Ultrafast photoconductive self-switching of subpicosecond electrical pulses

A novel photoconductive switch is proposed. The geometry of this ultrafast switch allows the rising edge of an ultra-short optical pulse to both turn on and turn off a terahertz electrical transient, making the device independent of the substrate material and charge carrier lifetime. A lumped-element model is used to analyze the operation of the switch. The model employed describes the photoexcitation of both a microstrip photoconductive switch layout and a coplanar photoconductive switch layout. It is found that both of the layouts are capable of achieving subpicosecond switching, with the coplanar layout offering greater ease of fabrication and device tunability.