1. A method, comprising: illuminating a selected area of a device under test (DUT) with laser pulses from a mode locked laser (MLL) while the DUT is receiving test signals; collecting reflected portions of the laser pulses from the selected area of the DUT; converting the reflected portions of the laser pulses into a corresponding electrical signal with a photodetector having a relaxation time that is less than a MLL laser pulse separation associated with a MLL pulse repetition rate; and sampling the electrical signal at a sampling clock rate corresponding to the MLL pulse repetition rate to produce an associated digital output.