combination with the finite conductivity of graphene due to its gapless nature,achieving 100%modulation depth using this approach remains challenging.Here,we embed nanoscale graphene capacitors within the gaps of the metamaterial resonators,and thus switch from a resistive damping to a capacitive tuning of the resonance.We further expand the optical modulation range by device excitation from its substrate side.As a result,we demonstrate terahertz modulators with over four orders of magnitude modulation depth(45.7 dB at 1.68 THz and 40.1 dB at 2.15 THz),and a reconfiguration speed of 30 MHz.These tuneable capacitance modulators are electrically controlled solid-state devices enabling unity modulation with graphene conductivities below 0.7 mS.The demonstrated approach can be applied to enhance modulation performance of any metamaterial-based modulator with a 2D electron gas.Our results open up new frontiers in the area of terahertz communications,real-time imaging,and wave-optical analogue computing.展开更多
基金supported by the UK Engineering and Physical Sciences Research Council(EPSRC)grant EP/S023046/1 for the EPSRC Centre for Doctoral Training in Sensor Technologies for a Healthy and Sustainable Futurefunding from the HyperTerahertz grant,no.EP/P021859/1the TeraCom grant,no.EP/W028921/1。
文摘Effective control of terahertz radiation requires fast and efficient modulators with a large modulation depth-a challenge that is often tackled by using metamaterials.Metamaterial-based active modulators can be created by placing graphene as a tuneable element shunting regions of high electric field confinement in metamaterials.However,in this common approach,the graphene is used as a variable resistor,and the modulation is achieved by resistive damping of the resonance.In combination with the finite conductivity of graphene due to its gapless nature,achieving 100%modulation depth using this approach remains challenging.Here,we embed nanoscale graphene capacitors within the gaps of the metamaterial resonators,and thus switch from a resistive damping to a capacitive tuning of the resonance.We further expand the optical modulation range by device excitation from its substrate side.As a result,we demonstrate terahertz modulators with over four orders of magnitude modulation depth(45.7 dB at 1.68 THz and 40.1 dB at 2.15 THz),and a reconfiguration speed of 30 MHz.These tuneable capacitance modulators are electrically controlled solid-state devices enabling unity modulation with graphene conductivities below 0.7 mS.The demonstrated approach can be applied to enhance modulation performance of any metamaterial-based modulator with a 2D electron gas.Our results open up new frontiers in the area of terahertz communications,real-time imaging,and wave-optical analogue computing.
