Physics Department Colloquium - “Strong-field physics in solids: From terahertz to extreme ultraviolet” - Dr. David Purschke – University of Ottawa

Strong-field physics is a discipline of laser science focused on the regime of light-matter interaction where the dynamics are governed by field-driven processes. In solids, there exists an extremely diverse range of strong-field interactions. In the low-frequencies regime, the dynamics are governed by incoherent scattering processes, while, in contrast, at higher frequencies the laser field can be used to coherently control charge-carrier motion. I present two experiments probing solid-state strong-field physics that illustrate the broad utility of ultrafast laser pulses in materials science and photonics. 

First, I study lightwave-driven carrier multiplication in HgCdTe excited by an intense terahertz pulse, observing up to 10 impact ionization events on a sub-cycle timescale. I discuss how the remarkable properties of HgCdTe make it an interesting platform to study the fundamental physics of carrier multiplication and, furthermore, argue that nonlinear terahertz spectroscopy could be an invaluable non-contact probe for the infrared detector industry. 

Second, I shift focus to the regime of coherent transport and adapt a technique from gas-phase attosecond physics to isolate the photon-mixing pathways of high-order harmonic generation in magnesium oxide. This demonstration paves the way for new techniques combining the photonic engineering of solids with the perturbative control of gas-phase attosecond physics to enable, for example, active control of extreme ultraviolet laser pulses or nanofocused structured light.