Progress in ultrafast scanning probe microscopy

Recently, we proposed a general technique to wed ultrafast laser spectroscopy and Scanning Probe Microscopies (SPM) to obtain simultaneous picosecond time and atomic space resolution. In the experiment, a short laser pulse activated a photoconductive switch on a SOS transmission line, in order to generate short voltage pulses. While the tip was in tunneling range from one of the conductors of the transmission line, a second laser pulse gated the Scanning Tunneling Microscope (STM) tip assembly. Thus, we could excite the tunneling gap of the STM with a short voltage pulse, and measure its response. To better understand these measurements, we now model the experiment by an equivalent circuit