Laser-pump-resistive-probe technique to study nanosecond-scale relaxation processes

Standard optical pump-probe methods analyze a system's temporal response to a laser pulse within sub-femtoseconds to several nanoseconds, constrained by the optical delay line's length. While resistance is a sensitive detector in various fields, its measurements are typically slow (>microseconds) due to stabilization requirements. We suggest here a time-resolved pump-probe technique which combines an optical pump pulse and a rectangular electrical probe pulse through the sample, measuring transmission in a 50 Ohm matched circuit with a digital oscilloscope. This allows electrically-driven delays from nanoseconds to seconds. Demonstrations include studying heat-induced changes in a thin amorphous VO$_x$ film and carrier relaxation in a CdS photoresistor, showcasing potential applications in heat transfer, biochemical reactions, and gradual electronic transformations.