DTU Fotonik Colloquia

The DTU Fotonik Colloquia in photonics are a recurring event. 2 or 3 times a year, DTU Fotonik will invite a highly renowned scientist to give a lecture. Attendance is free. 

The panel consists of Jørn Hvam, Peter Uhd Jepsen, Michael S. Berger, and Steen Hanson; all 4 are from DTU Fotonik. 

Registration for the events is not required.


Next Colloquium on June 2, 2015:


Title: Ultrafast terahertz scanning tunneling microscopy


By Prof. Frank Hegmann, Department of Physics, University of Alberta, Edmonton, Alberta, Canada 


Time: 15:00-16:00

Lyngby Campus

Building 421/74

The ability to directly probe ultrafast phenomena on the nanoscale is essential to our understanding of excitation dynamics on surfaces and in nanomaterials. The scanning tunneling microscope (STM) can image surfaces with atomic resolution, but the time resolution is typically limited to a few tens of microseconds by the bandwidth of the amplifier electronics. To achieve picosecond or sub-picosecond time resolution, various ultrafast STM techniques that integrate femtosecond lasers have been developed. Recently, we demonstrated a new ultrafast STM technique that couples terahertz (THz) pulses to the scanning probe tip of an STM, or THz-STM, providing simultaneous 0.5 ps time resolution and 2 nm spatial resolution under ambient laboratory conditions. THz-STM imaging of ultrafast carrier capture into a single InAs nanodot on GaAs photoexcited with 800 nm pump pulses was also shown.

This talk will provide an introduction to THz pulse spectroscopy, an overview of ultrafast STM techniques, and a description of THz-STM. The potential for imaging ultrafast dynamics on surfaces with atomic resolution will be discussed.