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Non-Linear Thz Spectroscopy

Recents technological advances allow for THz pump and THz probe experiemnts where THz pulses are used both as a time domain spectroscopic tool (probe) as well as the mean to drive matter into transient non-equilibrium states (pump). The key technological advances has been the capability to produce THz pulses intense enough to drive measurable perturbation into the material responses. In the lab we use two approaches to produce intense ultrashort THz pulses in different spectral region. 

In order to produce single cycle pulses with spectral content ranging from 0.3 to 3THz (100μm<λ<1mm) and energy as high as 1μJ/pp we use optical reptification of tilted wave front pulses. The intrinsic advantage of optical reptification techniques delivering carrier envelpe phase stables pulses allow to measure directly the effects of the phase and amplitude of the perturbing electric field. 

In order to perform experiment with higher energy pulses (5μm< λ <20μm, Energy>1μJ/pp) we use different frequency generation (DFG) between two signals produced in Twin Optical parametric amplifier seeded with same white light. This scheme allow for the production of nearIR carrier envelope phase stable pulses for selective excitations of low energy modes in matter. The nearIR source is combined with ultrashort probes (<20fs) allowing for the measurements of the response to phase and amplitude of the perturbing field. 

Fig.1: Photo control of the gap in GaAs by means of intense THz pulses.

For further information you can contact:
Daniele Fausti

Scientific Report, 3, 1227, 2013

Last Updated on Monday, 07 July 2014 12:31