Andrea Cavalleri

Abstract:

We present a pulse-shaping scheme operating in the mid-infrared (MIR) wavelength range up to 20 μm. The spectral phase is controlled by a specially designed large stroke 32-actuator deformable mirror in a grating-based 4f configuration. We demonstrate the shaper capability of compressing the MIR pulses, imparting parabolic and third-order spectral phases and splitting the spectral content to create two independent pulses.

Abstract:

Optical pulses at THz and mid-infrared frequencies tuned to specific vibrational resonances modulate the lattice along chosen normal mode coordinates. In this way, solids can be switched between competing electronic phases and new states are created. Here, we use vibrational modulation to make electronic interactions (Hubbard-U) in Mott-insulator time dependent. Mid-infrared optical pulses excite localized molecular vibrations in ET-F2TCNQ, a prototypical one-dimensional Mott-insulator. A broadband ultrafast probe interrogates the resulting optical spectrum between THz and visible frequencies. A red-shifted charge-transfer resonance is observed, consistent with a time-averaged reduction of the electronic correlation strength U. Secondly, a sideband manifold inside of the Mott-gap appears, resulting from a periodically modulated U. The response is compared to computations based on a quantum-modulated dynamic Hubbard model. Heuristic fitting suggests asymmetric holon-doublon coupling to the molecules and that electron double-occupancies strongly squeeze the vibrational mode.

Abstract:

Coherent control over the magnetization state of the rare-earth orthoferrite ErFeO3 is achieved by nonlinear lattice excitation via mid-infrared laser pulses. This low-dissipative approach enables new pathways in light-driven manipulation of magnetic materials. © 2014 OSA.

Abstract:

Time- and angle-resolved photoemission spectroscopy directly enables observation of electron dynamics in condensed matter. Using EUV high harmonic probe extends the observation window in energy and momentum. Tunable mid-infrared pumping allows control of excitation mechanisms. © 2014 OSA.