[MOS] April 17, 2007

[Zina Queen]

Seminar on
Modern Optics and Spectroscopy


  János Hebling, MIT

Generation and application of high field THz pulses

April 17, 2007

12:00 - 1:00 p.m.
Grier Room 34-401


During the last two decades the fast development 
of time domain THz spectroscopy (TDTS) created a 
renaissance of this field and related 
applications of near-single-cycle THz pulses. 
Although the majority of TDTS  work has been done 
by THz pulses having ralatively small energy on 
the fJ - pJ range there exists a strong and yet 
unmet need for high energy ultrashort THz pulses 
for applications in imaging, security control and 
nonlinear THz spectroscopy. For this purpose in 
the last few years we developed an efficient THz 
pulse generation technique based on optical 
rectification of ultrashort near-IR pump pulses 
in lithium niobate (LN) crystal. This method 
achieves matching of the effective pump pulse 
group velocity to the phase velocity of the THz 
pulses by so called 
tilted-pulse-front-excitation. After describing 
the principle, the set-up and the results 
achieved by this technique a few of our 
preliminary nonlinear THz optics and spectroscopy 
results will be presented. The possible 
combination of the tilted-pulse-front-excitation 
with shaped pump pulses will also be sketched. 
The latter was earlier used at MIT for 
generation, coherent addition and control of 
phonon-polaritons (mixture of THz electromagnetic 
field and lattice vibration) in ferroelectrics 
(i.e. LN). The combination of the two techniques 
will enable the generation of high energy THz 
pulses for (quantum) control experiments with 
practically arbitrary pulse shape if the spectrum 
is on the 0.1 - 2 THz range and the pulse 
duration shorter than 10 ps
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