Complete response characterization of ultrafast linear photonic devices

We present a method to fully characterize linear photonic devices that change their properties on ultrashort time scales. When we feed the device with a broadband input pulse and detect the resulting output field for a sufficient number of arrival times of the input, the device response to any other input with smaller bandwidth can be extracted numerically, without the need for additional measurements. Our approach is based on the formalism of linear time-varying systems, and we experimentally demonstrate its feasibility for the example of an ultrafast nanophotonic switch.