Dr. Eric Landahl
Optical phenomenon in semiconductors and other light-sensitive materials typically happen at very short time durations, and require instruments capable of measuring time resolutions on the order of nanoseconds to femtoseconds. Electronics can only measure up to nanosecond-time lengths. The purpose of this summer research project is to design a system capable of achieving variable time delays with resolutions up to femtosecond range to use in time-resolved experiments with the pump-probe technique. The time delay is achieved using a delay stage driven by a micro stepper-motor which moves in variable increments while an encoder counts the steps and tells a computer to make adjustments as necessary. This requires developing a program to communicate between electronics connected to a raspberry pi and the stepper motor. Results show that the system is limited by the encoder resolution, which yields roughly 100 femtosecond resolution at 1/25th of a step and 2400 femtoseconds per full step. A relatively inexpensive and programmable setup like this can be used to study optical phenomenon such as reflectivity, absorption, transmission, or polarization in semiconductors.
Marin, Fabricio S.
"Instrumentation of a Self-Correcting Data Acquisition System for Ultrafast Lasers,"
1, Article 21.
Available at: http://via.library.depaul.edu/depaul-disc/vol5/iss1/21