Speaker
Alex Frenzel
(Harvard / MIT)
Description
Alex Frenzel, Harvard University / MIT
Nityan Nair, Massachusetts Institute of Technology
Nathaniel Gabor, Massachusetts Institute of Technology
Nuh Gedik, Massachusetts Institute of Technology
The relaxation of the electronic system in graphene plays a crucial role in a variety of proposed optoelectronic devices, including bolometers, photodetectors, and solar cells. Time-resolved terahertz spectroscopy affords the ability to probe the low-energy electrodynamics of carriers during relaxation. This is accomplished by exciting the electronic system with a strong 100 fs, 1.5 eV optical pulse and probing at variable time delay with a picosecond far-infrared pulse. Using this method to investigate carrier dynamics in CVD-grown graphene, we observe a positive change in the differential terahertz transmission after optical excitation. This new behavior contrasts with the negative change seen in previous measurements. Our experiments reveal a maximum change in transmission which decreases with increasing temperature. Additionally, the relaxation dynamics slow down with increasing excitation density, a trend which is not expected from typical electron-hole recombination dynamics. This qualitatively different response reveals new opportunities for manipulating optical response in graphene.
Primary author
Alex Frenzel
(Harvard / MIT)
