Interview for Faculty Position

Ultrafast terahertz spectroscopy and photonics

David Cooke

DTU Fotonik

The field of terahertz science is dedicated to exploring the last untapped region of the electromagnetic spectrum between 0.1 30 THz. This low energy band contains signatures of a wide variety of quasiparticle excitations in matter, from lattice vibrations and free charge motion to correlated electronic effects such as superconductivity. Here I review a relatively new and powerful technique called time-resolved THz spectroscopy that uses single cycle electric-field transients called THz pulses to dynamically probe the evolution of these signatures in the THz range after optical excitation. I will demonstrate the power of this technique in revealing conduction dynamics and mechanisms in bulk and nanoscale semiconductors occurring on sub-picosecond time scales. Finally, a new technique called time-resolved THz waveguide spectroscopy is introduced where the sample is embedded inside a waveguide to enhance sensitivity, and a spin-off technology is discussed where the propagation of THz light in the waveguide can be controlled all-optically.